Review of "Extensive and anomalous grounding line retreat at Vanderford Glacier, Vincennes Bay, Wilkes Land, East Antarctica" by Picton et al. 2022

Abstract

Wilkes Land, East Antarctica, has been losing mass at an accelerating rate over recent decades in response to enhanced oceanic forcing. Overlying the Aurora Subglacial Basin, it has been referred to as the ‘weak underbelly’ of the East Antarctic Ice Sheet and is drained by several major outlet glaciers. Despite their potential importance, few of these glaciers have been studied in detail. This includes the six outlet glaciers which drain into Vincennes Bay, a region recently discovered to have the warmest intrusions of modified Circumpolar Deep Water (mCDW) ever recorded in East Antarctica. Here, we use remotely sensed optical imagery, differential satellite aperture radar interferometry (DInSAR) and datasets of ice surface velocity, ice surface elevation and grounding line position, to investigate ice dynamics between 1963 and 2022. Decadal trends in frontal position are observed across the Vincennes Bay outlet glaciers, potentially correlated to variations in sea ice production. Ice surface velocities were generally stable between 2000 and 2021, with some fluctuations measured across the grounding line of Bond East Glacier. Changes in ice surface elevation were spatially variable, but a clear and consistent thinning trend was measured at Vanderford Glacier between 2003 and 2020. Enhanced rates of ice thinning were seen across each of the Vanderford, Adams, Anzac, and Underwood Glaciers between 2017 and 2020. Most importantly, our results confirm extensive grounding line retreat at Vanderford Glacier, measured at 18.6 km between 1996 and 2020. Such rapid grounding line retreat (0.8 km yr-1) is consistent with the notion that warm mCDW is able to access deep cavities formed below the Vanderford Ice Shelf, driving high rates of basal melting. With a retrograde slope observed inland along the Vanderford Trench, such oceanic forcing may have significant implications for the future stability of Vanderford Glacier.