U.S. and UK rushing to understand risks of a rapidly shrinking Antarctic glacier

NASA
The Thwaites is on the move seaward.

Many a fresh finding from the climate-science frontier carries a whiff of impending catastrophe these days, despite the practitioners’ default dedication to dispassionate calm.

It’s unusual, though, to catch that scent in their discussion of research that has yet to get under way. For instance, the five-year crash program announced Monday, in which 100 U.S. and British scientists will probe beneath alarming indicators of trouble in a West Antarctic ice mass the press can’t stop calling “the doomsday glacier.”

Turns out that is not a wildly inappropriate tag for what’s officially called the Thwaites Glacier, located in a region where rapid melt, ice-shelf crackup and glacial retreat are of key concern because they raise sea levels.

A glacier is really an ice stream flowing toward the sea, but ever so slowly, having been brought nearly to standstill by deep cold (think of a river in flood, its surge captured in a stop-action photograph). The Thwaites and its neighbor, the Pine Island glacier, are two of the five largest such streams on the Antarctic continent. Both are melting more rapidly than normal — rather, what used to be normal — and also much faster than new snowfall can replace the losses.

The Thwaites is also on the move seaward, its leading edge traveling at 2.5 miles per year — not exactly what we think of as a glacial pace.

Varying in thickness from a half-mile to a mile, it sits on a bed of rock and other material whose contour is unusual, and whose characteristics are not well understood. Gaining a grasp of these will be key to understanding how rapidly this glacier is likely to melt and retreat inland, unplugging other streams of trapped water and even, potentially, collapsing in a massive and sudden failure that has no recorded precedent.

Right now, global sea levels are going up about 3.2 millimeters annually, and the Thwaites’ estimated contribution to that freshwater infusion is about 4 percent. That’s what happens when a glacier loses roughly 50 billion metric tons of ice each year.

(Using the calculators at ClimateSanity, I figure the volume of that loss to be about 65 billion cubic yards; a ready-mix cement truck holds 10.)

Because the Thwaites holds, and holds back, so much water all by itself, scientists commonly estimate its total potential contribution at about 10 feet of sea-level rise, enough to cause vast destruction in nearly every coastal city of the world. Even a rise of 3 feet, which used to be a standard yardstick of potential catastrophe, would displace perhaps 145 million people.

Decades, not centuries, in offing?

So the Thwaites has raised prospects that stand in startling contrast to the notion of sea-level rise as a gradual, worldwide process of ice melt that is inevitable but also really slow-moving; time frames that were typically measured in hundreds of years from now are also shrinking rapidly.

Speaking to the Washington Post’s Chris Mooney, geoscientist and project member David Holland said, “For global sea-level change in the next century, this Thwaites glacier is almost the entire story.”

And Scott Borg of the National Science Foundation told the Guardian’s Fiona Harvey, “We do not know how quickly this glacier will contribute to sea level rise, and whether we have decades or centuries to prepare for it.”

“The Doomsday Glacier” appears to be the coinage of Rolling Stone magazine and the writer Jeff Goodell, a noted science journalist who last October published a book on sea-level rise, “The Water Will Come: Rising Seas, Sinking Cities, and the Remaking of the Civilized World.”

His magazine article about the Thwaites last May remains the single most useful and readable discussion you can find, probably, of this glacier and its wider context of concern for the changing West Antarctica ice sheet, which has occupied a handful of scientists since the 1960s but didn’t attract nearly as much climate-focused attention as, say, Greenland until the sudden collapse of the Larsen B ice shelf in 2002.

What collapse could mean

Here’s how Goodell explains the Thwaites’ status as “a threshold system”:

That means instead of melting slowly like an ice cube on a summer day, it is more like a house of cards: It’s stable until it is pushed too far, then it collapses. When a chunk of ice the size of Pennsylvania falls apart, that’s a big problem. It won’t happen overnight, but if we don’t slow the warming of the planet, it could happen within decades.

And its loss will destabilize the rest of the West Antarctic ice, and that will go too. Seas will rise about 10 feet in many parts of the world; in New York and Boston, because of the way gravity pushes water around the planet, the waters will rise even higher, as much as 13 feet. “West Antarctica could do to the coastlines of the world what Hurricane Sandy did in a few hours to New York City,” explains Richard Alley, a geologist at Penn State University and arguably the most respected ice scientist in the world. “Except when the water comes in, it doesn’t go away in a few hours — it stays.”

With 10 to 13 feet of sea-level rise, most of South Florida is an underwater theme park, including Miami, Fort Lauderdale, Tampa and Mar-a-Lago, President Trump’s winter White House in West Palm Beach. In downtown Boston, about the only thing that’s not underwater are those nice old houses up on Beacon Hill.

In the Bay Area, everything below Highway 101 is gone, including the Googleplex; the Oakland and San Francisco airports are submerged, as is much of downtown below Montgomery Street and the Marina District. Even places that don’t seem like they would be in trouble, such as Sacramento, smack in the middle of California, will be partially flooded by the Pacific Ocean swelling up into the Sacramento River. Galveston, Texas; Norfolk, Virginia; and New Orleans will be lost. In Washington, D.C., the shoreline will be just a few hundred yards from the White House.

Key aims of the research

Several special concerns about the Thwaites are driving the new U.S./UK collaboration in eight separate projects budgeted at $25 million just for the research (logistical support will likely cost about as much).

  • Because most of the glacier’s mass sits on land, as opposed to extending out over the ocean as a shelf, nearly all of the Thwaites’ ice losses contribute new water to the rising ocean, and its outer edge is especially undefended against by waves of ice-melting saltwater.
  • The glacier crosses a high ridge before reaching the coast; so this “river of ice” deepens both inland of the ridge and also as it drops toward the sea. If the glacier retreats inland behind the ridge, it could fracture; new meltwater flowing into the fissures could accelerate the breakup; the resulting feedback loop could result in sudden collapse into the ocean.
  • Because so little is known about the underlying land’s composition or texture, potentially crucial factors in the pace of retreat, a major and early thrust of the new research will image the land surface with radar and also seismic sensors, gathering data from small explosive charges dropped into bore holes through the ice.
  • Finally, there is much uncertainty about just what’s happening at the “grounding line,” where the glacier leaves its land base and juts out over the sea in an ice shelf; scientists suspect that warming ocean water is accelerating the shelf’s melt, then warming further in another feedback loop. Remote-controlled instruments, including the UK’s famous Boaty McBoatface submersible, will be used to probe these conditions; so will seals, fitted with sensors to gather data from their own explorations of the West Antarctic coast.

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The National Science Foundation’s materials on the new research program can be found here

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