KomSO is a joint project of the marine research institutes AWI, GEOMAR, Hereon and IOW as well as the Federal Agency for Nature Conservation (BfN) and the non-governmental organisation Bund für Umwelt und Naturschutz Deutschland (BUND). The overall aim is to record and assess the carbon storage potential of marine sediments in the German Baltic Sea and to identify regions that are worthy of protection and suitable for restoration. Specifically, we want to combine measurements of the organic carbon content in the sediments and remineralisation rates with measurements of the sedimentation rate and the spatial distribution of the controlling environmental parameters in order to:

1. to quantify the content of organic carbon (OC) in the sediments of the Baltic Sea,
2. assess their OC accumulation rate and OC storage capacity,
3. parameterise OC sedimentation and remineralisation and extrapolate the rates in the Baltic Sea.

The ocean floor, which makes up 71% of the Earth’s solid surface, lies an average of 3,700 meters beneath the ocean surface. The difficulties related to accessibility necessitate ship expeditions and the use of highly specialized underwater equipment for its exploration. As yet, only a small fraction of the ocean floor has been scientifically investigated, but it is already known that this supposedly passive environment is an important interface with a wide range of functions that impact the entire Earth system. Geological, physical, biological and chemical processes interact at and within the ocean floor, thus influencing the climate system, the global carbon cycle, and biological productivity in the world ocean. We still know too little about ocean-floor processes to compile detailed global mass budgets.
The cluster aims to open a new chapter in ocean floor research and to quantify the exchange processes at this important interface and their role in the Earth system.
To achieve this, it is needed to:

1. decipher which processes control the transport of biogenic particles to the ocean floor and their transformation under changing environmental conditions,
2. balance the transfer of carbon and other elements between the ocean floor and seawater,
3. understand how ecosystems on the ocean floor react to environmental changes, and
4. develop scenarios for a "warmer world" from the climate archives of the ocean floor with the help of climate models.

These scientific tasks require novel technologies for observing and sampling the ocean floor, highly sensitive analytical methods and an expansion of numerical models. Due to their scientific and technological complexity, these goals can only be achieved through an interdisciplinary research network.
The cluster is based at the research faculty MARUM - Centre for Marine Environmental Sciences at the University of Bremen. With the cluster, the potential of ocean floor research can be strategically linked and utilised across all participating partner institutions. MARUM is one of around ten institutes in the world to have highly developed underwater vehicles and systems at its disposal, enabling it to access the ocean floor in the deep sea, collect data, take samples and carry out experiments. A globally unique range of analytical methods is available for their evaluation.

Within the cluster, employees from the Marine Geochemistry Section are involved in the following areas: 

• Receiver Theme 1: Transfer and transformation of sinking particles
• Receiver Theme 3: The transfer of matter and signals into the ocean floor
• Reactor Theme 1: Seawater-crust interactions
• Reactor Theme 2: Deep biosphere and element cycling in sediments
• Enabler Theme 3.4.5: Molecular and isotopic tracers (tracers)
• Enabler Theme 3.4.6: Ocean floor modeling framework (modeling) 

The international cooperation project called PAIGE (Chronologies for Polar Paleoclimate Archives - Italian-German Partnership) is funded by the Helmholtz Association and aims to strengthen joint research between the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) and the Italian Institute of Polar Sciences of the National Research Council of Italy (ISP-CNR). The main theme of the project revolves around the ambitious goal of linking chronologies for palaeoclimate archives from ice and sediment cores.

The Earth system is characterized by complex interactions whose dynamics and causalities are not fully understood. Feedbacks between different processes may cause the crossing of tipping-points leading to a new state of the climate system. This happened multiple times in the past and allows us to study the underlying processes.
The Helmholtz Young Investigator Group CLOC strives towards improving our understanding of these processes. Better dating methods are a key prerequisite in order to achieve this. Only they allow us to precisely compare different climate archives such as ice cores, sediments, tree-rings or speleothems which all hold pieces to the puzzle. CLOC investigates how we can use cosmogenic radionuclides such as ¹⁰Be, ¹⁴C, ³⁶Cl, ²⁶Al in order to synchronize different climate archives at high precision.

Manganese nodules cover large parts of the deep sea floor. Their structure, composition, growth rates and even parts of their microbiology are fairly well described. However, it is still unclear why they form. Two new findings now provide a new hypothesis with potentially far-reaching implications:
Firstly, the presence of a "deep biosphere" has recently been demonstrated that extends far into the Earth's crust. This life depends, at least in part, on the presence of tiny amounts of hydrogen.
Secondly, the outermost layer of manganese nodules has been shown to be extremely enriched in natural alpha emitters, which must produce significant amounts of hydrogen through radiolysis.
The project team is therefore investigating the hypothesis that manganese nodules are (symbiotic) life forms whose primary energy source is radioactive decay: radiotrophic life. This evidence would have far-reaching consequences for our understanding of the origins of life on Earth, for the prerequisites for extraterrestrial life and for Earth system science on long-term scales.
The aim is to prove the direct link between radioactivity and metabolism, which promises a deep insight into microbial metabolism in geological materials on the smallest scale.

In November 2023, a ten-week geochemical expedition (EASI-2 / PS140) on board the research vessel Polarstern will set off from Cape Town to East Antarctica. This is one of three coordinated Antarctic cruises that will work on independent but linked research topics (EASI-1-2-3). During this trip, water samples will be taken at regular intervals along two sections in the Indian sector of the Southern Ocean, as well as at a large number of stations in coastal waters on the East Antarctic shelf, using a trace metal-clean water sampler. The port of destination is Hobart (Tasmania), chief scientist will be co-applicant Dr. Marcus Gutjahr, and both applicants will take part on this scientific cruise. The scientific goal of this research proposal, which is to be realized as part of a two-year postdoctoral position, is the quantification of the input behavior of anthropogenic lead in the working area. In addition, we aim to explore how lead of anthropogenic origin enters Antarctic waters, where it mixes with naturally introduced dissolved lead. Anthropogenic lead in seawater can be easily distinguished from naturally introduced lead by significantly increased concentrations and a clearly distinguishable isotopic composition. Since the classic physical-oceanographic water parameters will also be measured during the trip, we can make clear statements as to where the dissolved lead in each examined body of water is derived from. Obtaining uncontaminated water samples for lead isotopic studies is very time-consuming and tedious, which requires the use of a special water sampler and work in clean room laboratories on the ship. This is the reason why there is almost no comparative data from the study area. The applicants were able to create the boundary conditions for this project through cooperation with scientists from the AWI Helmholtz Center for Polar and Marine Research, and the water samples obtained will be shared with international colleagues. A major focus will also be placed on the natural input behavior of dissolved lead via subglacial weathering below the Amery Ice Shelf in Prydz Bay (East Antarctica). These water samples will be compared with concentration and isotope data from sedimentary pore waters, which will also be obtained on the cruise. This part of the study will make it possible to depict the natural lead input and lead-specific exchange processes on the seabed and marine sediments. From this last aspect of the proposed project we hope to draw far-reaching conclusions for the interpretation of past hydrogenetic lead isotope data from sedimentary archives for paleo-climatic reconstructions.

The Transarc expeditions together with earlier Polarstern campaigns have yielded a unique time series of the chemical and physical properties of the Central Arctic Ocean (CAO). Only the observation of baselines, variability, and trends can provide solid evidence for change in biogeochemical and physical conditions, informing political decisions. This has inspired the concept of the Arcwatch expeditions. The SNAC-cluster now aims at providing a synoptic view of the changing CAO.
The “PaRaThA” project is based on the time-integrated information from the natural radiotracers ²³¹Pa and ²³⁰Th in the water column, which will be sampled during ArcWatch-2 (2024). These particle-reactive tracers are unique due to their precisely known production rate in seawater. Additionally, a newly developed method for high -precision ²²⁶Ra analysis promises now to trace prior contact with shelves. Combined with precise information on physical oceanography, these tracers quantitatively describe particle dynamics in a complex and rapidly changing current field. The power of the ²³⁰Th/²³¹Pa tracer pair has recently been demonstrated, finding  particulate removal by active hydrothermalism in the CAO, and revealing far-field effects from increased shelf inputs. Together with more tracers, we expect new insights and an update of the budgets of the CAO.

Global climate is critically sensitive to physical and biogeochemical dynamics in the Southern Ocean, where deep, carbon-rich layers of the world ocean outcrop and exchange carbon with the atmosphere (MacGilchrist et al. 2019). Here much of the anthropogenic carbon is taken up by the ocean, and glacial ocean carbon storage in the deep Southern Ocean is well established (Brovkin et al., 2012). Changes in Southern Ocean carbon uptake and its export to depth can thus strongly impact the global carbon cycle. The Southern Ocean’s role in anthropogenic carbon uptake has long been identified (Caldeira and Duffy, 2000), and it has been suspected, based on model simulations, that climate warming reduces its efficiency (Sarmiento et al., 1998; Le Quéré et al., 2007). However, more recently, the strength of this carbon sink has been described to have re-invigorated (Landschützer et al., 2015).

The distributions of deep ocean Δ¹⁴C data of dissolved inorganic carbon (DIC) is often used to illustrate the rate of deep ocean circulation, as radiocarbon is an invaluable tool to trace exchange processes in the carbon cycle and to estimate time in closed reservoirs. For instance, Δ¹⁴C of DIC can be used to map the uptake of atmospheric CO₂ into the ocean, or reflect input of aged carbon from the sea floor originating, e.g., from geologic sources. Despite its usefulness, high-resolution profiles of Δ¹⁴C of DIC in the water column are scarce, in particular for the Southern Ocean, and near the Antarctic continental margin, albeit the occurrence of deep-water formation at these locations. The current state of knowledge is based on a large international effort, the World Ocean Circulation Experiment conducted in the early 2000s.

The Laschamps event 42,000 years ago offers a natural analogue to nuclear bomb tests in the 20^th century: Due to the geomagnetic field minimum, large quantities of ¹⁴C were rapidly produced in the atmosphere and subsequently mixed into the reservoirs of the carbon cycle. This sudden isotopic disequilibrium between carbon cycle reservoirs offers a unique tracer experiment to study the state of the glacial carbon cycle. However, we are currently lacking detailed knowledge of Δ¹⁴C-changes during this period in the largest carbon cycle reservoir: The ocean.
In this project, we want to fill the gap of marine ¹⁴C-data and study the carbon exchange between atmosphere and ocean during the Laschamps event. New ¹⁴C-measurements on planktic and benthic foraminifera together with a compilation of existing data from different locations will be combined with recent updates of atmospheric Δ¹⁴C and independent ¹⁴C-production rate estimates. This will allow us to reconstruct changes in the ¹⁴C/¹²C disequilibrium between atmosphere, surface-, and deep ocean during the Laschamps event. Using carbon cycle models of different complexity, we will investigate the driving mechanisms to improve our understanding of the glacial carbon cycle and the accuracy of marine ¹⁴C-dating.

The Transpolar Drift transports nutrients, trace metals, and carbon from the Siberian shelves to the central Arctic Ocean. A GEOTRACES expedition in 2015 revealed that ice formed above shelf sediments provided the main source of trace elements and nutrients to the Central Arctic when the ice was transported via the Transpolar Drift. The bioavailability of the trace metals is not known and it is unclear how sea-ice derived nutrients and trace metals contribute to ocean productivity and carbon sequestration and what the role of different ice-types are. The continuous warming in the Arctic is predicted to increase ice-melt and freshwater inputs, which will further stratify Arctic waters, impacting upwelling of nutrient and trace metals from below the mixed layer, making the Transpolar Drift and nutrient release from ice formed on Siberian shelves even more important for primary productivity and carbon export. This project will study nutrient and trace metal release from different types of sea-ice during the GEOTRCES cruise ArcWatch-2. In situ ice-transport will be determined using back-tracking models and combined with export measurements using thorium radionuclides and sediment traps. Using natural phytoplankton incubation studies the influence of different types of ice-spiked with thorium on phytoplankton productivity and their export efficiency will be estimated. This will allow to identify phytoplankton responses to different ice types on productivity and aggregation and to link them to the observed in situ effects on carbon production and its export.

The development of high-resolution precise ¹⁴C-based sediment chronologies for high latitude marine sediment archives, in particular in ice-covered areas, is a prerequisite for studying paleoclimate records encoded in them, but remains a challenge. The main reasons are the lack of datable carbonate shells and the contribution of diverse sources to organic matter. Here we propose to introduce the innovative technique of ramped pyrolysis-oxidation to isolate organic fractions from the sediments that can be dated using radiocarbon. Next to providing much refined age constraints, the technique provides a more detailed characterization of the quality and reactivity of organic matter in sediments, allowing new insights into the high-latitude carbon cycle and thereby enabling better predictions of carbon cycle behaviour and its impact on climate.

The aim of this project is to identify major transport and reaction pathways of iron (Fe) from the South Georgia (SG) coast/shelf into the Southern Ocean (SO). We use SG as a model area to assess the role of (Sub)Antarctic coasts as Fe sources and their relevance for the biological car-bon pump in the surroundings. Potential sources like melt- and groundwater discharge as well as benthic fluxes will be studied during the dedicated PoF IV expedition PS133-2 “IslandImpact” using water (trace metal conc., Fe isotopes), sediment (reactive Fe, Fe isotopes) and pore water analyses. The PhD student will cooperate with scientists who apply oceanographic methods and radionuclides to identify/quantify freshwater discharges and export of matter. This is the first project combining work on different environmental compartments, namely sediment and water column, to trace Fe from source to sink (uptake/accumulation) using its isotopic “fingerprints”.

In order to obtain a holistic picture of past environmental changes, we must jointly interpret records from different parts of the Earth system. However, the current state-of-art of dating each record separately results in unacceptably large uncertainties and inconsistencies. Thus, a unified chronology for records from different archives is urgently needed. We aim to develop and apply the methodological framework needed to fuse stratigraphic information from different climatearchives and sites into one consistent chronology. We will use graph- or network-based Bayesian techniques combine absolute and relative age-information across published records in a flexible and extendable way. We will account for archive- and proxy-specific biases by including proxysystem-models directly into the age-modelling process. This will result in a consistently dated proxy-network allowing novel insights into the dynamics of past environmental changes.

Biological productivity in the Polar Southern Ocean (PSO) - like in all other oceans - depends on the availability of nutrients. While the main nutrients, such as nitrate, phosphorus or silicate, are highly abundant in the PSO, important micronutrients needed for the use of the main nutrients are lacking in large areas. Therefore, there are regions in PSO with varying levels of productivity. The regions with relatively high productivity appear to be linked to the availability of micronutrients such as iron and manganese. One example is the west side of the Antarctic Peninsula, where sediments can release these nutrients close to the sea surface. On the eastern side of the peninsula, in the Weddell Sea, enormous algal blooms occur in periodically ice-free areas, which indicate high productivity and characterise the local ecosystem. This productivity must be linked to a micronutrient source that has not yet been fully determined.
Preliminary data suggest that so-called marine ice, as known from "green icebergs" and found underneath the Filchner-Ronne Ice Sheet, contains up to a thousand times more iron and manganese than dissolved in the surface water of the Weddell Sea, and could therefore be considered as a source of deficient nutrients.

Marine ice is formed by a freezing process below the ice shelf edge, which is pushed from land to sea by glacier movement. The freezing process initially results from thawing of the ice shelf at the transition from the continent to the sea. As a result, the surrounding seawater becomes less saline and small ice flakes form at temperatures close to the freezing point. These platelets rise because of their lower density than the surrounding water, allowing particles to adhere to them, and then freeze as bubble-free marine ice below the ice shelf. This process takes place over hundreds of years, forming a marine ice layer up to 200 m thick.

At AWI we have access to two ice cores from the Filchner-Ronne ice shelf in the southern Weddell Sea, the lower parts of which consist of an approximately 60 or 165 m long sequence of marine ice. The wide geographical extent of the marine ice below the ice shelf is documented by seismic measurements.
Through geochemical investigation of these ice cores we will find out if marine ice represents a previously neglected nutrient source for productivity in the Weddell Sea and also in the whole PSO. For this purpose, dissolved trace metals, especially iron and manganese, but also many others, as well as the particulate composition in the ice will be analysed. Different analytical methods such as mass spectrometry, emission spectrometry and electron microscopy will be used. With the help of these methods, we will be able to show the previously unknown geochemical composition of marine ice, determine the origin of trace metal enrichment and evaluate its potential as an important nutrient source.

The Southern Ocean plays a critical role in the Earth system, both for the uptake of anthropogenic carbon and for the exchange of heat and nutrients between high and low latitudes. This is particularly valid for the Subantarctic Southern Ocean where atmosphere-ocean-cryosphere interactions and teleconnections between high and low latitudes play an important role in past and future climate change providing the major link between Antarctica and the low latitudes. In general, atmosphere-ocean interactions within the Southern Ocean are believed to control sea ice cover, upper ocean stratification, biological nutrient utilization, and exposure rates of CO₂-enriched deep water. Thus, they have been considered to play a key role in explaining the variability in atmospheric CO₂ concentrations, which are controlled by biogeochemical and physical processes. Beyond information from continental margin records, little is known on millennial-scale variability in the pelagic Southern Ocean.

High resolution sediment archives reaching back various glacial/interglacial cycles have not been explored so far. This includes the time span beyond the reach of the presently available ice-cores and will likely be critical for evaluating the extended time-interval of the planned European Beyond EPICA – oldest ice (BE-OI) ice core drilling initiative (drilling to ~1.5 million years). Our project focuses on high resolution paleoceanographic reconstructions (biomarker-based sea surface temperatures, biogenic opal, Antarctic Circumpolar Current strength, ice-rafted detritus) of upper ocean dynamics at Expedition 383 IODP Site 1539 in the subantarctic South Pacific in vicinity of the modern Subantarctic Front (SAF). This location is characterized by unusually high sedimentation-rates (~10-50 cm/kyr), mainly because Site U1539 is reached by the northerly extended opal belt during glacials with high diatom ooze deposition. This unique setting provides a high-resolution pelagic sediment archive in an area with strong oceanographic gradients (close to the SAF with strong dynamics of SST, ACC strength, and the influence of the opal belt). Therefore, high resolution records from IODP Expedition 383 Site U1539 could substantially enhance our understanding of sub-orbital climate variations and potential tipping points in the Southern Ocean and their link to the marine carbon cycle and Antarctic ice-sheet stability.