Transcript for Drift Ice as a Geologic Agent, segment 03 of 11


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First, consider the effects of river discharge into an ice-covered ocean where ice plays a passive role. Spring bursts of Arctic rivers yearly inundate the two-meter thick smooth, fast ice which extends from land. This closeup was taken several kilometers out on the ocean. The waters flood vast regions, reaching their maximum extent within a few days. Such regions are shown as black plumes on the fast ice in this satellite photo of several of northern Alaska's major river drainage systems. For a week, the submerged fast ice can be crossed by waiting or by power boats. The weight of the floodwater initially deflects the floating ice sheet downward. However, the buoyant force of the submerged ice then draws river water down through holes and cracks in swirling vortices called strudel.

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Strudel flow scours craters up to seven meters deep in the seabed.

After the floodwaters drain, the spouts in the ice are evident from the air, and strudel scour craters are visible in fathograms. Surprisingly, no levies are found surrounding the craters, suggesting that sediment is dispersed by subice turbulence and flow.