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Investigating heinrich events : a continuum model of iceberg drift and sedimentation La Prairie, Douglas I.

Abstract

Records from the North Atlantic reveal high deposition rates of ice-rafted sediments from the Laurentide ice sheet during at least six distinct periods. Known as Heinrich events, these episodes of rapid deposition are attributed to massive iceberg calving promoted by unstable behavior of the ice sheet. The exact mechanisms causing these occurrences of high iceberg flux are not well understood. As a means of elucidating and exploring the freshwater and sediment fluxes associated with Heinrich events, a computer model has been developed which attempts to simulate iceberg drift during these periods of massive calving. This enables reconstruction of the marine sedimentation pattern and provenance-labeled marine core stratigraphy. Using finite-difference methods over a discretized problem domain, the model treats the armada of icebergs as a continuum rather than tracking an ensemble of perhaps thousands of individual trajectories. In this manner the drift of the model icebergs in a multi-layer ocean is governed by advective, diffusive and Coriolis forces as well as being subject to melting. The stochastic nature of iceberg drift is dealt with using a tensorial diffusion coefficient to approximate the effects of heterogeneity, such as different shapes, which strongly influence iceberg drift.

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