The Eastern Bering Sea Shelf The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder . easternberingsea00hood Year: 1981 Ice as marine mammal hahllat 787 few barriers to movement. According to floe trajec- tories shown by Muench and Ahlnas (1976), ice in the vicinity of St. Lawrence Island could reach the southern limit of the pack in 30-45 days. The southern parts of the pack are subject to continuous melting and periodic disintegration because of warmer sea-surface temperatures and wave action. These forces produce two zones of variable width,
The Eastern Bering Sea Shelf The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder . easternberingsea00hood Year: 1981 Ice as marine mammal hahllat 787 few barriers to movement. According to floe trajec- tories shown by Muench and Ahlnas (1976), ice in the vicinity of St. Lawrence Island could reach the southern limit of the pack in 30-45 days. The southern parts of the pack are subject to continuous melting and periodic disintegration because of warmer sea-surface temperatures and wave action. These forces produce two zones of variable width, referred to as the fringe and the front. The fringe is the narrow, irregular southern margin of the pack, composed of tongues of wind-rafted, broken, melting ice, which directly receives the first impact of surface chop and waves from the open sea. The front is a broader zone, strongly affected by waves which, depending on conditions, are known to penetrate the pack as deeply as 133 km (Bums et al. 1980). It is the transition zone between the rapidly disintegrating fringe and the heavier, southward-drifting pack. The process of physical breakup caused by wave action is the major force affecting the size of floes in the front. The front can be considered a zone of dynamic equilibrium between regions sufficiently cold to produce and maintain ice and those where melt is rapid. As Muench and Ahlnas state (1976), under regional nearly steady conditions, like those existing mainly in March through April, the ice regime can be thought of as consisting of a northern source region, an intermediate region of southward ice advection, and a southern area of ice disintegration. During cold winters the northern source region extends considerably farther south, rapidly producing new ice in any openings formed in the drifting pack. The front is the beginning of the region of ice disinte- gration; the fringe represents the final stage of that process. The fringe and the front, during the stead
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