Author(s): Erk Reimnitz; P. W. Barnes; R. L. Phillips
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Abstract: Ice gouge patterns on the Alaskan Beaufort Sea shelf extend from the coast seaward to water depths of at least 64 m. The maximum measured draft of sea ice in the Arctic Ocean, however, is only 47 m. Thus the numerous gouges seaward of the 47 m isobath might be relict, cut during times of lower sea level many thousand years ago. Sedimentation rates along the shelf break are very low, and a rain of particles settling vertically in a quiet environment on these bedforms would not obliterate them soon. Several lines of evidence suggest, however, that these deep-water gouges are modern features. Continuous, 380-day current records at 60 m depth near the shelf edge show that the environment is dynamic, with long-period current pulses up to 70 cm sec-1 capable of transporting medium to coarse sand as bedload and fine sand in intermittent suspension. A rich benthic fauna also reworks the upper 20 cm of sediment and provides sedimentary particles for current transport. The water depth along the seaward limit of the ice-gouged shelf surface, if of relict origin, should shoal eastward in the region where isostatic rebound after deglaciation occurred. The deep limit of gouges instead varies irregularly between 49 and 64 m water depth along the shelf edge, as one would expect from an interaction of sporadic ice reworking to 64 m depth during the last 200 years and continuous reworking by currents and organisms. For offshore petroleum development, this interpretation has the important implications that bottom-founded structures at >47 m water depth may not be safe from ice impact.
Year: 1984