A global coupled atmosphere-ocean circulation model is driven by astronomical forcing in order to simulate the Holocene climate. In the Nordic Seas region, we find a long-term climate sea surface temperature decrease associated with changes in seasonal sunlight distribution. In the North Atlantic realm, a continuous cooling in the northeastern Atlantic was accompanied by a persistent warming in the Labrador Sea from the middle to the late Holocene. This temperature pattern during the Holocene can be attributed to a continuous weakening of the Icelandic Low and altered winds in the Nordic Seas. Part of the shift in the Northern Hemisphere atmospheric circulation is characterized by a tendency towards a negative phase of the Arctic Oscillation/North Atlantic Oscillation pattern. In contrast to the middle to late Holocene, where the insolation provides a crucial forcing for northern high latitudes, the strongest forcing for the Nordic Seas region in the early Holocene was probably caused by melting ice masses and a shallower Bering Strait. The effects of freshwater discharge and Bering Strait inflow are studied in a regional model of the Arctic and North Atlantic Ocean. It is suggested that a gradual increase in the influx of Pacific water through Bering Strait during the early Holocene slowly affected the polar climate by melting ice and causing circulation changes in the Nordic Seas.
Helmholtz Research Programs > MARCOPOLI (2004-2008) > MAR2-Palaeo Climate Mechanisms and Variability