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Melting Antarctic glaciers could raise global sea level 11 feet by 2100

posted by Jason Kottke   Nov 24, 2017

Writing for Grist, Eric Holthaus reports on some research about a pair of fast-melting glaciers in Antarctica that could add 11 feet to the global sea level.

The glaciers of Pine Island Bay are two of the largest and fastest-melting in Antarctica. (A Rolling Stone feature earlier this year dubbed Thwaites “The Doomsday Glacier.”) Together, they act as a plug holding back enough ice to pour 11 feet of sea-level rise into the world’s oceans — an amount that would submerge every coastal city on the planet. For that reason, finding out how fast these glaciers will collapse is one of the most important scientific questions in the world today.

To figure that out, scientists have been looking back to the end of the last ice age, about 11,000 years ago, when global temperatures stood at roughly their current levels. The bad news? There’s growing evidence that the Pine Island Bay glaciers collapsed rapidly back then, flooding the world’s coastlines - partially the result of something called “marine ice-cliff instability.”

The ocean floor gets deeper toward the center of this part of Antarctica, so each new iceberg that breaks away exposes taller and taller cliffs. Ice gets so heavy that these taller cliffs can’t support their own weight. Once they start to crumble, the destruction would be unstoppable.

“Ice is only so strong, so it will collapse if these cliffs reach a certain height,” explains Kristin Poinar, a glaciologist at NASA’s Goddard Space Flight Center. “We need to know how fast it’s going to happen.”

Eleven feet of sea level rise would be, uh, hugely problematic for the world’s coastal areas:

Three feet of sea-level rise would be bad, leading to more frequent flooding of U.S. cities such as New Orleans, Houston, New York, and Miami. Pacific Island nations, like the Marshall Islands, would lose most of their territory. Unfortunately, it now seems like three feet is possible only under the rosiest of scenarios.

At six feet, though, around 12 million people in the United States would be displaced, and the world’s most vulnerable megacities, like Shanghai, Mumbai, and Ho Chi Minh City, could be wiped off the map.

At 11 feet, land currently inhabited by hundreds of millions of people worldwide would wind up underwater. South Florida would be largely uninhabitable; floods on the scale of Hurricane Sandy would strike twice a month in New York and New Jersey, as the tug of the moon alone would be enough to send tidewaters into homes and buildings.

Alarming, but read the whole article. Scientists are still trying to figure out how probable this scenario is…early days still.

Update: The site Climate Feedback, a network of scientists that evaluates media coverage of climate change, recently rated Holthaus’ piece as “high” on the credibility scale and described it as both “accurate” and “alarmist”.

Scientists who reviewed the article found that while it accurately described recent research on these processes, it should have provided more accurate context on the timescale of these sea level rise scenarios and the scientific uncertainty about how likely these scenarios are to come to pass.