Weather Climate and Sea

In winter, the Bering Sea weather is largely determined by the Siberian High (anticyclonic high-pressure atmospheric system) and the Aleutian Low (cyclonic low-pressure system). The combined influence of both systems results in persistent strong winds from the north, 7-12 m s-1 in the mean. Frequent outbreaks of cold Arctic air make the Bering Sea one of the most hazardous seas, with a maximum observed wave height of 21 m. The absolute temperature minimum over the Bering Sea varies from -15°C (5°F) in the south down to -40°C (-40°F) in the north. In summer, the Siberian High weakens and shifts to the west, while the Aleutian Low almost disappears, whereas the North Pacific High strengthens and advances northward, resulting in persistent southern winds, 4-7 m s-1 on average. The Bering Sea notorious fog is most frequent in June-July.

The Bering Sea is partly ice-covered in winter and is ice-free in summer. Sea ice formation begins in late October in the northern Bering Sea, advances southward and accelerates in December-January, especially along the Siberian and Alaskan coasts. The sea ice cover is at a maximum in March-April, when it reaches the southern tip of Kamchatka. The sea becomes ice-free in June-July. Recurring polynyas are observed in the eastern Bering Sea north and south of large islands (Nunivak, St Lawrence, and St Matthew) and also south of Chukchi Peninsula (in Anadyr Gulf), southwest of Seward Peninsula, and north and south of Yukon Delta. The extent of the seasonal ice cover experiences significant interannual and decadal fluctuations. For example, over the Eastern Bering Sea Shelf the interannual range of the maximum ice extent exceeds 300 km in the north-south direction.

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