Formation of contrasting March surface air temperature trends in the eastern Bering Sea and the Sea of Okhotsk during 1979–2015

Abstract

An opposite trend in surface air temperature is observed with centers over the eastern Bering Sea (decreasing trend) and the Sea of Okhotsk (increasing trend) during 1979–2015. The present study analyzes the reasons for the formation of the contrasting surface air temperature trends in the above two regions. Analysis shows that downward longwave radiation and anomalous meridional advection are two major terms for surface air temperature trends in the above regions. The surface turbulent heat flux trends are results of surface air temperature trends. The cooling trend over the eastern Bering Sea is related to the cloud cover decreasing trend and northerly wind trend. The former reduces downward longwave radiation, and the latter leads to anomalous cold advection. The warming trend over the Sea of Okhotsk is associated with the cloud cover increase that leads to downward longwave radiation increase and the southerly wind trend that induces anomalous warm advection. The cloud changes are related to anticyclonic wind changes over the northern North Pacific. The surface air temperature increasing trends appear to contribute to the sea ice decreasing trends in the Sea of Okhotsk. The present analysis suggests an important role of atmospheric circulation changes in the formation of opposite March surface air temperature trends over the eastern Bering Sea and the Sea of Okhotsk.