. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering Figure 14-13. Overhead sequential photographs of an oil spill in grease ice. be released at the ice edge in the 10-20 km zone of floes agitated by ocean swell. In the first situation, Martin et al. (1978) show that pancake ice develops from grease ice, and thus also occurs in the lee-shore polynyas; in the second, Martin and Bauer (this volume) discuss ice-edge floes agitated by ocean swell. For oil entrainment, it is important in both situa- tions that (1) the f
. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering Figure 14-13. Overhead sequential photographs of an oil spill in grease ice. be released at the ice edge in the 10-20 km zone of floes agitated by ocean swell. In the first situation, Martin et al. (1978) show that pancake ice develops from grease ice, and thus also occurs in the lee-shore polynyas; in the second, Martin and Bauer (this volume) discuss ice-edge floes agitated by ocean swell. For oil entrainment, it is important in both situa- tions that (1) the floes and cakes exist as separate units with either open water or water and grease ice around them; (2) the incident swell or wind waves cause the floes to oscillate back and forth so that crude oil can be pumped onto their surfaces. For example, in the chapter about the ice edge by Martin and Bauer (this volume), Figs. 12-lOa, 12-lOb, 12- 11a, and 12-1 lb show ice floes which have been broken by the incident swell, are oscillating in this swell, and have wetted edges caused by the pumping of seawater onto the floe surfaces. Martin et al. (1978) show that pancake ice forms when grease ice becomes so thick that the circulation within the ice is suppressed; the surface then freezes into chunks of pancake ice floating over a layer of grease ice. In the field, the pancakes form downwind of the regions of grease-ice formation. On 19 March 1978, we surveyed the ice over a region stretching from Cape Thompson in Kotzebue Sound 90 km south. Within this region, we found an area of at least 100 km^ covered with pancakes about m in diameter. Fig. 14-15a shows the rough surface ap- pearance caused by rafted pancakes on the site at 67° 'N, 166° 'W, and Fig. 14-15b shows a close-up photograph of the pancakes on the surface. When we cored through the pancakes, we found that they were about 100 mm thick, over a layer of frozen grease ice 285 mm thick, so that the original grease i
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