Relationship between the decrease of sea ice and early summer atmospheric circulation in and around the Sea of Okhotsk

Abstract

The variability in sea ice extent in the Sea of Okhotsk during the sea ice disappearance period and its response to the atmospheric circulation in early summer are investigated. Significant correlations were found between the disappearance in sea ice in May and the geopotential heights in and around the northern part of the Sea of Okhotsk in June. A disappearance in sea ice is defined as the difference in the sea ice area between the end of the current month and the end of the previous month. Thus, large sea ice disappearance years and small disappearance years are selected from a time series of sea ice disappearance for the month of May. Composite maps of the geopotential heights in the northern part of East Asia are investigated annually. In small sea ice disappearance years, anticyclones and ridges of the geopotential heights are prominent in and around the Sea of Okhotsk in June. Conversely in large sea ice disappearance years, surface cyclones and troughs are dominant in and around the Sea of Okhotsk. A strengthening of the Okhotsk anticyclone is presumed to be related to variability in the decrease in sea ice in the Sea of Okhotsk.