“Our data show for the first time that stronger stratification of the Southern Ocean was crucial for the comparatively cool interglacials before the Mid-Brunhes Event,” says Dr Huang Huang, the study's lead author. He completed his PhD at ������Ƶ in 2019 and now works at the Laoshan Laboratory in Qingdao (China). The Mid-Brunhes Event refers to a significant climate change that occurred around 430,000 years ago. Following this event, the interglacial periods became warmer, longer and had higher CO₂ levels in the atmosphere. “With our new methodological approach, we were even able to detect shorter-term variations in the ocean – providing us with a much more detailed view of Southern Ocean dynamics.”

A look into the past with innovative laser technology

To address their research question, the team analysed a ferromanganese crust collected from the Antarctic continental margin at a depth of around 1,600 metres. These crusts grow extremely slowly and record the chemical signature of seawater over hundreds of thousands of years.

Using a novel laser-based technique – known as 2D laser ablation technique, in which tiny samples of material are precisely vaporised and then analysed – the researchers investigated the isotopic composition of lead preserved in the crust. Lead isotopes reveal how strongly the water layers in the ocean were mixed in the past. A new method also enables absolute dating of the layers of the same crust sample. In this way, past climate changes can be reconstructed at very high temporal resolution.

“This new laser method opens up completely new possibilities for climate reconstruction,” says Dr Jan Fietzke, a physicist and the head of the LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry) laboratory at ������Ƶ. “It enables us to gain a better understanding of the role of the Southern Ocean in the global carbon cycle, which is also relevant for predicting future climate developments.”

Stronger stratification: ocean processes determine the climate

The data show that during the lukewarm interglacials, the Southern Ocean was more strongly stratified – the upper and lower water layers mixed less. This meant that more carbon remained stored in the deep ocean instead of reaching the atmosphere. Less atmospheric CO₂ in turn led to a weaker greenhouse effect, cooler Antarctic temperatures and probably also a larger Antarctic ice sheet. The results highlight the crucial role of ocean changes for the sensitivity of the Earth’s climate system.

Publication:
Huang, H., Fietzke, J., Gutjahr, M., Frank, M., Kuhn, G., Zhang, X., Hillenbrand, C.-D., Li, D., Hu, J., & Yu, J. (2025). Enhanced deep Southern Ocean stratification during the lukewarm interglacials. Nature Communications.

Although phytoplankton in the ocean are tiny, they are of global importance: they account for only about 1-2 per cent of plant biomass, yet are responsible for nearly 40 per cent of global CO₂ uptake through photosynthesis. The new project at ������Ƶ and CAU will use AI to determine the role of phytoplankton in climate protection more precisely and quickly. The project aims to improve our understanding of the ocean’s natural climate protection functions and to strengthen them. The project is funded with around 2.16 million euros as part of the initiative AI Lighthouses for the Environment, Climate, Nature and Resources. Rita Schwarzelühr-Sutter, Parliamentary State Secretary at the Federal Ministry for the Environment (BMUKN), presented the funding notification in Berlin today.

The KIMMCO project – short for KI-gesteuertes Monitoring mariner Mikroalgen als CO2-Senke, AI-based monitoring of marine microalgae as a CO₂ sink – is embedded in the Action Programme for Natural Climate Protection (ANK), which was launched by the Federal Ministry for the Environment to protect ecosystems and to enhance their role as natural allies in climate protection.

Artificial intelligence meets climate protection

“Understanding the relationship between biodiversity and the CO₂ storage capacity of phytoplankton is a key prerequisite for effective marine conservation,” says Prof. Dr Anja Engel, project leader and Professor of Biological Oceanography at the ������Ƶ Helmholtz Centre for Ocean Research Kiel.

This is precisely where KIMMCO comes in. The researchers combine approaches at different scales – from in situ sensor measurements and microscopic camera systems to optical water properties and satellite-based remote sensing. AI applications analyse and integrate the collected data, providing a near real-time picture of phytoplankton productivity and species composition.

“With KIMMCO, our goal is to make large-scale measurements more efficient and accurate, while reducing resource usage and speeding up the process,” explains Prof. Dr Kevin Köser, Head of the Marine Data Science group at Kiel University. “This not only saves time and ship operations, but also aims to reduce the CO₂ footprint of marine observation itself.”

A lighthouse for science and policy

The project will run until the end of 2027, first being tested in the Baltic Sea. Its aim is to generate new insights into the ocean’s natural climate protection function and make these available to policymakers. KIMMCO will contribute valuable data to international monitoring programmes and environmental indicators, including those employed under the European Water Framework Directive, the Marine Strategy Framework Directive and within HELCOM.

The project will also include biodiversity and sustainability checks, comparing the new AI-based methods with classical techniques in terms of accuracy, resource use, and CO₂ footprint.

About: Action Programme for Natural Climate Protection (ANK)

Through the ANK, the Federal Ministry for the Environment is enhancing the capacity of ecosystems, including forests, moors, rivers, lakes and seas, to act as natural climate protectors. Between 2024 and 2028, more than 3.5 billion euros will be made available for this purpose. AI Lighthouses for the Environment, Climate, Nature and Resources, of which KIMMCO is one, are a key part of the programme.

To investigate this, a field experiment is now beginning off the coast of Gran Canaria. The experiment is led by Prof. Dr Ulf Riebesell, Professor of Biological Oceanography at the ������Ƶ Helmholtz Centre for Ocean Research Kiel. Marine biogeochemist Dr Kai Schulz, a visiting researcher from Southern Cross University (Australia), will be providing on-site direction. For the first time, two approaches are being compared systematically: adding already dissolved minerals and introducing finely ground rock into seawater.

Natural and Accelerated Rock Weathering
In the long term, nature binds carbon dioxide through the process of rock weathering. Minerals are transported into the ocean via rivers and chemically store CO₂ in dissolved form. However, this natural process takes millennia, which is far too long to mitigate human-induced climate change significantly in the coming decades. For this reason, researchers worldwide are investigating whether this process can be accelerated. In addition to the potential for long-term CO₂ storage, ocean alkalinity enhancement could have an added benefit: it could counteract the increasing acidification of seawater caused by the absorption of large amounts of CO₂ emissions.

Mesocosms as a Field Laboratory
For the Gran Canaria experiment, researchers are using Kiel mesocosms, which are 3.5-metre-long plastic tubes suspended in the sea on fixed frames. Within them, natural communities can be observed under controlled conditions, much like in oversized test tubes. The 12 mesocosms are currently being set up and filled. The crucial intervention will take place on 19 and 20 September, when minerals will be added. The aim is to compare the effects of dissolved alkalinity versus rock powder on the ecosystem.

Comparative Experiments in North and South
The current experiment builds on a series of field studies on OAE conducted in Gran Canaria in 2021, off the coast of Bergen (Norway) in2022, on Heligoland in 2023, and in the Kiel Fjord (Germany) last year. In the Kiel study, finely ground rock was used for the first time instead of previously dissolved minerals. Significantly stronger effects on zooplankton were observed under certain conditions, particularly at greatly increased concentrations. It remains unclear whether these differences are due to the particles not yet being fully dissolved, which could directly influence organisms within the first few hours or days.

Dr Kai Schulz: “The aim of this experiment is to find out whether the particles themselves have an additional effect on the ecosystem or if the observed effects are solely due to the increased alkalinity of the water.” The scientific director, Prof Dr Ulf Riebesell, explains why this is important: “Effects on zooplankton would also propagate to animals higher up the food chain. Only by fully understanding these mechanisms can we realistically assess the potential risks and benefits of ocean alkalinity enhancement.”

Meta-study on climate change scenarios

Together with Prof. Dr. Meryem Mojtahid, Professor of Paleo-Oceanography at the University of Angers and at Laboratory of Planetology and geosciences (France), they have investigated the effects of climate change on marine and coastal ecosystems in the Mediterranean region. The projections of the meta-study are based on recognized climate scenarios of the IPCC (Intergovernmental Panel on Climate Change). The research team analyzed 131 scientific studies on Mediterranean published up to August 2023. For the first time, this resulted in a so-called 'burning ember' diagram for Mediterranean marine and coastal ecosystems – a risk assessment tool originally developed by the IPCC. “The diagram clearly shows how strongly climate change threatens key ecosystems. I hope our results will help raise awareness and inspire real action to protect these unique ecosystems,” says Meryem Mojtahid. The study also draws on the Research Initiative on Climate Change and Environmental Degradation in the Mediterranean Region (MedECC). In 2020, the initiative published the first Mediterranean Assessment Report under the name MAR1, thus playing a key role in consolidating knowledge on climate and environmental changes in the Mediterranean area.

Mediterranean as a “Climate Change Hotspot”: Every Tenth of a Degree Counts

The Mediterranean Sea – similar to the Baltic Sea or the Black Sea – is a semi-enclosed sea and connected to the global ocean only through the Strait of Gibraltar. As a result, the Mediterranean Sea is warming faster and acidifying more strongly than the open ocean. Between 1982 and 2019, the surface seawater temperature already increased by 1.3°C, while the global increase was only 0.6°C. Therefore, the IPCC also refers to the Mediterranean Sea as a 'hotspot of climate change'. Also, scientists consider it as a natural laboratory because it reacts faster and more strongly to climate pressures than the open ocean, while at the same time concentrating multiple drivers and stressors in a relatively small, well-observed system. “What happens in the Mediterranean often foreshadows changes to be expected elsewhere, so the Mediterranean Sea acts like an early warning system for processes that will later affect the global ocean,” says Abed El Rahman Hassoun."

If international climate protection targets are met in the coming years, some environmental changes could still be slowed. Two IPCC scenarios – known as RCPs, or Representative Concentration Pathways – can be used to illustrate this: In a medium emissions scenario (RCP 4.5), emissions will stabilise over the next few years thanks to moderate climate policies. Even in this case, the Mediterranean Sea is expected to warm by an additional 0.6 to 1.3 °C (compared to current values) in 2050 and 2100 respectively. In contrast, the high emissions scenario (RCP 8.5) describes the “business as usual” path with continuously rising emissions. In this scenario, additional warming would likely range between 2.7°C and 3.8°C by 2050 and 2100 respectively. Such warming, together with sea level rise and ocean acidification, would have significant disruptions on ecosystems: seagrass meadows would be lost, coral reefs might witness significant damages, and severe chain reactions would occur in food webs.

“These scenarios show: We can still make a difference! Every tenth of a degree counts!” says study leader Abed El Rahman Hassoun. “Political decisions made now will determine whether ecosystems in the Mediterranean Sea collapse, partially or totally, or remain functional feeding the ecosystem services they provide. At the same time, our study also shows that even with moderate climate protection and an additional 0.8°C warming, we must expect some consequences. Thus, our focus should be on minimizing the impacts as low as possible.”

Impacts on Marine Ecosystems

The researchers examined a wide range of marine ecosystems: from seagrass meadows to fish and macroalgae, as well as marine mammals and turtles. Warming and acidification of the Mediterranean are altering entire communities. Plankton species are shifting, and toxic algal blooms and bacteria are occurring more frequently. With an additional warming of 0.8°C, seagrass plants such as Posidonia oceanica would decline massively and disappear completely by 2100. Seaweed species such as Cystoseira would also decline, while populations of heat-loving invasive algae could increase. Fish stocks are under pressure from +0.8 °C as well: they could shrink by 30 to 40 percent, shift northwards, and make room for invasive species such as the lionfish, which threatens biodiversity. Corals, probably due to their long evolutionary history, are relatively more resilient than other ecosystems, as they are at moderate to high risk from +3.1 °C. Data on marine mammals and sea turtles are limited, but changes in feeding grounds, migration behavior, and energy budgets are likely to occur.

Coastal Ecosystems: Particularly Vulnerable

Due to the combined effect of warming and sea-level rise, coastal ecosystems in the Mediterranean Sea are especially vulnerable to the impacts of climate change. The zone affected includes areas up to ten meters above sea level, such as dunes and rocky coasts. Rising sea levels increase coastal erosion and thereby threaten the nesting sites of sea turtles – more than 60 percent could be lost. Even at an additional warming of just +0.8 °C, the risk rises significantly: sandy beaches and dunes are particularly endangered, and rocky coasts also lose habitat and biodiversity, although they are somewhat more resilient.

Wetlands, lagoons, deltas, salt marshes, and coastal aquifers are also affected and can experience considerable damage already at +0.8°C to +1.0°C. Here, the loss of important plant species, the spread of invasive species, and large-scale vegetation changes are very likely. At the same time, rising sea levels can lead to reduced precipitation and consequently water scarcity. From +1.0 °C onward, the risks are expected to increase further due to flooding and higher nutrient inputs.

“We found that Mediterranean ecosystems are remarkably diverse in how they respond to climate-related stress. Some are more resistant than others, but none are invincible”, says Meryem Mojtahid. “Only strict climate protection measures can keep the risks at a level to which ecosystems can still adapt. Through this study, we were able to make visible that even a comparatively small increase in temperature and other climate change-related stressors has significant effects. “Now it’s time to turn knowledge into action”, adds Abed El Rahman Hassoun.

Research Gaps

For several ecosystems, scientific studies for the assessment of risks are still limited. There are only few projections for deep-sea habitats, salt marshes, macroalgae, and megafauna. Significant geographical gaps also remain, particularly in the southern and eastern Mediterranean, leading to a possible underestimation of risks in underrepresented countries. Moreover, long-term observations that address multiple stressors such as pollution and invasive species simultaneously are lacking. Addressing these gaps will require stronger interdisciplinary research efforts and expanded monitoring, especially in underrepresented regions.

Background:

The IPCC (Intergovernmental Panel on Climate Change), also known as the World Climate Council, is the United Nations’ international expert body that assesses the current state of climate research. Its reports summarize scientific findings, highlight risks, and provide a basis for decision-making for policymakers and society. A well-known tool from the IPCC reports is the so-called “Burning Ember Diagram.” It visualizes the likelihood of harm to humans and nature depending on global warming. Orange and red areas indicate where risks become high and very high – similar to a “glowing ember,” which explains the name.

Original Publication:

Hassoun, A.E.R., Mojtahid, M., Merheb, M. et al. Climate change risks on key open marine and coastal mediterranean ecosystems. Sci Rep 15, 24907 (2025).

Coastal sediment as a source of toxic hydrogen sulfide

In Kiel Bay, a strong decrease in oxygen levels occurs regularly in late summer – a consequence of climate change and eutrophication. This has severe consequences for ecosystems and thus also for the regional economy. The study area of expedition EMB374 in the southwestern Baltic Sea is known for the frequent occurrence of oxygen-depleted zones in late summer. Particularly problematic is the release of toxic hydrogen sulfide (H₂S) at the seafloor.

For the investigations, the ship remains close to the coast, because although coastal sediments make up only about nine percent of the seafloor, they play a central role in storing and breaking down organic material such as algae, plant, or animal remains. Under oxygen-rich conditions, the organic material can be degraded to CO₂. However, in the southwestern Baltic Sea, oxygen-poor and even oxygen-free zones occur near the seafloor in late summer. These conditions favor certain bacteria that couple the decomposition of organic material to respiration with oxygen alternatives. They use sulfate for this, which is abundant in seawater. When sulfate is reduced, hydrogen sulfide is produced. It has a characteristic smell of rotten eggs and is toxic to many marine organisms. If oxygen-poor or hydrogen sulfide-containing water rises into shallower water layers due to upwelling, it can lead to mass fish kills.

How hydrogen sulfide-containing water is formed

“We want to find out under which conditions and at which locations hydrogen sulfide is released from the sediment into bottom water. With this knowledge, we can better predict risks for marine organisms and more accurately assess the role of the Baltic Sea under the influence of climate change,” says chief scientist Prof. Dr. Mirjam Perner, Professor of Geomicrobiology at ������Ƶ.

The expedition is part of the PrimePrevention project of the German Marine Research Alliance (DAM). This project investigates factors that lead to the formation of hydrogen sulfide-containing bottom waters. During the expedition, oxygen and hydrogen sulfide concentrations in the water column are measured using sensors, and geochemical and microbiological factors at the seafloor are determined. In addition, water and sediment samples are collected for laboratory analyses. All available environmental data are then incorporated into numerical models that can be used to predict the release of hydrogen sulfide. The aim is to identify particularly vulnerable regions and to assess the risk of hypoxic events for stakeholders such as tourism, fisheries, and aquaculture.

Algal blooms in the Baltic Sea

During the cruise, various systems for detecting cyanobacteria will also be tested. These organisms account for a large part of the summer algal blooms in the Baltic Sea and can produce toxins that in some cases lead to bathing bans at beaches. When they die, this also leads to increased oxygen consumption in deeper water layers.

A newly developed optical measurement system (hyperspectral module) from the University of Oldenburg will be tested during the expedition and compared with other measurements to assess its suitability for routine use on ships or measuring platforms. For comparative measurements, the HyFiVe system (modular hydrographic measuring system) is also used. It was developed at the Leibniz Institute for Baltic Sea Research Warnemünde (IOW) and at the Thünen Institute in cooperation with Hensel Elektronik GmbH, with federal funding. A newly integrated sensor can measure the amount of cyanobacteria.

With the new system from the university, fishers are also to be enabled to collect additional measurement data for marine research (projects PrimePrevention and HyFiVe-Baltic). Early detection of cyanobacteria is then to be embedded in early warning systems to protect people in coastal regions from harm. To validate and calibrate the two systems, the Oldenburg-based company AquaEcology will also take water samples, which will later be microscopically analyzed in the laboratory.

Mirjam Perner: “In the Baltic Sea, processes such as warming, acidification, and eutrophication are more pronounced and occur more rapidly than in other seas. We therefore also refer to the Baltic Sea as a time machine. This is why it is so important to already understand how the processes work that in the future will increasingly affect other marine areas as well.”

Background: PrimePrevention

The research cruise and associated work are embedded in the PrimePrevention project of the Deutsche Allianz Meeresforschung (DAM) mission mareXtreme. The project investigates ways to predict biological hazards for the ocean to prevent socio-economic impacts and is funded by the Federal Ministry for Research, Technology and Space (BMFTR). The project is coordinated by Dr. Katja Metfies at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI).

Expedition at a glance:
Name: EMB 374 PrimePrevention
Chief Scientist: Prof. Dr. Mirjam Perner (������Ƶ)
Period: 04.09.2025 – 13.09.2025
Start and end: Kiel
Cruise area: Southwestern Baltic Sea

CO₂ storage in flood basalts beneath the seabed
“Our central research question is: does the basalt below the seabed, in its properties and composition, have the potential to store CO₂ permanently and safely?” explains Chief Scientist Dr Ingo Klaucke, a geologist at the ������Ƶ Helmholtz Centre for Ocean Research Kiel. The expedition will provide us with the necessary data to assess the storage potential of rocks and lay the foundation for their geophysical monitoring.”

The potential could be vast: globally, basalt deposits beneath the ocean theoretically have a storage capacity of 40,000 gigatons – several times the current annual global CO₂ emissions. This is why the expedition is named “Permanent sequestration of gigatons of CO₂ in continental margin basalt deposits, CO₂�ʸ�”.

Extensive lava layers off Norway’s coast
The cruise will focus on the Skoll High on the Vøring Plateau off the Norwegian coast, where cores from previous scientific drilling expeditions have indicated extensive lava layers. To determine the properties of the seabed rock, the researchers will employ high-resolution 2D and 3D surveying techniques, including reflection and refraction seismic as well as electromagnetic measurements. The resulting physical parameters, such as sound velocity and electrical resistivity, will then be fed into models to derive information on density and conductivity, and thus the rock’s storage potential. Artificial intelligence will support the data analysis. The aim is not only to identify suitable storage structures, but also to explore ways in which a future CO₂ storage site could be monitored remotely – for example, using seismic or electromagnetic signatures that might indicate leaks.

En route to the study area, the team will deploy two ARGO floats northeast of Iceland to help closing a gap in the ocean observation network.

Fewer conflicts with other sea uses
With its contribution to the international PERBAS initiative, Expedition MSM140 is providing important foundations for developing flood basalts as CO₂ storage sites. In addition to their sheer size and the potentially rapid and permanent fixation rates, such sites have the advantage of usually being far offshore and therefore less intensively used than the North Sea or other shallow shelf seas. Conflicts with other forms of use will likely be less frequent. However, the great distance from the coast would make implementation costly, as tankers would need to transport CO₂ far out to sea.

Expedition at a glance

Name: MSM140 “CO₂�ʸ�”
Chief Scientist: Dr Ingo Klaucke
Dates: 4 September – 9 October 2025
Start port: Reykjavik, Iceland
End port: Trondheim, Norway
Working area: Vøring Plateau, Norway

About PERBAS:

The international research project PERBAS (PERmanent sequestration of gigatons of CO₂ in continental margin BASalt deposits) investigates how carbon dioxide can be permanently stored in marine basalt rock. The aim is to lay the groundwork for the safe and geologically stable storage of CO₂ beneath the seabed – and thus contribute to the achievement of international climate targets. In addition to reducing emissions, large amounts of CO₂ will need to be removed from the atmosphere in future and stored safely and permanently. Basalt formations are considered a particularly promising candidate for this: they enable the mineral conversion of CO₂ into carbonate rock – a process that can be completed within just a few years.

In PERBAS, ten partners from science and industry in Germany, Norway, the USA and India pool their expertise. The ������Ƶ Helmholtz Centre for Ocean Research Kiel coordinates the project, which is funded with a total of 3.6 million euros over three years as part of the ACT (Accelerating CCS Technologies) initiative of the European Research Area Network (ERA-NET). The consortium’s goal is to systematically characterise potential storage sites in marine basalt rock, determine their geophysical properties, and scientifically underpin the technical feasibility and monitoring of future storage projects. The current research phase will be completed in summer 2026. After that, a CO₂ storage experiment in flood basalts off the Norwegian coast is planned – but this will require the support and financial commitment of industry.

Modelling studies suggest that volcanic activity along mid-ocean ridges responds to these pressure variations, for instance through changes in the thickness of newly formed crust, the composition of magma, or the intensity of hydrothermal activity, where hot, mineral-rich fluids emerge from the seafloor. However, a lack of long-term time series data from the seafloor has so far made it difficult to confirm these hypotheses directly.

Time series: A Key to understanding the Earth System

“We already have excellent reconstructions of past sea-level changes, but there are no similarly high-resolution records of how geological processes on the ocean floor have evolved over time. This is the gap we aim to close,” says Dr Martin Frank, a professor of chemical palaeoceanography at ������Ƶ. Frank will lead an international research team aboard the German research vessel (RV) SONNE for the next eight weeks, studying the Southeast Pacific Rise – one of the fastest-spreading and most active segments of the global mid-ocean ridge system.

“This area of the ocean acts like a conveyor belt for Earth’s geological history,” explains Frank. “We suspect that the processes taking place here have been influenced by climate over geological timescales – for example, through pressure changes driven by sea-level fluctuations during glacial and interglacial periods.”

Volcanic Glass as an Archive of the Deep Earth

Along the ship’s route from Papeete (Tahiti) to Antofagasta (Chile), the team will use a gravity corer to collect sediment cores up to 25 metres long. They will follow a transect running perpendicular to the ridge axis. This closely spaced sampling will provide a high-resolution time series.

“These seafloor sediments contain volcanic glass and metal deposits,” says Frank. “They reveal how magma chemistry and hydrothermal activity have varied over the past 1.5 million years. We can read these changes like entries in a geological archive.”

Meanwhile, seismic measurements conducted during the expedition will help reconstruct changes in the thickness of the ocean crust – another key indicator of how Earth’s interior processes may respond to climate-driven pressure shifts at the surface.

Understanding Earth System Dynamics

Expedition SO314 forms part of the large-scale European ERC Synergy Project T-SECTOR (Testing Solid Earth - Climate Connections), which investigates the links between processes in the atmosphere, the ocean, and the Earth’s interior. Alongside the ������Ƶ teams led by professors  Martin Frank, Heidrun Kopp and Kaj Hoernle, the project involves Professor Charles Langmuir from Harvard University (USA). Scientists from MARUM (the Centre for Marine Environmental Sciences at the University of Bremen) and the University of Hamburg are also participating in the expedition.

Expedition at a Glance:

Name: SO314
Chief Scientist: Professor Dr Martin Frank
Duration: 13 August – 5 October 2025
Departure Port: Papeete (Tahiti)
Arrival Port: Antofagasta (Chile)
Research Area: Southeast Pacific

"The aim of the project is to produce hydrogen using saltwater electrolysis in an environmentally friendly and cost-effective way - but with optimised efficiency and less use of chemical catalysts,” says Dr Mirjam Perner. She is Professor of Geomicrobiology at ������Ƶ Helmholtz Centre for Ocean Research Kiel and is leading the project together with Prof. Dr Jana Schloesser, Professor of Materials Engineering at Kiel University of Applied Sciences, and Florian Gerdts, lead process engineer at the Kiel-based technology company Element22.

Challenges of electrolysis with salt water

Up to now, electrolysis has required purified fresh water, as it contains neither salts nor minerals and therefore protects the electrolysis system from corrosion. However, only 2.5 per cent of the world's water reserves are fresh water. Furthermore, the desalination and purification of salt water causes additional costs that could be avoided by utilising seawater directly. As part of the SalYsAse project, the scientists want to utilise salt water directly from the sea. This presents them with a number of challenges: The salt it contains can produce toxic chlorine gas during the electrolysis of seawater. "Faster corrosion of the electrodes or undesirable side reactions can also occur. We want to prevent this by using suitable materials in combination with the microorganisms," says materials expert Jana Schloesser.

Efficient catalysts and membranes

In order to be able to utilise the seawater, the researchers want to use marine microbes, i.e. bacteria, in addition to conventional catalyst layers. The microbes come from the Baltic and North Sea, as they are best adapted to the conditions of salt water. Mirjam Perner explains: "The chemical element iridium is often used as a catalyst as it is very resistant to corrosion. However, it is rare and therefore only available in limited quantities. That's why we want to use biocatalysts in the form of microbes." The microbes should help to reduce or even circumvent the challenges posed by the use of salt water.

The project team is also using suitable materials for the membrane, which separates hydrogen and oxygen during electrolysis, and the porous transport layer. "The special feature of SalYsAse is that the porous transport layer not only conducts the current and the reaction media. We design it in such a way that this layer also acts as a carrier for the microbes. This means that biological catalysis takes place directly in the electrolysis cell - an exciting approach that brings together materials science and life sciences," says Florian Gerdts. The project participants want to use porous titanium structures for this, as titanium is particularly resistant to corrosion, which is essential for use in seawater.

In future, the entire process is to take place where the electricity is already generated: at offshore wind turbines. In this way, the scientists avoid having to transport the electricity to the mainland first. This route is expensive and energy is lost. Instead, clean, climate-neutral hydrogen is produced on site. This can be transported onwards efficiently and used in energy-intensive industries such as steel and chemical production, for example.

Background: Hydrogen as the energy source of the future

In order to replace fossil fuels, more renewable energies will be used in the future and sustainable energy sources will be required. Hydrogen plays an important role in this context, as it can be easily stored and transported. Hydrogen as an energy carrier thus enables the coupling of various sectors - from industry and mobility to energy supply.  Green hydrogen is particularly efficient and conserves resources. Hydrogen is considered green if it is produced by electrolysis using electricity from renewable sources such as solar or wind energy. This process does not produce any greenhouse gases. Hydrogen produced by seawater electrolysis at windy locations can be used in industry or heavy goods transport, for example.

Funding:

The Federal Ministry of Research, Technology and Space (BMFTR) is funding the project with a total of 733,000 euros over a period of three years.

Partners:

The project partners are Kiel University of Applied Sciences, coordinated by the Kiel University of Applied Sciences Research and Development Centre GmbH, and the technology company Element22 GmbH from Kiel, which manufactures the titanium components for this project. SalYsAse is linked to CAPTN Energy, an innovation alliance in Schleswig-Holstein that utilises renewable energies for maritime applications.

Using Citizen Science to Fill Data Gaps in the Mediterranean

The project team uses this citizen-sourced data, in compliance with data-protection regulations, to monitor and record temperature changes across different parts of the Mediterranean Sea and from coastal regions worldwide. Dr. Christophe Galerne and Prof. Achim Kopf, both from MARUM at the University of Bremen, Dr. Rebecca Zitoun from ������Ƶ Helmholtz Centre for Ocean Research Kiel, and Arne Schwab from Schwab Research Technology are leading the project.

Underwater Sensors: Calibration at Reference Dive Sites

To improve the quality of the collected data and ensure that temperature readings from the different dive computers are comparable, BlueDOT has installed permanent high-precision temperature sensors at selected reference dive sites on the Costa Brava, Heligoland, and the Maltese island of Gozo. These permanently deployed sensors record the temperature at various depths, allowing scientists to calibrate the data collected from dive computers against consistent, high-resolution measurements. To support this effort, BlueDOT is collaborating with two diving centers in Spain and Malta. These centers play a key role in engaging the diving community, raising awareness about the project, and helping to test and maintain the sensors.

Global Potential: Six Million Divers Worldwide

According to Christophe Galerne, the use of the sensors increases the accuracy of the database, “which creates a more reliable basis for research and helps to develop an optimal approach for the global expansion of the project in the long term.” These diver-sourced data are an important complement to existing ocean-monitoring platforms such as satellite observations, Argo floats, and hydrographic surveys. “With an estimated six million active scuba divers worldwide, this citizen science initiative represents a huge potential for enhancing climate research through widespread, community-driven observations of ocean temperature.”

The project is funded by the BMFTR – Federal Ministry of Research, Technology and Space, began in December 2024 and is initially scheduled to run for about 18 months. This serves as a test phase to develop the best approach for a possible global expansion.

Warming with Consequences: How Rising Sea Temperatures Affect Us

The team has already evaluated diving data from the Mediterranean Sea. As Galerne expected, these indicate that average ocean temperatures are rising steadily. The water masses of the oceans act as heat reservoirs that interact with the atmosphere and thus influence the climate. If this system becomes unstable with the continued warming of surface water, it could lead to intensified evaporation and, ultimately, regionally limited extreme precipitation events in the surrounding areas. Galerne explains that the associated rain belt has continuously shifted farther northward over the past 20 years, leading to sporadic droughts as well as heavy rainfall and flooding.

More Than Just Summer Data – Why Every Season Counts

“The constant warming and increasing frequency of marine heatwaves also have significant implications for biodiversity and the ecosystem services our oceans provide, making these phenomena a critical factor to consider in both research and management. There presently exists what is known as sampling bias in the data. This is exhibited by a clear predominance of data obtained during the warmer months and the holiday seasons. In order to be able to establish an average value, we would like to encourage divers to enter their data – including older data – into our portal and also to record and upload data from cooler seasons,” says Galerne. By filling these seasonal gaps, divers can play a crucial role in building a completer and more accurate picture of how ocean temperatures are changing throughout the year.

The project is officially endorsed by the UN Decade of Ocean Science for Sustainable Development.

“What helps the climate is not automatically good for the ocean,” says Prof. Dr Andreas Oschlies, lead author of the study and head of the Biogeochemical Modelling research division at ������Ƶ. Together with an international team that is part of the UNESCO Global Ocean Oxygen Network (GO₂NE), he conducted a comprehensive assessment using idealised global model simulations to analyse both the direct impacts of various mCDR approaches on ocean oxygen and their indirect effects through climate mitigation. The results have now been published in Environmental Research Letters.

Ocean fertilisation and seaweed sinking among the most critical approaches

The study identifies several biotic mCDR methods as particularly critical — including ocean fertilisation, large-scale macroalgae farming followed by sinking of the biomass, and artificial upwelling of nutrient-rich deep water. These approaches involve the enhancement of photosynthetic biomass production, followed by its decomposition in the ocean interior. This remineralisation process consumes oxygen — at levels comparable to the current rate of global deoxygenation caused by ocean warming.

“Methods that increase biomass production in the ocean, and subsequently lead to oxygen-consuming decomposition, cannot be considered harmless climate solutions,” says Oschlies. “Our model simulations show that such approaches could cause a decrease in dissolved oxygen that is four to 40 times greater than the oxygen gain expected from reduced global warming.”

By contrast, geochemical mCDR approaches that do not involve nutrient input – such as ocean alkalinity enhancement through the addition of alkaline substances based on limestone – appear to have minimal effects on ocean oxygen levels and are comparable to simply reducing CO₂ emissions.

Among all methods examined, only large-scale macroalgae farming with biomass harvesting (i.e. removal from the ocean) resulted in an overall increase in oceanic oxygen levels. In this case, no additional oxygen is consumed within the marine environment, and the removal of nutrients limits oxygen consumption elsewhere. Model results suggest that if deployed at sufficient scale, this approach could even reverse past oxygen losses — providing up to ten times more oxygen than has been lost due to climate change within a century. However, here it is the removal of nutrients that would negatively impact biological productivity in the ocean.

Call for systematic monitoring of ocean oxygen

Given these findings, the authors advocate for mandatory inclusion of oxygen measurements in all future mCDR research and deployment efforts.

“The ocean is a complex system which is already heavily under pressure,” says Oschlies. “If we intervene with large-scale measures, we must ensure that, no matter how good our intentions are, we are not further threatening marine environmental conditions that marine life depends on.”

Original publication:
Oschlies, A., Slomp, C. P., Altieri, A. H., Gallo, N. D., Gregoire, M., Isensee, K., Levin, L. A., & Wu, J. (2025): Potential impacts of marine carbon dioxide removal on ocean oxygen. Environmental Research Letters.

Background: Carbon dioxide removal as part of climate strategy

Even with ambitious climate policy, Germany is expected to emit 10 to 20 percent of today’s greenhouse gas levels in three decades’ time — continuing to drive global warming. Carbon dioxide removal (CDR) is therefore being considered to help reach net-zero emissions. The ocean is the key player in the global carbon cycle due to its natural CO₂ uptake and its huge storage capacity. However, these processes typically occur over long timescales. Marine Carbon Dioxide Removal (mCDR) approaches aim to accelerate these natural processes, thereby increasing the ocean’s carbon uptake capacity.

With a net bag and neoprene: Underwater gardening for nature and climate protection

The method is called single-shoot transplantation and is currently considered the most effective technique for reintroducing seagrass. It requires many hands. This summer, five non-governmental organisations (NGOs) and numerous volunteer divers are taking on seagrass restoration on a larger scale for the first time.

"The pilot phase is over – now we are moving into the field," says Prof. Dr. Thorsten Reusch, Head of the Marine Ecology research department at ������Ƶ. "The fact that the NGOs are now independently restoring seagrass meadows with the help of trained divers is great news for biodiversity in the Baltic Sea’s coastal areas and for natural climate protection."

Seagrass - the underestimated natural CO₂ sink

Seagrass is a true all-rounder underwater: it provides important habitats for fish and other creatures, stabilizes sediment, calms waves, and filters pathogens from the water. Most importantly, it binds carbon very effectively and over the long term. This makes seagrass meadows one of the most important natural CO₂ sinks in our coastal waters.

This is precisely where the ZOBLUC project, which is funded by the Federal Ministry for the Environment and started this year under the leadership of ������Ƶ, comes in. ZOBLUC stands for "Zostera marina as a blue carbon sink in the Baltic Sea" and combines research, protection, and restoration of seagrass meadows. The focus is on the extent to which these ecosystems act as natural carbon reservoirs – and how they can be specifically strengthened. The project is part of the Natural Climate Protection Action Programme (ANK) and is funded by the federal government and the state of Schleswig-Holstein.

“Seagrass meadows are like undersea moors,” explains Reusch. “They store carbon in the oxygen-poor sediment for centuries – this makes them an underestimated but effective weapon in the fight against climate change.”

But seagrass meadows are under threat. Excessive nutrient inputs and the resulting excessive growth of algae, mechanical disturbances such as anchors, and rising water temperatures have led to the disappearance of seagrass in many places in recent decades. However, according to ������Ƶ data, conditions have improved again on some stretches of coast. “In order to jump-start the slow natural colonisation, it makes sense to renaturalise seagrass in carefully selected areas.”

Citizen science for marine conservation

The involvement of citizens in renaturalisation as part of the citizen science approach is a central element of ZOBLUC. The training formats required for this were developed over several years and gradually expanded: in 2023, ������Ƶ researchers developed an eight-part pilot course and offered it in cooperation with Sea Shepherd for a small group of experienced “citizen divers.” In the following year, 2024, the training courses were extended to diving instructors and diving club leaders.

2025 now marks the transition to the area: the members of five NGOs – Sea Shepherd Germany, Mission Förde, Lake Divers (Just1Ocean), Seagrass Conservation e.V. (SeaGCon, in formation) and Greenpeace – will be trained. They will then look after nine scientifically selected areas in the Baltic Sea, from Holnis to Fehmarn, where seagrass has either completely disappeared or is only present in small remnants. Targeted planting is intended to fill these gaps and create a long-term network. The suitable renaturalisation areas and donor species are selected by ������Ƶ and approved in close consultation with the Schleswig-Holstein Ministry of the Environment (MEKUN). The measures are scientifically accompanied by a monitoring programme that documents environmental conditions and planting successes.

Nine areas, five NGOs, one common goal

For Christin Otto from Sea Shepherd, who is coordinating the training courses, this mission is a central concern: “We are thus consistently continuing our long-standing commitment to protecting the Baltic Sea – with direct, effective marine protection. Thanks to the cooperation with ������Ƶ, we are able to further expand our conservation efforts and make a sustainable contribution to the preservation of important habitats.” “We offer nature conservation that you can take part in,” says biologist and research diver Christian Lieberum. He is the full-time coordinator of the Citizen Science programme. “The response has been huge,” he says. Not all those interested could be offered a training course. “But we’re only just getting started. This success story will hopefully continue for a long time to come.”

'Various technical approaches have already been tested, some of which have had a positive effect on lakes,' says Prof Dr Andreas Oschlies, Professor of Marine Biogeochemical Modelling at the ������Ƶ Helmholtz Centre for Ocean Research Kiel. 'However, artificial oxygenation cannot work miracles — it only temporarily alleviates the symptoms and does not address the underlying causes.'

Together with Prof. Dr Caroline P. Slomp, Professor of Geomicrobiology and Biogeochemistry at Radboud University in the Netherlands, Andreas Oschlies heads the Global Ocean Oxygen Network (GONE). GO₂NE is an international expert committee of the United Nations Intergovernmental Oceanographic Commission (IOC UNESCO) researching the causes and consequences of declining oxygen levels in the ocean. GO₂NE held its first international workshop on artificial oxygenation in autumn 2024. The results of this workshop were published last week in the scientific journal EOS.

Main causes of oxygen loss in coastal seas

Coastal seas naturally obtain oxygen through exchange with the atmosphere and through photosynthesis by phytoplankton on the surface. Deeper water layers can only obtain oxygen through exchange with surface water. Seawater loses oxygen through bacteria consuming it when decomposing organic material. These bacteria can thrive particularly well when the nutrient supply is high, which is why excessive nutrient inputs (especially nitrogen and phosphorus) from wastewater and agriculture are among the main causes of falling oxygen levels. In addition, water bodies are warming, meaning less oxygen can be dissolved in warmer water. Warm layers of water overlying cooler ones also inhibit the mixing of the water layers.

Oschlies: “There are now huge zones in the Baltic Sea where there is no oxygen at all. We call these zones anoxic, i.e. oxygen-free. They are colloquially referred to as 'dead zones'. They are not completely devoid of life, as there are bacteria that can still survive in this environment. However, these areas are absolutely hostile to all other organisms.”

Limits and risks of artificial oxygen input

Oschlies and Slomp investigated two technical approaches for supplying oxygen to bodies of water: air or pure oxygen injection (bubble diffusion), and pumping oxygen-rich surface water into deeper layers (artificial downwelling). Both methods have already been tested locally, producing partially positive results. However, as soon as the measures are discontinued, the anoxia usually returns very quickly. Slomp: “This artificial introduction of oxygen can be used successfully in lakes, shallow estuaries or small bays. However, the effect only lasts as long as the operation is maintained.” The Chesapeake Bay near Baltimore in the USA is one example of this. After decades of aerating a shallow tributary, the systems were switched off and the oxygen levels fell back to their original levels within a day.

The artificial supply of oxygen also poses ecological risks. For instance, the injection of oxygen can intensify the upward movement of gases such as methane, which is a potent greenhouse gas. Changes in temperature and salinity distributions, as well as underwater noise, could affect marine habitats and, in extreme cases, lead to a further decrease in oxygen levels. “These processes should only be used after thorough testing and accompanied by environmental monitoring,” emphasises Oschlies.

No substitute for climate protection and reducing nutrient inputs

The expansion of plants for the production of green hydrogen is currently a topic of debate. Green hydrogen is produced by electrolysis, which splits water into hydrogen and oxygen. If the electrolysers are located near the sea, the oxygen produced as a by-product could be used for oxygen enrichment measures in coastal marine regions. However, the researchers urge caution, stating that while technical interventions could be beneficial where suitable conditions prevail, they would need to be part of comprehensive water protection strategies.

Slomp‘s conclusion: “The technical possibilities for supplying oxygen do not replace the need for consistent climate protection and the reduction of nutrient inputs from agriculture and wastewater. However, under certain conditions, they can help mitigate the worst consequences of oxygen deficiency, at least temporarily.”
 

Original Publication:

Slomp, Caroline P./Oschlies, Andreas (2025): Could bubbling Oxygen revitalize dying coastal seas?. Eos.

“Site-specific factors play a crucial role in determining which ocean-based CDR and storage methods could realistically be considered. Our analysis helps us to understand what scale we are talking about when discussing the deployment of these methods in German waters — and where along the process chains foreseeable bottlenecks or limitations to feasibility might arise,” says co-lead author Dr Wanxuan Yao, who was a climate modeller at ������Ƶ Helmholtz Centre for Ocean Research Kiel at the time of the study.

Comprehensive Assessment of CO₂ Removal Methods and Their Impacts

For their analysis, the team reviewed current scientific literature and incorporated findings from their own research as part of the CDRmare DAM research mission. For each method, they assessed factors such as the amount of water, materials, energy, land or sea area required, possible by-products and waste streams, necessary infrastructure and transport routes required, operating costs and what is currently known about potential environmental and societal impacts.

“In addition, we looked at whether there are already established processes for measuring and monitoring CO₂ removal rates and potential environmental impacts for each method. Without such monitoring frameworks, none of the proposed approaches has a realistic chance of ever being deployed on a large scale,” explains co-lead author Dr Teresa Morganti, a marine biologist at the Leibniz Institute for Baltic Sea Research Warnemünde at the time of the study.

Ten marine CDR methods shortlisted

At the end of the multi-year selection process, five methods of CO₂ removal remained that could potentially be implemented in German North Sea and Baltic waters. A further five approaches would require deployment in international waters or cooperation with other coastal states.

“The options we’ve outlined are intended to raise specific, practical questions and challenges that would need to be addressed in the event of any large-scale application, and to provide a basis for further discussion. It’s important to emphasise, however, that these outlines do not take into account the legal, political or economic frameworks, nor do they address whether the potential environmental impacts of targeted marine carbon removal are consistent with our societal values and ethical principles. These are essential questions that need to be addressed in follow-up studies,” says Dr Nadine Mengis of ������Ƶ Helmholtz Centre for Ocean Research Kiel, co-author of the study and CDRmare co-chair.

Expectations for marine CDR often too high

The research team is therefore working systematically to develop methods and processes that provide a realistic picture of how feasible marine CDR techniques actually are, and what their consequences might be for both people and ecosystems. “Once you scale up marine CDR methods for a particular region, making the true scale of interventions tangible, it becomes clear that earlier expectations were often too high because such practical considerations had not been taken into account. We need many more of these context-specific feasibility studies if we are to arrive at robust estimates of the potential for marine CDR,” says Nadine Mengis.

There is also a risk that high expectations might encourage countries like Germany to place too much hope in future technological solutions, while scaling back existing and proven measures to reduce greenhouse gas emissions in the meantime. “This must not be the outcome of our research,” stresses Nadine Mengis.

The marine CDR and storage methods described in the study include:

Methods to increase the CO₂ buffering capacity (alkalinity) of the ocean:

1. Production of a silicate-based alkaline solution and its distribution in shallow coastal waters along Germany’s North Sea coast

2. Production of a lime-based alkaline solution and its distribution along shipping routes in the German North Sea

3. Spreading of ground basalt of volcanic origin along the German coastline

4. Discharge of sodium hydroxide produced via electrolysis in desalination plants (there are currently no desalination plants in the North Sea or Baltic Sea)

Methods to restore and expand vegetated coastal ecosystems:

5. Establishing and expanding kelp forests around the German North Sea island of Heligoland

6. Restoration and expansion of mangrove forests in Indonesia

7. Artificial upwelling of nutrient-rich deep water to enhance plankton production in the North Atlantic (strengthening the ocean’s biological carbon pump)

8. Offshore Sargassum (algae) farming in the South Atlantic subtropical gyre, followed by biomass sinking

Methods for storing captured biogenic CO₂:

9. Cultivation of large macroalgae, with subsequent conversion of the biomass into biomethane; the CO₂ released during combustion would be captured and stored in saline aquifers in the German North Sea

10. Direct air capture of CO₂ with subsequent storage in subsea basalt crust off the coast of Norway

Original Publication:

Yao, W., Morganti, T. M., Wu, J., Borchers, M., Anschütz, A., Bednarz, L.-K., et al. (2025). Exploring site-specific carbon dioxide removal options with storage or sequestration in the marine environment – the 10 Mt CO₂ yr⁻¹ removal challenge for Germany. Earth’s Future, 13, e2024EF004902.

About: CDRmare

CDRmare is a research mission of the German Marine Research Alliance (DAM). Its full title is “Marine carbon storage as a pathway to decarbonisation”. The mission started in summer 2021 with six research consortia investigating promising ocean-based CO₂ removal and storage methods (alkalinisation, restoration of coastal vegetated ecosystems, artificial upwelling, CCS) in terms of their potential, risks and interactions, and integrating these findings into a transdisciplinary assessment framework. In August 2024, CDRmare entered its second three-year funding phase with five research consortia. CDRmare is funded by the German Federal Ministry of Education and Research (BMBF) and the science ministries of the northern German states of Bremen, Hamburg, Mecklenburg-Western Pomerania, Lower Saxony and Schleswig-Holstein.

The research, published today in Nature Communications and led by the University of Bristol, provides the clearest ever picture of how the underlying transport system, known as the Transpolar Draft, operates. It also uncovers the various factors controlling this major Arctic surface current, including warmer temperatures which could increase the spread of human-made pollutants.

The Pathways of Arctic Substances: The Transpolar Drift

The Transpolar Drift carries sea ice, fresh water, and suspended matter from the Siberian shelves across the central Arctic towards the Fram Strait channel, which connects to the Nordic Seas.

This cross-Arctic flow influences the delivery of both natural substances, such as nutrients, gases, organic compounds, and human-made pollutants – including microplastics and heavy metals – from Siberian river systems into the central Arctic and the North Atlantic. This material affects Arctic biogeochemistry and ecosystems, while the fresh water itself alters ocean circulation.

As the Arctic Ocean is a highly changeable environment, rather than following a steady course, river-sourced matter takes diverse, seasonally shifting routes shaped by changing shelf conditions and ocean currents, along with the formation, drift, and melting of sea ice. This results in rapid and widespread redistribution of both natural and pollutant matter.

Seasonal Variability and the Role of Sea Ice

Lead author Dr Georgi Laukert, Marie Curie Postdoctoral Fellow in Chemical Oceanography at the University of Bristol, UK and Woods Hole Oceanographic Institution in Massachusetts, US, said: “We found pronounced changes in the composition of Siberian river water along the Transpolar Drift, demonstrating this highly dynamic interplay. Seasonal shifts in river discharge and dynamic circulation on the Siberian shelf drive ocean surface variability, while interactions between sea ice and the ocean further increase the redistribution of river-borne matter.

“Another key discovery is the increasingly central role of sea ice formed along the Transpolar Drift – not only as a passive transport medium, but as an active agent in shaping dispersal patterns. This sea ice captures material from multiple river sources during growth, unlike most coastal sea ice, creating complex mixtures that are transported across vast distances.”

Geochemical Tracing and the Year-Long Study

To decode these complex pathways, the international research team analysed seawater, sea ice, and snow samples using oxygen and neodymium isotopes, along with measurements of rare earth elements to produce geochemical tracer data. This geochemical fingerprinting allowed the researchers to track the origins of river-sourced matter and follow how it evolved along its route through the central Arctic over a year-long period.

New Insights from the Largest-Ever Arctic Expedition

The study draws on samples from MOSAiC, the largest-ever Arctic expedition and among the most ambitious polar research efforts, involving seven ice breakers and more than 600 global scientists.

Co-author Dr Dorothea Bauch, Researcher at Kiel University in Germany, said: “The findings represent unprecedented year-round observations. Previously, we only had summer data because it was too slow and hard to break through the ice in the winter. This sustained, interdisciplinary Arctic evidence offers important and comprehensive insights, which help us better understand highly complex ocean systems and the possible future implications.”

As summer sea ice continues to retreat due to warmer temperatures, circulation and drift patterns are changing.

Co-author Professor Benjamin Rabe, Research Scientist from the Alfred Wegener Institute and Honorary Professor at the University of Applied Science, in Bremerhaven, Germany said: “These shifts could significantly alter how fresh water and river-derived matter spread through the Arctic, with far-reaching implications for ecosystems, biogeochemical cycles, and ocean dynamics.”

Transpolar Drift Not as Stable as Previously Thought

The research also challenges a long-standing perception of the Transpolar Drift as a stable conveyor of river water. First observed during Norwegian explorer Fridtjof Nansen’s historic Fram expedition in the 1890s, these latest findings discovered more than 130 years later indicate the Transpolar Drift is highly variable in both space and time.

Dr Laukert added: “While the study does not focus on individual compounds, it illuminates the underlying transport mechanisms—a critical step for predicting how Arctic matter transport will evolve in a warming climate. If even this iconic current is so dynamic, then the entire Arctic Ocean may be more variable and vulnerable than we thought.”

Original Publication:

Laukert, G., Bauch, D., Rabe, B., Krumpen, T., Damm, E., Kienast, M. Hathorne, E., Vredenborg, M., Tippenhauer, S., Andersen, N., Meyer, H., Mellat, M., D’Angelo, A., Simoes Pereira, P., Nomura, D., Horner, T.J., Hendry, K., Kienast, S. (2025). Dynamic ice–ocean pathways along the Transpolar Drift amplify the dispersal of Siberian matter. Nature Communications, 24, 28391.

“Answering whether and how a CO₂ removal option should be implemented should take its effectiveness, economic viability and its impact on people and the environment into account. However, existing assessment frameworks do not allow doing so. Our framework solves this problem by offering a structured guide for evaluating marine CO₂ removal projects. Stakeholders can use it to analyse all the key issues and make evidence-based decisions,' says Prof. Dr Christian Baatz, a climate and environmental ethicist at the Kiel University (CAU) and co-author of both new articles.

29 criteria for a comprehensive assessment of marine CO2 removal methods

The new framework includes 29 criteria that help to analyse seven key issues. These include questions about the technical, legal and political feasibility of the methods to be assessed, as well as questions about economic efficiency, equity and environmental ethics. Due to this complexity, the researchers recommend that experts from academia, industry, public administration, interest groups and affected populations be involved in the evaluation process.  In line with this principle, the researchers tested the practical suitability of the new evaluation guidelines in a series of transdisciplinary workshops attended by numerous representatives from public administration and interest groups.

“Our experience in testing the assessment framework shows that no one should attempt to assess a marine CO₂ removal method or a specific project on their own. Due to the high complexity of the issue, an assessment requires the expertise of many people,” says co-author Dr Lukas Tank, also a climate and environmental ethicist at Kiel University.

Ideally feasible and desirable

In addition to the list of criteria, the researchers defined five guiding principles to help ensure that the best possible information is collected during the evaluation process. These guiding principles aim to ensure that the evaluation process is transparent and involves all potentially affected parties.

“Ultimately, it is up to political and societal decision-makers to decide whether a particular marine CO₂ removal project should go ahead. At best, they will choose options that are effective, technically, legally and politically feasible, as well as economically, equitably and environmentally sound. Our assessment framework can help them do this”, says Prof. Dr Gregor Rehder, a chemist at the Leibniz Institute for Baltic Sea Research Warnemünde (IOW). He was also an author on both papers and led the CDRmare research network ASMASYS, under which the research for both papers took place.

Original Publications:

Tank, Lukas; Lieske Voget-Kleschin, Matthias Garschagen, Miranda Boettcher, Nadine Mengis, Antonia Holland-Cunz, Gregor Rehder & Christian Baatz (2025): Distinguish Between Feasibility and Desirability When Assessing Climate Response Options. NPJ Climate Action, DOI: 10.1038/s44168-025-00237-2

Christian Baatz, Lukas Tank, Lena-Katharina Bednarz, Miranda Boettcher, Teresa Maria Morganti, Lieske Voget- Kleschin, Tony Cabus, Erik van Doorn, Tabea Dorndorf, Felix Havermann, Wanda Holzhüter, David Peter Keller, Matthias Kreuzburg, Nele Matz-Lück, Nadine Mengis, Christine Merk, Yiannis Moustakis, Julia Pongratz, Hendrikje Wehnert, Wanxuan Yao and Gregor Rehder (2025): A holistic assessment framework for marine carbon dioxide removal options. Environmental Research Letters, DOI: 10.1088/1748-9326/adc93f

About: CDRmare

CDRmare is a research mission of the German Marine Research Alliance (DAM). The mission started in summer 2021 with six research consortia investigating promising methods for marine CO2 removal and storage (alkalinisation, expansion of vegetation-rich coastal ecosystems, artificial upwelling, CCS) with regard to their potential, risks and interactions, and bringing them together in a transdisciplinary assessment framework.

In August 2024, CDRmare entered its second three-year funding phase with five research consortia. CDRmare is funded by the German Federal Ministry of Education and Research (BMBF) and the science ministries of the northern German states of Bremen, Hamburg, Mecklenburg-Western Pomerania, Lower Saxony and Schleswig-Holstein.

Standardized Experiments at 19 Locations Worldwide

The “Ocean Alkalinity Enhancement Pelagic Impact Intercomparison Project (OAEPIIP) is coordinated by Prof. Dr Lennart Bach, a marine biologist at the University of Tasmania, Australia. Nineteen research groups from locations including New Zealand, Kenya, Chile, and Croatia will conduct standardised experiments in enclosed 55 liter containers, known as microcosms, throughout 2025. The microcosms are carefully controlled experimental systems that allow researchers to track changes in plankton community composition and biogeochemical parameters in response to alkalinity enhancement.

������Ƶ’s contribution: Research in the Baltic Sea and in Tropical Waters

������Ƶ is contributing to this project with two studies in contrasting environments: Dr Giulia Faucher, a researcher in the Biogeochemical Processes working group, will examine OAE impact on a temperate plankton community from Eckernförde Bay in the Baltic Sea. For this purpose, she started the experiment on 7 March 2025 by filling the microcosms aboard the research cutter LITTORINA at the Boknis Eck time-series station. “The containers used, the way they are filled, the way the alkalinity is added and the measurements taken – all of this is standardised to ensure comparability across the studies,” says Giulia Faucher.

Her colleague in the same research group, Dr Leila Kittu, will conduct the same experiment in tropical waters off Kenya from May onwards. To facilitate this, she has established a new collaboration between ������Ƶ, the Kenya Marine Fisheries Research Institute (KMFRI), and the Technical University of Mombasa (TUM).

Why Standardization Matters in OAE Research

OAEPIIP is the first globally coordinated study on ocean alkalinity enhancement. “These standardized experiments enable us to assess its ecological effects across diverse environmental conditions, from temperate to tropical waters, from nutrient-rich to nutrient-poor regions” says Giulia Faucher. The results will contribute to a comprehensive meta-analysis, offering new insights into potential ecological impacts of ocean alkalinity enhancement — critical information for policymakers considering large-scale deployment of this approach as part of climate change mitigation strategies.

About: Ocean Alkalinity Enhancement

Ocean alkalinity enhancement mimics natural rock weathering processes that gradually increase ocean alkalinity over geological timescales. However, since human-caused CO₂ emissions occur approximately a hundred times faster than these natural weathering processes, OAE accelerates this mechanism through the direct addition of alkaline minerals to seawater. This addition increases seawater's pH and carbonate ion concentration, enhancing its capacity to chemically bind more CO₂. This enhanced carbon sequestration pathway effectively accelerates a natural carbon sink to help counterbalance rapid human-induced CO₂ emissions. While OAE is primarily aimed at increasing CO₂ uptake and storage, the resulting increase in pH could simultaneously provide a buffering effect against ocean acidification at local scales where alkalinity is added.

The ������Ƶ Helmholtz Centre for Ocean Research Kiel, in cooperation with the Kiel University (CAU) and the State Office for the Environment of Schleswig-Holstein (Landesamt für Umwelt, LfU), has launched a new project to study the role of seagrass meadows as natural carbon sinks and to develop strategies for their conservation and restoration.

The name of the project, ZOBLUC, stands for “Zostera marina as a Blue Carbon Sink in the Baltic Sea” – Zostera marina being the scientific name for seagrass. The project is funded by the German Federal Environment Ministry's Nature-based Climate Action Programme (ANK) and state funds, with a total budget of around €6 million.

Three Focus Areas for Seagrass Conservation

“Seagrass meadows are like underwater peatlands,” explains the scientific project leader, Dr Thorsten Reusch, Professor of Marine Ecology at ������Ƶ. “They store carbon, which is preserved in oxygen-poor sediments for centuries.” The project will examine under which conditions seagrass meadows store the most CO₂ to find blue carbon hot spots, which in turn would be prime areas for protection. Reusch: “For example, areas with strong wave-driven erosion store less carbon than calm bays with faster sedimentation.” The research will not only quantify the carbon storage capacity of seagrass meadows but also model how it might change under different environmental conditions.

Another focus of ������Ƶ is the restoration of seagrass meadows. It is crucial to ensure that restored meadows are resilient and sustainable. “There’s little point in replanting seagrass that won’t survive rising water temperatures in a few years’ time”, says Reusch. Experimental studies will expose seagrass to various stressors in order to cultivate robust, climate-resilient populations and practice ‘assisted evolution’.

Community Involvement in Underwater Gardening

The third focus is on involving local people in the restoration process. After developing training programmes and testing small-scale seagrass restoration in previous years, ������Ƶ now plans to significantly expand its efforts with the help of volunteers. Reusch: “The pilot phase has been successfully completed; now we’re scaling up.”

This support is urgently needed, as the most reliable way to restore lost seagrass meadows is still to plant individual shoots manually by diving. Reusch says: “It’s important to complete the training course and only use areas that we have checked for suitability for restoration.”

Diving clubs and NGOs will use volunteer divers to plant seagrass in scientifically selected restoration sites. Observational data collected during these efforts will be analysed at ������Ƶ to refine future restoration practices.

The development of other planting techniques, such as seeding, is the focus of the parallel project SeaStore II, which started last September.

Mapping with Multibeam Sonar and Drones

The first step, however, is a comprehensive mapping of the existing seagrass meadows in the Baltic Sea. Professor Natascha Oppelt and Dr Jens Schneider von Deimling from CAU and their teams, will use remote sensing methods that combine advanced optical and acoustic surveying technologies. CAU will also be responsible for monitoring the newly planted areas using drones.

Results from ZOBLUC will be shared through workshops and policy recommendations to advance the protection and restoration of seagrass meadows in the Baltic Sea.

Background: Blue Carbon

Blue Carbon is the carbon dioxide stored by marine and coastal ecosystems such as mangroves, salt marshes, and seagrass meadows. Seagrass meadows sequester carbon in the form of dead biomass and organic sediment particles that remain in the oxygen-poor seabed for centuries – much like peatlands on land.

Background: Assisted Evolution

Assisted Evolution is a technique that aims to accelerate the evolutionary adaptation of organisms to make them more resilient to environmental change. In this project, seagrass plants are exposed to experimental heat waves in ������Ƶ’s climate chambers. This approach identifies potentially heat-tolerant local populations and uses advanced methods – from cellular physiological reactions (metabolomics) to genetic analysis (gene expression studies) and microbiome research – to understand the mechanisms behind plant resilience.

Experimenting in giant test tubes

The study adopted an approach with moderate perturbations to seawater chemistry: CO₂-equilibrated Ocean Alkalinity Enhancement. With this approach, the alkalised water has already absorbed CO₂ intended for carbon dioxide removal (CDR) before being released to the marine environment. For their experiment, the scientists used KOSMOS mesocosms (Kiel Off-Shore Mesocosms for Ocean Simulations) - large test tubes that are lowered directly into the seawater, isolating eight cubic metres of the water column.

Different concentrations of sodium carbonate and bicarbonate were added to achieve varying intensities of CO₂-equilibrated OAE, ranging from no increase in alkalinity to a doubling of natural alkalinity. Over a period of 33 days, the researchers monitored the effects of alkalinisation on zooplankton, which plays a key role in transferring energy through the food web up to fish. A range of responses were studied in the zooplankton, from biomass and production to diversity and fatty acids.

Overall, researchers found that the plankton communities remained stable and that the zooplankton largely tolerated the moderate chemical changes associated with CO₂-equilibrated OAE. During the experiment, the nutritional quality of the particulate matter on which zooplankton can feed potentially deteriorated, but this did not seem to affect the consumers. The researches argue that food limitation, a result of the oligotrophic conditions under which this experiment took place, and which characterize subtropical waters, could have buffered these possible indirect responses of zooplankton to OAE.

“Our study shows that the increase in alkalinity has minor impacts on the zooplankton and that the food web as a whole remains stable,” says Nicolás Sánchez, PhD student and first author of the study.

Potential in climate protection and need for further research

Ocean Alkalinity Enhancement could become an important ally in reducing CO₂ emissions to combat climate change. By enabling the ocean to absorb more CO₂ without becoming more acidic, this approach could strengthen the ocean’s role as a buffer against global warming. It could help bridge the transition to a future where fossil fuels are replaced by renewables, emissions from industries that cannot be decarbonized are neutralised, and historical carbon emissions are safely removed and stored. However, extensive research is urgently needed in order to determine the impact of OAE on the whole marine environment.

“Our experiment has shown that CO₂-equilibrated OAE does not have a lasting impact on zooplankton and the food web in the nutrient-poor subtropical area we studied,” says Nicolás Sánchez, “but this does not say anything about how it will affect other marine environments, nor about the safety of other, technically more feasible forms of OAE that cause greater changes to seawater chemistry”.

The scientists recommend further research on the method and across different ecosystems, as there will not be a single OAE approach that can be applied everywhere. Sánchez: “Our study is a promising first step towards defining a responsible framework for the application of alkalinity enhancement”.

Original Publication

Sánchez, N., Goldenberg, S., Brüggemann, D., Taucher, J., & Riebesell, U. (2024). Plankton food web structure and productivity under Ocean Alkalinity Enhancement. Science Advances.

Funding:

The OceanNET (Ocean-based Negative Emission Technologies) project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement number 869357. The study was co-financed by the Helmholtz European Partnering Project Ocean-CDR.

Susanne Neuer Receives Prof. Dr Petersen Foundation Excellence Professorship

13 November 2024/Kiel. Professor Dr Susanne Neuer, renowned marine biogeochemist and professor at Arizona State University, was today awarded the 31st Excellence Professorship from the Prof. Dr Werner Petersen Foundation. The award ceremony took place at the ������Ƶ Helmholtz Centre for Ocean Research Kiel, Germany. In her keynote lecture, Susanne Neuer highlighted how phytoplankton and bacteria contribute to the global carbon cycle through the biological carbon pump. These processes play a crucial role in climate protection and are a core focus of Professor Neuer’s current research.

The ocean absorbs about a quarter of annual carbon dioxide emissions. One mechanism that facilitates this is known as the biological carbon pump. This process starts with the photosynthesis of tiny microscopic algae, phytoplankton, floating in the sunlit upper layers of the ocean. Professor Dr Susanne Neuer and her team study the Biological Carbon Pump, focusing particularly on the role of plankton organisms in the formation of sinking particles, both in the laboratory and at sea. Since 2004, she has been a Professor of Marine Biogeochemistry at Arizona State University in Tempe, USA. Since 2022, she is also the founding director of the new School of Ocean Futures. For her contributions, she has been awarded the 31st Excellence Professorship of the Prof. Dr Werner Petersen Foundation, which includes €20,000 in funding and a six-week research stay at the ������Ƶ Helmholtz Centre for Ocean Research Kiel.

Dr h.c. Klaus Wichmann, Chair of the Prof. Dr Werner Petersen Foundation, said: “On behalf of the Foundation, I am very pleased to award another outstanding scientist with an Excellence Professorship today. Since its inception in 2009, the Excellence Initiative has been an indispensable part of our mission to promote scientific excellence in Schleswig-Holstein and to intensify international cooperation. It is an honour for us to continue to support this and I hope that this initiative will set an example for others to follow.”

Professor Dr Katja Matthes, Director of ������Ƶ, congratulated the awardee: “I am delighted that we can honour Susanne Neuer with this well-deserved award. With her outstanding research on the biological carbon pump, she has made an invaluable contribution to our understanding of the processes that influence our climate. Professor Neuer has excelled not only as a scientist but also as a mentor. She is a dedicated advocate for the advancement of women in science, having played leading roles with the Association for Women in Science and at Arizona State University. Her expertise and extraordinary achievements have made her a leading voice internationally. We are proud to welcome her to ������Ƶ today and look forward to the inspiring contributions she will make during her stay.”

In her laudatio, Professor Dr Anja Engel, Head of the Marine Biogeochemistry Research Division at ������Ƶ, emphasised the importance of the awardee's research: "Professor Neuer plays a leading and internationally visible role in marine biogeochemistry, the carbon cycle and particle export. Her highly acclaimed work has contributed significantly to our current understanding of the biological carbon pump in the ocean. Her analyses of ocean time series have laid the foundation for comparative studies of the efficiency of this central mechanism in the carbon cycle".

Insights into the Work of the Ocean’s Biological Carbon Pump

In her keynote lecture, Susanne Neuer discussed the significance of the Biological Carbon Pump for our planet’s climate. A fascinating aspect of this mechanism is the formation of so-called marine snow—sticky aggregates of phytoplankton, bacteria, and other organic matter held together by larger particles such as dust. These aggregates can grow large enough to be visible to the naked eye and form the basis for the transport of carbon into the deep ocean. Planktonic animals such as krill and copepods also contribute to carbon export by releasing phytoplankton particles into the ocean's twilight zone, an area of near darkness where the light barely penetrates.

“The processes initiated by phytoplankton and bacteria in the upper ocean layers of the ocean are a fundamental component of the long-term storage of CO₂ and thus play a critical role in the context of climate change,” explained Prof. Neuer. “In the deep ocean, there is a fascinating interplay between microscopic cells that not only remove carbon from the atmosphere, but also sustain life throughout the ocean,” said Neuer. “The next time you look at the ocean, think of all the microscopic life in the water and all that it does for the well-being of our planet.”

Back to the roots: a reunion with Kiel and the chance for new collaborations

Kiel is not new territory for Susanne Neuer: some 40 years ago, she began her training as a marine scientist here at the former Institut für Meeresforschung (IfM), before moving on to the USA for further studies. This is not the first time she has returned to Kiel to talk about her research. At the invitation of ������Ƶ's Women's Executive Board, she gave a talk in 2016 as part of the Marie Tharp Lectures, discussing career issues with young female scientists.

“I am very honoured to receive the Excellence Professorship,” she says, “it will allow me to expand my collaboration with ������Ƶ and especially with Prof. Dr Anja Engel and to develop synergies in our research on the biology of the global carbon cycle.” She is particularly looking forward to the exchange with young scientists at ������Ƶ. Susanne Neuer: “It is important that the next generation receives special support in their careers so that they can not only be successful, but also make a sustainable contribution to solving environmental problems.”

About: Prof. Dr Werner Petersen Foundation

The Prof. Dr Werner Petersen Foundation, based in Schleswig-Holstein, Germany, aims to promote science, research, technology, and culture. A central area of support is the Excellence Initiative, which, in close cooperation with ������Ƶ, honours outstanding scientists with international reputations. Through this initiative, leading marine scientists from around the world are invited to come to Kiel as guest scientists for up to six weeks.

Published today in the journal Earth System Science Data, the report analyses emissions from fossil fuels, land-use changes (such as deforestation), and the complex interactions between the atmosphere, oceans, and land. It assesses the amount of carbon absorbed or released by plants, soils, and oceans and projects future carbon flows to calculate the remaining CO₂ budget critical for meeting global climate goals.

The Marine CO₂ Sink Remains Stable – But Challenges are Mounting

The report shows that the ocean continues to absorb around 26 per cent of global CO₂ emissions – a crucial function, yet one increasingly threatened by climate change. Higher water temperatures reduce the solubility of CO₂, thus diminishing the ocean’s capacity to act as a carbon sink. “Climate change has reduced the ocean’s CO₂ uptake capacity by around six per cent over the past decade,” explains Professor Dr Judith Hauck, environmental scientist at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). The 2023 El Niño cycle temporarily boosted the ocean’s carbon uptake as less carbon-rich deep water reached the surface, but ongoing warming could weaken the ocean’s role as a carbon store in the long term.

CO₂ Monitoring in the North Atlantic – A Long-Term ������Ƶ Project

The ocean sink – the amount of CO₂ the ocean absorbs and stores from the atmosphere – is estimated through measurements of CO₂ levels in the surface ocean and simulations with global ocean models. Scientists from ������Ƶ Helmholtz Centre for Ocean Research have been contributing data through long-term monitoring in the North Atlantic. This ongoing dataset, collected by ������Ƶ’s CO₂ research group for over 20 years, relies on sensors installed on the container ship MS ATLANTIC SAIL in cooperation with the shipping company Atlantic Container Lines (ACL). Operating between North America and Europe, the vessel continuously collects data on temperature, salinity, dissolved oxygen, and CO₂ in surface waters. This data is part of the Integrated Carbon Observation System (ICOS) European research infrastructure, providing annual data for the Global Carbon Budget.

The monitoring systems on board are maintained by Dr Tobias Steinhoff, chemical oceanographer and co-author of the Global Carbon Budget report. “Last year, we had to remove the instruments from the vessel to overhaul and upgrade them after a decade of continuous operation,” says Dr Steinhoff. “As a result, fewer data were available this year.”

SOCAT Data Platform: Key to Carbon Research and Climate Policy

Beyond ������Ƶ’s own measurements, Dr Tobias Steinhoff is actively involved in the Surface Ocean CO₂ Atlas (SOCAT) platform, an international initiative that compiles and quality-checks surface CO₂ data. SOCAT data provides an early estimate of oceanic carbon uptake and also feeds into the Global Carbon Budget. Dr Steinhoff notes, “Our work in SOCAT strengthens the global understanding of oceanic CO₂ dynamics and highlights the ocean’s role as a CO₂ �����������Ǿ���.”

About: The Global Carbon Project

The Global Carbon Project (GCP) is part of the international Future Earth research initiative. Its goal is to develop a comprehensive picture of the global carbon cycle, including its biophysical and human dimensions and their interactions. Climate scientists worldwide contribute to the annual report on the global carbon budget. The Global Carbon Budget 2024 is the 19th edition, with the first published in 2006. Each year, the report is published in the journal Earth System Science Data.

Numerous researchers from German-speaking countries contributed to the Global Carbon Budget 2024, including scientists from the Alfred Wegener Institute (Bremerhaven), ETH Zurich, ������Ƶ (Kiel), Helmholtz Centre Hereon (Geesthacht), International Institute for Applied Systems Analysis (IIASA), Karlsruhe Institute of Technology, Leibniz Institute for Baltic Sea Research (Warnemünde), Ludwig Maximilian University (Munich), Max Planck Institute for Meteorology (Hamburg), Max Planck Institute for Biogeochemistry (Jena), Potsdam Institute for Climate Impact Research, and the universities of Bremen, Bern, and Hamburg.

Original Publication

Friedlingstein et al. (2024) Global Carbon Budget 2024. Earth System Science Data.

Gaps in Ocean Observation: Technological and Financial Shortfalls

Members of the EU project EuroSea have reviewed ocean observation in Europe. Their two recent reports, “Urgent Gaps and Recommendations to Implement During the UN Ocean Decade” and “Towards a Sustained and Fit-for-Purpose European Ocean Observing and Forecasting System”, identify the main gaps in monitoring marine biodiversity, invasive species, and ocean phenomena such as warming and sea level rise. Many of these gaps are due to technological shortcomings or insufficient funding.

“We urgently need a more sustainable and effective ocean observation system to track changes in the state of the ocean and to mitigate the effects of climate change,” says Dr Toste Tanhua, chemical oceanographer at the ������Ƶ Helmholtz Centre for Ocean Research Kiel and leader of the recently completed EU project EuroSea, on which the reports are based.

He himself is attending the UN Climate Change Conference COP29 in Baku, which starts today, to lend his voice to the issue of ocean observation at the international level. At the Ocean Pavilion, in which ������Ƶ is a partner this year, he will speak on a panel on the participation of non-scientific actors, such as sailors, in ocean observation.

In their position papers, the scientists stress the need to improve data collection, use innovative technologies such as environmental DNA (eDNA) and more autonomous devices, and strengthen international cooperation. A key recommendation is to secure long-term funding and establish central coordination bodies to ensure the long-term effectiveness of ocean observation.

“The recommendations we have developed together are aimed at the scientific community as well as policy makers and industry,” says Dr Tanhua. “The challenges are great, but the solutions we propose provide a clear course of action. We need to generate as much information as possible to better understand and protect marine ecosystems. This is a very important building block in efforts to mitigate the climate crisis. Observation alone will not reduce the effects of climate change, but it will enable us to understand and propose appropriate measures. After all, you can only manage what you can measure!”

Recommended Actions to Improve Ocean Observation

For example, the reports recommend the development of comprehensive programmes to monitor marine biodiversity. In particular, the use of innovative technologies such as eDNA could help detect invasive species at an early stage and improve data collection.

The use of autonomous devices (e.g. Argo floats and sensors) should be increased to validate data from satellites and improve observations of the deep ocean. This is particularly important for extremely cold regions that are difficult to access.

In addition, common measures for monitoring eutrophication indicators such as nutrient concentrations and oxygen levels should be developed to better monitor and reduce the negative impact of human activities on the marine environment.

In regions with high nutrient inputs, the use of autonomous sensors should be promoted. These systems will allow continuous monitoring of algal blooms and ocean acidification.

The reports also call for increased cooperation between countries and stakeholders to harmonise monitoring strategies and facilitate data sharing.

Recommendations for Ocean Observation Coordination and Management

Increased cooperation between different countries and stakeholders is recommended to harmonise monitoring strategies and facilitate data exchange. Coordination requires a single entity responsible for the management and strategic planning of ocean observing activities. This structure would promote efficiency and facilitate collaboration across countries and disciplines.

To ensure that ocean observation systems are sustainable and can be continuously updated, a funding strategy for long-term observation programmes should be developed. “Our research funding structures support knowledge generation, but not monitoring,” explains Dr Abed El Rahman Hassoun, lead author of the first position paper. “To close this gap, we need cross-sectoral collaboration and co-funding between different ministries. This is a problem we see not only in Germany, but also in other EU countries”.

About the EuroSea Project

The EU project EuroSea, led by Dr Toste Tanhua at ������Ƶ, brought together over 150 experts from 53 partner institutions across 16 countries from 2019 to 2023 to better integrate existing ocean observation systems and improve the delivery of ocean information. The focus was on the entire value chain of ocean observation, from measurements to data users. The European Union funded the project with €12.6 million.

Original Publications:

Hassoun A.E.R., Tanhua T., Lips I., Heslop E., Petihakis G., and Karstensen J. (2024) The European Ocean Observing Community: urgent gaps and recommendations to implement during the UN Ocean Decade. Frontiers in Marine Sciences, 11:1394984.

Tanhua T., Le Traon P-Y., Köstner N. et al. (2024) Towards a sustained and fit-for-purpose European ocean observing and forecasting system. Frontiers in Marine Science, 11:1394549.

By computer and ship: evidence of volcanic influence in the South Pacific

For a comprehensive analysis of the eruption’s effects, the researchers used a combination of advanced computer simulations and precise sample analysis. To simulate the spread of volcanic ash after the eruption, they used the HYSPLIT computer model from the National Oceanic and Atmospheric Administration (NOAA), a US federal agency. The model simulates the transport of substances in the atmosphere. It was used to calculate the dispersion of volcanic ash at different altitudes for 72 hours and the trajectories of the ash for up to 315 hours.

During the SONNE expedition SO289 as part of the international GEOTRACES programme from February to April 2022, the researchers collected water samples along a designated route to analyse the distribution of trace elements and their biogeochemical effects. A large amount of floating tephra, mostly pumice, was observed and collected in the western SPG during the expedition. Using radiogenic neodymium isotopes and rare earth element concentrations, the researchers were able to fingerprint a marked volcanic input into the western SPG. This is the region identified as the primary site of post-eruption deposition based on the volcanic ash dispersal model. In addition, seawater analyses of neodymium isotopes and rare earth elements were used to track volcanic input and chlorophyll-a as an indicator for phytoplankton.

Phytoplankton Benefits from Trace Elements in volcanic material

In the western SPG the researchers identified significant amounts of trace elements such as iron and neodymium, which normally only enter the ocean in minimal quantities via atmospheric dust. The volcanic eruption released an additional 32,000 tonnes of iron and 160 tonnes of neodymium. The amount of iron is equivalent to what the region normally receives in a year, while the amount of neodymium is equivalent to a year’s worth of global input.

“At the same time, we measured increased chlorophyll-a concentrations in surface waters, indicating increased phytoplankton growth and hence biological activity,” says Dr Zhouling Zhang, a research associate in the Palaeo-Oceanography Research Unit and lead author of the study.

Long-term Climate Implications

The team was able to show that trace elements released by volcanic eruptions play an important role for marine life. These elements, particularly the micronutrient iron, act as nutrients in the ocean that stimulate the growth of phytoplankton. Phytoplankton play an essential role in the global carbon cycle, absorbing CO₂ from the atmosphere through photosynthesis and storing it in the ocean. Increasing biological productivity may therefore also improve the ocean's ability to absorb CO₂ from the atmosphere - a process that could have a long-term impact on climate.

The researchers estimate that the release of the micronutrient iron from the HTHH eruption is comparable to the iron fertilisation caused by the eruption of Mount Pinatubo in the Philippines in June 1991, when around 40,000 tonnes of volcanic material was released and a 1.5 ppm slowdown in the rise of atmospheric CO₂ was measured about two years after the eruption. Zhouling Zhang says, 'We think the Hunga Tonga eruption could have a similar effect.

Original Publication:

Zhang, Z., Xu, A., Hathorne, E. et al. (2024): Substantial trace metal input from the 2022 Hunga Tonga-Hunga Ha’apai eruption into the South Pacific. Nat Commun 15, 8986.

Originally from China, Dr Yuanxu Dong's most recent academic stint was in Norwich, England, where he earned his doctorate at the University of East Anglia. Ideally, the newly minted oceanographer Dr Yuanxu Dong would have set sail immediately afterward with his current co-host: Dr Christa Marandino, Senior Lecturer and Head of the Air-Sea Gas Exchange Research Group at ������Ƶ, served as expedition leader on a five-week voyage to the Labrador Sea last December. During this winter expedition, she investigated the contribution of bubbles to gas exchange between the atmosphere and the ocean. This very topic is what Dr Yuanxu has chosen for his postdoctoral research project at ������Ƶ.

“I am interested in the global air-sea CO2 flux,” he says. While it is known that the ocean absorbs a significant portion of CO₂ emissions, the role of bubbles in this process remains a mystery.

His host, Dr Marandino, outlines the challenge: “Quantification is often done mathematically, based on laboratory data. Laboratory studies are useful to understand mechanisms, but the laboratory is not a real ocean environment.” However, field observations of the bubble-mediated transfer are challenging because of the rough sea state at very high wind speeds and with wave breaking. It's not surprising that there are still no measurement data for gas exchange under storm conditions, i.e., at high wind speeds of 20 to 30 meters per second (approximately 70 to 100 kilometres per hour). However, the number of storms is expected to increase due to climate change, making it increasingly important to understand the role of bubbles in air-sea gas exchange.

Recently, Dr Yuanxu Dong published a significant study in the renowned journal Science Advances. Together with an international team, he demonstrated that the Southern Ocean surrounding Antarctica absorbs around 25 per cent more carbon dioxide than previously thought. This new study employed a high-precision measurement method called “eddy covariance,” which measures the movement of atmospheric eddies to calculate the net gas flow by computing the correlation of the vertical wind speed and gas concentration fluctuations. This allows for the direct determination of CO₂ exchange between the ocean and the atmosphere. Data was collected using this method during seven research cruises in the Southern Ocean. The results represent a significant advance in understanding the role of this ocean in regulating the global climate, although winter data is still lacking.

Since the summer, Dr. Yuanxu Dong has been involved in the innovative design and construction of a CO₂ eddy covariance system for deployment on a buoy as part of the MUSE research project (Marine Environmental Robotics and Sensors for Sustainable Research and Management of Coasts, Seas, and Polar Regions). This rare type of installation has the potential to significantly enhance our direct measurements of CO₂ flux between the air and sea, expanding our understanding of air-sea exchange processes.

In March and September, he has been hosted by his co-host Prof. Dr Bernd Jähne at the Institute of Environmental Physics at Heidelberg University. In the Aeolotron facility there, one of the largest and most modern annular wind-wave channels in the world, he conducted experiments on bubble-mediated transfer processes. He will now cross-link these laboratory results with the data from his field experiments to understand the mechanisms of the bubble-mediated gas exchange.

Just in time for the start of the dark season, Dr Yuanxu is back in Kiel. However, he is not afraid of the northern German winter: “I survived Norwich, and Kiel is only slightly further north,” he says with a hearty laugh.

Original publication:

Yuanxu Dong et al. (2024): Direct observational evidence of strong CO2 uptake in the Southern Ocean. Sci. Adv.10.

DOI:10.1126/sciadv.adn5781

Professor Katja Matthes, ������Ƶ Director: “The Global Stocktake for COP28 in Dubai last year showed that the world is heading towards 2,6 degrees Celsius rather than the 1,5 degrees set out in the Paris Agreement in 2015. We need to cut greenhouse gas emissions immediately and drastically. Meanwhile, we have to find solutions for residual emissions that cannot be avoided. Ocean research provides essential knowledge on natural and technical approaches to Carbon Dioxide Removal (CDR) and Carbon Capture and Storage (CCS) so that the ocean can help us in the fight climate change. We call on world leaders to support this research and to promote activities that protect the ocean.”

Peter de Menocal, President and Director of Woods Hole Oceanographic Institution: “Our future relies on humanity making smart decisions on how to manage the ocean. And making smart decisions demands that we have the best scientific information possible about the ocean and the many ways it affects everyone on the planet. Long-term, multi-scale ocean observations provide the critical data necessary to ensure a sustainable future for all.”

The ocean has absorbed more than 90 percent of the excess heat and almost 30 percent of the excess carbon dioxide caused by human activity. As a result, the ocean’s continued health will determine the magnitude and rate of such factors as sea-level rise, increasing atmosphere and ocean temperatures, changes to the hydrological cycle, trends in ocean acidification and deoxygenation, ecosystem and biodiversity declines, and severe weather events. Despite this, international investment in ocean observing systems has not kept pace with the need for information to guide climate adaptation efforts and other critical decisions.

Margaret Leinen, Director of Scripps Institution of Oceanography at UC San Diego: “The ocean has an outsized impact on global climate even when it comes to desertification and is impacted itself by climate change. At least half of macro-organisms on the planet are marine. Most have not even been discovered, much less named, so ongoing discovery of the system supporting life on Earth is imperative to say the least.”

The Intergovernmental Panel on Climate Change (IPCC) has concluded that the world must take coordinated action to avoid exceeding 1.5°C increase over pre-industrial temperatures—a key threshold that climate scientists say staying below will avoid the most severe effects of climate change. At the same time, there is growing interest in the many opportunities that the ocean offers, including methods to mitigate rising greenhouse gasses in the atmosphere, adapt to current and future climate change, and build a healthy blue economy that benefits humanity and protects critical ecosystems.

The COP29 Baku Ocean Declaration calls on the parties of the UN Climate Conference and beyond to adopt measures to improve observations of critical ocean variables to preserve these benefits and includes key points for negotiators and attendees to consider in discussions during the two-week long conference. In addition, the Declaration highlights opportunities that improved observations offer in addressing the interconnected objectives of the UN conventions on climate, biodiversity, and desertification, known collectively as the Rio Conventions.

Specific efforts spelled out in the COP29 Bakui Ocean Declaration include:

• Expand international collaboration to achieve progress in addressing the Earth’s climate, biodiversity, and freshwater crises.
• Enhance public and private funding to scale-up and diversify support of long-term ocean observation, research, and innovation for decision-making.
• Build capacity and access, particularly in small-island developing states, low-lying coastal regions, and other under-represented people and places to further develop ocean data, knowledge, and innovation.
• Improve awareness of the ocean’s role in planetary systems and the need for its preservation as a vital step towards mobilizing decision-makers to prioritize ocean protection and restoration.

Background

The Ocean Pavilion is organized by the Woods Hole Oceanographic Institution and UC San Diego’s Scripps Institution of Oceanography. It is a dedicated space in the Blue Zone at COP29 that returns for a third year to put the ocean center-stage at a crucial time in international climate negotiations. The pavilion brings together diverse and influential partners who will call for ocean-focused solutions to be recognized as critical in the world’s response to the climate crisis. Throughout the two-week conference, the pavilion will feature more than 50 events to stimulate discussion on a wide range of topics related to the future of the ocean. Visitors will also be able to learn more about the work of Ocean Pavilion partners and to speak with scientists, thought leaders, and students engaged in the search for solutions to some of the world’s most pressing challenges.

During the expedition, the scientists want to focus on three research projects in particular: Firstly, they will take sediment cores along the East Greenland shelf. This will allow them to reconstruct past climate changes and carbon storage in fjord sediments. "The sediment cores serve as a climate archive and are used to reconstruct the variability of the climate in the past and the changes that have resulted from shifts in sea ice cover, salinity and productivity in the East Greenland system over the last 2000 years," explains cruise leader Professor Dr Eric Achterberg. In addition, the scientists are measuring the iron and manganese fluxes from the sediments into the overlying water in order to assess the effects of these micronutrients on primary production along the East Greenland coast. Primary production describes the process by which microscopic plant organisms, mainly phytoplankton, produce organic material from inorganic substances (such as carbon dioxide and nitrogen) and light through photosynthesis. This is the basis of the marine food web.

The researchers also want to understand the effects of meltwater runoff from Greenland glaciers and Arctic freshwater runoff on the circulation and biogeochemistry of the North Atlantic. Increasing amounts of freshwater inputs are observed in the East Greenland Current (EGC), which is related to the increasing sea ice melt in the Arctic Ocean, melting of Greenland glaciers and the increasing discharge of European and Asian rivers into the Arctic Ocean. The East Greenland Current therefore leads to a freshening of the North Atlantic with possible consequences for the climate through changes in the AMOC and increases in sea surface temperatures. The freshwater inputs may also affect the primary productivity in the North Atlantic and consequently the uptake of carbon dioxide (CO₂) by the ocean.

The international research team is therefore also measuring carbon dioxide (CO₂), pH, alkalinity, nitrate, phosphate, methane and primary productivity at the sea surface. These surveys complement data from surveys and moorings in the fjord systems, which are collected by Greenlandic scientists throughout the year.

"Our data and improved understanding will be used to improve model projections for the Arctic and low latitudes under future climate scenarios, assess the impact of climate change on society and inform stakeholders," says Dr Achterberg. At the beginning of the expedition, increased temperatures were detected in the North Atlantic near Iceland and a significantly stronger ice cover on the coast of East Greenland in the East Greenland Current compared to recent years. The causes of this contrast are not clear yet.

Expedition at a Glance:

MARIA S: MERIAN Expedition MSM130

Project Name: POLAR BEAST

Chief Scientist: Prof Dr Eric Achterberg

Dates: 09.07.2024 – 14.08.2024

Departure: Reykjavik, Iceland

Arrival: Reykjavik, Iceland

Study Area: East coast of Greenland

Funding:

The MERIAN expedition MSM130 is funded by the German Research Foundation (DFG) and the Federal Ministry of Education and Research (BMBF) under the name "Investigation of the relationship between Arctic freshwater discharge, Atlantic biogeochemistry and Atlantic Meridional Overturning Circulation (AMOC)", or "POLAR BEAST" for short.

Previous research has identified a suite of global scale processes, referred to as Planetary Boundaries, that regulate the overall habitability and stability of the planet. If critical thresholds in these processes are passed, the risk of large-scale, abrupt or irreversible environmental changes ("tipping points") increases and the resilience of our planet, its stability, is jeopardised. Among the nine Planetary Boundaries are climate change, land use change, and biodiversity loss. The authors of the new study argue that aquatic deoxygenation both responds to, and regulates, other Planetary Boundary processes.

“It’s important that aquatic deoxygenation be added to the list of Planetary Boundaries,” said Professor Dr. Rose from the Rensselaer Polytechnic Institute in Troy, New York, lead author of the publication. “This will help support and focus global monitoring, research, and policy efforts to help our aquatic ecosystems and, in turn, society at large.”

Across all aquatic ecosystems, from streams and rivers, lakes, reservoirs, and ponds to estuaries, coasts, and the open ocean, dissolved oxygen concentrations have rapidly and substantially declined in recent decades. Lakes and reservoirs have experienced oxygen losses of 5.5 and 18.6 per cent respectively since 1980. The ocean has experienced oxygen losses of around 2 per cent since 1960. Although this number sounds small, due to the large ocean volume it represents an extensive mass of oxygen lost. Marine ecosystems have also experienced substantial variability in oxygen depletion. For example, the midwaters off of Central California have lost 40 per cent of their oxygen in the last few decades. The volumes of aquatic ecosystems affected by oxygen depletion have increased dramatically across all types.

“The causes of aquatic oxygen loss are global warming due to greenhouse gas emissions and the input of nutrients as a result of land use,” says co-author Dr. Andreas Oschlies, Professor of Marine Biogeochemical Modelling at ������Ƶ Helmholtz Centre for Ocean Research Kiel: “If water temperatures rise, the solubility of oxygen in the water decreases. In addition, global warming enhances stratification of the water column, because warmer, low-salinity water with a lower density lies on top of the colder, saltier deep water below. This hinders the exchange of the oxygen-poor deep layers with the oxygen-rich surface water. In addition, nutrient inputs from land support algal blooms, which lead to more oxygen being consumed as more organic material sinks and is decomposed by microbes at depth.”

Areas in the sea where there is so little oxygen that fish, mussels or crustaceans can no longer survive threaten not only the organisms themselves, but also ecosystem services such as fisheries, aquaculture, tourism and cultural practices. Microbiotic processes in oxygen-depleted regions also increasingly produce potent greenhouse gases such as nitrous oxide and methane, which can lead to a further increase in global warming and thus a major cause of oxygen depletion.

The authors warn: We are approaching critical thresholds of aquatic deoxygenation that will ultimately affect several other Planetary Boundaries. Professor Dr. Rose “Dissolved oxygen regulates the role of marine and freshwater in modulating Earth's climate. Improving oxygen concentrations depends on addressing the root causes, including climate warming and runoff from developed landscapes. Failure to address aquatic deoxygenation will, ultimately, not only affect ecosystems but also economic activity, and society at a global level.”

Aquatic deoxygenation trends represent a clear warning and call to action that should inspire changes to slow or even mitigate this Planetary Boundary. The study of Professor Rose and colleagues will pave the way for further research and open the door to new regulatory actions. It was developed in the context of the Global Ocean Oxygen Network (GO2NE) of the Intergovernmental Oceanographic Commission (IOC) of the United Nations Educational, Scientific and Cultural Organisation (UNESCO), and the Global Ocean Oxygen Decade (GOOD) programme of the United Nations Decade of Ocean Science for Sustainable Development, both co-chaired by Professor Dr. Oschlies.

Original publication:

Rose, K.C., Ferrer, E.M., Carpenter, S.R. et al. (2024): Aquatic deoxygenation as a planetary boundary and key regulator of Earth system stability. Nature Ecology and Evolution, doi:

In recognition of his engagement as an ambassador for the ocean and for communicating marine research topics to the general public, Boris Herrmann receives today the “Deutscher Meerespreis” (German Ocean Award) of the Prof. Dr Werner Petersen Foundation. The award, endowed with 20,000 euros, will be presented under the patronage of Daniel Günther, Minister President of Schleswig-Holstein, in cooperation with ������Ƶ Helmholtz Centre for Ocean Research Kiel. Around 200 invited guests from the worlds of science, sport, business, and politics are expected to attend the ceremony at ������Ƶ in Kiel, Germany this evening.

“The fight against climate change is a race against time – and we can only win it if everyone in the world becomes involved. This engagement needs a broad knowledge base, and it needs data from all regions of the ocean,” says ������Ƶ Director Professor Dr Katja Matthes. “On the one hand, Boris Herrmann carries the message of protecting our ocean around the world and on the other, he collects important information for our research around the globe. His actions inspire many people around the world, including us researchers. The German Ocean Award recognises his important role as an ambassador and his impressive commitment. We congratulate him most sincerely and will be following the upcoming regattas with excitement and look forward to further joint projects.”

Minister President Daniel Günther honoured the awardee as a committed climate activist and supporter of science. “Boris Herrmann is a great sportsman and a champion of environmental education. The fight against global warming is literally written on your sails, and you are a role model with your way of tackling challenges,” says Günther. With his many years of commitment to climate protection and the ocean, Boris Herrmann is a more than worthy and deserving winner: “We in Schleswig-Holstein are very proud to be able to present you with the German Ocean Award 2024. Thank you very much for your great commitment.”

“The Professor Dr Werner Petersen Foundation sees it as its duty to also promote such activities that serve sustainable development and the protection of the ocean,” explains Dr h.c. Klaus-Jürgen Wichmann, Chairman of the Prof. Dr. Werner Petersen Foundation. “By awarding of the German Ocean Prize endowed with 20,000 euros, together with ������Ƶ and under the patronage of the Minister President of Schleswig-Holstein, the foundation once again makes it possible to honour people who have made outstanding contributions to the conservation, protection or communication of knowledge about the ocean. The engagement of the professional sailor Boris Hermann, globally recognised ambassador of the ocean, are thus impressively honoured.”

For Boris Herrmann, a childhood dream came true in 2020 when he became the first German to complete the Vendée Globe. In 2024, he will once again participate in the non-stop single-handed race around the world. In 2023, he and his team took part in the Ocean Race with their Malizia - Seaexplorer – with a spectacular fly-by in the Kiel Fjord. Team Malizia has also announced their participation in the Ocean Race Europe, which will start in Kiel in August 2025. In May 2024, Boris Herrmann was second in New York after the transatlantic race The Transat CIC. He also recently finished the New York Vendée return race to Les Sables d’Olonne in a celebrated second place. He has been awarded the Order of Merit of the Federal Republic of Germany.

“I am proud of what we have achieved with our Team Malizia. This includes the growing popularity and enthusiasm for our sport, but above all the visible commitment to education and science to protect the climate and the ocean. This award honours the long-standing and focused work of the entire team, our partners and supporters worldwide and, last but not least, my wife Birte with our educational programme ‘My Ocean Challenge’,” says award winner Boris Herrmann. “We see this award as an incentive to continue our mission with vigour, to look for solutions and, above all, to get people around the world excited about ocean and climate protection.”

The sailor has a long-standing collaboration with ������Ƶ, which can also be seen as an origin of the now diverse connections between research and German professional sailing. Since the beginning of 2024, Boris Herrmann has also been an ambassador of the German Committee of the Ocean Decade, whose coordination office is based at ������Ƶ.

������Ƶ coordinates various programmes within the framework of the United Nations Decade of Ocean Science for Sustainable Development and also contributes in many other ways to achieving the goals of the Decade. One focus of ������Ƶ's work is global ocean monitoring for researching and predicting the effects of climate change and other human influences on the ocean.

In addition to scientific expeditions, autonomous measuring devices and merchant ships, sailing yachts also contribute to the collection of data as “ships of opportunity”. The innovation platform “Shaping an Ocean Of Possibilities” (SOOP), which is funded by the Helmholtz Association, is leading the way here. In line with its project title, SOOP aims to create an “ocean of possibilities” for cooperation between science and industry. The aim is to create sustainable structures and technologies for ocean observation in order to improve access to measurement data and expand knowledge about our oceans. The project “Sailing for Oxygen”, which is supported by the German Federal Ministry of Education and Research (Bundesministerium für Bildung und Forschung, BMBF), is aimed at water sports enthusiasts in the Baltic Sea and involves sailing crews collecting data on oxygen concentrations in the Baltic Sea.

Agriculture was responsible for 74 percent of anthropogenic nitrous oxide emissions in the 2010s, mainly due to the use of synthetic fertilisers and animal manure on cropland, according to the Global Nitrous Oxide Budget 2024 report, recently published in the journal Earth System Science Data. Another major source is the ocean and adjacent coastal areas.

The comprehensive study of nitrous oxide emissions and sinks is based on millions of measurements taken on land, in the atmosphere, in freshwater systems, and in the ocean. An international team of 58 researchers from 15 countries compiled these measurements, resulting in the most extensive assessment of the global N₂O budget to date.

At a time when greenhouse gas emissions must be drastically and rapidly reduced to limit global warming, the study shows that more nitrous oxide was emitted in 2020 and 2021 than ever before in history. Excess nitrogen burdens soil, water, and air. In the atmosphere, N₂O destroys the ozone layer and exacerbates climate change through its powerful greenhouse effect. In addition to emissions from soils, the ocean and adjacent coastal areas are a major source of atmospheric N₂O.

Data from the ������Ƶ Helmholtz Centre for Ocean Research Kiel were used to estimate oceanic nitrous oxide emissions. ������Ƶ operates the world's largest database of N₂O measurements from the ocean and adjacent coastal areas. Its name, MEMENTO (Latin for “remember!”), stands for MarinE MethanE and NiTrous Oxide.

“Human-induced nitrous oxide emissions must be reduced to keep global warming below the two-degree threshold of the Paris Agreement,” emphasises the report’s lead author, Dr Hanqin Tian, professor of global sustainability and director of the Centre for Earth System Science and Global Sustainability at the Schiller Institute for Integrated Science and Society at Boston College. “There are currently no technologies to remove nitrous oxide from the atmosphere.”

According to Dr Hermann Bange, Professor of Marine Biogeochemistry at ������Ƶ and head of the Trace Gas Biogeochemistry Research Group, the international study is a milestone because it describes the global sources and sinks of nitrous oxide in unprecedented detail. Effective action to reduce emissions requires a thorough understanding of these sources and sinks.

The researchers therefore call for more frequent assessments of the N₂O budget and recommend the establishment of a global N₂O measurement network. “The ocean is one of the largest sources of nitrous oxide and must be included in this network,” says Professor Bange.

Original Publication:

Tian, H. et al (2023): Global Nitrous Oxide Budget 1980-2020, Earth Syst. Sci. Data Discuss. Global Carbon Project.

Article DOI: 10.5194/essd-2023-401

Additional Data DOI: 10.18160/RQ8P-2Z4RDOI:

Background to the Global Carbon Project:

Founded in 2001, the Global Carbon Project (GCP) is an international research project established to work with the international scientific community to build a shared and agreed knowledge base to support policy debate and action to slow down and ultimately halt the rise of greenhouse gases in the atmosphere. Its projects include global budgets for the three dominant greenhouse gases – carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) – and complementary efforts on urban, regional, cumulative, and negative emissions.

The Labrador Sea is one of the few regions in the world where the Deep Western Boundary Current is close to the surface, making the region  a gateway to the abyssal ocean. Changes in properties, such as temperature, oxygen or carbon dioxide levels, are exported to the deep sea where they can persist for centuries. Understanding the processes that lead to changes in the Deep Western Boundary Current is crucial for climate prediction using models.

Data indicate that changes are already occurring, and research has linked these changes to oceanic and atmospheric processes, such as the spread of temperature and salinity anomalies, and fluctuations in winds and heat fluxes. Long-term data series are needed to distinguish between climate and short-term variability, and to identify their oceanic and atmospheric drivers.

“Since last year, we have observed an unprecedented warming in the North Atlantic, with regions such as the Labrador Sea showing temperatures more than five degrees above average,” says Dr Johannes Karstensen, oceanographer at the ������Ƶ Helmholtz Centre for Ocean Research Kiel and chief scientist of the international MSM129 expedition, which set out on Saturday on the MARIA S. MERIAN from Rostock to the North Atlantic. Karstensen adds: “A key question during our expedition will be whether this heat anomaly can also be detected in deeper layers of the North Atlantic and whether it is already affecting the currents.”

To find out, the researchers will collect data associated with a long-term climate observation programme. Since 1997, ������Ƶ has been operating an ocean observatory off the coast of Labrador (Canada) with seven measuring stations over a length of 120 kilometres. Each station is equipped with a couple of instruments to continuously record data on currents, temperature, oxygen, and salinity – from the seafloor to just below the sea surface. Every two years, researchers travel to the region to retrieve the data and collect additional samples along the way.

During the transit from Rostock to the first stop in St. John's, Canada, the MARIA S. MERIAN will also collect various types of underway data. It will be tested how quickly international data centers can access the data to enable its use for ocean and weather forecasts.

“The ocean has properties that have so far mitigated the effects of rapidly advancing climate warming,” says Karstensen. For example, because of its high heat capacity, the ocean has absorbed more than 90 per cent of the excess heat and stored it at increasing depths. However, as the deep sea changes, the ocean's ability to mitigate human-induced changes in the atmosphere, such as warming and increases in greenhouse gases, is diminishing. “At some point, even the deep sea’s capacity will reach its limits.”

Expedition at a Glance:

Expedition Name: MARIA S. MERIAN Expedition MSM129

Project Name: LabSeaFlow2024

Chief Scientist: Dr Johannes Karstensen

Dates: 25.05.-06.07.2024

Departure: Rostock (Germany)

Arrival: Reykjavik (Iceland)

Study Area: North Atlantic/Labrador Sea

The ship's position and initial data can be tracked live online via the ������Ƶ-developed BELUGA platform.

But how effective and efficient are the various possible measures? What are the hurdles to implementing them? What are the costs? How environmentally friendly are they? The research team investigated these and other questions in its latest study in which it analysed the feasibility of 14 CDR measures that could be implemented in Germany. The measures include direct air carbon capture and storage (DACCS) and bioenergy with carbon capture and storage (BECCS) as well as measures to increase carbon uptake by ecosystems.

For their investigations, the researchers used an evaluation framework they had jointly developed in a previous study. Six different dimensions are assessed: ecological, technological, economic, social, institutional, and systemic. “For a good and comparable assessment of the feasibility, taking into account the risks and opportunities of different CDR measures, various aspects must be considered. Because these are not easy to keep track of and compare, we wanted to shed light on them with our study”, says Dr Malgorzata Borchers from the UFZ and co-first author of the study together with Dr Johannes Förster from UFZ and Dr Nadine Mengis from ������Ƶ.

Within the framework of workshops in multidisciplinary teams of the Helmholtz Climate Initiative, the expertise of 28 co-authors was incorporated into the study. “We thus had an incredibly large pool of expert knowledge at our disposal. This enabled us to assess the current state of knowledge on the CDR methods analysed in our study”, says Mengis. The researchers have presented their results in a clear evaluation matrix using a traffic light colour system. Red means that the hurdles to introducing a CDR measure are high in a certain area (e.g. ecological or economic). Yellow means they are medium, and green means they are low.

The study results show that the CDR measures with the lowest technological hurdles include mainly ecosystem-based measures such as the restoration of seagrass meadows, the cultivation of intermediate crops in agriculture, the rewetting of peatlands, and the reforestation of degraded land. “Ecosystem-based measures are already being used to avoid emissions in particular. They also contribute to the removal of carbon dioxide from the atmosphere. However, the potential of these measures is limited because Germany is quite restricted in terms of area and because we cannot rewet peatlands or reforest large areas indefinitely”, says Förster. “Nevertheless, we should try to leverage these synergies. In order to achieve the climate target, it will be necessary to combine different CDR measures in a portfolio of climate protection measures”.

For measures with a higher CO₂ removal potential such as BECCS, the traffic light colour in the evaluation matrix is red in many areas. “With technological CDR measures, the economic and institutional hurdles in particular are still quite high”, says Prof Daniela Thrän, who heads the Department of Bioenergy at the UFZ. “Because there are regional differences in the feasibility and potential of these CDR measures, we believe that more practical experience is needed at the regional and local level in order to better understand how the technologies can be further developed and established as part of local value chains”. In the evaluation matrix, there are also white spots, which indicate that there are currently no data available. “This is particularly the case with the social assessment aspects of the CDR measures. Further research is urgently needed. For example, on how the costs and disadvantages of CDR measures could be distributed fairly across society and how their implementation would benefit society as a whole”, says Mengis.

The scientists hope that their feasibility study for possible CDR measures in Germany can help decision-makers to better understand and categorise the complex information. This is the only way to set the right course for achieving the climate target for 2045.

Original publication:

Borchers M., Förster J., Thrän D., Beck S., Thoni T., Korte K., Gawel E., Markus T., Schaller R., Rhoden I., Chi Y., Dahmen N., Dittmeyer R., Dolch T., Dold Ch., Herbst M., Heß D., Kalhori A., Koop-Jakobsen K., Li Z., Oschlies A., Reusch Th., Sachs T., Schmidt-Hattenberger C., Stevenson A., Wu J., Yeates C. and Mengis N.: A Comprehensive Assessment of Carbon Dioxide Removal Options for Germany. Earth’s Future; DOI: