Earth-rebound reduces Antarctic sea-level rise by 40%

The Antarctic Ice Sheet (AIS) may contribute 40% less to sea-level rise in the future if carbon emissions are kept near the lower range of emission scenarios.

The response of the AIS to climate change is the greatest uncertainty in projections of future sea-level rise. Estimates of future ice loss in these regions differ substantially between researchers.

Scientists led by Professor Natalya Gomez of McGill University in Canada, used a state-of-the-art three-dimensional model of the Earth’s mantle beneath Antarctica, along with models of ice sheet response to changing land levels and carbon dioxide concentrations.

They found that, as melting ice reduces the weight of Antarctica, the mantle below expands and raises the land above it. This reduces the flow of the ice sheet towards the sea, because the rising land limits the thickness of the ice sheet at its edge, thereby reducing the overall amount of ice delivered into the sea. They concluded that rapid uplift in the coastal regions of the AIS lowered Antarctica’s contribution to global sea level in the coming centuries by up to ~40%.  

The researchers say,

Our results indicate that ice sheet–glacial isostatic adjustment models drives two competing effects that alter the AIS contribution to global sea levels: (i) the sea-level feedback on grounding line dynamics, in which solid Earth uplift and sea-level fall reduces grounding line retreat in marine basins in Antarctica, and (ii) the water expulsion effect, in which uplifting marine sectors freed of ice expel water out of Antarctica, increasing sea-level rise.’

They found that the effect of the isostatic adjustment is to reduce the Antarctic contribution to global sea-level rise for low emissions and amplify it for high emissions. They say reducing greenhouse gas emissions will allow the rebound of the solid Earth to play a greater role in preserving more of the AIS.