West Antarctic ice sheet faces ‘unavoidable’ melting, a warning for sea level rise
In November 2013, a large iceberg separated from the front of Antarctica’s Pine Island Glacier and began its journey across Pine Island Bay, a basin of the Amundsen Sea. (NASA/GSFC/LANCE/EOSDIS Rapid Response/Jeff Schmaltz)
Accelerating ice losses are all but “unavoidable” this century in vulnerable West Antarctic ice shelves as waters warm around them, according to new research. And the analysis could mean scientists were too conservative in predicting about one to three feet of sea level rise by 2100.
by Scott Dance and Chris Mooney
A study found that regardless of how aggressively humans act to reduce fossil fuel emissions — and thus limit how much the planet heats up — waters around some of West Antarctica’s glaciers are forecast to warm at a pace three times faster than they have in the past.
That is expected to cause “widespread increases in ice-shelf melting, including in regions crucial for ice-sheet stability,” according to a study published in the journal Nature Climate Change on Monday. Unlike relatively thin and floating sea ice, the ice shelves are thicker and hold back massive glaciers that contain far more ice.
“It appears we may have lost control of the West Antarctic ice shelf melting over the 21st century,” Kaitlin Naughten, the study’s lead author and an ocean modeler with the British Antarctic Survey, told reporters in a media briefing. “That very likely means some amount of sea level rise that we cannot avoid.”
The research helps to solidify an understanding that humans have probably already pushed some polar ice systems past a tipping point and into escalating decline.
Arctic sea ice has been decreasing for decades, with data suggesting an “irreversible” thinning around the North Pole since 2007. And while Antarctic sea ice has been more stable, it now may be showing signs of dramatic declines as well. Sea ice cover hit a record low around the South Pole in February and last month reached a winter maximum that was its smallest ever observed, by a wide margin.
As the Southern Ocean warms, thinning the floating sea ice, it also increasingly threatens the ice shelves. The new research underscores what dozens of studies have suggested for three decades, said glaciology researcher Ted Scambos: The West Antarctic ice sheet appears to be headed for an eventual “collapse.”
“It is the opposite of resilient,” Scambos, a senior research scientist at the Earth Science & Observation Center at the University of Colorado at Boulder, said in an email. “It takes an ice age to build it, but in a warm period, like now, it teeters on instability.”
The new research focused on the Amundsen Sea, an area of the Southern Ocean that surrounds some of Antarctica’s largest glaciers, which are buttressed by the thinning and retreating ice shelves. They include Thwaites Glacier, which scientists have nicknamed the “doomsday” glacier because if it retreats far enough, it would essentially compromise the center of West Antarctica.
Scientists have estimated that losses to Thwaites could eventually trigger as much as 10 feet of sea level rise, with recent research suggesting that the glacier is already showing signs of disintegration.