Slowdown of Shirase Glacier, East Antarctica, caused by strengthening alongshore winds

Abstract

Abstract. Around large parts of West Antarctica and in Wilkes Land, East Antarctica, increased wind-forced intrusions of modified Circumpolar Deep Water (mCDW) onto the continental shelf have been associated with mass loss over the last few decades. Despite considerable seasonal variability, observations in 2018 have also confirmed relatively high basal melt rates of up to 16 m a−1 underneath the Shirase ice tongue in Enderby Land, East Antarctica. These high basal melt rates are also caused by intrusions of mCDW onto the continental shelf, but the catchment of Shirase Glacier has been gaining mass, a trend often attributed to increased precipitation. Here, we document the dynamical ocean-driven slowdown, ice surface thickening and grounding line advance of Shirase Glacier in response to strengthening easterly winds that reduce mCDW inflow and decrease basal melt rates. Our findings are significant because they demonstrate that warm ice shelf cavity regimes are not universally associated with glacier acceleration and mass loss in Antarctica, and they highlight the overlooked role of the impact of easterly winds in the recent mass gain of the Shirase Glacier catchment.

The Multi-decadal Collapse of East Antarctica’s Conger-Glenzer Ice Shelf

“…We suggest that the overall thinning of CGIS in the last ~decade, the significant increase in cumulative fracture length after 2017, and lack of pack ice to the north in late February 2022 made CGIS particularly susceptible to both wind 60,61 and sea-surface slope changes associated with the AR. Intriguingly, fast ice surrounded the eastern margin of CGIS as it collapsed, a counterexample to several recent studies showing that ice shelves are generally afforded stability during times of extensive fast ice (or consolidated pack ice) coverage [63][64][65] , with notable exception at Shirase Glacier 33,66 . It also maintained its location and structure through 2022-2023 in the absence of CGIS, perhaps pointing to a future role for fast ice: filling a role in polynya formation in regions where ice shelves used to be.…”

“…While most EAIS drainage basins are presently close to steady-state, satellite observations track subtle signs of change 27 . Recent protracted and staged retreats have been observed in EAIS [29][30][31][32][33] , and there is evidence for significant past retreat 34,35 . However, there are no documented cases of EAIS ice shelf collapse.…”

Antarctic Landfast Sea Ice: A Review of Its Physics, Biogeochemistry and Ecology

“…Also in East Antarctica, a major calving of the Shirase Glacier Tongue (SGT) immediately followed a large fast-ice breakup in Lützow-Holm Bay (Aoki, 2017). Miles et al (2023) confirmed the relationship between fluctuations in the seaward extent of the SGT and fast-ice presence/absence, with periods of ice-tongue advance and lengthening being correlated with persistent fast ice and shortening/loss events following sporadic fast-ice breakouts (largely in summer; see also Aoki, 2017). The effect of fast ice in limiting iceberg calving (and dispersal), thereby enabling ice-front advance, is also shown for the Cook Ice Shelf (George V Land) by .…”

“…Moreover, Gomez-Fell et al (2022) showed that in summer with its lower fast-ice coverage, the Parker Ice Tongue experienced higher velocities (by 11%) compared to winter. Elsewhere, there is little/ no evidence that fast ice plays any substantial role in buttressing the Shirase Glacier (Miles et al, 2023), with Nakamura et al (2010) recording only a minimal (0.8% ± 1.3%) change in ice speed at the grounding line following a partial fast-ice breakout event in 1998, and Nakamura et al (2022) reporting no distinguishable ice-speed change after a subsequent fast-ice breakout in 2017.…”

Modeling the Trooz Glacier’s movement using air temperature data and satellite SAR observations in 2015–2022

“…This is associated with the significant length of the coastline (18.000 km) as well as gaps in our knowledge about the current rates of ice cover change. In particular, this is caused by spatiotemporal changes in the velocity of glaciers, even for relatively small areas (within 100 km 2 ) (Tretyak, 2016;Li et al, 2023;Miles et al, 2023).…”