9321457 MacAyeal This award is for support for a project to conduct a finite-element modeling study of the mechanism for Heinrich Events (brief, but violent episodes of iceberg disgorgement from the Laurentide Ice Sheet occuring approximately every 7000 years). The research assumes that Heinrich events were caused by free-oscillations in the flow of the Laurentide ice sheet ("binge/purge" oscillator theory) which arose because the floor of Hudson Bay and Hudson Strait is covered with soft, unconsolidated sediment that forms a slippery lubricant when thawed. The modeling work will be novel in the sense that two separate finite-element grids, each designed to optimize computational performance under the restrictions of diverse ice flow mechanisms, will be used to asynchronously advance the ice thickness distribution (and other fields) of the Laurentide ice sheet through time. The outcome of the proposed research will include: 1) a verification of the binge/purge oscillator theory of Heinrich Events through comparison of model output with the geologic record, 2) estimation of the ice-rafted debris flux associated with various methods of basal debris entrainment, and 3) determination of the pre- and post-Heinrich Event ice topographies for use in atmospheric circulation models. ***
