Impact of glacial isostatic adjustment on zones of potential grounding line stability in the Ross Sea Embayment (Antarctica) since the Last Glacial Maximum

Abstract. Ice streams in the Ross Sea Embayment (West Antarctica) retreated up to 1,000 kilometers since the Last Glacial Maximum, constituting one of the largest changes in deglacial Antarctic ice sheet volume and extent. One way that bathymetry influenced this retreat was through the presence of local bathymetric highs, or “pinning points”, which decreased ice flux through the grounding line and slowed grounding line retreat. During this time, glacial isostatic adjustment vertically shifted the underlying bathymetry, altering the grounding line flux. Continental scale modeling efforts have demonstrated the impact of solid Earth-ice sheet interactions on the deglacial retreat of marine ice sheets, however, these models are too coarse to resolve small scale bathymetric features. We pair a high-resolution bathymetry model with a simple model of grounding line stability in an ensemble approach to predict zones of potential grounding line stability in the Ross Sea Embayment for given combinations of surface mass balance rate, degree of ice shelf buttressing, basal friction coefficient, and bathymetry (corrected for glacial isostatic adjustment using three different ice sheet histories). We find that isostatic depression within the interior of the Ross Sea Embayment during the Last Glacial Maximum restricts zones of potential grounding line stability to near the edge of the continental shelf. Zones of potential grounding line stability do not appear near the present-day grounding line until sufficient uplift has occurred (mid-Holocene; ~5 ka), resulting in a net upstream migration of zones of potential grounding line stability across the deglaciation. Additionally, our results show that coarse resolution bathymetry underpredicts possible stable grounding line positions, particularly near the present-day grounding line, highlighting the importance of bathymetric resolution in capturing the impact of glacial isostatic adjustment on ice stream stability.