Paleo-biogeochemistry

The Paleo-biogeochemistry group is interested in how the carbon and the nitrogen cycles operated in the past, how they are coupled to each other and how they are linked to past climatic changes. Our primary research tool are climate models of different complexity. At the moment, we investigate changes in the marine carbon cycle on glacial-interglacial time scales with a focus on processes in the Southern Ocean and in the North Pacific with the aim to link constraints from marine isotope and ice core records with model results. Further emphasis is on N₂ fixation and denitrification and how past variations in these two processes altered the oceanic nitrogen pool, and hence oceanic productivity, as well as contributed to past atmospheric N₂O variations.

A couple of key paleo-records for our research are shown in the figure below.

Fig.: Compilation of key paleo-records over the last 75,000 years measured along polar ice cores and a marine sediment core from the Arabian Sea together with recent atmospheric measurements of CO₂ and N₂O. Shown are Greenland (black) and Antarctic (dark blue) temperature proxy records, atmospheric CO₂ (orange) and N₂O concentrations (red), and δ¹⁵N of organic nitrogen (cyan), a proxy for marine denitrification, measured along a sediment core from the Arabian Sea. The figure was adapted from Gruber and Galloway [2008].