PhD // GEOMAR Helmholtz Centre for Ocean Research Kiel

Sina Acksen

What is my general research focus?

As a modeler, I work with Earth system models to better understand complex processes within the Earth system and to make predictions about how the global system responds to different stimuli over long timescales. As part of my work at GEOMAR, my current research focus is on future changes in the marine system and the investigation of the influence of biogeochemical processes on the global carbon cycle.

What is my specific contribution in RETAKE?

In my research, I use an Earth system model of intermediate complexity (UVic 2.10) to investigate the long-term potential of marine alkalinity enhancement (OAE) and the stability of added alkalinity in the seawater. Key aspects of my work include predicting the development of calcifying organisms as well as processes in marine sediments that could influence the OAE potential.

What is my personal motivation for doing research within this topic?

I am convinced that it is crucial to actively contribute to ensuring the long-term viability of life on Earth for future generations. In addition to comprehensive emission reductions, methods for CO₂ mitigation are increasingly being discussed as complementary measures. I believe it is essential to thoroughly investigate these technologies in order to identify and exclude potential risks when implementing such methods.

WP 3.2.

Postdoc // Leibniz Institute for Baltic Sea Research Warnemünde

Dr. Anna-Adriana Anschütz

What is my general research focus?
I have a background in biological oceanography and developed models of the ecophysiology of mixotrophic microplankton for my PhD. The focus and common factor of my research is the marine biological realm and its connection to marine chemistry, carbon export and climate change.

What is my specific contribution in RETAKE?
As part of RETAKE I will integrate experimental and field data into a joint physical and ecosystem model of the Baltic Sea and look at the effects and side effects of alkalinisation.

What is my personal motivation for doing research within this topic?
I want to dedicate my research to marine conservation and finding solutions to counter climate change and its effects on biodiversity and habitats.

Topic: Extrapolation through models, WP2.4

Postdoc // Leibniz Institute for Baltic Sea Research Warnemünde

Dr. Jannine Avila

What is my general research focus?
Broadly, my research focus is marine biogeochemistry. Especially the marine carbonate system, its dynamics, and interactions with other biogeochemical cycles from coastal areas to the open ocean.

What is my specific contribution in RETAKE?
To enhance the understanding of how the Baltic Sea carbonate system acts and reacts to different types of alkalinity enhancement (AE). And also help untangle AE’s potential benefits and side effects depending on the chosen approach.

What is my personal motivation for doing research within this topic?
Having studied the carbonate system for a few years now, I look forward to engaging in science that directly impacts society and our future.

Topic: Extrapolation through models, WP2.4

PI // MARUM/Bremen University

Prof. Dr. Wolfgang Bach

What is my general research focus?
My research focuses on the interactions between the ocean floor and seawater and their effects on geochemical cycles. These interactions release energy carriers for chemosynthesis. I study the underlying mechanisms and the importance of these processes for microbial assemblages in the ocean floor.

What is my specific contribution in RETAKE?
In our project we aim to achieve an improved understanding of the dissolution processes of olivine and basaltic glass using a microscopic approach in which we image the retreat of surfaces to gauge dissolution rates and determine under what conditions they may be maximised.

What is my personal motivation for doing research within this topic?
Knowing the rates and mechanisms of mineral dissolution is essential for examining the potential of enhanced weathering in CDR.

Topic: Mechanisms, WP1.3

PhD // GEOMAR Helmholtz Centre for Ocean Research Kiel

Rebecca Bährle

PhD candidate // Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research

Amrita Bhaumik

What is my general research focus?
Marine ecosystems are under constant pressure due to ever-increasing anthropogenic activities, resulting in climate change. Ultimately, these activities are altering the present environmental conditions on a global scale and could affect key marine organisms like zooplankton.
Therefore, the focus of my research is to understand the impact of changing environmental conditions on the different physiological functions of zooplankton.

What is my specific contribution in RETAKE?
Global warming and subsequent ocean acidification pose a great threat, not only to human civilization but to the entire planet. Thus, carbon dioxide removal techniques, such as ocean alkalinisation, could be instrumental to mitigate the consequences of ocean acidification. Undoubtedly, we need to be sure about these techniques before adopting them, especially when it comes to risks to marine life. As a part of the RETAKE team, I am assessing the possible impacts of artificial ocean alkalinisation on zooplankton. In the process, I would like to determine whether threshold limits exist, below which any possible negative impacts are negligible.

What is my personal motivation for doing research within this topic?
My ambition is to be part of a research team that is motivated to find possible solutions to mitigate problems associated with climate change. Potentially, ocean alkalinisation is one of the probable solutions to diminish the effect of ocean acidification. Before being able to carry this out on larger scales we need to check and recheck every possible outcome in the laboratory. Only then can we avert any unwanted side effects while trying to mitigate existing problems.

Topic: Mechanisms, WP1.2

PI // Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research

Prof. Dr. Maarten Boersma

What is my general research focus?
The investigation of multiple stressors on planktonic organisms, with a special focus on the interactions between nutrient loads and temperature.

What is my specific contribution in RETAKE?
We will investigate the effects of alkalinisation on zooplankton, both direct effects (effects on pH), but also indirect effects will be assessed, for example through changes in the quality of resources when the availability of CO₂ changes.

What is my personal motivation for doing research within this topic?
Without measures to capture CO₂ from the atmosphere, we will not be able to attain the targets that we have set ourselves with respect to climate change. We need to investigate the effects of such measures to be able to make informed decisions on the viability and the risks of such measures.

Topic: Mechanisms, WP1.2

PI // GEOMAR Helmholtz Centre for Ocean Research Kiel

Dr. Stefanie Böhnke Brandt

What is my general research focus?

My research focuses on exploring microbial diversity and function, with a particular emphasis on microorganisms from marine environments that have so far remained uncultivated. I am investigating their role in biogeochemical cycles, especially in relation to carbon conversion and fixation mediated by enzymes such as RubisCO and CODHs. To unravel the ecological significance of these microbes, I apply a combination of modern approaches, including functional metagenomics, transcriptomics, artificial intelligence (AI), as well as ecophysiological and biogeochemical experiments. My goal is to better understand how microbial communities function and interact within sediments and under the influence of climate change.

What is my specific contribution in RETAKE?

Within the RETAKE project, I am involved in Work Package 1.4. Here, we investigate the effects of the addition of carbonates and their accelerated dissolution on microbial processes at the seabed. My specific contribution lies in analyzing shifts in the composition of benthic microbial communities and their functional properties, particularly their potential role in the transformation of CO₂ and other relevant fluxes. To achieve this, we conduct incubation experiments, apply molecular biological methods to characterize the involved microorganisms and their enzymes, and use biogeochemical techniques to quantify active processes and fluxes.

What is my personal motivation for doing research within this topic?

I am fascinated by the immense – and often hidden – potential of microbial communities to actively shape environmental processes with global relevance. It motivates me to contribute foundational knowledge that can support the development of sustainable strategies for climate mitigation. At the same time, I am driven by the curiosity to further unlock the “microbial black box.”

PI // Helmholtz Centre Hereon

Dr. Ute Daewel

What is my general research focus?
My research focuses on the interactions of physics and biology in marine ecosystems. I develop and use numerical models to describe, explain and predict changes in the ecosystem.

What is my specific contribution in RETAKE?
The advantage of numerical models is that, in a “digital” ocean, one can assess the influence of local interventions on the regional ecosystem. In RETAKE, we want to use an ecosystem model for the North Sea to assess the efficiency of coastal alkalinity enhancement and to understand which secondary effects on the ecosystem are to be expected.

What is my personal motivation for doing research within this topic?Artificial interventions in the ocean system can prove to be an efficient and feasible method to counteract man-made climate change. However, in order to be able to apply them safely and efficiently, it is absolutely necessary to examine the methods for the efficiency of different application concepts and possible side effects before they are actually used. Numerical models can provide information here without actually having to intervene in the sensitive marine ecosystem.

Topic: Extrapolation through models, WP2.2

PI // GEOMAR Helmholtz Centre for Ocean Research Kiel

Dr. Andrew Dale

What is my general research focus?
My research is mainly focused on the biogeochemistry and recycling rates of organic matter in marine sediments, from the coast to the deep sea. I rely on empirical field data, laboratory experiments and numerical analysis using reaction-transport models to investigate pressing scientific questions.

What is my specific contribution in RETAKE?
In RETAKE I am involved in WP1.4: Enhanced Benthic Weathering of Carbonate and Olivine in Baltic Sea. We will use lander technologies to conduct in situ experiments to quantify mineral dissolution rates on the seafloor in Kiel Bight and the Gotland Basin, following on from our previous laboratory experiments.

What is my personal motivation for doing research within this topic?
I am interested how we can use the ocean to reliably and sustainably remove CO₂ from the atmosphere as a means to achieve neutral or negative CO₂ emissions.

Topic: Mechanisms, WP1.4

Postdoc // MARUM/Bremen University

Dr. Alexander Diehl

What is my general research focus?
Whether in high-temperature geological processes or in the cold weathering of rocks, the reaction of solid matter with aqueous solutions shapes the chemical composition of all water reservoirs on Earth. As a geochemist, I have been intensively studying the solution composition of hot springs on the ocean floor in recent years. Due to the high temperature in the subsurface, hot solutions and rocks are predominantly in thermodynamic equilibrium and thus mineral reactions and solution compositions can be predicted well using thermodynamic methods. If the temperature is low, chemical reactions often no longer take place at all or very slowly, although the thermodynamic driving force for a reaction is given. This is where the concept of reaction kinetics and kinetic barriers comes into play, which can prevent chemical systems from reaching their optimal energy state. This plays an important role in processes of weathering, and whether, and how quickly, minerals form or dissolve must be determined empirically in cold systems independently of thermodynamic predictions.

What is my specific contribution in RETAKE?
In RETAKE, I am investigating the dissolution kinetics of rocks and minerals on a microscopic scale. Basalt glasses and olivines from dunites are considered undersaturated in seawater and dissolve when they come into contact with it. The question is how fast this dissolution takes place. This is one of the central questions to estimate the effectiveness of alkalinity enhancement by basalt or olivine weathering. The process of dissolution is very dynamic and the rate of dissolution of minerals and rocks is neither constant in space nor time. The microscopically determined dissolution rates will generate a basic understanding of the dissolution process and will lay a foundation for modelling the effectiveness of alkalinity enhancement by mineral components.

What is my personal motivation for doing research within this topic?
It is almost utopian to assume that we will sufficiently reduce global CO₂ emissions in the coming decades. It is therefore obvious that, in addition to efforts to reduce CO₂ emissions, we should also explore the framework for various tactics to actively remove CO₂ from the atmosphere. With weathering, the rock cycle has been buffering atmospheric CO₂ concentrations for billions of years on our planet and has a significant influence on the climate. Thus, it is obvious to use it to contribute to the reduction of atmospheric CO₂.

Topic: Mechanisms, WP1.3

Postdoc // GEOMAR Helmholtz Centre for Ocean Research Kiel

Dr. Giulia Faucher

PhD candidate // GEOMAR Helmholtz Centre for Ocean Research Kiel

Michael Fuhr

What is my general research focus?
The large image behind my scientific efforts is the fact that our and future generations are obliged to cope with the arrears of two generations of Miracles on the Rhine. Large efforts are thus to be made in order to rebalance the system that we call Earth. My research focuses on the understanding of this system and ways to interact with it that lead to a long-term stabilisation of our planets climate.

What is my specific contribution in RETAKE?
Against the back-drop of a mater’s in marine geosciences, my current work focuses on enhanced weathering in the oceans water column and on sediments.
The overarching goal is to investigate materials that have the potential to both economically and chemically efficiently sequester CO₂ from the athmosphere, if used for enhanced benthic weathering.

What is my personal motivation for doing research within this topic?
“Still fighting for the Big Issues, but now in my small, individual way.” – Dame Marjorie “Maude” Chardin

Topic: Mechanisms, WP1.4

Postdoc // GEOMAR Helmholtz Centre for Ocean Research Kiel

Dr. Silvan Goldenberg

What is my general research focus?
I am interested in food webs with a special focus on the trophic function and behaviour of fishes. In the past, I worked on ecosystem impacts of human activities such as climate change and ocean acidification. Now, I study nature-based solutions to climate change and food security including natural and artificial upwelling and negative emission technologies.

What is my specific contribution in RETAKE?
In RETAKE, I will conduct community level experimentation in pelagic mesocosms to identify the ecological risks and co-benefits of ocean alkalinity enhancement.

What is my personal motivation for doing research within this topic?
I am excited to be part of this project as it is time to look for solutions.

Topic: Mechanisms, WP1.2

PhD candidate // Kiel University

Caroline Grünhagen

What is my general research focus?
After completing my M.Sc. in Environmental and Resource Economics at the Christian-Albrechts-Universität zu Kiel, I focused on marine resources. As a PhD student at the Center for Ocean and Society, I am working on the development of bio-economic models. Potential effects of climate change and fisheries on fish stocks in the North Sea and Baltic Sea are of particular interest.

What is my specific contribution in RETAKE?
As part of work package 3.4, I am working on the impacts of alkalinity enhancement on fisheries and food security. I am involved in the development of regional scenarios, which are embedded in our bio-economic models for the North and Baltic Seas. In addition, larger marine ecosystems are also considered in order to map all consequences and affected actors.

What is my personal motivation for doing research within this topic?
It is up to us humans to mitigate the course of climate change. Methods such as geoengineering are a conceivable solution, but they must be sufficiently studied before they can be applied. Thus, it is indispensable to quantify possible consequences in advance.

Topic: Sociological Aspects and Economics, WP3.4

PI // Hamburg University

Prof. Dr. Jens Hartmann

What is my general research focus?
Aquatic Geochemistry and CDR with focus on alkalinity production.

What is my specific contribution in RETAKE?
Alkalinity production and ocean alkalinity enhancement with reactors.

What is my personal motivation for doing research within this topic?
Solving the CO₂-problem.

Topic: Mechanisms, WP1.1

PI // Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research

Dr. Judith Hauck

What is my general research focus?
Marine biogeochemistry and Earth System Modelling: the global and polar ocean carbon sink and the response of the biological carbon pump to climate change.

What is my specific contribution in RETAKE?
Using an ocean biogeochemical model (FESOM-REcoM) to assess the role of deep and bottom water formation regions for ocean alkalinisation. Also to determine requirements for a monitoring system that could track the effects and efficiency of alkalinisation.

What is my personal motivation for doing research within this topic?
A critical assessment of ocean negative emission technologies is needed to inform societal discussions.

Topic: Extrapolation through models, WP3.2

PI // Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research

Prof. Dr. Sabine Kasten

What is my general research focus?
My research focuses on the investigation, quantification and modelling of geochemical, biogeochemical and early diagenetic processes in marine sediments of different depositional environments. A special focus of my work is the investigation of transient and non-steady (bio)geochemical processes in nearshore and marine sediments, that are triggered by erosion, resuspension and sedimentation events, among others.

What is my specific contribution in RETAKE?
The aim of our sub-project in RETAKE is to gain a better understanding of the dissolution processes and dissolution rates of olivine and basalt in dynamic and permeable sediments – as they are found in natural coastal areas. Furthermore, we want to investigate and quantify the release and fixation of other substances mobilised during silicate weathering – such as nutrients and heavy metals.

What is my personal motivation for doing research within this topic?
In addition to investigating and quantifying the potential of enhanced silicate weathering to bind carbon dioxide, I am very interested in better understanding which other substances with potentially negative consequences for coastal ecosystems can be released, or how the input of these substances can be minimised as best as possible.

Topic: Mechanisms, WP1.3

PI // GEOMAR Helmholtz Centre for Ocean Research Kiel

Dr. David Keller

What is my general research focus?
Assessing the potential, feasibility, side effects, and sustainability of carbon dioxide removal (CDR) approaches for climate change mitigation, understanding feedbacks between biogeochemical cycles and the climate, and investigating interactions between marine ecosystems and biogeochemical cycles. To do this I use marine biogeochemical and Earth system modelling approaches. I also collaborate with a wide range of other disciplinary experts when working on the complex task of assessing CDR.

What is my specific contribution in RETAKE?
In work package 3.2 I am part of the group modelling ocean alkalinity enhancement with the FOCI Earth system model. In work package 3.3 I am contributing to the use of Earth system model output to help determine how carbon accounting can be done for ocean alkalinity enhancement.

What is my personal motivation for doing research within this topic?
To better understand to what extent, and under what conditions, the large-scale deployment of ocean alkalinity enhancement approaches could contribute to realistic, safe, and effective pathways for the world to achieve climate neutrality and the goals established in the Paris Agreement.

Topics: Extrapolation through models, WP3.2 and Sociological Aspects and Economics, WP3.3

Postdoc // GEOMAR Helmholtz Centre for Ocean Research Kiel

Dr. Leila Kittu

Postdoc // Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research

Dr. Male Köster

What is my general research focus?
I have a background in marine geochemistry and I am interested in biogeochemical and early diagenetic processes in marine sediments, including the dissolution of primary and precipitation of secondary mineral phases. During my PhD, I investigated biogeochemical processes – especially the cycling of iron – in deep and hot subseafloor sediments from the Nankai Trough offshore Japan by applying various geochemical analyses including sequential extractions of iron mineral phases as well as stable iron isotope analyses.

What is my specific contribution in RETAKE?
Within the RETAKE project, our aim is to examine the dissolution rates of olivine under different depositional, geochemical and advective conditions. For this purpose, we perform laboratory flow-through experiments with natural sandy coastal sediments from the North Sea amended with olivine of different grain sizes. The experiments are operated under different flow velocities. We further would like to assess potential negative effects of enhanced silicate weathering including the release, availability and cycling of trace metals and nutrients as well as to investigate and quantify the formation of secondary mineral phases that may represent potential long-term sinks for these trace metals and nutrients.

What is my personal motivation for doing research within this topic?
Mitigating global warming is one of the greatest challenges facing our society and, thus, it is indispensable to work on possible solutions that could counteract climate change. At the same time, however, any risks that might be associated with increased silicate weathering should be carefully examined and critically evaluated in advance. I am excited to be part of this very interdisciplinary project and to be able to contribute to climate change mitigation in this way.

Topic: Mechanisms, WP1.3

PhD candidate // Potsdam Institute for Climate Impact Research

Katarzyna Kowalczyk

What is my general research focus?
I am committed to investigating ocean alkalinisation’s potential – a carbon dioxide removal option thus far overlooked in the portfolio across available integrated assessment models.

What is my specific contribution in RETAKE?
Within RETAKE, I want to integrate ocean alkalinity enhancement into the REMIND model (REgional Model of Investment and Development), which will require estimating the method’s regional deployment costs and specifying its technical details. Using the model would allow us to, among others, assess the possible contribution of ocean alkalinisation to the Paris climate target.

What is my personal motivation for doing research within this topic?
I believe it is crucial to critically look at high-risk approaches aiming to mitigate climate change. Given that the mitigation pathways rely on carbon dioxide removal technologies, we must understand these measures’ environmental and socio-economic implications.

Topic: Sociological Aspects and Economics, WP1.1

Postdoc // Helmholtz Centre Hereon

Dr. Feifei Liu

What is my general research focus?
My research mainly focuses on the interactions between physical and biogeochemical processes in marine ecosystems. I use numerical models to reconstruct and interpret observed changes in the past/present and predict possible changes in the future of the ecosystems.

What is my specific contribution in RETAKE?
I’m involved in work package 2.2 “Regional modelling North Sea”, to conduct scenario simulations with a regional model for the North Sea trying to shed light on the possible efficiency of different coastal alkalinity enhancement measures and their side effects and ecosystem impacts on the Northwest European Shelf (NWES) system, both in the present and in the future.

What is my personal motivation for doing research within this topic?
A thorough evaluation of the advantages and disadvantages of artificial interventions in the marine ecosystem is crucially important before those methods are being put into action. Numerical models provide a unique approach for this purpose and help to give suggestions for the optimized ways to implement alkalinity enhancement for climate protection.

Topic: Extrapolation through models, WP2.2

Scientist // Helmholtz Centre Hereon

Dr. Moritz Mathis

PhD candidate // Helmholtz Centre Hereon

Chantal Mears

1.) What is my general research focus?
My research focuses on mapping watermasses distribution patterns within coastal shelf sea systems through the use of radiotracers, and resolving how these flow patterns relate to the carbonate system within these areas.

2.) What is my specific contribution in RETAKE?
My aim is to build on the previously defined relationship between the effective natural radiotracer radium (Ra) and total alkalinity within the North Sea, to map alkalinity distribution patterns, most particularly investigating the inflows and outflows (and their carbonate signatures) of the shelf sea.

3.) What is my personal motivation for doing research within this topic?
Global shelf seas are widely considered to be significant contributors to the global carbon budget, therefore gaining a better understanding of the distribution over shelf sea systems is crucial. This is especially important for climate change, where in order to accurately and adequately project future climatic scenarios, a sufficient baseline understanding of the current carbon budget along shelf sea systems as well as on a more local scale; sink, source, and pathways, must be understood.

Topic: Observation & Monitoring, WP2.1

Scientist // GEOMAR Helmholtz Centre for Ocean Research Kiel

Neha Mehendale

What is my general research focus?
The central theme of my current research is understanding what role the ocean plays in the global carbon cycle. I am interested in understanding the combined effect of marine biogeochemistry and ocean circulation on the uptake of carbon dioxide from the atmosphere.

What is my specific contribution in RETAKE?
Modelling ocean alkalinity enhancement as a carbon dioxide removal method using the earth system model FOCI (Flexible Ocean and Climate Infrastructure).

What is my personal motivation for doing research within this topic?
Research in a consortium like this at the intersection of science and society has the potential to inform actual future decisions. This driving factor combined with scientific curiosity about the results motivates me.

Topic: Extrapolation through models, WP3.2

Scientist // Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research

Dr. Cedric Meunier

PI // Leibniz Centre for Tropical Marine Research

Prof. Dr. Nils Moosdorf

What is my general research focus?
My research focuses on the interaction of groundwater and ocean water along global coasts.

What is my specific contribution in RETAKE?
My contribution to RETAKE is the estimation of the influence of environmental conditions and land-based groundwater on rates of carbon sequestration by Enhanced Weathering.

What is my personal motivation for doing research within this topic?
Through this research, I hope to contribute to pointing out paths to implement the negative emissions necessary for climate protection.

Topic: Extrapolation through models, WP2.3

PhD candidate // Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research

Tanvi Nagwekar

What is my general research focus?
My research focus is to understand the role of oceans in regulating the carbon dioxide concentration in the atmosphere and how the oceans could respond to the changing climate conditions. Specifically, I am interested in investigating how the changes in ocean-atmosphere interactions could affect marine biogeochemistry in the long run and what measures could be implemented to maintain a balance in the atmosphere.

What is my specific contribution to RETAKE?
As a part of work package 3.2 “Global Modelling”, I will be working with the global biogeochemical ocean model FESOM2-REcoM and carrying out simulations for Ocean Alkalinity Enhancement (OAE) in deep and bottom water formation regions. Along with it, a fully coupled AWICM-REcoM model will also be used for OAE simulations. All these simulations are to be carried out to analyse the efficiency, potential, side effects and biogeochemical feedbacks of the OAE technique for sequestering carbon dioxide from the atmosphere into the oceans.

What is my motivation for researching this topic?
Increasing concentrations of carbon dioxide in the atmosphere are now a primary concern, and I believe it is high time to take some action against it. Ocean Alkalinity Enhancement is one such geoengineering technique, which, if researched and studied in detail, could aid the current situation. Along with sequestering more CO₂ from the atmosphere in the ocean, it could also help the ocean acidification issue to some extent. But there is a lot of hard work and research to be carried out by the scientific community to implement these methods on a large and practical scale. As a Ph.D. student, it is an excellent opportunity to contribute to this attempt at this career level.

Topic: Extrapolation through models, WP3.2

Coordinator RETAKE & PI // GEOMAR Helmholtz Centre for Ocean Research Kiel

Prof. Dr. Andreas Oschlies

What is my general research focus?
I am an Earth system modeller and especially interested in ocean deoxygenation and the assessment of CDR methods with a focus on marine alkalinity enhancement.

What is my specific contribution in RETAKE?
As the Coordinator of RETAKE I am responsible for the overall coordination of this consortium. This includes fostering exchange between consortium members in order to find synergies between the different work packages. Further, I’m scientifically involved in the modelling work of RETAKE.

What is my personal motivation for doing research within this topic?
Having tried to reduce my personal CO₂ footprint for many years now, there is -despite some success- a very long way to go before I can reach zero. This also holds on a national and global basis. I see it as responsibility of scientists to generate knowledge and to investigate and assess options that can help society to reach the promised climate goals. Transparency is essential to avoid losing even more time.

Topics: Extrapolation through models, WP3.2 and Sociological Aspects and Economics, WP3.3

Scientist // Helmholtz Centre Hereon

Dr. Johannes Pein

PI // GEOMAR Helmholtz Centre for Ocean Research Kiel

Prof. Dr. Mirjam Perner

What is my general research focus?
In my group we investigate the interactions between microbes and their environment. The focus is on two core questions: How do microbes influence their environment? What influences do (changing) environmental conditions have on microbes, their metabolic pathways and the chemical reactions they catalyse? We also use the knowledge gained for biotechnological applications.

What is my specific contribution in RETAKE?
In work package 1.4 “enhanced benthic weathering of carbonates and olivine in the Baltic Sea” we as microbiologists work together with the geochemists. Here we are investigating the effects that the artificial addition of carbonates and olivine, their accelerated dissolution and the resulting (chemical) changes have on the microbial processes on the seabed. It is also unclear to what extent the microbes themselves influence these environmental changes: Can the microbes further stimulate the accelerated dissolution processes, inhibit them, or do they have no influence?

What is my personal motivation for doing research within this topic?
My personal motivation is, among other things, to contribute to the assessment of the possible microbiological and chemical consequences that accelerated mineral dissolution has on the environment.

Topic: Mechanisms, WP1.4

Scientist // Kiel Institute for the World Economy

Prof. Dr. Sonja Peterson

What is my general research focus?
European and International Climate Policy, General Equilibrium Models

What is my specific contribution in RETAKE?
Providing country specific marginal abatement cost curves for analysing the potential cost savings of marine carbon dioxide removal measures for reaching ambitious climate targets.

What is my personal motivation for doing research within this topic?
In my view carbon pricing should be the leading climate policy instrument and I am interested in the role it can play in different contexts.

Topic: Sociological Aspects and Economics, WP3.3

PhD candidate // GEOMAR Helmholtz Centre for Ocean Research Kiel

Svetlana Petric

PI // Helmholtz Centre Hereon

Dr. Daniel Pröfrock

What is my general research focus?
As an environmental scientist and analytical chemist my main expertise lies in the field of trace-metal, speciation and non-traditional stable isotope analysis based on ICP-MS and hyphenated techniques and their application for different kinds of environmentally related research topics as well as analytical method development.

What is my specific contribution in RETAKE?
Within RETAKE I will contribute to the analysis and evaluation of the potential release of metals by alkalinity-enhancing minerals and their potential effects. Furthermore I will support the investigations on the utilisation of metals and metal isotopes to trace and to attribute artificial alkalinity enhancement.

What is my personal motivation for doing research within this topic?
Many ideas exist to reduce the global CO₂ release or its consequences such as the use of renewable energy sources or the utilisation of geoengineering methods such as alkalinity enhancement. However, unwanted side effects of such measures affecting other processes within complex ecosystem are often not considered in a sufficient way. Sound analytical methods and data will be essential to study the consequences and finally the effectiveness and future role of such techniques.

Topic: Observation & Monitoring, WP2.1

PI // Leibniz Institute for Baltic Sea Research Warnemünde

Dr. Hagen Radtke

What is my general research focus?
I am working on numerical modelling of the Baltic Sea ecosystem (physical and biogeochemical).

What is my specific contribution in RETAKE?
I am supervising the modelling work on the possible consequences of near-bottom alkalinity enhancement in the Baltic Sea.

What is my personal motivation for doing research within this topic?
I would like to learn more about the sensitivity of the ecosystem to changes in the sediments and seabed.

Topic: Extrapolation through models, WP2.3

Postdoc // Leibniz Centre for Tropical Marine Research

Dr. Murugan Ramasamy

What is my general research focus?
My main areas of expertise are groundwater contamination and remediation, as well as the interaction of groundwater and ocean water.

What is my special contribution in RETAKE?
My contribution to RETAKE will be to model the effects of sediment hydrodynamics and climatic variables on enhanced weathering rates, as well as to look for favourable locations for enhanced weathering.

What is my personal motivation for researching this topic?
From the perspective of a hydrogeologist, I hope that by conducting this research, I will be able to contribute to providing recommendations for the most efficient ways to implement alkalinity enhancement for climate protection.

Topic: Extrapolation through models, WP2.3

Coordinator ASMASYS & PI // Leibniz Institute for Baltic Sea Research Warnemünde

Prof. Dr. Gregor Rehder

PI // Bremen University

Prof. Dr. Monika Rhein

PI // Kiel Institute for the World Economy

Dr. Wilfried Rickels

What is my general research focus?
My research focus is climate economics. I am particularly concerned with negative emissions and solar geoengineering.

What is my specific contribution in RETAKE?
My contribution to RETAKE is in particular the analysis of ocean-based alkalinity enhancement in an integrated assessment model.

What is my personal motivation for doing research within this topic?
Negative emissions are a prerequisite for achieving ambitious climate goals. So far, marine methods for negative emissions have received too little attention in climate economic analyses.

Topic: Sociological Aspects and Economics, WP3.3

PI // GEOMAR Helmholtz Centre for Ocean Research Kiel

Prof. Dr. Ulf Riebesell

What is my general research focus?
My working group and me study the impact of climate change on the ocean, especially on marine carbon sinks of pelagic ecosystems and their biogeochemistry, as well as ocean-based solutions for carbon sequestration.

What is my specific contribution in RETAKE?
I want to assess the efficacy and potential ecosystem impacts of ocean alkalinity enhancement.

What is my personal motivation for doing research within this topic?
I see an urgency in providing scientifically sound information on possible climate intervention measures.

Topic: Mechanisms, WP1.2

PI // Kiel University

Prof. Dr. Marie-Catherine Riekhof

What is my general research focus?
I work conceptually and with quantifiable ecological-economic models and conduct empirical studies to investigate the effects of different institutional regulations in the field of marine and coastal resources on the state of natural resources and on different actors. In doing so, problems in the implementation of regulation are addressed in order to consider, for example, the different effects on transaction costs or on risks.

What is my specific contribution in RETAKE?
I am part of work package 3.4 “Impacts on fisheries and food security”. Here we are developing bio-economic models and different scenarios to assess potential effects of marine alkalinity enhancement, especially on fish stocks and fisheries, and thus also on (local) food security.

What is my personal motivation for doing research within this topic?
I am interested in understanding the synergies and trade-offs between the different sustainable development goals and the economic impacts of the different management systems.

Topic: Sociological Aspects and Economics, WP3.4

PhD candidate // Helmholtz Centre Hereon

Ann-Cathrin Rohrweber

What is my general research focus?
As a geoscientist focusing on geochemistry, I perform metal analysis via ICP-MS to serve different applications.

What is my specific contribution in RETAKE?
I am taking part in observation and monitoring (WP2.1) of marine alkalinity enhancement by analysing trace metals and non-traditional stable isotopes that are released during weathering of minerals in mesocosm experiments. This allows assigning of additional alkalinity to its source and distinguishing it from natural variability of alkalinity in seawater samples.

What is my personal motivation for doing research within this topic?
Negative emission technologies such as marine alkalinity enhancement are a key factor in our attempt to limit global warming as best as possible. For responsible large-scale application, it is crucial to assess ecological risks as well as identify effectiveness. Having used chemical analysis of environmental samples to produce data on climate change already during my Master thesis, I am now glad to continue to add to this important research field.

Topic: Observation & Monitoring, WP2.1

PI // Helmholtz Centre Hereon

Prof. Dr. Corinna Schrum

PI // Kiel University

Dr. Hans Sloterdijk

What is my general research focus?
I am a researcher at the Center for Ocean and Society at the University of Kiel. I am interested in the sustainable management of human activities with a focus on fisheries affecting marine ecosystems. I work in partnership with scientists of different fields, policy-makers, and local stakeholders to generate knowledge that promotes food security and positive sustainable changes. For that, I am developing scientific fisheries scenarios that can be applied to integrated climate change research. I also spend time explaining to new people I meet how is it possible to be a French Canadian named Hans Sloterdijk!

What is my specific contribution in RETAKE?
In RETAKE, I contribute to work package 3.4 “Impacts on fisheries and food security”. I will be involved in the development of novel socio-economic pathways for the fishery sector together with stakeholders, which take alkalinity enhancement (AE) effects into account. Changes in the development of fish stocks and the demand for fish caused by AE could potentially affect fisheries and food security far beyond the mere geographical scope of the Baltic and North Seas. With a consortium of resource economists, fisheries ecologists, and marine scientists with expertise in ecological-economic modelling, the potential advantages and conflicts associated with the introduction of AE in achieving the UN’s Sustainable Development Goals (SDGs), including issues of food security and distributive justice, will be examined.

What is my personal motivation for doing research within this topic?
The impacts of climate change are and will affect our ability to preserve biodiversity and to prosper as a global society. Our response to climate change can basically be through two strategies: mitigation and adaptation. Therefore, I see the value in solution-oriented research that can help us to address these challenges and build a better future.

Topic: Sociological Aspects and Economics, WP3.4

PhD candidate // GEOMAR Helmholtz Centre for Ocean Research Kiel

Nicolas Smith Sanchez

Postdoc // GEOMAR Helmholtz Centre for Ocean Research Kiel

Carsten Spisla

What is my general research focus?
My general research focus are marine zooplankton communities. Since my bacherlor thesis I dealt with in-depth analyses of zooplankton communities in various ecosystems, as a part of evaluating the effects of antrophogenic influences like ocean acidification, artificial upwelling or in this case ocean alkalinisation, on these communities.

What is my specific contribution in RETAKE?
In RETAKE I want to contribute to the evaluation of how and if abundance, biomass or physical condition of the zooplankton community, and, wherever possible, primary, secondary, tertiary (etc.) biomass production and the energy transfer inbetween (Trophic Transfer Efficiency) is affected by ocean alkalinity enhancement.

What is my personal motivation for doing research within this topic?
The personal motivation to work within the RETAKE consortium is clearly that we finally moved over from assessing and predicting consequences from ongoing climate change to finding ways to weaken, stop, or even reverse the effects we studied for decades now. This is what makes this project so immensly interesting, exciting, and important to me.

Topic: Mechanisms, WP1.2

Project manager Test-ArtUp & Scientist // GEOMAR Helmholtz Centre for Ocean Research Kiel

Dr. Michael Sswat

PI // Bremen University

Dr. Reiner Steinfeldt

What is my general research focus?
As a trained physicist, I have been involved in oceanography since my doctorate. Regionally, the focus is on the (North) Atlantic. One focus of my work is the evaluation of trace substance measurements such as CFCs. From these data, the oceanic uptake of CO₂ emissions can also be determined.

What is my specific contribution in RETAKE?
For RETAKE, I am investigating which regions of the open ocean (e.g. upwelling or deep water formation areas) are particularly well suited for alkalinity enhancement and the additional carbon dioxide uptake hoped for as a result. Furthermore, the magnitude of these effects will be determined and whether they are detectable at all with regard to the natural variations in the ocean.

What is my personal motivation for doing research within this topic?
The question which proportion of carbon dioxide emissions is absorbed by the ocean plays an important role in climate change and is therefore of great societal significance. If this share could be increased in an environmentally friendly way (possibly by alkalinity enhancement), climate change could even be mitigated.

Topic: Observation & Monitoring, WP3.1

PI // Potsdam Institute for Climate Impact Research

Dr. Jessica Strefler

What is my general research focus?
My general research focus is the analysis of global transformation pathways using the integrated assessment model REMIND. I’m especially interested in carbon management, including carbon dioxide removal and carbon capture and usage and storage.

What is my specific contribution in RETAKE?
Integrated assessment models have so far focused on land and energy systems and excluded oceans. We will integrate ocean alkalinisation in the integrated assessment model REMIND. We will then use the model to analyse the possible contribution of ocean alkalinisation to the Paris climate target, and its interaction with land and energy systems.

What is my personal motivation for doing research within this topic?
Carbon dioxide removal is a crucial part of net-zero emission strategies. There are a number of different options discussed, which all have their risks and limitations. To reduce risks, a broad portfolio of options should be researched.

Topic: Sociological Aspects and Economics, WP1.1

PhD candidate // GEOMAR Helmholtz Centre for Ocean Research Kiel

Philipp Süßle

PhD candidate // Hamburg University

Niels Suitner

What is my general research focus?
Aquatic geochemistry with a focus on Ocean Alkalinity Enhancement. Main focus: Carbonate system, laboratory experiments on alkalinity generation and stability

What is my specific contribution in RETAKE?
Generation of alkalinity and marine alkalinity enhancement with reactors

What is my personal motivation for doing research within this topic?
To provide a practical contribution to the impact assessment and application of CDR methods.

Topic: Mechanisms, WP1.1

PhD candidate // GEOMAR Helmholtz Centre for Ocean Research Kiel

Juliane Katharina Tammen

Scientist // GEOMAR Helmholtz Centre for Ocean Research Kiel

Dr. Jan Taucher

What is my general research focus?
As a trained physicist, I have been involved in oceanography since my doctorate. Regionally, the focus is on the (North) Atlantic. One focus of my work is the evaluation of trace substance measurements such as CFCs. From these data, the oceanic uptake of CO₂ emissions can also be determined.

What is my specific contribution in RETAKE?
For RETAKE, I am investigating which regions of the open ocean (e.g. upwelling or deep water formation areas) are particularly well suited for alkalinity enhancement and the additional carbon dioxide uptake hoped for as a result. Furthermore, the magnitude of these effects will be determined and whether they are detectable at all with regard to the natural variations in the ocean.

What is my personal motivation for doing research within this topic?
The question which proportion of carbon dioxide emissions is absorbed by the ocean plays an important role in climate change and is therefore of great societal significance. If this share could be increased in an environmentally friendly way (possibly by alkalinity enhancement), climate change could even be mitigated.

Topic: Observation & Monitoring, WP3.1

PI // Helmholtz Centre Hereon

Prof. Dr. Helmuth Thomas

What is my general research focus?
My research focuses on the biogeochemistry of coastal seas and the Arctic Ocean. We couple observations of the marine carbonate system and oceanographic tracers to understand and quantify carbon and elemental transports in these regions.

What is my specific contribution in RETAKE?
My contribution to RETAKE focuses on the development of methods to detect and quantify a targeted increase in alkalinity against its highly variable background.

What is my personal motivation for doing research within this topic?
My motivation is to use basic biogeochemical findings, to prove the effectiveness of successful CDR methods and, on the other hand, to identify problems or non-effectiveness at an early stage.

Topic: Observation & Monitoring, WP2.1

Postdoc // Hamburg University

Dr. Maria-Elena Vorrath

What is my general research focus?
My research focus is the alkalinity increase of seawater under controlled conditions.

What is my specific contribution in RETAKE?
I test the dissolution properties of different materials in seawater using a reactor to find the best material.

What is my personal motivation for doing research within this topic?
In the face of the climate crisis, I want to do solution-oriented and application-based research.

Topic: Mechanisms, WP1.1

PI // Kiel University

Dr. Rüdiger Voss

What is my general research focus?
In 2002, I completed my doctorate in fisheries biology at the Christian-Albrechts-Universität zu Kiel. This was followed by 6 years as a PostDoc and project leader at the GEOMAR Research Centre. In 2008, I then moved to the interdisciplinary research group “Resource and Ecological Economics” at CAU, which was established within the Future Ocean Cluster of Excellence at the Institute of Economics. I am a specialist in bio-economic modelling and investigate trade-offs that can arise from different management decisions and quantify environmental impacts on the stock dynamics of marine fish. I am involved in the development and implementation of an ecosystem-based fisheries management of the Baltic Sea. Within this framework, I am working on improving multi-species bio-economic models, quantifying ecosystem services in the context of climate change and engaging non-scientific stakeholders.

What is my specific contribution in RETAKE?
In RETAKE, I contribute to work package 3.4 “Impacts on fisheries and food security”. I will be involved in the development of bio-economic models that investigate the potential effects of marine alkalinity enhancement, especially on fish stocks. Both, biological and economic factors play an important role in this.

What is my personal motivation for doing research within this topic?
I think that climate change is the greatest challenge of our time. As the father of a daughter, I want to help ensure that she and future generations have a planet worth living on. Somewhat less pathetic, I appreciate the opportunity to work together with many leading colleagues from Germany in an interdisciplinary way. In this context, communication across disciplinary boundaries is a very appealing (part of) the task!

Topic: Sociological Aspects and Economics, WP3.4

Postdoc // Helmholtz Centre Hereon

Dr. Tristan Zimmermann

What is my general research focus?
My main expertise lies in the field of trace-metal and non-traditional stable isotope (Zn, Sr, Nd, Pb) analysis, as well as analytical method development based in ICP-MS.

What is my specific contribution in RETAKE?
Within RETAKE I will evaluate the potential release of metals by alkalinity-enhancing minerals. Furthermore, analysis of metals and metal isotopes could be used as a proxy to trace artificial alkalinity enhancement.

What is my personal motivation for doing research within this topic?
I am very happy to share my expertise as an analytical chemist within RETAKE, because geoengineering methods like alkalinity enhancement may become of great importance for our (future) society.

Topic: Observation & Monitoring, WP2.1

Associate member // GEOMAR Helmholtz Centre for Ocean Research Kiel

Dr. Sandy Avrutin

What is my general research focus & what is my specific contribution in RETAKE?

My general research focus, and my specific contribution to RETAKE, is monitoring, reporting and verification for ocean alkalinity enhancement (specifically modelling to consider detectability, efficiency and impacts). I use the FOCI Earth system model for this.
As well as modelling, I am also interested in standards for ethical mCDR research and communication.

What is my personal motivation for doing research within this topic?

My personal motivation to conduct research in this field is a wish to promote effective and responsible use of mCDR. Although emissions reductions are first and foremost, CDR is a necessary part of maintaining warming in line with the Paris range of 1.5-2 degrees – but thorough research is vital to make sure that we implement in an effective, environmentally safe and societally acceptable way.

Associate member // Portuguese Institute for Sea and Atmosphere

Mafalda Freitas

Associate member & PI // Utrecht University

Assistant Prof. Dr. Sonja Geilert

What is my general research focus?
My research focuses on natural marine silicate weathering at continental margins and the deep sea and on enhanced silicate weathering as a carbon dioxide removal technique. I am using geochemical analyses including stable isotope measurements and modelling approaches to identify and quantify marine cation and CO₂ fluxes. Marine silicate weathering is an important process regarding global carbon cycling and might represent a unique way to mitigate climate change.

What is my specific contribution in RETAKE?
In RETAKE, I am coordinating work package 1.4 on alkalinity enhancement in the Baltic Sea. Together with my team, we are designing sediment incubation and benthocosm experiments to quantify the net alkalinity enhancement and CO₂ sequestration efficiency for olivine and carbonate minerals. Further, we will investigate the impact on microbial communities and macrofauna after addition of the alkaline minerals. Our overarching goal is to provide data on the efficiency of alkalinity enhancement in the Baltic Sea and give recommendations to political institutions.

What is my personal motivation for doing research within this topic?
My motivation is the urgent need to actively remove CO₂ from the atmosphere as reducing greenhouse gas emissions alone is not sufficient anymore to keep global warming below 2°C. Already today, the increasing number of worldwide natural disasters clearly shows the impact of climate change. We have to act now, in order to avoid reaching tipping points after which changes to the Earth system will be irreversible. With this project I can actively contribute to providing solutions mitigating climate change and communicate the risks of climate change but also the potentials of mitigating actions to a large community.

Topic: Mechanisms, WP1.4

Associate member // German Centre for Integrative Biodiversity Research

Dr. Patricia Grasse

Associate member // RWTH Aachen University

Prof. Dr. Thomas Matschei

Associate member // Bundesverband der Deutschen Kalkindustrie e.V.

Dr. Frank Ohnemüller

Associate member // Southern Cross University

Dr. Kai Schulz

Associate member // Bundesverband der Deutschen Kalkindustrie e.V.

Marlena Wissel

Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research

Prof. Dr. Jelle Bijma

GEOMAR Helmholtz Centre for Ocean Research Kiel

Isabel Diercks

GEOMAR Helmholtz Centre for Ocean Research Kiel

Dr. Mathias Haunost

Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research

Dr. Cara Nissen

Associate member // GEOMAR Helmholtz Centre for Ocean Research Kiel

Dr. Joachim Schönfeld

Kiel Institute for the World Economy

Sneha Thube