Abstract
Abstract. Antarctica's Getz Ice Shelf has been rapidly thinning in recent years, producing more meltwater than any other ice shelf in the world. The influx of fresh water is known to substantially influence ocean circulation and biological productivity, but relatively little is known about the factors controlling basal melt rate or how basal melt is spatially distributed beneath the ice shelf. Also unknown is the relative importance of subglacial discharge from the grounded ice sheet in contributing to the export of fresh water from the ice shelf cavity. Here we compare the observed spatial distribution of basal melt rate to a new sub-ice-shelf bathymetry map inferred from airborne gravity surveys and to locations of subglacial discharge from the grounded ice sheet. We find that melt rates are high where bathymetric troughs provide a pathway for warm Circumpolar Deep Water to enter the ice shelf cavity and that melting is enhanced where subglacial discharge fresh water flows across the grounding line. This is the first study to address the relative importance of meltwater production of the Getz Ice Shelf from both ocean and subglacial sources.
Highlights
The Getz Ice Shelf (Getz ) in West Antarctica is over 500 km long and 30 to 100 km wide; it produces more fresh water than any other source in Antarctica (Rignot et al, 2013; Jacobs et al, 2013), and in recent years its melt rate has been accelerating (Paolo et al, 2015)
Published ship track bathymetry (Nitsche et al, 2007) shows that the Dotson–Getz Trough on the inner continental shelf extends to the ice front, and our results suggest that Duncan–Wright Trough (DWT) is the continuation of the Dotson–Getz Trough, providing a pathway for Circumpolar Deep Water (CDW) to enter into the ice shelf cavity without obstruction
Our new bathymetry of the Getz Ice Shelf reveals troughs that are continuous from the inner continental shelf to the ice sheet grounding line, which provide natural pathways for CDW to enter into the ice cavity and drive rapid basal melt
Summary
The Getz Ice Shelf (Getz ) in West Antarctica is over 500 km long and 30 to 100 km wide; it produces more fresh water than any other source in Antarctica (Rignot et al, 2013; Jacobs et al, 2013), and in recent years its melt rate has been accelerating (Paolo et al, 2015). The fresh, buoyant water that emanates from the Getz cavity drives regional and global ocean circulation (Nakayama et al, 2014; Jourdain et al, 2017; Silvano et al, 2018) while providing critical nutrients for biological production (Raiswell et al, 2006), but little is known about the origins or sensitivities of this major freshwater source. Despite the major role that fresh water from Getz plays in the Southern Ocean, no studies have considered the contribution of subglacial meltwater that originates beneath grounded ice or its role in influencing the circulation and melt patterns beneath the ice shelf.
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