Atlantic deep water mass distribution since the Last Glacial Maximum
The last glacial maximum about 20 thousand years ago, and the following deglaciation and warm Holocene form the best and most precisely investigated time interval for palaeoclimate research. My primary goal is to further question and improve our understanding of the changes that occurred in this period in the oceans and the whole climate system. I am particularly interested in investigating this problem from different angles with different sedimentary proxies such as stable isotopes in foraminifera shells, the neodymium (Nd) isotope composition of authigenic precipitates, or the ratio of the two uranium-derived isotopes protactinium and thorium. Combining different proxies allows for more comprehensive and accurate conclusions and the evasion of biases that may occur if we only investigate one proxy at a time. Most of our established views of changes in the distribution of water masses in the deep ocean rely on nutrient-based proxies and, for example, Nd isotopes as an inorganic water mass provenance tracer can add a complementing different view to these studies.
Biological productivity, ocean circulation, and carbon storage in the Southern Ocean
The Southern Ocean connects all world oceans and hosts formation of the densest waters that fill the deep ocean basins. Active vertical mixing around its frontal systems leads to high primary productivity. Apart from its ecological importance, this productivity binds the greenhouse gas carbon dioxide from the atmosphere and exports it to the deep ocean via sinking organic particles, where it can be stored for hundreds and thousands of years. Therefore, the circulation and productivity of the Southern Ocean are an integral modulator of global climate. In this project I investigate both these processes with biogenic and non-biogenic proxies across the last glacial cycle.
Deep sea sediments as sinks and sources of dissolved trace metals
The oceans are full of trace metals that reside in the water column for different durations, depending on their chemical speciation and specific conditions of the seawater. Marine sediments are a major sink for most of them, leading to their long time storage and geological recycling. Thus, the distribution of these trace metals in the seawater-derived phase of sediments can yield information about the conditions of past seawater. For example, the speciation and thus reactivity and residence time of many trace metals depends on the seawater redox conditions, which are tightly linked to oxygen concentrations and can therefore serve as a proxy for past deep ocean oxygenation.