Faster in the past: New seafloor images – the highest resolution of any taken off the West Antarctic Ice Sheet – upend understanding of Thwaites Glacier retreat

At times in its past, retreat of the massive Thwaites Glacier was even quicker than it is today, heightening concerns for its future

Peer-Reviewed Publication

UNIVERSITY OF SOUTH FLORIDA

 

IMAGE: THE R/V NATHANIEL B. PALMER PHOTOGRAPHED FROM A DRONE AT THWAITES GLACIER ICE FRONT IN FEBRUARY 2019. view more 

CREDIT: ALEXANDRA MAZUR/UNIVERSITY OF GOTHENBURG

TAMPA, Fla. (Sept. 2, 2022) – The Thwaites Glacier in West Antarctica – about the size of Florida – has been an elephant in the room for scientists trying to make global sea level rise predictions.

This massive ice stream is already in a phase of fast retreat (a “collapse” when viewed on geological timescales) leading to widespread concern about exactly how much, or how fast, it may give up its ice to the ocean.

The potential impact of Thwaites’ retreat is spine-chilling: a total loss of the glacier and surrounding icy basins could raise sea level from three to 10 feet.

A new study in Nature Geoscience led by marine geophysicist Alastair Graham at the University of South Florida’s College of Marine Science adds cause for concern. For the first time, scientists mapped in high-resolution a critical area of the seafloor in front of the glacier that gives them a window into how fast Thwaites retreated and moved in the past.

The stunning imagery shows geologic features that are new to science, and also provides a kind of crystal ball to see into Thwaites’ future. In people and ice sheets alike, past behavior is key to understanding future behavior.

The team documented more than 160 parallel ridges that were created, like a footprint, as the glacier’s leading edge retreated and bobbed up and down with the daily tides.

“It’s as if you are looking at a tide gauge on the seafloor,” Graham said. “It really blows my mind how beautiful the data are.”

Beauty aside, what’s alarming is that the rate of Thwaites’ retreat that scientists have documented more recently are small compared to the fastest rates of change in its past, said Graham.

To understand Thwaites’ past retreat, the team analyzed the rib-like formations submerged 700 meters (just under half a mile) beneath the polar ocean and factored in the tidal cycle for the region, as predicted by computer models, to show that one rib must have been formed every single day.

At some point in the last 200 years, over a duration of less than six months, the front of the glacier lost contact with a seabed ridge and retreated at a rate of more than 2.1 kilometers per year (1.3 miles per year) – twice the rate documented using satellites between 2011 and 2019.

“Our results suggest that pulses of very rapid retreat have occurred at Thwaites Glacier in the last two centuries, and possibly as recently as the mid-20th Century,” Graham said.

“Thwaites is really holding on today by its fingernails, and we should expect to see big changes over small timescales in the future–even from one year to the next–once the glacier retreats beyond a shallow ridge in its bed,” said marine geophysicist and study co-author Robert Larter from the British Antarctic Survey.

To collect the imagery and supporting geophysical data, the team, which included scientists from the United States, the United Kingdom and Sweden, launched a state-of-the-art orange robotic vehicle loaded with imaging sensors called ‘Rán’from the R/V Nathaniel B. Palmer during an expedition in 2019.

Rán, operated by scientists at the University of Gothenburg in Sweden, embarked on a 20-hour mission that was as risky as it was serendipitous, Graham said. It mapped an area of the seabed in front of the glacier about the size of Houston – and did so in extreme conditions during an unusual summer notable for its lack of sea ice.

This allowed scientists to access the glacier front for the first time in history.

“This was a pioneering study of the ocean floor, made possible by recent technological advancements in autonomous ocean mapping and a bold decision by the Wallenberg foundation to invest into this research infrastructure,” said Anna Wåhlin, a physical oceanographer from the University of Gothenburg who deployed Rán at Thwaites. “The images Ran collected give us vital insights into the processes happening at the critical junction between the glacier and the ocean today.”

“It was truly a once in a lifetime mission,” said Graham, who said the team would like to sample the seabed sediments directly so they can more accurately date the ridge-like features.

“But the ice closed in on us pretty quickly and we had to leave before we could do that on this expedition,” he said.

While many questions remain, one thing’s for sure: It used to be that scientists thought of the Antarctic ice sheets as sluggish and slow to respond, but that’s simply not true, said Graham.

“Just a small kick to Thwaites could lead to a big response,” he said.

According to the United Nations, roughly 40 percent of the human population lives within 60 miles of the coast.

“This study is part of a cross-disciplinary collective effort to understand the Thwaites Glacier system better,” said Tom Frazer, dean of the USF College of Marine Science, “and just because it’s out of sight, we can’t have Thwaites out of mind. This study is an important step forward in providing essential information to inform global planning efforts.”

The study was supported by the National Science Foundation and the UK Natural Environment Research Council through the International Thwaites Glacier Collaboration.

The 2019 expedition was the first in a five-year project dubbed THOR, which stands for Thwaites Offshore Research, and also included team members from a sister project called the Thwaites-Amundsen Regional Survey and Network Integrating Atmosphere-Ice-Ocean Processes, or TARSAN.

For more information, read this companion story authored by Graham and the team.

About the University of South Florida

The University of South Florida, a high-impact global research university dedicated to student success, generates an annual economic impact of more than $6 billion. Over the past 10 years, no other public university in the country has risen faster in U.S. News and World Report’s national university rankings than USF. Serving more than 50,000 students on campuses in Tampa, St. Petersburg and Sarasota-Manatee, USF is designated as a Preeminent State Research University by the Florida Board of Governors, placing it in the most elite category among the state’s 12 public universities. USF has earned widespread national recognition for its success graduating under-represented minority and limited-income students at rates equal to or higher than white and higher income students. USF is a member of the American Athletic Conference. Learn more at www.usf.edu

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JOURNAL

Nature

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Rapid retreat of Thwaites Glacier in the pre-satellite era

ARTICLE PUBLICATION DATE

5-Sep-2022

A 3D-rendered view of the multibeam bathymetry (seafloor shape) colored by depth, collected by Rán across a seabed ridge, just in front of Thwaites Ice Shelf.

CREDIT

Alastair Graham/University of South Florida

Rán, a Kongsberg HUGIN autonomous underwater vehicle, amongst sea ice in front of Thwaites Glacier, after a 20-hour mission mapping the seafloor.

CREDIT

Anna Wåhlin/University of Gothenburg

THOR scientists Alastair Graham (right) and Robert Larter (left) look on in awe at the crumbling ice face of the Thwaites Glacier margin, from the bridge deck of the R/V Nathaniel B. Palmer.

CREDIT

Frank Nitsche

SEE LA REVUE GAUCHE - Left Comment: Search results for THWAITES 

The threat from Thwaites: The retreat of Antarctica's riskiest glacier

by British Antarctic Survey

Thwaites ice cliff. The glacier currently contributes four percent of annual global sea level 

rise. Credit: Rob Larter, BAS

Antarctica's Thwaites Glacier is retreating rapidly as a warming ocean slowly erases its ice from below, leading to a faster flow, more fracturing and a threat of collapse, according to an international team of scientists. The glacier currently contributes four percent of annual global sea level rise. If it does collapse, global sea levels would rise by several feet—putting millions of people living in coastal locations in danger from extreme flooding.

Dr. Peter Davis, Physical Oceanographer at British Antarctic Survey (BAS), says: "Thwaites Glacier in West Antarctica is a river of ice the size of Great Britain that has been changing dramatically over the past 30 years. The speed at which it flows into the ocean has doubled, and there are fears that a complete collapse of the glacier could raise sea levels by over 60cm. Critically, the glacier is currently held back by an ice shelf, a floating extension of the glacier that is held in place by an underwater mountain.

Recent research as part of the International Thwaites Glacier Collaboration has shown that this ice shelf is under attack from all sides. It is being melted from below by warm ocean waters, causing it to lose its grip on the underwater mountain. At the same time, massive fractures are forming and growing across the ice shelf surface. The research suggests that at the current rate of change, this critical ice shelf will begin to break apart within the next two decades, with severe consequences for the stability of Thwaites Glacier and ultimately sea level here in the UK."

Thwaites field camp. Thwaites Glacier is retreating rapidly as a warming ocean slowly

 erases its ice from below. Credit: BAS

The International Thwaites Glacier Collaboration is a collaboration between UK and US scientists, involving over 60 scientists and students. This five year project is aimed at collecting instrument data throughout the glacier and the adjacent ocean, and modeling ice flow and the future of the ice sheet. Their work has revealed major changes in the ice, the surrounding water and the area where it floats of the bedrock below. The ITGC It is one of BAS' flagship projects and several of our science and support staff are currently being deployed for the start of the 2021–2022 field research season.

Thwaites sits in West Antarctica, flowing across a 120km stretch of frozen coastline. A third of the glacier flows more slowly than the rest—it's braced by a floating ice shelf which prevents faster flow of the upstream ice. But the brace of ice slowing Thwaites won't last for long, said Erin Petitt, an associate professor at Oregon State University. Beneath the surface, warmer ocean water circulating beneath the floating eastern side is melting the ice directly from beneath. This floating extension of the Thwaites Glacier will likely only survive a few more years.

Peter Davis, whose team use hot water to drill access holes from the surface of the ice shelf to the ocean cavity hundreds of meters below, adds: "Warm water is also a threat for the so-called 'grounding zone,' the area where the glacier lifts off the seabed. The ocean waters in the grounding zone are warm, by polar standards, and salty, and this generates prime conditions for melting the ice shelf from beneath."

Credit: British Antarctic Survey

Peter Washam, a research associate at Cornell University, also studies the grounding zone. His team lowered a remote-controlled underwater robot through the borehole to take measurements of the ocean, ice and seafloor in this region. They mapped these properties up to the point where the ice and seafloor came in contact. Washam describes the grounding zone as "chaotic," with warm water, rugged ice, and a steep, sloping bottom that allows the water to quickly melt the ice sheet from below.

Upstream of here, researchers have found that water is pumped under the ice sheet by tides. Lizzy Clyne, an adjunct professor at Lewis and Clark College, and their team study the tidal pumping mechanism that physically forces warm water between the ice and bedrock at Thwaites. The floating portion of the glacier rises and falls with the tides—and that motion acts like a lever, pumping water under the ice sheet. Also, downstream of the grounding zone on the bottom of the floating ice shelf, constant stretching and melting is rapidly creating long channels through the ice where water can flow, impacting the long term stability of the ice shelf, said Clyne.

As Thwaites retreats upstream and into the ice sheet, it may form very tall ice cliffs at the ocean front. Anna Crawford, a postdoctoral researcher at the University of St. Andrews, and her team use computer modeling to study ice cliff failure: a process by which ice can break off the ends of the glacier into the open ocean. The process can take on many forms, but all of them could lead to very rapid retreat of the massive glacier. The bedrock shape of West Antarctica makes the region vulnerable to rapid retreat via ice-cliff failure, as increasingly tall cliffs could be exposed as the ice retreats. This could lead to a chain-reaction of fracturing, resulting in collapse, said Crawford. A challenge for the team is assessing if, when, and how fast this might occur, but major ice loss is possible within several decades to a few centuries.

Thwaites Glacier is one of Antarctica’s most unstable glaciers. Credit: Jeremy Harbeck

Ted Scambos, a senior research scientist at the Cooperative Institute for Research in Environmental Sciences (CIRES) says: "If Thwaites were to collapse, it would drag most of West Antarctica's ice with it, so its critical to get a clearer picture of how the glacier will behave over the next 100 years. "

ITGC research, including future sea-level projections, will be vital for policy makers in their efforts to mitigate and adapt to the impacts of global sea level rise.Scientists find record warm water in Antarctica, pointing to cause behind troubling glacier melt

More information: For more information, see thwaitesglacier.org/

Provided by British Antarctic Survey 

What if the Doomsday Glacier Collapses?

BY ROBERT HUNZIKERFacebook

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The Thwaites “Doomsday Glacier” in West Antarctica is spooking scientists. Satellite images shown at a recent meeting December 13^th of the American Geophysical Union showed numerous large, diagonal cracks extending across the Thwaites’ floating ice wedge.

This is new information, and it’s a real shocker if only because it’s happening so quickly, much sooner than expectations. It could collapse. And, it’s big, 80 miles across with up to 4,000 feet depth with a 28-mile-wide cracking ice shelf that extends over the Amundsen Sea.

Meanwhile, and of special interest because of the underlying threat posed by Thwaites, the Intergovernmental Panel on Climate Change (IPCC) COP26 meeting in November 2021 held in Glasgow was panned by scientists as one more sleepy affair, failing to come to grips with Western Civilization’s biggest challenge since the Huns trampled Rome. This outrageous failure by the world’s leaders, evidenced by weak-kneed proposals, is decidedly threatening to coastal cities throughout the world, especially with Thwaites glacier showing signs of impending collapse.

According to glaciologist Erin Pettit of Oregon State University, the weak spots on the Thwaites ice sheet are like cracks in a windshield: “One more blow and they could spider web across the entire ice shelf surface.” (Source: Crucial Antarctic Ice Shelf Could Fail Within Five Years, Scientists Say, SFGATE, December 13, 2021)

An article in NewScientist d/d December 13, 2021 discussed the AGU meeting of the satellite images of massive cracks: “Antarctica’s Thwaites glacier could break free of the continent within 10 years, which could lead to catastrophic sea level rise and potentially set off a domino effect in surrounding ice.”

Thwaites is a monster, one of the largest glaciers in the world. A 2017 Rolling Stone article, which followed the footsteps of a team of glaciologists at Thwaites glacier, summed up the situation, according to Ohio State glaciologist Ian Howat: “If there is going to be a climate catastrophe, it’s probably going to start at Thwaites… if we don’t slow the warming of the planet, it could happen within decades.” (Source: The Doomsday Glacier, Rolling Stone, May 9, 2017)

That was five years ago but after rapidly changing conditions on the ice sheet in only five years, scientists are no longer saying: “It could happen within decades.” Now the timeline has changed to: “Within a decade,” meaning by 2032. Moreover, as suggested in the aforementioned SFGATE article, there’s some speculation that it could burst wide open “sooner rather than later.”

The world is not prepared for a major disaster on a scale that spreads across the planet unimpeded and totally out of control. In that regard, it’s unfortunate that the world’s leaders have failed to take adequate measures, especially since scientists have been warning for decades of dire consequences for failure to limit and/or stop CO2 emissions. The truth of the matter is the world’s leaders have failed to protect their own people because of ignorance, greed, and tons of dark money.

Thwaites is what scientists refer to as “a threshold system.” Which 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’s pushed too far, then it collapses with a resounding thud!

What happens after the Ice Shelf collapses?

Thwaites’ ice shelf is one of the most significant buttresses against sea level rise in West Antarctica. New data provides clear evidence that warming ocean currents are eroding the eastern ice shelf from underneath. Meanwhile, a major risk is that the series of cracks spotted on the surface shatter into hundreds of icebergs. In the words of glaciologist Erin Pettit: “Suddenly the whole thing would collapse.”

A collapse of the ice shelf would not immediately impact sea level rise as the ice shelf itself already floats on the ocean surface. Its weight is already displaced in the water. But, once it collapses, the landlocked glacier containing a much larger volume of ice behind the ice shelf will be released, or sprung lose, and dramatically increase its rate of flow to the sea.

A collapse of Thwaites is no small deal. Depending upon several factors, it would trigger the onset of raised sea levels by some number of feet, and paradoxically, it would be happening in the face of IPCC guidance expecting sea levels to rise by a foot or so by 2100, assuming business as usual. That could turn out to be peanuts compared to a collapse of Thwaites if it triggers a domino effect of surrounding ice in West Antarctica, as alluded to in the aforementioned NewScientist article.

Thwaites’ significance to the normal course of life is so potentially impactful as a negative force that a team of scientists studies the glacier under the title: The International Thwaites Glacier Collaboration. According to the lead glaciologist of the team, Ted Scambos (University of Colorado, Boulder): “Things are evolving really rapidly here… It’s daunting.” He spoke on Zoom from Thwaites glacier.

Once the ice shelf collapses, it’ll lead to massive “ice cliff collapsing,” ongoing collapse of towering walls of ice directly overlooking the ocean that crumbles into the sea. And, once ice cliff collapsing starts, it will likely become a self-sustaining “runaway collapse.”

This alarming signal of impending collapse of one of the world’s largest glaciers underscores a potent political message: What do the world’s leaders, e.g., the US Congress, plan to do about the fossil fuel-derived greenhouse gas emissions from cars, trucks, trains, planes, agriculture, and industry that blanket the atmosphere and heat up the oceans to the extent that a bona fide behemoth of ice is getting much closer to splintering apart and collapsing with attendant sea level rise that will flood Miami, just for starters?

Does Build Back Better include funding for continent-wide seawalls?

And yet, the biggest unknown in this grisly affair is timing, assuming Thwaites does collapse within a decade, how soon will ice cliff collapses bring on sea level rise that drowns the world’s coastal metropolises? Nobody knows the answer to that daunting question, but it certainly appears to be forthcoming.

Robert Hunziker lives in Los Angeles and can be reached at rlhunziker@gmail.com.

Warming seas are carving into glacier that could trigger sea level rise

New research provides a startling look at how warmer 

oceans, driven by climate change, are gouging the 

West Antarctic’s Thwaites Glacier

By Chris Mooney

Updated February 15, 2023

A robot called the Icefin operates under the sea ice near McMurdo Station, an Antarctic research station. (Schmidt-Lawrence/NASA PSTAR RISE UP)

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Rapidly warming oceans are cutting into the underside of the Earth’s widest glacier, startling new data and images show, leaving the ice more prone to fracturing and ultimately heightening the risk for major sea level rise.

Using an underwater robot at Thwaites Glacier, researchers have determined that warm water is getting channeled into crevasses in what the researchers called “terraces” — essentially, upside-down trenches — and carving out gaps under the ice. As the ice then flows toward the sea, these channels enlarge and become spots where the floating ice shelf can break apart and produce huge icebergs. If the remaining shelf is further undermined, Thwaites Glacier will flow into the ocean faster and boost global sea levels on a large scale.

A team deploys the Icefin at Thwaites Glacier in January 2020. (Andrew Mullen/International Thwaites Glacier Collaboration)

Warm water carves underwater crevasses into glacier

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Underwater video taken of the Thwaites Glacier in Antarctica in January 2020 shows carvings of potential break points beneath the glacier. (Video: International Thwaites Glacier Collaboration)

The results from overlapping teams of more than two dozen scientists, published Wednesday in two papers in the journal Nature, reveal the extent to which human-caused warming could destabilize glaciers in West Antarctica that could ultimately raise global sea level by 10 feet if they disintegrate over the coming centuries.

Scientists with the International Thwaites Glacier Collaboration, a historic scientific collaboration organized by the United States and the United Kingdom, arrived at one of the safest spots to land on the West Antarctic behemoth in 2019 and 2020, and used hot water to drill through nearly 2,000 feet of ice to the ocean below.

Here, in a region known as the eastern ice shelf, they deployed an ocean sensor at the base of the floating ice shelf and sent down an 11-foot-long pen-shaped robot called Icefin. The vessel collected data and images in an environment in which warm ocean water, in some places more than 2 degrees Celsius above the local freezing point, is weakening the glacier.

The biggest revelation was that the ice melt is very uneven, with relatively slow loss in flat areas on the underside of the glacier. But the warm water entering Thwaites Glacier’s crevasses poses a serious threat, according to Britney Schmidt, a Cornell University scientist who is the lead researcher behind Icefin and deployed it with a group of 12 other researchers who encamped on the ice.

“The warm water is getting into the weak spots of the glacier, and kind of making everything worse,” Schmidt said.

“It shouldn’t be like that,” Schmidt continued. “That’s not what the system would look like if it wasn’t being forced by climate change.”

The new observations emerge from what is the very definition of an extreme environment. In this part of Thwaites Glacier — perhaps its most stable region — 1,900-foot-thick ice lifts upward from the seafloor and spreads over the ocean. Where the ice first departs from the seafloor is called the “grounding line” — the three-dimensional intersection of ice, ocean and bedrock. Outward from there, the floating ice creates a dark cavity that warm seawater and some fish can enter — but that humans cannot.

Underwater robot deployed beneath Antarctic glacier

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The Icefin underwater robot was deployed beneath the Thwaites Glacier in Antartica in January 2020 to measure ice melt beneath the surface of the glacier. (Video: International Thwaites Glacier Collaboration)

That’s why the observations from Icefin — which scientists pulled back up the borehole after the experiments and can be deployed again — are so unprecedented and revealing. “That’s the first time we’ve had data from that kind of environment, for Thwaites or any other glacier,” Schmidt said.

They give breathtaking details of what it looks like beneath the glacier.

Near the grounding line, video from the robot shows an underside of the ice that is dark and grainy because seafloor mud and sediment is frozen into it. Further downstream, the robot observed sand and pebbles falling out of the ice as it melted.

Within the crevasses and terraces, the robot captured video of scalloped side walls that resemble a round coffered ceiling.

“The technical achievement of getting this amazing range of data in a very difficult environment, and getting out safely, is just wonderful,” said Richard Alley, a glaciologist at Penn State who was not directly involved in the research.

The unique data and images come from what is arguably the most important ocean-facing glacier of them all — at least so far as humans are concerned.

The Icefin at Kamb Ice Stream after being pulled from the water. (Schmidt-Lawrence/NASA PSTAR RISE UP)

Antarctica’s Thwaites Glacier in 2019. (Jeremy Harbeck/OIB/NASA)

Thwaites is some 80 miles across and is the exit point for an area of ice larger than Florida. It is, essentially, the heart of West Antarctica, so large that if lost, it could be replaced only by a new Thwaites Sea.

Thwaites has been losing ice at an accelerating pace, based on data provided by Eric Rignot, one of the studies’ co-authors, at the University of California at Irvine.

The rate of loss overall since 1979 has been a little less than 20 billion tons per year, but that has increased to more than 40 billion tons since 2010, according to the data Rignot provided.

“This robot is getting to the hard places where we need to go to understand the future of the continent,” Rignot said. “We cannot understand what we cannot observe and measure.”

The terraced and scalloped features are generally not included in the simulations, or models, which attempt to forecast what the all-important Thwaites Glacier system will do in the future, the new research noted.

That’s critical because as the ice flows outward over the ocean — that is why this part of the glacier is called an ice shelf — crevasses that begin at the grounding line grow and develop over the course of this motion.

“This melting that starts right at the grounding line in crevasses is really important for what happens downstream,” Schmidt said. “Downstream, where it’s falling apart, these crevasses become these giant features.”

In the main trunk of Thwaites — where the seafloor is deeper and the glacier’s movement much faster, and which is difficult to safely reach — the floating ice shelf has largely collapsed. In the calmer eastern region, where the research took place, it is still intact but features large cracks.

In both regions, the grounding line of the glacier is retreating toward the center of Antarctica. And in both regions the glacier is out of balance, meaning it is getting thinner, and losing more ice to the ocean than is being replaced by flow from the inland parts of Antarctica.

A borehole drilling site on the Thwaites Glacier is seen in 2022. (Peter Davis/British Antarctic Survey)

When it comes to the Icefin robot, “my hope is that we will have a chance to take it to [the] main trunk of Thwaites, which is harder to get to, but also more important (deeper, warmer, moving faster, etc.),” Rignot said in an email. “These studies show it can be done and that we learn enormously from it.”

There was some good news in the research: In areas measured beneath Thwaites that were not characterized by crevasses and terraces, the melt rates were fairly slow. That’s because cold fresh meltwater created a protective layer that insulated the ice from the warmer water below — which could mix up into the crevasses but was thwarted in the more linear environment. Thus, nearly a third of melting occurred in the crevasses, the scientists calculated.

And the slower melt rate outside of them is not much consolation, considering that this slow rate may not be characteristic of the faster-changing part of Thwaites, and at any rate does not change the fact that the glacier is losing ice and retreating.

“What the results show is that you don’t need a large increase in melting to drive rapid retreat,” said Peter Davis, a researcher with the British Antarctic Survey who led a second paper published with Schmidt’s by a largely overlapping team of scientists. “You just need to shift it out of equilibrium.”

Scientists consulted by The Washington Post had different readings of what the new research means for our overall understanding of what Thwaites Glacier will do to coastlines in our coming lifetimes.

For Ted Scambos, a glaciologist at the University of Colorado, the results from the International Thwaites Glacier Collaboration dampen somewhat the fear of catastrophic collapse of the glacier any time soon. It is retreating and that may not be stoppable, Scambos said, but the pace will still be manageable in coming decades.

“While we might see only a moderate add-on to sea level rise in the next 50 years, the processes are real, and the triggers for accelerating the collapse are bound to occur,” he said. “But we have also seen how to apply the brakes, what parts of the climate and ocean system are the main drivers, and what makes them drive. … We have some time to get this under control. Otherwise, the century of our grandchildren’s children will be very, very difficult.”

Alley, the glaciologist at Penn State, had a somewhat different overall outlook — that at least we are finally learning how these gigantic glaciers work.

“Overall, these papers don’t really change my level of worry about Thwaites collapse or not,” Alley said. “But the papers increase my optimism that we can make sense of this incredibly difficult and important system, and improve our ability to project what it may do in the future.”