Hydraulic control of the submarine glacier melt in Greenlandic sill fjords

Abstract

The oceanic forcing of basal melt remains a major source of uncertainty in climate ice sheet modelling.Several factors such as ice and fjord geometry, ambient water properties and subglacial discharge in-fluence the submarine melt processes. We use a high resolution, non-hydrostatic configuration of theMassachusetts Institute of Technology general circulation model (MITgcm, see Wiskandt et al., 2022)to investigate the dependence of basal melt rates and melt driven circulation in the Sherard OsbornFjord (SOF) under the floating ice tongue of Ryder Glacier (RG), northwest Greenland, on the fjordsbathymetry in connection with variable subglacial discharge. In SOF, a sill in front of the floating iceshields the cavity underneath the ice from warm Atlantic water (AW) penetrating towards the groundingline, providing an effective shielding of the glacier from oceanic thermal forcing. The volume flux of theAW inflow is controlled by the sill height and the melt water outflow. The outflow volume flux is in turndependent on basal melting, subglacial discharge and the mixing of the two with the AW. For sufficientlystrong outflow, hydraulic control at the sill crest can limit the available glacier–ward flux and thereforethe available oceanic thermal forcing for basal melting creating a stabilizing feedback. In this studywe investigate the sensitivity of the AW inflow into an idealized fjord to the presence of a sill, variablesill height and seasonal forcing from subglacial discharge. The model results are compared to theory ofhydraulic control (Nilsson et al., 2022).ReferencesNilsson, J., van Dongen, E., Jakobsson, M., O’Regan, M., and Stranne, C. (2022).Hydraulic suppression of basal glacier melt in sill fjords. EGUsphere, 2022:1–33.Wiskandt, J., Koszalka, I. M., and Nilsson, J. (2022). Basal melt rates and oceancirculation under the Ryder Glacier ice tongue and their response to climate warming: a high resolutionmodelling study. EGUsphere, 2022:1–29.