Two decades of dynamic change and progressive destabilization on the Thwaites Eastern Ice Shelf

Abstract

Abstract. The Thwaites Eastern Ice Shelf (TEIS) buttresses the eastern grounded portion of Thwaites Glacier through contact with a pinning point at its seaward limit. Loss of this ice shelf will promote further acceleration of Thwaites Glacier. Understanding the dynamic controls and structural integrity of the TEIS is therefore important to estimating Thwaites' future sea-level contribution. We present a ~20-year record of change on the TEIS that reveals the dynamic controls governing the ice shelf's past behavior and ongoing evolution. We derived ice velocities from MODIS and Sentinel-1 image data using feature tracking and speckle tracking, respectively, and combined these records with ITS_LIVE and GOLIVE velocity products from Landsat 7 and 8. In addition, we estimated surface lowering and basal melt rates using the REMA DEM in comparison to ICESat and ICESat-2 altimetry. Early in the record, TEIS flow dynamics were strongly controlled by the neighboring Thwaites Western Ice Tongue (TWIT). Flow patterns on the TEIS changed following the disintegration of the TWIT in ~2008, with a new divergence in ice flow developing around the pinning point at its seaward limit. Simultaneously, the TEIS developed new rifting that extends from the shear zone upstream of the ice rise and increased strain concentration within this shear zone. As these horizontal changes occurred, sustained thinning driven by basal melt reduced ice thickness, particularly near the grounding line and in the shear zone area upstream of the pinning point. This evidence of weakening at a rapid pace suggests that the TEIS is likely to fully destabilize in the next few decades, leading to further acceleration of Thwaites Glacier.

Contemporary sea-level changes from global to local scales: a review

“…Its contribution to global mean sea-level rise is around 4%. Recent research shows that if Thwaites Glacier fragmentation and retreat continues, leading to total collapse, it has the potential to increase the contribution to the global mean sea-level rise by up to 65 cm [65–68].…”

Rapid retreat of Thwaites Glacier in the pre-satellite era

“…1a). As the stabilizing effects of these ice-shelf pinning points lessen 12 , future retreat of Thwaites becomes increasingly predicated on processes that occur in the grounding zone-the region in which the glacier comes afloat in the ocean. Sea-floor topography can help stabilize ice sheets against grounding-line retreat 13 , and grounding-line migration affects ice-sheet stability on timescales spanning months to millennia 14 .…”

Basal Melting, Roughness and Structural Integrity of Ice Shelves

“…(2021; https://doi.org/10.1029/2021GL094743) would be compare results from data of different vintages for ice shelves where there are high basal melt rates, to reveal how roughness has changed through time. RES surveys over the Thwaites Eastern Ice Shelf, which has the highest basal melt rates among those analyzed, have been conducted several times since 2004 (Holt et al., 2006; Jordan et al., 2020; Paden et al., 2010) so this would seem to present an ideal opportunity, particularly in view of recent studies that conclude this ice shelf will soon become critically vulnerable (Alley et al., 2021; Wild et al., 2022).…”

“…After more than six decades in which there was no overall migration of the Pine Island Glacier ice front, it's northern part stepped back more than 30 km through a succession of large calving events from 2015 to 2020 (Arndt et al., 2018; Joughin et al., 2021; Lhermitte et al., 2020). The current Thwaites Glacier Tongue is pervasively rifted and vestigial compared to the >75 km‐long and >40 km‐wide tongues that grew and calved through the twentieth century and earliest part of this century, and recent analysis of changes taking place in the Thwaites Eastern Ice Shelf (Figure 1) suggest that it is likely to fully destabilize in the next few decades (Alley et al., 2021; Wild et al., 2022).…”