Near-term ocean warming around Antarctica affects long-term rate of sea level rise

February 1, 2019, US Department of Energy
The Thwaites Ice Shelf in West Antarctica is one of the largest regional contributors to sea level rise. Credit: US Department of Energy

In the West Antarctic Ice Sheet, which is particularly susceptible to influencing sea levels, rates of mass loss are especially sensitive near the point at which a glacier or ice shelf transitions into a regime of self-sustained retreat. In this state, the effects of ocean warming and other changes are sustained by the dynamics of a retreating ice sheet, with the rate of glacier loss depending strongly on how quickly the ocean melts the ice shelf. These findings are thanks to a team's research into the processes that regulate basin-wide ice mass loss.

The portions of the West Antarctic Ice Sheet that rest over water contain enough vulnerable ice to raise the global sea level by 3 meters (nearly 10 feet). Recent incursions of warmer water and from this region will be exacerbated by projected changes in global climate.

The rapid change now underway on Thwaites Glacier, located in the West Antarctic Ice Sheet, raises concern that a threshold for unstoppable grounding line retreat has been or is about to be crossed, after which further retreat is inevitable even in the absence of continued forcing. The grounding line is the point where the base of the glacier is on land. Beyond this point, the glacier is floating in the . To examine processes regulating basin-wide ice mass loss from the West Antarctic Ice Sheet, researchers applied the high-resolution BISICLES model to capture realistic grounding line dynamics at 250-meter resolution. In a set of modeling experiments, they slowly ramped up ocean melting of the surrounding ice shelves to identify the point at which mass loss from melt may become self-sustaining from a change in ice flow dynamics. In the experiments, this occurred at 13 meter/year melt and the system continued to lose mass until nearly all of the West Antarctic Ice Sheet is evacuated. The ice is a critical player in global sea level rise. The study identifies an important characteristic of this change in flow regimes. Near the transition point, small differences in ocean forcing had a long-term effect on discharge rates. The team found that with only 0.5 meter/year additional forcing at the time the system is experiencing this flow transition, discharge rates were upwards of 50 percent higher for centuries. This result is due to the role of added forcing in creating steeper slopes at the grounding line that, in turn, cause higher discharge rates. This for the Marine Ice Sheet Instability mechanism means that details concerning how the ocean forces ice sheets across the threshold for instability will be critical for determining long-term rates of sea level rise.

Explore further: Huge cavity in Antarctic glacier signals rapid decay

More information: M. S. Waibel et al. Rate of Mass Loss Across the Instability Threshold for Thwaites Glacier Determines Rate of Mass Loss for Entire Basin, Geophysical Research Letters (2018). DOI: 10.1002/2017GL076470

Related Stories

Huge cavity in Antarctic glacier signals rapid decay

January 31, 2019

A gigantic cavity—two-thirds the area of Manhattan and almost 1,000 feet (300 meters) tall—growing at the bottom of Thwaites Glacier in West Antarctica is one of several disturbing discoveries reported in a new NASA-led ...

Improved modelling of ice-ocean processes

May 19, 2016

Pine Island Glacier in West Antarctica is currently one of the single biggest contributors to sea-level rise with an estimated volume loss of 1.2mm sea-level equivalent per decade. The loss is caused, at least partly, by ...

'Scars' left by icebergs record West Antarctic ice retreat

October 25, 2017

Thousands of marks on the Antarctic seafloor, caused by icebergs which broke free from glaciers more than ten thousand years ago, show how part of the Antarctic Ice Sheet retreated rapidly at the end of the last ice age as ...

Sediment wedges not stabilizing West Antarctic Ice Sheet

September 3, 2013

The stability of the West Antarctic Ice Sheet is uncertain as climate changes. An ice sheet such as the West Antarctic Ice Sheet that is grounded well below sea level on a bed that slopes toward the interior of the sheet ...

Recommended for you

Japan to make crater on asteroid to get underground samples

March 18, 2019

Japan's space agency said Monday that its Hayabusa2 spacecraft will follow up last month's touchdown on a distant asteroid with another risky mission—dropping an explosive on the asteroid to make a crater and then collect ...

Bright X-ray galactic nuclei

March 18, 2019

All massive galaxies are believed to host supermassive black holes (SMBH) at their centers that grow by accreting mass from their environment. The current picture also imagines that the black holes grow in size as their host ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.