During March 1979, hydrographic, meteorological and ice floe data were collected over the Bering Sea shelf. The ice pack extended to 59°N; however, there appeared to be little in situ freezing south of 62°N farther than 100 km from land. Hydrographic data from the southern margin of the ice (seaward limit) showed that a lens of less saline, colder water existed in the upper 20 m of the water column along the southern ice margin. During north-to-northeast wind events, floes were advected toward the south to southwest at rates as high as 0.5 m s–1 and rotted along the margin on the order of days. Little ridging of ice was observed over the open shelf. Rafting was prevalent among floes battered by wind and swell at the ice edge. Each year in the fall, northerly winds cool the water of Norton Sound and the Bering Sea north of St. Lawrence Island until the water column is isothermal and at freezing temperatures. Further cooling causes freezing. Under northerly wind conditions, ice is advected south into water where it is no longer in thermodynamic equilibrium. The resulting melt water is mechanically mixed and is a source of cooling for the waters of the southern Bering shelf. These observations suggest that ice characteristics in the Bering Sea can be described as a "conveyor belt": growth occurs primarily in the north, advection due to wind stress is generally southward; decay occurs at the thermodynamic limit; and the sea ice limit advances as meltwater cools the upper layer. |
