The world’s oceans play an important role for the global carbon cycle: They do not only constitute a large carbon reservoir, but also control the redistribution of carbon on global and regional scales by carbon pumping. Connected to this is the exchange of CO2 between ocean and atmosphere. Accordingly, the ocean carbon cycle is both influenced by changes in the climate system and influencing it.
The aim of this PhD project is to unravel determinations of the carbonate production of planktonic foraminifera in the Arctic and Subarctic Ocean. Planktonic foraminifera, marine protists building up calcite shells, are major contributors to carbonate fluxes. Those lead to transport of inorganic carbon from surface to bottom waters in the ocean. On a global scale, planktonic foraminifera can represent more than 50% of the total inorganic CaCO3 flux in the oceans. On regional scales, both the magnitude of carbonate fluxes and the proportion of planktonic foraminifera in there varies. In the Arctic Ocean, peaks in fluxes are present during summer, when increasing insolation is enhancing primary production. By examination of counts and weights of planktonic foraminifera in existing data sets representing several areas of the Arctic and Subarctic Ocean, recent carbonate fluxes will be quantified and analysed. Gaining an overview on the whole Arctic Ocean is targeted.
The amount of carbonate that is finally stored in ocean sediments is not equal to the magnitude of carbonate fluxes due to dissolution. Therefore, in a further step, this research projects intends to contrast calculated planktonic foraminifera carbonate fluxes with the inorganic carbon content in the upper part of ocean sediments. By this, the rate of dissolution and processes connected to it shall be detected. This is needed to estimate the intensity of carbon burial in the ocean and its effect on the carbon cycle.
Subsequently, the research will focus on future changes in the Arctic Ocean and its basin. Previous studies have projected strong ocean acidification in the Arctic Ocean, which will affect the formation of calcite of planktonic species. Still, it remains an unresolved question how the total magnitude of carbonate fluxes and the amount of stored carbon in the sediments will change in the future. This research project aims to evaluate the effect of climate change on planktonic foraminifera carbonate fluxes and the storage of carbon in the Arctic Ocean basin, which is highly relevant for the total ocean carbon cycle.
