Antarctic Ice-sheet May Cause Less Sea-level Rise than Earlier Estimates

Collapse of the Antarctic ice sheet may cause less sea-level rise than earlier studies indicated. That’s according to researchers from France and the UK, who found that the resulting sea-level rise by the end of the century is extremely unlikely to be more than 30 cm

"Up to now, assessments of Antarctica's contribution to sea-level rise have used a combination of extrapolation of the observed rate of mass loss, expert opinion and idealized modelling – indeed, this is what the IPCC Fifth Assessment Report used,"Tony Payne of the University of Bristol, UK, toldenvironmentalresearchweb. "Ours is one of a number of new studies that incorporate realistic models of these key processes."

Warming of the Circumpolar Deep Water is causing the grounding lines – the point at which ice leaves the bedrock to become an ice shelf floating on the ocean – of Pine Island Glacier, Thwaites Glacier and other glaciers around the Amundsen Sea embayment in West Antarctica to retreat. In much of West Antarctica the bedrock lies below sea-level and slopes downwards towards the interior of the continent. So once this retreat of marine ice begins it may continue, even if the original trigger for the grounding line movement has disappeared.

"Our study is new because it combines a physically-based model of the ice sheet, in which the key processes controlling Antarctic's contribution to future sea level are represented, with a robust statistical method for evaluating the consequences of uncertainty in our knowledge – of things such as future triggers to ice sheet collapse," said Payne.

The team modelled three different responses of ice-sliding velocity to friction at the base of the ice sheet, as this is a key unknown. What's more, the model only allowed grounding lines to retreat where bedrock sloped downwards from the continent's margin, and kept retreat rate within a theoretical limit. The researchers generated a 3000-member ensemble, weighting the members according to how well they simulated the ice mass loss seen in the Amundsea Sea embayment.

Source: Environmental Research

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