Co-evolution of tidewater glacier calving front morphology and submarine melt rates in a high resolution ocean model

Abstract:

Rapid dynamic changes at the margins of the Greenland Ice Sheet, synchronous with ocean warming, have raised concern that tidewater glaciers can respond rapidly and sensitively to ocean forcing. One way in which ocean forcing would manifest is through the melting of the submerged parts of tidewater glacier calving fronts, with the spatial distribution of submarine melt a control on their morphology. Calving front morphology has thus far received little attention and yet has the potential to significantly impact calving rates and therefore tidewater glacier dynamics.

Here we present a model which allows us to study the evolution of calving front morphology in two dimensions. We outline a new routine for calculating submarine melt rates from ocean models at calving fronts of arbitrary geometry, and for adjusting this geometry according to the calculated melt rates. This routine is applied to a high resolution (~1m) non-hydrostatic ocean model (MITgcm) with a glacier boundary (calving front) which evolves in time according to the simulated submarine melt rates.

The model shows, consistent with recent observations, that submarine melting leads to undercutting of tidewater glacier calving fronts. We examine how undercut magnitude, undercut depth and potential steady states respond to variation in subglacial discharge, ice velocity, and fjord depth, temperature and stratification. In addition to this analysis we use a diagnostic full-Stokes flow-line ice model to examine how these geometries affect ice internal stress and potential for calving. In undertaking this work we aim to elucidate a process which - supposing tidewater glaciers are sensitive to ocean forcing - must provide a fundamental link between the ocean and the ice.