. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder . 100 km Figure 15-5. Distribution and density of ice gouging, direction of movement of pack ice, and limits of shorefast ice in northern Bering Sea (from Thor and Nelson 1979). the Yukon prodelta. Consequently, numerous zones of pressure ridges are formed. In this region, where the water is 10-20 m deep, the density of ice gouges is highest. Gouges are found in water to 30 m deep, and furrows are as much as 1 m deep. Ice gouging affects the sea floor under shorefast areas only minimally o
. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder . 100 km Figure 15-5. Distribution and density of ice gouging, direction of movement of pack ice, and limits of shorefast ice in northern Bering Sea (from Thor and Nelson 1979). the Yukon prodelta. Consequently, numerous zones of pressure ridges are formed. In this region, where the water is 10-20 m deep, the density of ice gouges is highest. Gouges are found in water to 30 m deep, and furrows are as much as 1 m deep. Ice gouging affects the sea floor under shorefast areas only minimally or not at all (Thor and Nelson, this vol- ume). Current scour depressions Zones of large flat-floored depressions in Norton Sound occur mainly in two areas: west of the Yukon prodelta and 50 km southeast of Nome on the flank of a broad shallow trough (Fig. 15-6) (Larsen et al. 1979a). These features range from individual more or less elliptical depressions 10-30 m in diameter to large areas with irregular margins, 80-150 m in diameter. The depressions are 60-80 cm deep (Larsen et al. 1979b). Bottom current speeds in depression areas are 20- 30 cm/sec under nonstorm conditions and were measured at 70 cm/sec during a typical autumn storm (Cacchione and Drake 1979a). Both zones of depres- sions are on flanks of gently sloping shoals, where strong tidal or geostrophic currents shear against the slopes. Small-scale ripple bedforms are associated with depression areas and mean grain size ranges from 4 to 0 ( mm). Depressions in the Yukon Delta area are aissociated with extensive ice gouging. The gouge furrows commonly expand into large shallow depressions (Larsen et al. 1979 and Thor and Nelson, this volume). Experiments in flumes containing fine sand and silt have shown that currents flowing over an obstruc- tion will scour material immediately downcurrent
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