Global ocean response to orbital forcing in the Holocene

Abstract

Global upper ocean evolution in the Holocene is studied in two coupled ocean-atmosphere models under orbital forcing conditions at 3, 6, 8, and 11 ka. The annual mean sea surface temperature (SST) changes in the early to mid-Holocene are found to be forced mainly by the annual mean insolation forcing with an overall symmetric response of colder equator (<0.5°C)/warmer high latitudes (<0.4°C in the Southern Ocean and >1°C in the Arctic). This SST change is consistent with a synthesis of mid-Holocene paleo-SST records. In contrast, the temperature response in the thermocline is dominated by an antisymmetric pattern with a cooling (warming) in the Northern (Southern Hemisphere midlatitudes. The thermocline response is determined predominantly by surface water subduction, and ultimately, the insolation forcing in local late winter.