Interannual Variations of Sea-ice Extent in the Okhotsk Sea – A Pan-Okhotsk Climate System Perspective

ABSTRACT This study investigated interannual variations in the late winter (January–March) sea-ice extent in the Okhotsk Sea (OS) and its relationship with the atmospheric circulation from 1971 to 2018. During heavy sea-ice years, negative air temperature anomalies are broadly discernable between the northeastern part of Eurasia and the North Pacific including the coastal polynyas adjacent to the northern and western coast of the OS. Cold air mass (CAM) genesis indicates the importance of the insulation effect of sea-ice in the persistent cold air temperatures in the OS. Light sea-ice years are marked by anomalous southeasterly winds and the resultant warm air advection associated with increases in extratropical cyclones. Southeasterly anomalies are associated with the weakening of the Aleutian low. Upper-tropospheric anticyclones dominating around the OS are closely connected with intensified convection in the vicinity of the South China Sea through propagation of a stationary Rossby wave relevant to La Niña-like warm sea surface temperature anomalies. The seasonal evolution of the CAM amount, sea ice in the Sea of Okhotsk, and the Aleutian low suggest that there may be chain feedback between them.