Drivers of Change of Thwaites Glacier, West Antarctica, Between 1995 and 2015

Abstract

Thwaites Glacier, one of the largest ice streams in the Amundsen Sea Embayment (Figure 1), drains a large area of the West Antarctic Ice Sheet (WAIS). Its ice volume holds the equivalent of  E 0.65 m of sea level (Morlighem et al., 2020), and is resting on deep bedrock, a wide channel below sea level that spreads under WAIS to the Ross Sea Embayment (Fretwell et al., 2013;Holt et al., 2006). The retrograde slope of this channel makes Thwaites potentially vulnerable to marine ice sheet instability (Gudmundsson et al., 2012;Schoof, 2007;Weertman, 1974), a positive feedback of grounding line retreat and increased ice discharge which may lead ultimately to WAIS's collapse over the coming centuries (

Strong Ocean Melting Feedback During the Recent Retreat of Thwaites Glacier

“…The West Antarctic Ice Sheet (WAIS) is losing ice at an ever‐increasing rate (Rignot et al., 2019; Shepherd et al., 2019) and forms a major uncertainty in projections of global sea‐level rise (Fox‐Kemper et al., 2021). The most rapid ice loss is occurring in the Amundsen Sea sector, where thinning and retreat of the floating ice shelves is causing acceleration of their tributary glaciers (De Rydt et al., 2021; dos Santos et al., 2021). Thwaites Glacier is one of the largest contributors to sea‐level rise (Rignot et al., 2019; Shepherd et al., 2019), and offers the largest, and least‐certain, potential future contribution (Alevropoulos‐Borrill et al., 2020; Arthern & Williams, 2017; Joughin et al., 2014; Seroussi et al., 2020; Yu et al., 2018).…”

Limited Impact of Thwaites Ice Shelf on Future Ice Loss From Antarctica

“…Because of the importance of Thwaites Glacier for future SLR, a large number of modeling studies have previously considered various aspects of its flow regime (Barnes & Gudmundsson, 2022; Benn et al., 2022; Docquier et al., 2014; Joughin et al., 2014; Parizek et al., 2013; Santos et al., 2021; Seroussi et al., 2017; Waibel et al., 2018; Yu et al., 2017, 2018). While none of these studies have provided direct quantification of ice‐shelf buttressing as done here, several published studies have assessed the importance of the pinning point of TEIS.…”

“…The glacier rests below sea level on a retrograde bed, and in the absence of lateral side drag and buttressing provided to the grounding line by abutting ice shelves, this configuration can give rise to an unstable and irreversible retreat (Schoof, 2007a, 2007b), generally referred to as the marine‐ice sheet instability. The continuing mass loss, and the potential precarious geometrical setting of Thwaites Glacier, has made it the focus of a large number of studies aimed at understanding the drivers of current change, and the potential of irreversible large‐scale retreat (e.g., Barnes & Gudmundsson, 2022; Docquier et al., 2014; Joughin et al., 2014; Parizek et al., 2013; Santos et al., 2021; Seroussi et al., 2017; Waibel et al., 2018; Yu et al., 2017; Yu et al., 2018).…”

The Relative Impacts of Initialization and Climate Forcing in Coupled Ice Sheet‐Ocean Modeling: Application to Pope, Smith, and Kohler Glaciers

“…Our study makes use of a coupled ice‐ocean model, as opposed to using an ice‐sheet model with a parameterization of ocean‐driven melt. Such parameterizations are often depth‐dependent in nature for purposes of simplicity (Dos Santos et al., 2021; Favier et al., 2014; Joughin et al., 2010; Seroussi et al., 2017) but sometimes take account of spatial variation such as far‐field hydrography or distance to grounding line (e.g., Lazeroms et al., 2018; Pelle et al., 2019; Reese et al., 2018; Snow et al., 2017). Our modeled melt does not exhibit a strong melt‐depth relationship; at the end of the warm‐forced transiently‐initialized run, the melt‐depth correlation has an R 2 of 0.1 (Figure 8e).…”

“…A number of ice‐sheet modeling studies have examined the response of fast‐flowing Amundsen glaciers to ocean forcing (e.g., Dos Santos et al., 2021; Favier et al., 2014; Joughin et al., 2014; Lilien et al., 2019), the majority of which have used a depth‐dependent parameterization for melting. Such parameterizations largely neglect the influence of the ocean circulation in ice‐shelf cavities, leading to important deficiencies in both the spatial distribution of melting, and the ice‐shelf response to changes in ocean forcing.…”