Modeling the Arctic sea-ice cover from the early Holocene

Paleo-evidence suggests that the mean state of the atmosphere in the early Holocene resembles the positive phase of the modern North Atlantic/Arctic Oscillation (NAO). To test this theory we use a coupled ice-ocean model to study the effects of atmospheric and ocean forcing from the positive phase of the NAO and altered surface radiation on sea-ice concentration and thickness in the Arctic during the early Holocene. The resulting sea-ice concentrations are compatible with reconstructions based on dinofagellate cysts assemblages. Sensitivity studies show that local winds dominate the changes in sea-ice concentration from the East Siberian Sea, whereas ocean currents and sea surface and air temperatures all contribute significantly to anomalous sea ice concentrations in the Barents Sea. Patterns in sea-ice thickness anomalies show similar results but are spread out over larger areas. The net radiation is shown to have little effect on the Arctic sea-ice cover during the early Holocene.