Petermann Glacier Ice Shelf in a warming world : Insights from 3-D numerical modelling of ice shelf-ocean interactions at Petermann Fjord, Northwest Greenland

The Greenland Ice Sheet (GrIS) is currently the largest contributor to global mean sea level rise, and contemporary mass loss rates are likely lower bounds for the rates to be observed in decades to come. At present, marine outlet glaciers along the northern GrIS margin, with an ice volume estimated at 400 cm mean global sea level rise equivalent, are still largely buttressed by ice shelves. However, thinning and retreat of these ice shelves, combined with perturbations of the outlet glacier’s grounding line (GL) can lead to a loss of backstress and accelerated mass loss via dynamic ice discharge, and likely render the latter the major contributor (as opposed to surface mass balance) to GrIS mass loss towards the end of the century. Here, the focus is on processes that drive basal melting of the Petermann Glacier Ice Shelf (PGIS), northwest Greenland, because contemporary knowledge regarding the full spectrum of mechanisms that dictate basal melting, and how they respond to a warming climate, is incomplete. This often results in poorly constrained oceanic boundary conditions, and consequently, afflicts estimates of GrIS’s contribution to future sea level rise with uncertainty. To address these questions, a non-idealized, nested, three-dimensional ocean-sea ice-ice shelf setup centered on PGIS and Petermann Fjord (PF) was created, based on the Finite Volume Community Ocean Model. With the setup developed and a “standard run” validated against observations from the fjord, the following scientific questions were investigated: How are basal melt rates at PGIS affected by 1. the presence, and likely future absence, of sea ice arches in Nares Strait? 2. subglacial discharge (Qsg), through increased surface runoff from the GrIS and entering PF across the GL? 3. changes in the PGIS cavity geometry in a post future-calving scenario? Our results indicate that climate warming driven transition towards a mobile and thin sea ice cover from a landfast and thick one could result i