A novel approach to improving the reconstruction of bed elevation with special consideration of bathymetry at the ice/ocean interface of the Greenland ice sheet

Abstract:

Measurements of ice sheet basal topography provide vital boundary conditions for numerical modelling of ice sheet evolution and are key to understanding observations of ice-sheet dynamics. A consistent issue with existing bed topography products for the Greenland ice sheet (developed using ice thickness observations from ice penetrating radar, interpolation, and mass conservation) is the limited knowledge of bathymetric topography close to the coast of Greenland. Addressing this issue is important as glaciers local to these regions have been observed to have the largest velocities, greatest associated mass changes, and are therefore most sensitive to uncertainties in basal boundary conditions when modelling ice motion. Poor resolution at the edges of the contemporary ice sheet poses issues, particularly when integrating models over longer periods of time. Fjord bathymetry is known to provide a strong control on ocean circulation and ice/ocean forcing so improving data coverage in these regions is further a priority.

Channels are observable between existing maps of bathymetry and the glacier bed as derived from regions of dense point observations. Combined with information regarding former ice sheet extent, it is expected that many of these observed channels are likely continuous; however, limited observations along full channel length prevents resolving the continuous nature of these features using isotropic kriging techniques. Coupled with gravity inversion surveys of bathymetric elevation along flight lines, we have developed a refined vectorial interpolation approach using channel direction inferred from modelled velocities to condition an anisotropic kriging algorithm to resolve these finer topographic details. We present the results of the inclusion of three new data sets and application of our novel interpolation approach for bathymetry for a number of fjords and compare these results with previous versions of the Greenland bed digital elevation model.