Discharge Promotes Melt and Formation of Submarine Ice-Shelf Channels at the Beardmore Glacier Grounding Zone

Abstract

Using radar data from the Beardmore Glacier grounding zone, we image a narrow subglacial channel ($300-500$ m wide) that reaches a height of 200 m above the ambient ice-shelf draft. Using repeat ICESat-2 observations and Worldview digital elevation models, we show that this channel we observe with radar is part of a system of channels. These channels form near the grounding zone where the axis of the channels runs up-gradient in smoothed ice base elevation (perpendicular to smoothed ice base elevation contours). Downstream, these features are advected with the flow and expressed as Eulerian surface elevation change in differenced co-registered digital elevation models. Continuity calculations indicate that melt rates within the channel are at least 20 m ${\text{yr}}^{-1}$. Idealized one-dimensional plume modeling indicates these melt rates require substantial meltwater discharge and are geographically continuous extensions of subglacial conduits we image upstream of the grounding zone. These basal-melt rates are $27\times$ higher than the ambient basal-melt rates in the Ross. Asymmetric melt across the width of the channel suggests there is cross-channel ocean boundary current that may affect the efficiency of energy exchange across the ice-shelf ocean boundary layer within the channel. This is consistent with recent model experiments that suggest ice shelf basal channel shape determines channelized ice-ocean interactions.