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A glacier the size of Florida is on track to change the course of human civilization

A glacier the size of Florida is on track to change the course of human civilization



Elizabeth Rush Twitter screenshot

written by Daily Kos

April 2, 2019

Thwaites glacier in West Antarctica is enormous and is often referred to as the most dangerous glacier on Earth. It has also been dubbed the doomsday glacier. The glacier holds two feet of sea level but more importantly, it is the “backstop” for four other glaciers which holds an additional 10-13 feet of sea level rise. When Thwaites collapses it will take most of West Antarctica with it. This is not new information for those of us that follow the science, for example, Eric Rignot in 2014, stated that the loss of West Antarctica is unstoppable. You can listen to an excellent interview from 2019 between Rignot and Radio Eco-shock on Antarctica.

According to researchers at the University of Washington in 2014, Thwaites is already collapsing. “The simulations indicate that early-stage collapse has begun,” notes their paper. What’s more, the Thwaites Glacier is a “linchpin” for the rest of the West Antarctic Ice Sheet; its rapid collapse would “probably spill over to adjacent catchments, undermining much of West Antarctica.”

These might be the oldest (1947!) pictures around of Thwaites Glacier, one of Antarctica’s fastest flowing and most rapidly thinning glaciers. US Navy mapped the area in during Operation Highjump, a mission including 4,700 men, 13 ships, and 33 aircraft (Operation Highjump - Wikipedia). pic.twitter.com/DBFJPd28Lj
— Bert Wouters (@bert_polar) March 19, 2019

Thwaites glacier in 2019.
Thwaites’ calving edge: sailing through what was solid ice sheet just a few years ago, my elation matched only by my grief. @glacierthwaites pic.twitter.com/Dc0q0JqUGf
— Elizabeth Rush (@ElizabethaRush) February 26, 2019

NASA’s Jet Propulsion Laboratory made news this past January by revealing that there is a massive cavity carved in the underbelly of the glacier due to warm ocean water raising alarms that the chunk of ice could collapse and disintegrate the ice shelf.


It reportedly has an area the size of two-thirds of a Manhattan and, it as tall as a ten story building, at 1000 feet. The newfound hole had held fourteen billion tons of ice and, NASA observed that the horrifying melt and decay was not there just three short years ago. It was NASA’s Icebridge program that made the discovery using ice-penetrating radar through the miles deep glacier as well as ”data from a constellation of Italian and German spaceborne synthetic aperture radars”.


But that was just one of the terrors that the satellites found, it confirmed fears that “Thwaites was not attached to the bedrock”.


Another changing feature is a glacier’s grounding line – the place near the edge of the continent where it lifts off its bed and starts to float on seawater. Many Antarctic glaciers extend for miles beyond their grounding lines, floating out over the open ocean.​

Just as a grounded boat can float again when the weight of its cargo is removed, a glacier that loses ice weight can float over land where it used to stick. When this happens, the grounding line retreats inland. That exposes more of a glacier’s underside to seawater, increasing the likelihood its melt rate will accelerate.​
For Thwaites, “We are discovering different mechanisms of retreat,” Millilo said. Different processes at various parts of the 100-mile-long (160-kilometer-long)front of the glacier are putting the rates of grounding-line retreat and of ice loss out of sync.​
The huge cavity is under the main trunk of the glacier on its western side – the side farther from the West Antarctic Peninsula. In this region, as the tide rises and falls, the grounding line retreats and advances across a zone of about 2 to 3 miles (3 to 5 kilometers). The glacier has been coming unstuck from a ridge in the bedrock at a steady rate of about 0.4 to 0.5 miles (0.6 to 0.8 kilometers) a year since 1992. Despite this stable rate of grounding-line retreat, the melt rate on this side of the glacier is extremely high.​
“On the eastern side of the glacier, the grounding-line retreat proceeds through small channels, maybe a kilometer wide, like fingers reaching beneath the glacier to melt it from below,” Milillo said. In that region, the rate of grounding-line retreat doubled from about 0.4 miles (0.6 kilometers) a year from 1992 to 2011to 0.8 miles (1.2 kilometers) a year from 2011 to 2017. Even with this accelerating retreat, however, melt rates on this side of the glacier are lower than on the western side.​

With increased warming and the rise of sea levels, superstorms will become an entirely new animal. I can’t wrap my head around a storm like Sandy destroying Manhattans infrastructure every five years by 2030.


Recently scientists returned from a two-month journey aboard the Nathanial B. Palmer to Thwaites glacier. Jeff Goodell of Rolling Stone Magazine was aboard the research vessel and has filed some dispatches that are quite interesting.


On March 3rd, Bastien Queste, an oceanographer at the University of East Anglia who is a key member of the science team aboard the ship, got a WhatsApp message from a colleague back in the UK. She had sent him a satellite image of Thwaites glacier and the surrounding region in West Antarctica. At the time, we had just completed our own close encounter with the awesome craggy blue glacier and were only a few miles away, mapping the seabed in front of the glacier with the ship’s sonar device.​

On this trip, satellite images have been indispensable in helping scientists track the ever-changing ice in the regions we’ve been exploring. But the map Queste received that morning was different. He noticed dark cracks in parts of the ice shelf, which floats out over the sea like a huge fingernail from the glacier itself. They had not been there before. The ice shelf was clearly starting to break up. Queste’s first thought: “Oh, shit.”​
Queste knew as well as anyone, the whole point of this research trip is to better understand the risk of collapse of Thwaites glacier, one of the most consequential tipping points in the Earth’s climate system. It’s not just that Thwaites is big, although it is (imagine a glacier the size of Florida). But because of how the glacier terminates in deep water, as well as the reverse slope of the ground beneath it, Thwaites is vulnerable to particularly rapid collapse. Even more troubling, Thwaites is like the cork in the wine bottle for the rest of the West Antarctica ice sheet. If Thwaites were to fall apart, scientists fear the entire ice sheet could begin to collapse, eventually raising sea levels more than 10 feet.​

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[…] In a matter of 48 hours or so, a mélange of ice about 25 miles wide and 15 miles deep cracked up and scattered into the sea. As Queste says, “A part of the glacier that is as big as the city I live in — it was just gone.”​

18 years of @ThwaitesGlacier changes from @NASAEarth #MODIS imagery showing the almost complete disintegration of the Thwaites Glacier Tongue pic.twitter.com/qqIsFB88ow
— Stef Lhermitte (@StefLhermitte) March 6, 2019

Two months of shuffling around of the armada of icebergs in front of @ThwaitesGlacier as seen from @CopernicusEU #sentinel1 pic.twitter.com/Kz7t5jpRa9
— Stef Lhermitte (@StefLhermitte) March 4, 2019

4 years of @ThwaitesGlacier ice tongue from @CopernicusEU #sentinel1 satellite imagery showing how this chaotic ice tongue has become a collection of icebergs glued together by sea ice. pic.twitter.com/0QgeXed8yg
— Stef Lhermitte (@StefLhermitte) March 2, 2019

In a separate dispatch, Goodell writes:


We tagged 12 seals with a high-tech instrument that allows them to gather ocean data as they dive and swim; those hard-working seals have already completely more than 10,000 dives, and logged nearly 700 temperature, depth, and salinity reports. We retrieved two moorings that contain important long-term oceanographic measurements. We mapped hundreds of miles of previously uncharted seabed with sonar devices. We launched and recovered underwater gliders to measure ocean temperature and salinity. We completed three missions with the Hugin, an automated underwater device, that created very high-resolution maps of the sea floor in front of Thwaites glacier. We explored old beaches on five remote islands, looking for evidence of past sea level rise in the region. And we bagged 27 sediment cores from the bottom of the Amundsen Sea.​

snip
It will take a while for scientists to analyze the data we’ve collected and say anything definitive. But it’s already clear that some our findings were notable, if not historic: We mapped an uncharted part of the Amundsen Sea, gaining crucial understanding of the topography of the seabed in front of Thwaites that will help scientists understand the flow of warm water beneath the glacier. Using high-resolution instruments in the Hugin, we found tracks on the bottom of the seabed, likely made by retreating glaciers, that will be enormous help for researchers trying to determine when, and if, Thwaites glacier has collapsed in the recent past. And we have gathered the first direct evidence of warm Circumpolar Deep Water flowing under Thwaites, as well as come up with several hypothesis about the mechanism that drives it.​

snip​

I also learned plenty about climate scientists and the work they do. Like the rest of us, they capable of making mistakes, pushing flawed hypothesis and over-interpreting data. Money matters a lot to them, but not in the ways that climate deniers think (it’s all about research funding, not ski condos in Aspen). I learned that some scientists can read sediment cores like a book, with each chapter full of new characters engaged in a mighty struggle to survive on our ever-ever-changing planet. I learned that science is not only hard and often dangerous work, but that it is also impromptu, improvisational and weather-dependent. And that on a ship like the Palmer, scientists are only as good as the marine technicians and crew members who are working with them. Most importantly, I learned that the best scientists are radical and fearless in ways that few outsiders can understand or appreciate. They are heroes of our time.​

John Gertner of Wired Magazine writes:


Anandakrishnan stood up and walked over to a whiteboard to draw me a picture of the glacier bed’s geometry. It was a line that began with a bump in the front, where the glacier met the sea, and sloped gently downward as it went inland. At the moment, he said, it’s unclear how long Thwaites has before it pulls off its bump—its grounding line—and starts a rapid decline. “It’s kind of hanging on by its fingernails right about there,” he explained, gesturing at the bump.​

Glaciers like Thwaites that terminate in the ocean tend to follow a familiar pattern of collapse. At first, water gnaws at the ice shelf from below, causing it to weaken and thin. Rather than sitting securely on the seafloor, it begins to float, like a beached ship lifted off the sand. This exposes even more of its underside to the water, and the weakening and thinning continue. The shelf, now too fragile to support its own weight, starts snapping off into the sea in enormous chunks. More ice flows down from the glacier’s interior, replenishing what has been lost, and the whole cycle starts over again: melt, thin, break, retreat; melt, thin, break, retreat.​

It is difficult to find any scientist, Anandakrishnan especially, who thinks that Thwaites can avoid this fate. Because its bed lies below sea level, water will pursue it far inland. When Thwaites’ grounding line starts to retreat, possibly within the next few decades, Anandakrishnan says, it could do so fairly fast. That retreat may raise sea levels only modestly at first. From radar studies, scientists believe they have detected another bump, now called the Ghost Ridge, that runs about 45 miles behind the existing one. This is what Anandakrishnan’s Ghost team will trace with their seismic experiments from the surface. Is the ridge made of wet sediment, or is it firm and dry? Is it low, or is it high? Such esoteric differences may have extraordinary effects. If any good news arises from his fieldwork at Thwaites, Anandakrishnan says, it may come from the discovery that the glacier has a chance of getting firmly stuck on the Ghost Ridge.​

You might therefore think of Thwaites as a man dangling from the edge of a cliff. Just as he falls, he grips a rock, a sturdy handhold, to avoid the abyss. Of course, the rock may loosen and dislodge tragically in his hands. And then he’ll drop.​

We are not alone in experiencing the trauma from climate change:


Thanks for reading and keeping vigil with me.

A glacier the size of Florida is on track to change the course of human civilization – Alternet.org
 
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