Journal Article

Strong Ocean Melting Feedback During the Recent Retreat of Thwaites Glacier

Luckman, Adrian J., Holland, Paul R., Bevan, Suzanne L.

2023

Overview

Accelerating ice loss from Thwaites Glacier is contributing approximately 5% of global sea‐level rise, and could add tens of centimeters to sea level over the coming centuries. We use an ocean model to calculate sub‐ice melting for a succession of Digital Elevation Models of the main trunk of Thwaites Glacier from 2011 to 2022. The ice evolution during this period induces a strong geometrical feedback onto melting. Ice thinning and retreat provides 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 over 30% without any change in forcing from wider ocean conditions. This geometrical feedback over just 12 years is comparable to melting changes arising from plausible century‐scale changes in ocean conditions and subglacial meltwater inflow. These findings imply that ocean‐driven ice loss from Thwaites Glacier may only be weakly influenced by anthropogenic emissions mitigation. Plain Language Summary The West Antarctic Ice Sheet is losing ice, making a substantial contribution to global sea‐level rise. This ice loss is known to be triggered by changes in ocean melting of the floating parts of the ice sheet. Computer predictions show that this ice loss could make a large contribution to global sea‐level over the coming centuries, but the future trajectory is very uncertain. In this study we simulated the ocean melting of Thwaites Glacier during 2011–2022, a period when the glacier rapidly thinned and retreated. We show that the geometrical evolution of the glacier during this period led to a substantial increase in ocean melting, caused by the exposure of more ice base to warm ocean waters, and changing ocean currents beneath the ice. This change in melting is similar to what might be expected from 100 years of ocean warming under anthropogenic climate change. These results imply that the future melting of such glaciers is strongly controlled by the geometrical evolution of the ice through internal ice and ocean feedbacks, and will therefore only weakly be influenced by reductions in the emissions of greenhouse gases. Key Points Model simulations are used to investigate oceanic melting of the main trunk of Thwaites Glacier during its rapid retreat between 2011 and 2022 The evolution of the ice geometry leads to an increase in melting by more than 30% without any change in ocean forcing This strong feedback means the future ocean melting of Thwaites Glacier may only be weakly influenced by changes in anthropogenic forcing

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Ablation / Antarctic Ice Sheet / Anthropogenic climate changes / Anthropogenic factors / Climate change / Digital Elevation Models / Emissions / Evolution / Feedback / Gases / Glaciation / Glacier melting / Glacier retreat / Glaciers / Global warming / Greenhouse effect / Greenhouse gases / Human influences / Ice / Ice melting / Ice sheets / ice‐ocean interaction / Inflow / Melting / Meltwater / Mitigation / Ocean currents / Ocean models / Ocean temperature / Ocean warming / Oceans / Sea level / Sea level rise / Southern Ocean / Thwaites Glacier / Water circulation / Water column / Water inflow