Satellite photo of a massive ice shelf with a couple of large cracks
Two large cracks in the Pine Island Ice Shelf appear clearly in this image taken by the Copernicus Sentinel-2 satellite on 14 September 2019. Credit: European Space Agency, CC BY-SA 3.0 IGO
Source: Journal of Geophysical Research: Oceans

The Pine Island Ice Shelf (PIIS) is the seaward extension of the Pine Island Glacier, a large and rapidly retreating glacier that drains part of the West Antarctic Ice Sheet. Beneath the floating PIIS is a seafloor ridge that narrows the gap through which relatively warm seawater from the open ocean can flow in and circulate beneath the ice shelf.

This narrowing helps protect the underside of the PIIS on the landward side of the seafloor ridge from melting. But in the past decade, the ice shelf has seen large amounts of calving, causing the ice front to retreat toward the continent and approach the ridge—and the calving shows no sign of slowing.

Bradley et al. investigated how calving affects melting of the PIIS. The team used a high-resolution ocean model to simulate ocean circulation and melt rates below the ice shelf, modeling and comparing results from both an idealized setting meant to represent the most important features of the ice shelf and ridge and real-world conditions that closely match the site characteristics for the PIIS.

They found that ice shelf melt rates are sensitive to the thickness of the gap between the PIIS and the seafloor ridge, suggesting that the changing geometry of the gap with a retreating ice front leads to strengthening of seawater circulation beneath the ice. As calving from the PIIS ice front continues, the melt rate will increase linearly, the team found, becoming 10% higher than it is now by the time the ice front retreats to the ridgeline.

The researchers say the results highlight that calving could be an important contributor to melting of the West Antarctica Ice Sheet. (Journal of Geophysical Research: Oceans,, 2022)

—Sarah Derouin, Science Writer

Citation: Derouin, S. (2022), Melting below the Pine Island Ice Shelf minds the gap, Eos, 103, Published on 3 October 2022.
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