YEAR-TO-YEAR VARIATIONS IN BERING SEA-ICE COVER AND SOME CONSEQUENCESFOR FISH DISTRIBUTIONS

The southernmost extension of winter ice cover varies interannually an d on longer time scales, reflecting large-scale changes in driving for ces, especially in the position and intensity of the winter Aleutian L ow Pressure System. A conspicuous pattern is alternating warm and cool periods of several years' duration. These variations in sea ice cover are reflected in the character of a subsurface cold pool, formed as s tratification isolates the deeper cold waters from surface exchanges. The cold pool is better developed and more extensive in summers that f ollow deep southward penetration of winter sea ice. Interannual and de cadal-scale variations in the distributions of some fish stocks reflec t those of ice and thermal conditions. In particular, the distribution of walleye pollock, Theragra chalcogramma, varies significantly with multiannual cool and warm years while Arctic cod, Boreogadus saida, is only present within the cold pool. The relation among climate variati ons, sea ice cover, subsurface thermal conditions, and fish distributi on provides information on how climate affects marine ecosystems and m ay also have practical application in predicting fish distributions.