High Spatial Melt Rate Variability Near the Totten Glacier Grounding Zone Explained by New Bathymetry Inversion

• Published in: Geophysical research letters Vol. 50; no. 10
• Main Authors: Vaňková, Irena, Winberry, J. Paul, Cook, Sue, Nicholls, Keith W., Greene, Chad A., Galton‐Fenzi, Benjamin K.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 28.05.2023; American Geophysical Union (AGU); Wiley
• Subjects: Antarctic ice sheet; Antarctica; ApRES; Asymmetry; basal melt rate; Bathymeters; Bathymetry; ENVIRONMENTAL SCIENCES; Glaciation; Glacier flow; Glacier melting; Glaciers; Global sea level; Gravity; Holes; Ice; Ice sheets; Ice shelves; Land ice; Measuring instruments; Melting; Oceans; Remote sensing; Seasonal variation; Seismic activity; Totten; Water circulation; Water column
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2023GL102960

Totten Glacier is a fast‐moving East Antarctic outlet with the potential for significant future sea‐level contributions. We deployed four autonomous phase‐sensitive radars on its ice shelf to monitor ice‐ocean interactions near its grounding zone and made active source seismic observations to constrain gravity‐derived bathymetry models. We observe an asymmetry in basal melting with mean melt rates along the grounding zone differing by up to 20 m/a. Our new bathymetry model reveals that this melt rate asymmetry coincides with an asymmetry in water column thickness and that the low‐melting ice‐shelf portion is shielded from the main cavity circulation. A 2‐year record yields year‐to‐year melt rate variability of 7–9 m/a with no seasonal cycle. Our results highlight the key role of bathymetry near grounding lines for accurate modeling of ice‐shelf melt, and the importance of sustained multi‐year monitoring, especially at ice‐shelf cavities where the dominant melt rate drivers vary primarily inter‐annually. Plain Language Summary The point were the Antarctic Ice Sheet goes afloat on the ocean represents a critical region, where minor variations in melt rates can impact glacier flow and influence the rate of sea‐level rise. East Antarctica's Totten Glacier holds the potential to raise global sea level by several meters. Therefore, to understand the conditions it is exposed to, we measured melt rates for 2 years in several key locations near the point where the ice first touches the ocean. Our new measurements of the shape of the Totten Ice Shelf cavity help explain an observed spatial pattern of basal melting and together with local melt rate data resolve a disagreement between existing melt rate estimates from remote‐sensing methods. Key Points Totten Glacier melt rates vary spatially between 0 and over 20 m/a; differences are explained by water column thickness variations from updated bathymetry Temporal melt rate variability is primarily inter‐annual; melt rates differ by 7–9 m/a over two observed years and there is no clear seasonal cycle Contrary to previous findings, we find no topographic barriers to the intrusion of warm water to the Totten Glacier grounding zone