PALICE - Palaeo Sea Ice and Climate Dynamics

The decline in sea ice is one of the most prominent features of climate change. Besides the discussions on the ecological effects of the ice-loss, a high focus is on the associated feedback mechanisms within the global climate system. Sea ice is not only highly responsive to climate change, it also has a strong impact on it. The major goal of the Helmholtz Young Investigator Group PALICE is to investigate changes in polar sea ice cover and associated shifts in oceanic and atmospheric circulation patterns during past climate fluctuations. Reliable and primarily quantitative indicators (proxies) to reconstruct sea ice conditions and ocean temperatures in the polar latitudes are, however, missing yet. The development of these urgently needed proxies and their systematic application for studying marine sediment cores from the Antarctic are a key aspect of our research. In close cooperation with the University of Bremen and the MARUM, these geological studies are accompanied by modelling approaches, which permit uncertainty estimates and hypothesis testing.

Lessons from the past...

With the start of remote sensing (satellite) observations in the 1970s, polar research benefited from a wealth of critical data on the recent development of sea ice coverage in the polar latitudes. For the assessment of how sea ice responded or even contributed to natural climate fluctuations in the geological past, we study marine sediment cores. Fossil organic molecules - so-called biomarkers - that are preserved in the several thousand year old sediment layers, reveal if and when the core site was covered with sea ice.

The main focus of our biomarker studies is on highly branched isoprenoids produced by marine diatoms, some of which live within the sea ice. With the melting of the ice, these diatoms sink towards the seafloor where their fragile silica frustules are often dissolved. The isoprenoids are more robust and may be preserved within the sediments for several thousand or even million years. In addition to the isoprenoids, we also look at other biomarkers to gain further information e.g. on the productivity of marine algae.