Seabed gouging by ice

Seabed gouging by ice is a process that occurs when floating ice features (typically icebergs and sea ice ridges) drift into shallower areas and their keel comes into contact with the seabed. As they keep drifting, they produce long, narrow furrows most often called gouges, or scours. This phenomenon is common in offshore environments where ice is known to exist. Although it also occurs in rivers and lakes, it appears to be better documented from oceans and sea expanses.

Seabed scours produced via this mechanism should not be confused with strudel scours. These result from spring run-off water flowing onto the surface of a given sea ice expanse, which eventually drains away through cracks, seal breathing holes, etc. The resulting turbulence is strong enough to carve a depression into the seabed. Seabed scouring by ice should also be distinguished from another scouring mechanism: the erosion of the sediments around a structure due to water currents, a well known issue in ocean engineering and river hydraulics – see bridge scour.

It appears Charles Darwin speculated in 1855 about the possibility that icebergs could gouge the seabed as they drifted across isobaths. Some discussion on the involvement of sea ice was brought up in the 1920s, but overall this phenomenon remained poorly studied by the scientific community up to the 1970s. At that time, ship-borne sidescan sonar surveys in the Canadian Beaufort Sea began to gather actual evidence of this mechanism. Seabed gouges were subsequently observed further north, in the Canadian Arctic Archipelago, and in the Russian Arctic as well. Throughout that decade, seabed gouging by ice was investigated extensively.

What sparked the sudden interest for this phenomenon was the discovery of oil near Alaska’s northern coastlines, and two related factors: 1) the prospect that oilfields could abound in these waters, and 2) a consideration that submarine pipelines would be involved in future production developments, as this appeared to be the most practical approach to bring this resource to the shore. Since then, means of protecting these structures against ice action became an important concern. An oil spill in this environment would be problematic in terms of detection and clean-up.

Scientists in fields of research other than offshore engineering have also addressed seabed gouging. For instance, biologists have linked regions of the seabed reshaped by seabed gouging by ice to the formation of black pools, seabed depressions filled with anoxic high-salinity water which are death traps for small marine organisms. However, much of it appears to have been documented from an offshore engineering perspective, for the purpose of oil exploration.

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Wikipedia