Marine Ice Sheet Collapse Potentially Under Way for the Thwaites Glacier Basin, West Antarctica

TLDR

Resting atop a deep marine basin, the West Antarctic Ice Sheet has long been considered prone to instability. The study investigates whether the unstable retreat of Thwaites Glacier is already underway by examining its sensitivity to ocean melt. A numerical model was used to assess this sensitivity. The model reproduces observed losses with realistic ocean melt, predicts moderate 21st‑century sea‑level rise (<0.25 mm yr⁻¹) that accelerates thereafter, indicates early‑stage collapse has already begun (except in the lowest‑melt case), and projects rapid collapse (>1 mm yr⁻¹) to start within 200–900 years.

Abstract

Resting atop a deep marine basin, the West Antarctic Ice Sheet has long been considered prone to instability. Using a numerical model, we investigated the sensitivity of Thwaites Glacier to ocean melt and whether its unstable retreat is already under way. Our model reproduces observed losses when forced with ocean melt comparable to estimates. Simulated losses are moderate (<0.25 mm per year at sea level) over the 21st century but generally increase thereafter. Except possibly for the lowest-melt scenario, the simulations indicate that early-stage collapse has begun. Less certain is the time scale, with the onset of rapid (>1 mm per year of sea-level rise) collapse in the different simulations within the range of 200 to 900 years.