Simulating the evolution and impact of Fimbulisen basal channels in a coupled ice shelf -ocean model

<p>Small-scale basal features, such as channels and crevasses, are abundant on many ice shelves and play a role in determining spatial basal melt patterns, impacting on freshwater released to the Southern Ocean. &#160;These features may also, either directly or via basal melt patterns, impact on ice shelf stability and therefore also global sea level. However, simulating the effect of these features on basal melting at a hundred-meter scale or smaller is still challenging even for dedicated regional simulations, which typically ignore the small-scale features and instead smooth the ice draft. &#160;In this study, we simulate the effect of small-scale basal features on the Fimbulisen Ice Shelf (FIS) with the unstructured grid Finite-Volume Community Ocean Model (FVCOM), which allows refinement of model resolution in selected regions to resolve the small-scale features. Fine-resolution (8 m) basal topography of the FIS, retrieved from the Reference Elevation Model of Antarctica (REMA) data, reveals that the ice thickness of the Jutulstraum ice stream changes rapidly northwards from ~1500 m to ~ 600 m within 60 km of the grounding line. It also reveals that channelized basal features of several tens of kilometers traverse the ice base both along and across the ice stream, providing an intricate ice base topography. We set up a fine-scale FVCOM model of the FIS ice cavity to resolve the complicated basal topography, with grid resolution varying from 50 m in the focused region along the Jutulstraum ice stream to 1500 m in the open ocean. Sensitivity studies are performed, using the high-resolution ice draft from REMA as well as smoothed versions of it, to assess the effect of small-scale basal features on the cavity circulation and melt rates of the FIS. Ice shelf simulations, using Elmer/Ice, are carried out on the same refined mesh, to investigate the ice dynamic response to finely resolved ocean-induced melting. &#160;Finally, coupled Elmer/Ice - FVCOM simulations are carried out to investigate the coupled evolution of the channelised system. &#160;We aim to quantify the net basal mass balance contributions from small-scale basal features and finally to parameterize their effects in coarser ocean models.</p>