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west antarctic ice sheet
Antarctic Tipping Point That Occurred 8,000 Years Ago 'Could Happen Again'
"We now have direct evidence that this ice sheet suffered rapid ice loss in the past," said a Cambridge researcher.
Feb 09, 2024
As European Union scientists confirmed that last month continued a worrying trend of historically high temperatures, U.K. researchers released a study Thursday warning how fossil fuel-driven global heating could lead to catastrophic and rapid ice loss in Antarctica not seen for thousands of years.
The study, published by researchers at the British Antarctic Survey (BAS) and the University of Cambridge in Nature Geoscience, relies on an ice core from the West Antarctic Ice Sheet that is over 2,100 feet long.
"We now have direct evidence that this ice sheet suffered rapid ice loss in the past," said senior author and Cambridge Earth sciences professor Eric Wolff in a statement. "This scenario isn't something that exists only in our model predictions and it could happen again if parts of this ice sheet become unstable."
"The very same processes we are seeing just beginning now, in areas like Thwaites Glacier, have played out before in similar areas of Antarctica and indeed, the pace of ice loss was equal to our worst fears about a runaway ice loss."
Study co-author and BAS researcher Isobel Rowell explained that "we wanted to know what happened to the West Antarctic Ice Sheet at the end of the Last Ice Age, when temperatures on Earth were rising, albeit at a slower rate than current anthropogenic warming."
"Using ice cores we can go back to that time and estimate the ice sheet's thickness and extent," she continued. The team measured stable water isotopes and the pressure of air bubbles in the core, and found that the ice sheet "shrank suddenly and dramatically" about 8,000 years ago.
"We already knew from models that the ice thinned around this time, but the date of this was uncertain," Rowell noted, referencing estimates of 5,000-12,000 years ago. "We now have a very precisely dated observation of that retreat that can be built into improved models."
The West Antarctic Ice Sheet is vulnerable because lots of it is on bedrock that's below sea level.\n\nIt looks like warm ocean water getting underneath triggered melting 8,000 years ago, before it stabilised at today's size.\n\nHuman-induced warming could restart the retreat.\n\n\ud83e\uddf53/3— (@)
Previous models also didn't indicate how quickly the retreat happened. However, the team's measurements showed that "once the ice thinned, it shrunk really fast," said Wolff.
"This was clearly a tipping point—a runaway process," he added. "It's now crucial to find out whether extra warmth could destabilize the ice and cause it to start retreating again."
University of Colorado Boulder glaciologist Ted Scambos was not involved with the study, but he called it "an excellent piece of detective work" and toldCNN that its takeaway message is "the amount of ice stored in Antarctica can change very quickly—at a pace that would be hard to deal with for many coastal cities."
CNN pointed out that the study contributes to mounting warnings from scientists about conditions in Antarctica:
For example, the Thwaites Glacier, also in West Antarctica, is melting rapidly. A 2022 study said the Thwaites—dubbed the Doomsday Glacier for the catastrophic impact its collapse would have on sea-level rise—was hanging on "by its fingernails" as the planet warms.
This new study adds to these concerns, Scambos said. "[It] shows that the very same processes we are seeing just beginning now, in areas like Thwaites Glacier, have played out before in similar areas of Antarctica and indeed, the pace of ice loss was equal to our worst fears about a runaway ice loss."
As Common Dreamsreported in October, a study published in Nature Climate Change found that the West Antarctic Ice Sheet—which contains enough ice to increase the global mean sea level by over 17 feet—faces an "unavoidable" increase in melting for the rest of this century.
"If we wanted to preserve it in its historical state, we would have needed action on climate change decades ago," lead author and BAS researcher Kaitlin Naughten said at the time—while also stressing that "we must not stop working to reduce our dependence on fossil fuels."
The release of that study preceded the 28th United Nations Climate Change Conference in Dubai. After COP28 ended in December with a final agreement that did not explicitly endorse a global phaseout of fossil fuels, scientists called it a "tragedy for the planet."
Despite the heat that the United Arab Emirates caught for having a fossil fuel CEO lead the latest summit, COP29 host Azerbaijan plans to have an oil executive head the next one, scheduled for November. Azerbaijan also plans to boost its gas production by a third during the next decade.
The COP29 host is far from alone. Global Witness revealed last month that the oil and gas companies that signed a decarbonization pact at last year's conference plan to burn through around 62% of the world's carbon budget by 2050—which sparked fresh demands for governments to stop caving to polluters and implement more ambitious climate policies.
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Study Warns Even With Emissions Cuts, West Antarctic Ice Sheet Melt 'Unavoidable'
"It looks like we've lost control of melting of the West Antarctic Ice Sheet," said one author. "The bright side is that by recognizing this situation in advance, the world will have more time to adapt to the sea-level rise that's coming."
Oct 23, 2023
Even if humanity dramatically reduces planet-heating pollution from fossil fuels, the West Antarctic Ice Sheet faces an "unavoidable" increase in melting for the rest of this century, according to a study published Monday in the journal Nature Climate Change.
The West Antarctic Ice Sheet is the continent's largest contributor to rising seas and contains enough ice to increase the global mean sea level by over 17 feet, the study explains. Enhanced melting of ice shelves, "the floating extensions of the ice sheet, has reduced their buttressing and caused upstream glaciers to accelerate their flow" toward the Southern Ocean. Ice shelf melting could "cause irreversible retreat" of the glaciers.
Using the United Kingdom's national supercomputer, scientists ran simulations on ocean-driven melting of ice shelves in the Amundsen Sea. They simulated a historical scenario of the 20th century and four future scenarios: two involving medium and high emissions and two using the goals of the Paris agreement, which aims to keep global temperature rise this century below 2°C, with a more ambitious target of 1.5°C, relative to preindustrial levels.
"We must not stop working to reduce our dependence on fossil fuels."
The trio of British Antarctic Survey (BAS) and Northumbria University researchers found that "rapid ocean warming, at approximately triple the historical rate, is likely committed over the 21st century, with widespread increases in ice-shelf melting, including in regions crucial for ice sheet stability."
"When internal climate variability is considered, there is no significant difference between mid-range emissions scenarios and the most ambitious targets of the Paris agreement," the study states. "These results suggest that mitigation of greenhouse gases now has limited power to prevent ocean warming that could lead to the collapse of the West Antarctic Ice Sheet."
In other words, "it looks like we've lost control of melting of the West Antarctic Ice Sheet," said lead author and BAS researcher Kaitlin Naughten in a statement. "If we wanted to preserve it in its historical state, we would have needed action on climate change decades ago."
"The bright side is that by recognizing this situation in advance, the world will have more time to adapt to the sea-level rise that's coming," Naughten noted. "If you need to abandon or substantially re-engineer a coastal region, having 50 years lead time is going to make all the difference."
"We must not stop working to reduce our dependence on fossil fuels," she stressed. "What we do now will help to slow the rate of sea-level rise in the long term. The slower the sea-level changes, the easier it will be for governments and society to adapt to, even if it can't be stopped."
As Reutersreported Monday:
The collapse of the West Antarctic Ice Sheet is one of nine global climate "tipping points" scientists identified in 2009. The passing of these environmental red lines would be catastrophic for life on Earth.
An international team of scientists said in 2022 we may already have passed the point of no return for the West Antarctic Ice Sheet at just 1.1°C of warming above preindustrial levels.
Tiago Segabinazzi Dotto, a senior research scientist at the U.K.'s National Oceanography Center who was not involved in the study, said in a statement that "it is likely that we passed a tipping point to avoid the instability of the West Antarctic Ice Sheet."
"This work fits with existing evidence that suggests that the collapse of ice shelves in the Amundsen Sea is imminent, such as the Thwaites Ice Shelf," he continued. "However, the pace of this collapse is still uncertain—it can happen in decades for some specific ice shelves or centuries."
"The conclusions of the work are based on a single model and need to be treated carefully since different models and even ensembles of the same model can give different responses," he added, while also emphasizing that "this study needs to be taken in consideration for policymakers."
Other experts who were not involved with the research also regarded its revelations as significant and echoed Naughten's call for ramping up worldwide efforts tackle the climate emergency by cutting emissions.
"This is a sobering piece of research," said University of Southampton physical oceanography professor Alberto Naveira Garabato. "It should also serve as a wake-up call. We can still save the rest of the Antarctic Ice Sheet, containing about 10 times as many meters of sea level rise, if we learn from our past inaction and start reducing greenhouse gas emissions now."
Alessandro Silvano, an independent research fellow at the Natural Environment Research Council (NERC), said that "particularly important will be the future of East Antarctica, where about 90% of the Antarctic ice is stored."
Andrew Shepherd, head of Northumbria's Department of Geography and Environment and director of the NERC Center for Polar Observation and Modeling, said that while the "conclusion about the inevitability of West Antarctic Ice Sheet collapse is pessimistic, sticking to 1.5°C of global warming buys us 50 years on the extreme scenario... and even 20 years on sticking to 2°C."
"This could make all the difference to coastal planners, and so is not to be sniffed at," he added. "It's vitally important that these ocean forcing trajectories are translated into projections of ice sheet losses so that we know what sea-level rise to expect."
The research comes as the international community prepares for COP28, the next major United Nations climate summit, set to be hosted by the United Arab Emirates in Dubai beginning next month.
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'Absolutely Devastating News': Antarctica Warming Quicker Than Models Projected
The new study's lead author said that "it is extremely concerning to see such significant warming in Antarctica, beyond natural variability."
Sep 08, 2023
Antarctica is warming at about double the rate of the rest of the planet and far more quickly than widely cited models projected, according to a study published Thursday in the journal Nature Climate Change that swiftly alarmed scientists around the world.
"This is absolutely devastating news," declared climate scientist and University College London professor emeritus Bill McGuire.
"First, one has to wonder if perhaps we have already passed the West Antarctic collapse tipping point," the expert added on social media. "Second, it begs the question, are other climate model projections underestimating the speed of climate breakdown?"
Polar amplification, a phenomenon that causes higher temperatures near the poles, is well established in the Arctic, with a study published last yearshowing that the northern region is warming nearly four times faster than the global average. However, it has been less clearly identified across Antarctica, where scientists must contend with limited available temperature records and natural climate variability.
Due to the lack of Antarctic weather stations covering more than the past six decades, the four researchers behind the new study—who come from various European institutions—analyzed 78 ice cores to determine temperature variability over 1,000 years across seven regions.
The team found "direct evidence of Antarctic polar amplification at regional and continental scales," which major climate models don't show. The study states that "failing to consider the feedback loops causing polar amplification could lead to an underestimation of the magnitude of anthropogenic warming and its consequences in Antarctica."
Lead author Mathieu Casado, of the Laboratoire des Science du Climat et de l'Environnement in France, toldThe Guardian that "it is extremely concerning to see such significant warming in Antarctica, beyond natural variability."
Kyle Clem, a scientist at Victoria University of Wellington in New Zealand who was not involved with the new research but has studied record high temperatures at one South Pole weather station, told the newspaper that "the implications of this study are of particular importance for considering future changes in Antarctic sea ice, terrestrial and marine ecosystems, and potentially even sea-level rise."
"As far as sea-level rise, ocean warming is already melting protective ice shelves in West Antarctica and causing the West Antarctic ice sheet to retreat," Clem said. He also highlighted the potential impact on coastal ice shelves that protect glaciers, explaining that "this has already been seen on the Antarctic peninsula in recent decades, and it could become a more widespread occurrence around Antarctica sooner than anticipated in a more strongly warming Antarctic climate."
The research from Casado's team was published the same day as a study about the West Antarctic ice sheet published in The Cryosphere.
"With more and more ice being lost in Antarctica over the last years, concerns have been raised whether a tipping point has already been crossed and an irreversible, long-term collapse of the West Antarctic ice sheet has already been initiated," noted lead author Ronja Reese of the Potsdam Institute for Climate Impact Research in Germany and England's Northumbria University.
"The results of our studies deliver two messages: First, while a number of glaciers in Antarctica are retreating at the moment, we find no indication of irreversible, self-reinforcing retreat yet, which is reassuring," Reese said. "However, our calculations also clearly indicate that an onset of an irreversible retreat of the ice sheet in West Antarctica is possible if the current state of the climate is sustained."
The new studies follow findings throughout this year that have elevated fears about the impact of human-caused global heating on Antarctica—from researchers revealing in February that Antarctic sea ice coverage hit its lowest January level ever recorded, to a May study that showed a 30% slowdown in vital deep water currents around the continent.
Research from last month warned it is "virtually certain that future Antarctic extreme events will be more pronounced than those observed to date" as humanity continues to burn fossil fuels, the key driver of the climate emergency. Another August study found that when Antarctic sea ice melted last year, it likely killed over 9,000 emperor penguin chicks.
Both Reese and Casado's studies also cap off a week of alarming global data about the climate emergency. International researchers confirmed that greenhouse gas concentrations, global sea level, and ocean heat content broke records last year. Scientists also announced that this summer of deadly heat is the hottest on record.
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