Strong ocean melting feedback during the recent retreat of Thwaites Glacier

Abstract

<p>The accelerating ice loss from Thwaites Glacier is making a substantial contribution to global sea-level rise, and could add tens of centimetres to sea level over the coming centuries. This ice loss is associated with rapid thinning and disintegration of the floating sections of Thwaites Glacier, and retreat of its grounding line. In this study, we use a high-resolution ocean model and a series of Digital Elevation Models of the floating part of Thwaites Glacier from 2011 to 2022 to simulate the evolution of sub-ice melting during this rapid retreat.</p> <p>The results show that the ice evolution induces a strong geometrical feedback onto melting. The ice thinning and retreat provide a larger melting area, thicker and better-connected sub-ice water column, and steeper ice base. This leads to stronger sub-ice ocean currents, increasing melting by ~50% without any change in forcing from wider ocean conditions. This geometrical feedback over just 12 years is stronger than the melting changes expected from century-scale changes in ocean conditions and subglacial meltwater input. The strength of this feedback implies that greenhouse gas emissions policy may have a very weak influence over future ocean-driven ice loss from Thwaites Glacier.</p>

The Non‐Local Impacts of Antarctic Subglacial Runoff

“…Melt time series from baseline are shown in Figure 3b. Pine Island and Dotson melt are similar to shipboard observations (Naughten et al., 2022), but Thwaites melt rates are much lower than other published results, which are in the range of 70–80 Gt/a for modeling studies (Holland et al., 2023; Seroussi et al., 2017) and 60–100 Gt/a for satellite studies (Adusumilli et al., 2020; Depoorter et al., 2013; Rignot et al., 2013).…”

“…Rather, we present our scenarios as end‐members representing time‐constant and episodic modes of runoff. Furthermore, our model resolution may be too coarse to capture detailed melt patterns of ice‐shelf melt response to runoff and near the grounding line (Holland et al., 2023; Nakayama et al., 2021). Our focus is rather on the hydrographic impacts of runoff within and externally to ice‐shelf cavities, and the influence they have on ice‐shelf melt and sea‐ice reduction.…”

Response of Onshore Oceanic Heat Supply to Yearly Changes in the Amundsen Sea Icescape (Antarctica)

“…This being said, the present study does not cover all the possible types of icescape changes. Other perturbations that took place in recent years include a retreat of the ice front of PIS (see Bradley et al., 2022, 2023; Yoon et al., 2022) and changes in the grounding zone of TIS (see Holland et al., 2023; Milillo et al., 2019). Future extreme icescape changes of such types (which were not explored in this study) could possibly lead to a reduction in ice shelf basal melt rates.…”

Widespread seawater intrusions beneath the grounded ice of Thwaites Glacier, West Antarctica

“…The mass loss is not caused by a decrease in snowfall, but by a speed-up of glaciers in West Antarctica, the Antarctic Peninsula, and the Wilkes Land sector of East Antarctica. Glacier speed-up has been attributed to an increase in glacier melt in contact with warm, salty ocean waters of circumpolar origin, or circumpolar deep water (CDW) ( 2 ). CDW has gained access to the continental shelf, ice cavities, and glaciers over the past 40 y ( 3 ) due to an increase in the strength of the westerly winds ( 4 ), itself caused by the combined effect of rapid climate warming over the rest of the planet from human-induced greenhouse gas emissions and a cooling of the Antarctic stratosphere from the human-induced depletion of the stratospheric ozone ( 5 , 6 ).…”