Northern High-Latitude Climate Changes During the Holocene as Simulated by Circulation Models

To simulate the evolution of Holocene climate, forcing factors for the northern high-latitude climate are examined using different numerical models. A global coupled atmosphere–ocean circulation model driven by astronomical forcing over the last 7,000 years shows a long-term sea-surface temperature decrease in the Nordic Seas region associated with changes in seasonal insolation. A continuous cooling in the northeastern Atlantic is accompanied by a persistent warming in the Labrador Sea from the midto late Holocene. This temperature pattern can be attributed to a progressive weakening of the Icelandic Low and altered winds over the Nordic Seas induced by changes in insolation. In the early Holocene, important forcing for the Nordic Seas in the early Holocene was probably caused by melting land ice masses and “deepening” of the Bering Strait. The effects of meltwater discharge and Bering Strait inflow are studied in a regional model of the Arctic and North Atlantic Oceans. It is suggested that a gradual increase in the flux of Pacific water through the Bering Strait during the early Holocene slowly affected the polar climate by melting ice and causing ocean circulation changes in the Nordic Seas. This high-latitude response to sea level change is shown to be different from the signature obtained by a freshwater release linked to the final outburst drainage of Laurentide lakes.