9 May

Numerical simulations of the ice flow dynamics of the Brunt Ice Shelf – Stancomb Wills Ice Tongue System

first_imgIce shelves play an important role in determining regional ocean properties and in modulating ice flux fromland to sea. Their dynamics are complex, however, and localised rifts and zones of weakness can have asignificant but poorly understood effect on flow and ultimately on the integrity of the shelf.The Brunt Ice Shelf (BIS)- Stancomb Wills Ice Tongue (SWIT) System, situated on the Caird Coast, OatesLand, Antarctica, is characterised as a thin, unbounded ice shelf with a highly heterogeneous structure. Incontrast to most ice shelves, icebergs calve along much of the grounding line but are trapped and subsequentlybound together by sea ice. This calf-ice / sea-ice aggregate makes up a large part of the Brunt Ice Shelf inparticular, and this heterogeneity makes the BIS-SWIT a good test case for investigating the importance ofweak zones in shelf dynamics.We applied a diagnostic, dynamic/thermodynamic ice-shelf model to simulate the present flow of the iceshelf that results from the ice-thickness distribution, the influx at the grounding line and the surface andbottom temperature. We then compared the model results with flow velocities measured by SyntheticAperture Radar feature tracking. We found that our simulations were clearly improved by the use of ahigh- resolution ice thickness distribution on the heterogeneous ice shelf calculated from ICESat surfaceelevation data using an assumption of hydrostatic equilibrium. We then assessed the model’s sensitivity toice thickness, inflow velocities and a flow enhancement factor that parameterises the role of sea ice, whosemechanical properties are known to be significantly different from those of meteoric ice.We found that the numerical simulations were improved by incorporating the detailed variations in shelfstructure. Simulated flow velocities on either side of rifts in the ice shelf became decoupled as we softenedthe sea ice within the rifts. On a larger scale, we found that soft sea ice can lead to a decoupling of themovement of the Stancomb-Wills Ice Tongue and the Brunt Ice Shelf. When we simulated a regime wheresea ice was absent, ice shelf flow speeds increased along the western edge of the SWIT ice front, in generalagreement with observations made in just such a sea- ice-free dynamic regime that occurred inlast_img

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