Observational Evidence for Oceanic Forcing of Atmospheric Variability in the Nordic Seas Area

Abstract

ubstantial predictability of the wintertime atmospheric variability in the Nordic (Greenland?Iceland?Norwegian and Barents) seas region is reported based on oceanic observations and atmospheric reanalysis data. In particular, about 60% of the variance of the winter (December?March) regional average surface air temperature (SAT) and early-winter (November?February) zonal geostrophic winds over the western Barents Sea Opening (BSO) area in the period 1982?2006 is explained by the previous summer (June?September) Atlantic water temperature (AWT) anomalies in this area. The atmospheric response to oceanic heat anomalies mainly occurs in the marginal ice zone (MIZ), where the sea ice and corresponding surface heat flux (SHF) anomalies should be triggered by entrainment of subsurface heat anomalies into the deepening mixed layer and sustained through winter by anomalous oceanic heat transport. The latter should be caused by geostrophic current anomalies forced by anomalous ocean Ekman suction and/or onshore Ekman transport appearing as a feedback from the oceanically driven anomalous atmospheric circulation. The wintertime atmospheric links to the previous summer?s AWT anomalies in the BSO area reflect to a large extent a climate feedback from reemerging, atmospherically driven sea surface temperature (SST) anomalies. Indeed, about 70% of the variance of the winter average SAT over the Nordic seas and winter average surface wind vorticity in the MIZ area in the 1982?2006 (or extended 1982?2011) period is explained by the previous early-spring (February?May) SST anomalies in the open water area and the previous late-winter (January?April) SHF anomalies at the Barents Sea ice edge, respectively.