Abstract
Abstract. Thwaites Glacier (TG), West Antarctica, has experienced rapid, potentially irreversible grounding line retreat and mass loss in response to enhanced ice shelf melting. Results from recent numerical models suggest a large spread in the evolution of the glacier in the coming decades to a century. It is therefore important to investigate how different approximations of the ice stress balance, parameterizations of basal friction and ice shelf melt parameterizations may affect projections. Here, we simulate the evolution of TG using ice sheet models of varying levels of complexity, different basal friction laws and ice shelf melt to quantify their effect on the projections. We find that the grounding line retreat and its sensitivity to ice shelf melt are enhanced when a full-Stokes model is used, a Budd friction is used and ice shelf melt is applied on partially floating elements. Initial conditions also impact the model results. Yet, all simulations suggest a rapid, sustained retreat of the glacier along the same preferred pathway. The fastest retreat rate occurs on the eastern side of the glacier, and the slowest retreat occurs across a subglacial ridge on the western side. All the simulations indicate that TG will undergo an accelerated retreat once the glacier retreats past the western subglacial ridge. Combining all the simulations, we find that the uncertainty of the projections is small in the first 30 years, with a cumulative contribution to sea level rise of 5 mm, similar to the current rate. After 30 years, the contribution to sea level depends on the model configurations, with differences up to 300 % over the next 100 years, ranging from 14 to 42 mm.
Highlights
Thwaites Glacier (TG), located in the Amundsen Sea Embayment (ASE) sector of West Antarctica, is one of the largest outflows of ice in Antarctica
Apart from the stress balance model, the choice of friction law and the treatment of ice shelf melt near the grounding line may have a significant impact on the rate of grounding line retreat and glacier mass loss (Seroussi et al, 2014; Golledge et al, 2015; Arthern and Williams, 2017)
For FS, the difference is large in the interior, up to 100 m yr−1 due to the tiling method, but this difference has a limited impact on our results because it takes place far from the grounding line region (> 100 km), where changes are relatively small
Summary
Thwaites Glacier (TG), located in the Amundsen Sea Embayment (ASE) sector of West Antarctica, is one of the largest outflows of ice in Antarctica. The rate of mass loss of TG has increased from 28 Gt yr−1 in 2006 to 50 Gt yr−1 in 2014 (Medley et al, 2014; Mouginot et al, 2014; Rignot, 2008). The rate of change in mass loss increased from 2.7 Gt yr−2 in 1978–2014 to 3.2 Gt yr−2 in 1992–2014 and 5.6 Gt yr−2 in 2002–2014 (Mouginot et al, 2014) If these rates of acceleration in mass loss were to persist over the coming decades, they would raise global sea level by, respectively, 41, 48 and 81 mm by 2100
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