Thwaites model doubles sea-level contribution when seawater reaches grounded ice
Seawater entering beneath Thwaites Glacier changes how much ice a new model loses. The peer-reviewed simulation reproduces past retreat and thinning more closely when it includes this transition zone, and estimates roughly twice the earlier average sea-level contribution under constant climate conditions. Its result concerns one Antarctic glacier and depends on the model’s physical assumptions.
Science··Morning
Thwaites loses more ice when its melting zone is widened
Seawater entering underneath grounded ice changed the projected losses from Thwaites Glacier in Antarctica. A newly published peer-reviewed model includes melting across the zone where ice resting on the seabed becomes floating ice. The research links this wider melting zone to a larger contribution to global sea level.[1], [2]
Under constant climate forcing, a grounding zone of 5 ± 1 kilometres gave a sea-level contribution of 30.1 ± 5.7 millimetres by 2100 in the researchers’ simulations. The earlier multi-model comparison averaged 15.2 millimetres under the same forcing. These are conditional calculations for one glacier.[1]
Satellite measurements constrain the model’s melting zone
Researchers compared the simulations with retreat, thinning and acceleration observed from 1996 to 2023. Grounding zones of 2–5 kilometres and submarine melt rates of 90–120 metres per year reproduced those changes more closely. The seabed elevation beneath eastern Thwaites also received a local correction within its measurement uncertainty, aligning the starting geometry with observations.[1]
Seawater lubrication remains outside the calculation
The model holds past average climate conditions constant when extending its calculations into the future. It does not incorporate reduced basal friction from additional seawater lubrication or future year-to-year changes in ocean thermal forcing. Simulations without seawater intrusion failed to capture the subsequent thinning and discharge adequately, while the remaining assumptions leave uncertainty about the glacier’s full response.[1]
