Scientists believe they've identified a key process affecting the melting of an enormous glacier in East Antarctica, bigger than the state of California. And the effects may only worsen with future climate change.
New research published yesterday in the journal Science Advances suggests that wind patterns around the coast of Antarctica may help drive warm water up from the seafloor and into the cavities below East Antarctica's Totten Ice Shelf, causing it to melt from the bottom up.
"We knew that there was warm water around; we knew that all the physical setting was there to make this process possible—but no one had observed the cause and effect," said the new study's lead author, Chad Greene, a geological scientist at the University of Texas, Austin. The new paper may be the first to demonstrate how the influx of warm water underneath the ice shelf is influenced by Antarctic winds.
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These processes are expected to become more intense over the next century, the researchers noted, meaning the glacier could eventually start to melt at a faster rate. And that's concerning news, given the sheer size of the Totten Glacier. If all the ice it contains were to melt into the ocean, it would raise global sea levels by more than 11 feet. Some scientists have even begun to refer to it as East Antarctica's "sleeping giant."
The outward flow of all that ice is held back by the Totten Ice Shelf, a kind of floating ledge of ice that juts out into the ocean and is disconnected from the bedrock grounding the rest of the glacier. Ice shelves are crucial stabilizing components of glaciers—but as they melt and become thinner, they become more likely to break and release a flood of ice behind them. Now, scientists are increasingly worried about the Totten Ice Shelf's vulnerability to warm ocean water seeping up from the bottom of the sea.
The ocean's influence on thinning ice shelves is a phenomenon researchers have mainly observed in West Antarctica, where several rapidly melting glaciers remain—for now—scientists' chief preoccupation on the Antarctic ice sheet. It's a field of research that has been gaining traction in recent years. Where before rising air temperatures were thought to be the dominant force affecting the melting of the world's ice sheets, studies increasingly suggest that the interaction of ice and ocean is a critical factor.
Data on the processes affecting East Antarctica are more scant, but over the last few years, several major studies have indicated that the Totten Ice Shelf may also be melting from below. One of the most recent of these, a major paper published in Science Advances last December, confirmed that warm water is actually flowing into a cavity at the front of the glacier through a previously undiscovered channel.
Yesterday's study helps explain what's driving the movement of that water. Using satellite imagery and wind data from the past 15 years, Greene and his colleagues—a group of scientists from the University of Texas, Austin, and the University of Tasmania in Australia—demonstrate that increases in Totten's ice flow are associated with changes in surface winds, which help to sweep colder surface waters aside and allow warm water to well up from the bottom of the ocean. This warm water is then able to seep into the cavity beneath the ice shelf, as previous studies have indicated, causing an increase in melting and a faster flow of ice.
Climate projections suggest that the upwelling of warm water may increase over the next century, Greene noted.
"Upwelling is driven not purely by the broad-scale magnitude of wind, but by the gradient in wind—how strong the wind is at one latitude versus how strong it is at a different latitude," he explained. "And CO2 in the atmosphere is modeled to increase the wind gradient around Antarctica, and then therefore increase upwelling around Antarctica."
What that actually means for the future of the sleeping giant is unclear for now. How the flow of ice could change in real time is closely tied to the region's underwater topography, which affects how quickly the glacier retreats as the ice shelf melts. These are issues scientists are still investigating.
"In all reality, Totten isn't going to destabilize in our lifetimes and then dump that 11 feet of sea-level rise into the ocean," Greene said. In fact, the increasingly unstable glaciers of West Antarctica remain a far bigger near-term concern among scientists for now.
But over longer time scales, the giant glacier's destabilization could become a possibility, depending on the success of future efforts to mitigate greenhouse gas emissions. And in the meantime, the new study helps advance scientists' understanding of the complex ways the ocean interacts with the world's melting ice sheets and how those interactions may change in a warming world.
Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at www.eenews.net.
