We conduct 500-year projections of Thwaites Glacier, Antarctica, including crustal uplift from glacier isostatic adjustment and considering the anomalously weak solid Earth structure in this region. Rapid uplift from the weak crust and mantle conditions significantly slow glacier retreat and reduce ice mass loss by 20% or more within a century.
Our results show that crustal uplift is a negative feedback that will substantially slow retreat of Thwaites Glacier on human timescales. This process is typically not included in model projections of the Antarctic Ice Sheet over the next century but should be added.
Thwaites Glacier, Antarctica, is subject to rapid retreat and could raise sea level by up to 1.5 meters. However, it overlies a region of anomalously low mantle viscosity and thin lithosphere, meaning the crust could rebound quickly as the ice thins, slowing further retreat. Our goal was to investigate the effects of glacial isostatic adjustment on glacier mass loss here. We ran 500-year simulations of a coupled higher-order ice-sheet, MALI, and planar glacial isostatic adjustment model, giapy. We considered solid-earth rheologies that included typical-Earth values and likely and extreme values for the region. We then compared the results using the different rheologies to a control excluding bedrock uplift. The most likely rheology reduced glacier mass loss by >20% beyond about 100 years. The extreme but possible rheology reduced mass loss by over 70%. Our results show that crustal uplift will substantially slow retreat of Thwaites Glacier and this process should be included in Antarctic Ice Sheet projections. More observations are needed to reduce the uncertainty in the rheology and the strength of this negative feedback.