Talk by Henrik Sadatzki @CIC- RF 235
Northern sea ice variability during Dansgaard-Oeschger climate cycles
Changes in sea ice cover in the Nordic Seas likely played a crucial role in amplifying ocean circulation and climate changes of the Dansgaard-Oeschger (D-O) cycles during the last glacial. We investigate the role of sea ice for abrupt Greenland climate changes, using a high-resolution sea ice record from Norwegian Sea core MD99-2284 covering four D-O cycles at 32–40 ka. The sea ice reconstruction is based on abundances of the sea ice diatom biomarker IP25 and the open-water phytoplankton biomarker dinosterol, as well as on semi-quantitative phytoplankton-IP25 (PIP25) sea ice estimates. Our biomarker records indicate that the Norwegian Sea was characterized by a near-perennial sea ice cover during cold stadials and enhanced open-ocean conditions during warmer interstadials. Moreover, we find that initiation of sea ice retreat systematically preceded the onset of major deep-water formation in the Nordic Seas and probably the abrupt D-O warming in Greenland. We thus conclude that the glacial sea ice variability acted as precursor and feedback mechanism for abrupt ocean circulation and Greenland climate change during D-O cycles.