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Engels, J.L., 2004

New evidence for ice shelf flow across the Alaska and Beaufort margins, Arctic Ocean

Bibliographic Reference

Engels, J.L., 2004, New evidence for ice shelf flow across the Alaska and Beaufort margins, Arctic Ocean: University of Hawaii, Manoa, Ph.D. dissertation, 108 p.


The Arctic Ocean may act as a lynchpin for global climate change due to its unique physiography as a mediterranean sea located in polar latitudes. In our modern warming climate, debate over the bounds of natural versus anthropogenically-induced climate variability necessitates a comprehensive understanding of Arctic ice extent and configuration over the last interglacial cycle. Longstanding controversy exists as to the volume, timing, and flow trajectories of ice in the Arctic Ocean during glacial maxima when continental ice sheets mantled circum-arctic landmasses. As a result of the Science Ice Exercise surveys of the Arctic Ocean in 1999, new evidence for ice grounding at depths down to 980 m on the Lomonosov Ridge and 750 m on the Chukchi Borderland indicates the likelihood that large ice shelves flowed into the ocean from both the Barents/Kara Sea and the Canadian Arctic Archipelago or eastern Alaska. Sidescan imagery of about 14,100 km2 of seafloor along the Alaska and Beaufort margins in water depths from 250 to 2,800 m maps a repetitive association of recognizable sub-glacially generated bedforms, ice carved-bathymetry, and ice-marginal turbidite gullies over a 640 km stretch of the margin between Point Barrow and the MacKenzie River delta. Glaciogenic bedforms occur across the surface of a flattened bathymetric bench or 'second shelf break' that is interpreted to have been formed by an ice shelf eroding the continental slope. The glacial geology of surrounding areas suggests that an ice shelf on the Alaska and Beaufort margins likely flowed from the mouths of overdeepened glacial troughs in the Canadian Arctic Archipelago westward and across the Chukchi Borderland due to an obstruction in the central Canadian basin. Evidence for an ice shelf along the Alaska and Beaufort margins supports an expanded interpretation of ice volume and extent during Pleistocene glacial periods. This has far-reaching implications for Arctic climate studies, ocean circulation, sediment stratigraphy, and the stability of circum-arctic continental ice masses. This dissertation provides compelling evidence for the provenance of the most recent major ice shelf transgression into the Arctic basin, and these data are critical for reconstructing Pleistocene ice history throughout the region.

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