Kai Boggild

B.Sc. (Honours) Thesis

Morphological examination of the NP-28 submarine channel-fan complex in the Amundsen Basin, Arctic Ocean

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Submarine channels are common features along continental margins, yet relatively little is known about how these systems behave at polar latitudes. Emerging hypotheses concerning the influence of Coriolis effect on these systems predict that straighter geometries will dominate at high latitudes due to the increased Corio lis forcing of sediment-laden currents. This research examines the morphology of the NP-28 submarine channel in the Amundsen Basin and evaluates its form in the context of inertial and Corio lis forcing. At latitudes between 85° and 90° N, the NP-28 submarine channel is the northernmost modern submarine channel on Earth and offers a promising opportunity to test models of high latitude submarine channels. This study uses recently acquired multibeam bathymetry to provide the first plan-view constraints on channel path and high resolution subbottom profiler data to describe turbidite system elements at a finer vertical resolution than previously possible.

The NP-28 submarine channel is an example of a low-gradient, low-sinuosity channel, broadly fitting recently identified global trends in peak channel sinuosity relative to latitude. The modern geometry of the channel is likely to have been established by a combination of suspension and traction-dominated flow regimes resulting in the formation of external and confined levees. Subbottom profiler data further reveal the nature of these deposits, as well as other elements of the channel system including low-amplitude sediment waves, external levee sediments and a distributary channel on the lower fan surface.

Consistent right-dominant levee asymmetries of external levee deposits indicate that Corio lis forces dominate for suspension-dominated regimes. Rossby numbers calculated based on morphometrically estimated bankfull flow velocities are consistently low. The geometry of intrachannel deposits and thalweg incision, however, appears to be consistent with experimental models for both high latitude and equatorial channels, indicating that the relative influence of Coriolis forces to centrifugal forces may vary along the channel length for faster, tractiondominated flows in the NP-28 channel.

Keywords: Submarine channels; turbidity currents; Coriolis effect; Amundsen Basin; sinuosity
Pages: 44
Supervisor: David Mosher