The Pine Island Glacier is one of the largest bodies of ice in Antarctica, and one of the most active. It moves as rapidly as 4,000 meters a year (2.49 miles), and together with the Thwaites Ice Stream is the frozen version of a watershed for as much as 5 percent of the entire Antarctic Ice Sheet. It stretches for over 160 miles, at an average thickness of just over a mile. Nearly all of the glacier sits on land which is over half a mile below sea level, which makes it unstable, according to environmental scientists.
Since the 1970s, the Pine Island Glacier has been retreating with worrying speed, but it has been protected by the massive ice shelf at its terminus, a 50-mile-wide barricade of floating ice sheet protecting the foot of the glacier from relatively warm polar sea water. But the shelf is shrinking too.
Since 2017, the ice shelf has retreated by almost 12 miles, with several major breakup events. Icebergs as large as Long Island have split off from the sheet and drifted north to break up and melt.
“You can see stuff just tearing apart,” said Ian Joughin, a University of Washington glaciologist and leader of a study of the ice sheet. “So it almost looks like the speed-up itself is weakening the glacier. … And so far we’ve lost maybe 20% of the main shelf.”
The Pine Island Glacier, if it were to melt or be reduced far enough that it floats, could raise the world’s oceans by between four and six feet. Sounds like small numbers, but a six-foot rise in sea level would drown large parts of cities like Boston, New Orleans, London, and Washington, D.C., to say nothing of every coastal community worldwide that isn’t on a cape or bluff.
Joughin’s study tracked two points on the main body of the Pine Island Glacier and found that they were moving 12 percent faster toward the sea since 2017 than they had been before.
“So that means 12 percent more ice from Pine Island going into the ocean that wasn’t there before.”