. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering 38 Physical oceanography 166. 54' TEMPERATURE (C) BOTTOM ( Sep-Oct W^S __ 168" 166' Figure 4-4. Bottom temperature (°C), late September and early October 1976. Even in autumn, low temperatures persist in the bottom layer of the middle domain. domains, but since they have been called fronts (, by Iverson et al. 1980), we adopt this usage also. Proceeding seaward, we label these fronts as inner, middle, and shelf break (Fig. 4-1). The inner front separates
. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering 38 Physical oceanography 166. 54' TEMPERATURE (C) BOTTOM ( Sep-Oct W^S __ 168" 166' Figure 4-4. Bottom temperature (°C), late September and early October 1976. Even in autumn, low temperatures persist in the bottom layer of the middle domain. domains, but since they have been called fronts (, by Iverson et al. 1980), we adopt this usage also. Proceeding seaward, we label these fronts as inner, middle, and shelf break (Fig. 4-1). The inner front separates the homogeneous coastal domain from the two-layered middle domain. It was hinted at by Dodimead et al. (1963), and noted by Muench (1976) farther north. Schumacher et al. (1979) have called it a structural front, to stress the separation of two vertical structures or marked change of stratification rather than the sepairation of two water masses. The front is about 10 km wide and generally follows the 50 m isobath (Fig. 4-1). Approaching shallower water from the middle do- main, isotherms, isohalines, and isopycnals all spread from the thin thermocline, halocline, and pycnocline over the middle shelf (Fig. 4-6). Within 10 km the vertical hydrographic structure changes from dis- tinctly two-layered to neairly homogeneous. Away from the front, within the strongly stratified middle domain, the thickness of the bottom mixed layer (as judged by nearly isothermal and isohaline profiles) is nearly 50 m, about the same as the total water depth where the front is found. In general, we find that over the middle shelf the bottom mixed layer is ~50 m thick, the surface mixed layer is 15-20 m thick, and the front occurs where the water depth approx- imately equals the thickness of the bottom mixed layer (, 50 m); the strongest stratification occurs where the sum of the bottom and surface mixed layer thickness equals the water depth (, 20 m + 50 m = 70 m). During winter, the middle
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