Past Polar Ocean Circulation and Carbon Cycling

Since the Ocean contains up to 60 times more carbon than the atmosphere, any change in ocean circulation and stratification affects oceanic-atmospheric gas exchange. Therefore, even small variations in the oceanic carbon budget may strongly affect atmospheric CO2 concentrations. Particularly, the Polar Oceans are considered to play the key role for the variability of atmospheric CO2-concentrations on glacial-interglacial and millennial time-scales. In the high northern and southern latitudes, atmosphere-ocean-interactions largely control ocean stratification, biological nutrient utilization, and upwelling rates of old deep-waters. In combination, these key processes control the oceanic uptake or release of CO2 especially across glacial terminations.
In this context, we investigat

  • Ocean stratification and carbon cycling
  • Nutrient utilisation
  • Mineral dust input changes and their role for iron fertilization

In order to assess nutrient utilisation, carbon cycling and circulation changes we apply both established (e.g. stable isotopes; 14C) and newly developed proxies (e.g. silicate isotopes in siliceous microfossils; B/Ca-analyses on benthic foraminifera). Our reconstructions of forcings and feedbacks of the Polar Oceans help to better understand the global carbon cycle and to improve ocean/climate system models.