We're in for a four foot sea level rise over the next few centuries as the entire West Antarctic Ice Shelf slides into the sea, and the West Antarctic Peninsula gets warm Southern Ocean winds and ten times faster land rebound.
A rapidly melting section of the West Antarctic Ice Sheet appears to be in irreversible decline, with nothing to stop the entire glacial basin from disappearing into the sea, according to researchers at UC Irvine and NASA.
The new study presents multiple lines of evidence – incorporating 40 years of observations – that six massive glaciers in the Amundsen Sea sector “have passed the point of no return,”...
These glaciers already contribute significantly to sea level rise, releasing as much ice into the ocean each year as the entire Greenland Ice Sheet does. They contain enough ice to boost the global sea level by 4 feet (1.2 meters) and are melting faster than most scientists had expected. Rignot said the findings will require that current predictions of sea level rise be revised upward.
“This sector will be a major contributor to sea level rise in the decades and centuries to come,” Rignot said. “A conservative estimate is that it could take several centuries for all of the ice to flow into the sea.”
Three major lines of evidence point to the glaciers’ eventual demise: changes in their flow speeds, how much of each glacier floats on seawater, and the slope and depth below sea level of the terrain they’re flowing over. [emphasis mine]
This is happening despite strengthened Southern Ocean winds keeping Antarctic cold, while the rest of the planet heats us.
Researchers have found rising levels of carbon dioxide in the atmosphere are strengthening the stormy Southern Ocean winds which deliver rain to southern Australia, but pushing them further south towards Antarctica.
... the findings explained the mystery over why Antarctica was not warming as much as the Arctic, ...
While most of Antarctica is remaining cold, rapid increases in summer ice melt, glacier retreat and ice shelf collapses are being observed in Antarctic Peninsula, where the stronger winds passing through Drake Passage are making the climate warm exceptionally quickly.
"Strengthening of these westerly winds helps us to explain why large parts of the Antarctic continent are not yet showing evidence of climate warming,"...
We can expect the land under the Antarctica Peninsula to rise up as the ice melts, keeping the angle toward the sea high. New evidence shows the land is rebounding ten times faster than expected, due to extra thin mantle 250 miles below.
... the mantle below Earth's crust in the Antarctic Peninsula is flowing much faster than expected, ...
"You would expect this rebound to happen over thousands of years and instead we have been able to measure it in just over a decade. You can almost see it happening which is just incredible.
"Because the mantle is 'runnier' below the Northern Antarctic Peninsula it responds much more quickly to what's happening on the surface. So as the glaciers thin and the load in that localised area reduces, the mantle pushes up the crust. [emphasis mine]
Two articles reporting on the above study mention a 10 foot, not 4 foot, rise. I must have missed some nuance.
A massive collapse of an ice sheet in Western Antarctica has begun and, according to scientists, is most likely an unstoppable event that will cause an inevitable rise in global sea levels of at least 10 feet.
The rise will be relatively slow at first, but by 2100 will ramp up sharply. This could happen sooner, warn the scientists, as the impacts of anthropogenic climate disruption (ACD/climate change) continue to intensify. [emphasis mine]
... a joint study by NASA and the University of California, Irvine revealed that large chunks of the Western Antarctic Ice Sheet have already begun to collapse — and there is little we can do to stop it.
What does this mean? The Antarctic ice report foreshadows a likely catastrophic 10-foot rise in global sea levels over the next few centuries. [emphasis mine]
A NASA Study Just Showed Us What a Terrifying Moment in Global Warm... provides a mechanism for the melting, tied to the stronger winds.
From the Times:
"Scientists said the ice sheet was not melting because of warmer air temperatures, but rather because of the relatively warm water, which is naturally occurring, from the ocean depths. That water is being pulled upward and toward the ice sheet by intensification of the winds around Antarctica.
... his team had based their projections for the demise of the Thwaites glacier on current melting rates. [emphasis mine]
Why is West Antarctic wind-driven melting likely to speed up? Because the rest of the planet keeps getting hotter while the South Pole is isolated by circular wind and water currents. As the temperature gradient gets steeper, circumpolar winds blow even faster and circulate closer to the South Pole
Antarctica as a whole has not warmed as fast as some other parts of the planet,... This temperature differential is the main reason that Antarctica's winds have sped up.
The greater the temperature difference at the pole, the stronger the winds get and the more they shift southward. The southward shift of the strong westerly winds ... is part of the same process,..
This is the opposite of what's happening to the temperature gradient toward the warming North Pole. The jet stream has slowed and turned wavy.
West Antarctic Ice sheet melt, detail.
The University of Washington study used satellite measurements and computer models to determine that the Thwaites could melt in as little as 200 years, or the melting could take as long as 1,000 years. Ian Joughin, a university glaciologist and the lead author of that study, said the most likely scenario is at the lower end of that range.
“There is quite a bit of ongoing destabilization,” he said, and the disappearance would begin slowly and accelerate over time, with no available “stabilizing mechanism.”
The Thwaites is an important test case because it is viewed as particularly unstable, and a linchpin for the stability of the rest of the West Antarctic Ice Sheet. As goes the Thwaites, many scientists fear, so goes the rest of the ice sheet - its disappearance would undermine the entire glacial system, exposing many more miles of grounding lines to the warming ocean water.
“You can’t just remove this glacier cleanly,” Joughin said. “You pull one part out, the rest will move into the void.”
If the entire ice sheet disappeared, the global sea level could rise by a catastrophic 15 feet.
“Eventually, this could lead to the demise of ice across Antarctica,” Rignot said. [emphasis mine]
“There is quite a bit of ongoing destabilization,” he said, and the disappearance would begin slowly and accelerate over time, with no available “stabilizing mechanism.” nicely captures overall Climate Destabilization's timeline too, in my view.
More details on Thwaites Glacier instability. The current grounding line is on a 600 meter ridge. Initially Thwaites will retreat slowly, raising sea level less than a millimeter per year. Once the grounding line retreats behind this shallower ridge into a deep area - BOOM! - the remaining glacier will melt in just a few decades. Chaotic rapid collapse is most likely 200 to 500 years from now.
... The place where the glacier meets land, the grounding line, now sits on a shallower ridge with a depth of about 2,000 feet (600 meters). Results show that as the ice edge retreats into the deeper part of the bay, the ice face will become steeper and, like a towering pile of sand, the fluid glacier will become less stable and collapse out toward the sea.
"Once it really gets past this shallow part, it's going to start to lose ice very rapidly," Joughin said.
"All of our simulations show it will retreat at less than a millimeter of sea level rise per year for a couple of hundred years, and then, boom, it just starts to really go," Joughin said. Researchers did not model the more chaotic rapid collapse, but the remaining ice is expected to disappear within a few decades.[emphasis mine]
Thwaites glacier is being melted from below by volcanic heat.
The findings significantly change the understanding of conditions beneath the West Antarctic Ice Sheet where accurate information has previously been unobtainable.
... UTIG researchers were able to estimate ice melting rates and thus identify significant sources of geothermal heat under Thwaites Glacier. They found these sources are distributed over a wider area and are much hotter than previously assumed.
... the glacier sits on something more like a multi-burner stovetop with burners putting out heat at different levels at different locations. "It's the most complex thermal environment you might imagine," said co-author Don Blankenship, a senior research scientist at UTIG and Schroeder's Ph.D. adviser. "And then you plop the most critical dynamically unstable ice sheet on planet Earth in the middle of this thing,...
... the minimum average geothermal heat flow beneath Thwaites Glacier is about 100 milliwatts per square meter, with hotspots over 200 milliwatts per square meter. For comparison, the average heat flow of the Earth's continents is less than 65 milliwatts per square meter.
"The combination of variable subglacial geothermal heat flow and the interacting subglacial water system could threaten the stability of Thwaites Glacier in ways that we never before imagined,"... [emphasis mine]
Thanks for helping us stay up to date on how complex the situation is!
(What a contrast between actual science and the climate deniers' insistence on lying and twisting facts to support their "business as usual", "growth forever", and "fossil fuels are good" worldview!)
NASA animation of West Antarctic Ice Shelf melt.
As with many of your serious posts, I don't "like" the underlying events, but appreciate the reporting!
Greenland and Antarctica are "competing" to melt the fastest.
“It’s like a terrible competition between Greenland and Antarctica for Biggest Loser,” ... “Multiple factors have been combining to produce surprisingly rapid change. This is the hallmark of a system unable to catch up with an exponentially increasing forcing.” [emphasis mine]
West Antarctic melt could be even faster than 200 years. Once Thwaites glacier goes the remaining West Antarctic ice sheet will follow.
Because inland basins connect Thwaites Glacier to other major glaciers in the region, both research teams say its collapse would flood West Antarctica with seawater, prompting a near-complete loss of ice in the area over hundreds of years.
“The next stable state for the West Antarctic Ice Sheet might be no ice sheet at all,” says the Science paper’s lead author, glaciologist Ian Joughin of the University of Washington, Seattle.
And once Thwaites is gone, the rest of West Antarctica would be at risk.
Eric Rignot, a climate scientist at the University of California, Irvine, and the lead author of the GRL study, is skeptical of Joughin’s timeline because the computer model used estimates of future melting rates instead of calculations based on physical processes such as changing sea temperatures. “These simulations ought to go to the next stage and include realistic ocean forcing,” he says. If they do, he says, they might predict an even more rapid retreat. [emphasis mine]
This great 5 minute video by Yale Climate Connections gives the best explanation yet of what's happening in Antarctica.
They say that while the current rate of melt would predict collapse in 200 years, evidence indicates that the rate of melt is increasing. Also, many similar glaciers in East Antarctica aren't as well studied, so we don't know what they'll contribute in addition.
During the meltwater pulse 1A (in the past), sea level rose one meter every 20 years for 400 years.
It's interesting that James Hansen predicted this 2014 event in 2009.
Glaciologist John H. Mercer predicted in 1978 that the West Antarctica Ice sheet would melt.
Mr. Mercer made a groundbreaking contribution with a peer-reviewed research paper about West Antarctica’s instability he got published on Jan. 26, 1978, in the scientific journal Nature. In it, he warned the world that West Antarctica’s massive ice sheet — one of Earth’s largest and most important — would eventually melt from beneath, become dislodged, and cause global sea levels to rise 5 meters, the equivalent of nearly 16.5 feet.“I contend that a major disaster — a rapid 5-meter rise in sea level, caused by deglaciation of West Antarctica — may be imminent or in progress after atmospheric CO2 [carbon dioxide] content has only doubled. This concentration of CO2 will be reached within about 50 years if fossil fuel continues to be consumed at its recent accelerating rate,...“He was labeled an alarmist,”... “He had difficulty getting funded [after his paper]. ...
... the pending disaster Mr. Mercer warned about in 1978 is now virtually unstoppable.
John Mercer's "alarmist" prediction came true 14 years early.