Transcript for Drift Ice as a Geologic Agent, segment 02 of 11


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Floating ice exists year-round or forms at least seasonally off many thousands of kilometers of high latitude coastlines. In spite of this fact, the various geologic processes related to ice in either sea water or in fresh water are largely unknown. In the Arctic shorelines recede at rates as high as ten meters each year. This has been puzzling because Arctic shorelines are armored against erosion for nine months each year by sea ice which covers the entire ocean. Even during short summers, drifting ice remnants calm the ocean offshore and linger in the coastal zone, greatly reducing surf action. These facts have supported the idea that ice protects polar coasts from erosion. While this may be true for beaches themselves during part of the year, studies of coastal retreat by the U. S. Geological Survey suggest that ice may actually be the primary cause of coastal erosion in the Arctic.

In this diagram we assume that modern coastal retreat rates have been sustained for one thousand years, continually removing materials not only above sea level but from several tens of meters below. Estimated wave energy in the Arctic is totally inadequate to remove these materials, suggesting that some other mechanism is eroding and transporting Arctic coastal sediments. Ice is that mechanism. It plays a major role in polar sediment dynamics by resuspending, incorporating, and moving material. Due to harsh conditions, these processes have been shunned by researchers and remain extremely difficult to quantify.

This videotape describes mechanisms and processes of ice-related sediment movement, including river flooding of fast ice, drifting ice, ice gouging, ice wallow, frazil and slush ice, sediment entrainment and ice rafting, and turbid ice. These phenomena extend beyond the Arctic, affecting regions where ice forms on both saltwater and freshwater coastlines around the Earth.