ABRUPT Arctic Climate Change

At unprecedented resolution we investigate the nature of Dansgaard-Oeschger events in the Fram Strait, the gateway between the Nordic Seas and the Arctic Ocean. The new reconstructions of biomarkers and sea ice variability, stable isotopes and IRD will be seen in context of sea ice conditions, ocean hydrography and climate of the Nordic Seas as seen in multi-model output from three transient glacial GCM simulations (NorESM, CESM, MPI-ESM) and high-resolution reconstructions from an eastern Nordic Seas transect (from the Faeroe-Shetland Channel, via the Norwegian Sea to the Fram Strait). The combined results show that ocean-atmosphere-sea ice processes and dynamics during the transition from H4 to GI8 are strongly coupled. Both model results and reconstructions suggest subsurface ocean warming and polynya events in the southern- and northernmost Nordic Seas during the cold stadial. For a short time during the stadial to interstadial transition, a corridor of open water and hence sea ice-free conditions existed from the southern Nordic Seas all the way to the Fram Strait. The breakup of the sea ice cover is likely caused by the overshoot of AMOC during the transition and the associated enhanced ocean heat transport into the Nordic Seas. After the transition, winter sea ice grows back in the Fram Strait during the interstadial state, but the Southern Nordic Seas remain ice-free.