This map shows the amount of ice gained or lost by Antarctica between 2003 and 2019. Dark reds and purples show large average rates of ice loss near the coasts, while blues show smaller rates of ice gain in the interior.
Two new satellite images remind us that Earth’s ice sheets are losing so much mass it’s becoming obvious from space.
In the vivid new maps published as part of an April 30 study in the journalScience, researchers illustrated 16 years of ice loss inGreenland andAntarctica as seen by a laser-emitting NASA satellite. The images paint a picture of rapid melt around the coasts of both regions (shown in red and purple in the maps), far outweighing modest ice-mass gains (shown in light blue) farther inland.
Greenland’s ice sheet lost an average of 200 gigatons of ice per year, while Antarctica’s ice sheet lost an average of 118 gigatons per year; for reference, a single gigaton of ice is enough to fill 400,000 Olympic-sized swimming pools, the researcherssaid in a statement.
All that melting ice was responsible for a total 0.55 inches (14 millimeters) of sea-level rise between 2003 and 2019, the researchers found. That rise puts Earthon track for the worst-case climate warming scenario laid out in the Intergovernmental Panel on Climate Change’s (IPCC) latest report, previous research found. That scenario would put hundreds of millions of people living in coastal communities at risk of losing their homes — or their lives — to flooding.
For the new study, the researchers used the newest data from NASA’s ICESat-2 satellite, which launched in 2018 to monitor elevation changes on land (and ice) around the world by bathing the planet in laser beams. The team compared 2019 elevation levels with data recorded by the satellite’s predecessor — named simply ICESat — between 2003 and 2009. At thousands of locations where the two datasets overlapped, the team could see precisely how much ice had vanished from Greenland and Antarctica between 2003 and 2019.
Ice shelves — enormous ledges of ice floating over the ocean at the edges of Greenland and Antarctica — lost the most mass by far in both regions, the researchers said. While ice shelves are already partially submerged in water and therefore do not actively raise sea levels when they melt, they provide a structural integrity to glaciers that prevents ice farther inland from gushing into the sea.
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“It’s like an architectural buttress that holds up a cathedral,” study co-author Helen Amanda Fricker, a glaciologist at Scripps Institution of Oceanography at the University of California, San Diego, said in the statement. “The ice shelves hold the ice sheet up. If you take away the ice shelves, or even if you thin them, you’re reducing that buttressing force, so the grounded ice can flow faster.”
Predictably, the new research shows, as the ice shelves surrounding Antarctica and Greenland have thinned and melted over the last two decades, grounded ice farther inland has thinned and melted too.
The new analysis reveals, with unprecedented detail, the response of these ice sheets to changes in climate, “revealing clues as to why and how the ice sheets are reacting the way they are,” study co-author Alex Gardner, a glaciologist at NASA’s Jet Propulsion Laboratory in Pasadena, California, said in the statement.
The polar ice caps are melting six times faster than in the 1990s, according to the most complete analysis to date.
The ice loss from Greenland and Antarctica is tracking the worst-case climate warming scenario set out by the Intergovernmental Panel on Climate Change (IPCC), scientists say. Without rapid cuts to carbon emissions the analysis indicates there could be a rise in sea levels that would leave 400 million people exposed to coastal flooding each year by the end of the century.
Rising sea levels are the one of the most damaging long-term impacts of the climate crisis, and the contribution of Greenland and Antarctica is accelerating. The new analysis updates and combines recent studies of the ice masses and predicts that 2019 will prove to have been a record-breaking year when the most recent data is processed.
The previous peak year for Greenland and Antarctic ice melting was 2010, after a natural climate cycle led to a run of very hot summers. But the Arctic heatwave of 2019 means it is nearly certain that more ice was lost last year.
The average annual loss of ice from Greenland and Antarctica in the 2010s was 475bn tonnes – six times greater than the 81bn tonnes a year lost in the 1990s. In total the two ice caps lost 6.4tn tonnes of ice from 1992 to 2017, with melting in Greenland responsible for 60% of that figure.
The IPCC’s most recent mid-range prediction for global sea level rise in 2100 is 53cm. But the new analysis suggests that if current trends continue the oceans will rise by an additional 17cm.
“Every centimetre of sea level rise leads to coastal flooding and coastal erosion, disrupting people’s lives around the planet,” said Prof Andrew Shepherd, of the University of Leeds. He said the extra 17cm would mean the number of exposed to coastal flooding each year rising from 360 million to 400 million. “These are not unlikely events with small impacts,” he said. “They are already under way and will be devastating for coastal communities.”
Erik Ivins, of Nasa’s Jet Propulsion Laboratory, in California, who led the assessment with Shepherd, said the lost ice was a clear sign of global heating. “The satellite measurements provide prima facie, rather irrefutable, evidence,” he said.
Almost all the ice loss from Antarctica and half of that from Greenland arose from warming oceans melting the glaciers that flow from the ice caps. This causes glacial flow to speed up, dumping more icebergs into the ocean. The remainder of Greenland’s ice losses are caused by hotter air temperatures that melt the surface of the ice sheet.
The combined analysis was carried out by a team of 89 scientists from 50 international organisations, who combined the findings of 26 ice surveys. It included data from 11 satellite missions that tracked the ice sheets’ changing volume, speed of flow and mass.
About a third of the total sea level rise now comes from Greenland and Antarctic ice loss. Just under half comes from the thermal expansion of warming ocean water and a fifth from other smaller glaciers. But the latter sources are not accelerating, unlike in Greenland and Antarctica.
Shepherd said the ice caps had been slow to respond to human-caused global heating. Greenland and especially Antarctica were quite stable at the start of the 1990s despite decades of a warming climate.
Shepherd said it took about 30 years for the ice caps to react. Now that they had a further 30 years of melting was inevitable, even if emissions were halted today. Nonetheless, he said, urgent carbon emissions cuts were vital. “We can offset some of that [sea level rise] if we stop heating the planet.”
The IPCC is in the process of producing a new global climate report and its lead author, Prof Guðfinna Aðalgeirsdóttir, of the University of Iceland, said: “The reconciled estimate of Greenland and Antarctic ice loss is timely.”
She said she also saw increased losses from Iceland’s ice caps last year. “Summer 2019 was very warm in this region.”
A few weeks ago, scientists at Ukraine’s Vernadsky Research Base in Antarctica awoke to find their usually pristine white surrounds drenched in a shocking blood-red.
From the gory-looking images, you could be forgiven for wondering if there’d been some sort of horror-movie-style penguin massacre. The good news is that the real cause is far less dramatic; unfortunately, it still has dire implications.
Marine ecologist Andrey Zotov from the National Academy of Sciences of Ukraine, captured these images while conducting research at the Antarctic station. For such an epic mess, the culprits behind this dramatic redecoration are incredibly tiny.
“Our scientists have identified them under a microscope as Chlamydomonas nivalis,” said the National Antarctic Scientific Centre of Ukraine in a Facebook post.
These microscopic green algae (we’ll get to why they look red in a moment), a type of single-cellular seaweed, are common in all icy and snowy regions of Earth, from the arctic to alpine regions.
They lie slumbering during the brutal winter, but once the sunlight warms enough to soften their crystallised world, the algae spring awake, making use of the meltwater and sunlight to rapidly bloom.
“The algae need liquid water in order to bloom,” University of Leeds microbiologist Steffi Lutz told Gizmodo in 2016.
Young C. nivalis are green due to their photosynthesising chloroplasts and they have two tail-like structures called flagella, which they flail about to swim with. As they mature, they lose their mobility and develop unique adaptations to survive their extreme environment, including a secondary insulating cell wall and a layer of red carotenoids, which changes their appearance from green to orange to red.
“This layer protects the algae from ultraviolet radiation,” explained the National Antarctic Scientific Centre of Ukraine on their Facebook page.
The carotenoids also help the algae to absorb more warmth, which in turn creates more meltwater for them to thrive in. This is all well and good for the algae and all the critters that eat them, like roundworms and springtails, but unfortunately there are other consequences, too.
In 2017 environmental scientists calculated that microbial communities, which include C. nivalis, contributed to over a sixth of the snowmelt where they were present in Alaskan icefields. Their experiments showed that areas with more meltwater led to the growth of 50 percent more algae and places with more algae melted further.
This Antarctic summer has certainly seen a lot more meltwater than usual. Temperature records keep tumbling, leading to rapid melting at a scale previously only seen in the Northern Hemisphere.
“These events are coming more frequently,” warned glaciologist Mauri Pelto from Nichols College.
So, increased temperatures lead to more melting of crystalised water, which encourages the growth of more algae, which leads to more melting and so on.
But at least C. nivalis infested snow… smells sweet? This phenomenon is also known as ‘watermelon snow’, although it is definitely not edible, because the algae are toxic to humans.
The effects of February’s record heat wave on Eagle Island in Antarctica. Photo: NASA
Antarctica’s Eagle Island now has a side that’s almost ice-free following this month’s searing heat wave in the region, images released by NASA show.
Why it maters: “The warm spell caused widespread melting on nearby glaciers,” NASA said in its report. It’s the third major melt event of the 2019-2020 Southern Hemisphere summer, following warm spells in January and last November, according to the United Nation’s World Meteorological Organization (WMO).
Such persistent warmth was not typical in Antarctica until the 21st century, but it has become more common in recent years.”
— NASA statementDriving the news: The Argentine Antarctic research base Esperanza reported a temperature of 64.9°F on Feb. 9 — indicating a “likely legitimate record,” per the WMO, which is still verifying the statistics.
The island “experienced peak melt” — about 1 inch — on the day of the reported heat record, leading to a loss of 4 inches in total within 10 days, NASA said in a statement Friday.
“About 20% of seasonal snow accumulation in the region melted in this one event on Eagle Island,” the statement added.
What they’re saying: Mauri Pelto, a glaciologist at Nichols College, who observed the warming event as 0.9 square miles of snowpack became saturated with meltwater, said in NASA’s report: “I haven’t seen melt ponds develop this quickly in Antarctica. You see these kinds of melt events in Alaska and Greenland, but not usually in Antarctica.”
Of note: The event comes after scientists in January found for the first time warm water beneath Antarctica’s “doomsday glacier,” so-called because it’s one of the region’s fastest melting glaciers.
The bottom line: “If you think about this one event in February, it isn’t that significant,” Pelto said. “It’s more significant that these events are coming more frequently.”
There are signs Antarctica just experienced its highest melt extent ever recorded in the satellite era. The big meltdown hit on Christmas Eve and is bad news for a continent already dealingwitha lot. With summer is just getting started there, this is a serious case of Summertime Sadness.
Antarctic is the largest stash of ice on the planet. Warm oceans have posed the biggest threat to that ice by undercutting the ice shelves that float out into the sea, particularly the tongues of ice around West Antarctica. But surface melt could become a bigger concern, and the Christmas Eve meltdown is indicative of the concerns. Preliminary findings from modeling done at the University of Liège in Belgium show that the percentage of surface melt on the continent spiked on December 24. The modeling uses weather forecasts to simulate surface melt. Because the environment is so harsh in Antarctica, weather station data is tough to come by so these are best estimates.
Antarctic surface melt season starts in mid-November and runs into February. Late December and early January are the height of the melt season. On average, just eight percent of Antarctica’s surface melts at the peak. But this year has been anything but average, with everyday since late November showing well above normal surface melt extent. That culminated in a big melt spike on Christmas Eve when about 16 percent of the continent’s icy surface went into meltdown.
That’s an area equivalent to the size of Denmark. West Antarctica—home to some of the most endangered ice on the planet—has seen the worst of the melt season according to the University of Liège data. But even the normally colder and higher East Antarctic hasn’t escaped a more watery fate.
When the surface melts, a glaze of ice can form when it refreezes. But if enough ice melts, then the melt can cause water to start pooling on the surface or flowing and sneaking into ice cracks, where it can fracture the ice apart. Scientists have observed this in the heart of Antarctica, but Antarctic Peninsula has had it the worst.
Robin Bell, a geophysics professor at Columbia University’s Lamont-Doherty Earth Observatory, told Earther that if this melt continues or worsens, it could hasten the collapse of the ice shelves already under threat from below. And that could pose serious risks to people who live along the coast by allowing land ice to tumble into the sea.
“[The ice shelves are] kind of like the cork in the bottle. They’re holding back a lot of the ice in Antarctica,” Bell said. “It means you’re pumping more ice into the ocean, and that’s what matters for sea level.”
Antarctic is unfortunately not the only stash of ice to be dealing with more extreme melt season. Researchers have observed the same phenomenon in Greenland as well. This summer’s melt season set a record for daily ice loss as a result of surface melting. Greenland has been the main contributor to sea level rise. With Antarctica’s ice loss accelerating, we’re starting to get into dangerous territory.
New research warns that the earth may be approaching key tipping points, including the runaway loss of ice sheets, that could fundamentally disrupt the global climate system. A growing concern is a change in ocean circulation, which could alter climate patterns in a profound way.
Some of the most alarming science surrounding climate change is the discovery that it may not happen incrementally — as a steadily rising line on a graph — but in a series of lurches as various “tipping points” are passed. And now comes a new concern: These tipping points can form a cascade, with each one triggering others, creating an irreversible shift to a hotter world. A new study suggests that changes to ocean circulation could be the driver of such a cascade.
A group of researchers, led by Tim Lenton at Exeter University, England, first warned in a landmark paper 11 years ago about the risk of climate tipping points. Back then, they thought the dangers would only arise when global warming exceeded 5 degrees Celsius (9 degrees Fahrenheit) above pre-industrial levels. But last week, Lenton and six co-authors argued in the journal Nature that the risks are now much more likely and much more imminent. Some tipping points, they said, may already have been breached at the current 1 degree C of warming.
The new warning is much starker than the forecasts of the Intergovernmental Panel on Climate Change, which critics say has until now played down the risks of exceeding climate tipping points, in part because they are difficult to quantify.
The potential tipping points come in three forms: runaway loss of ice sheets that accelerate sea level rise; forests and other natural carbon stores such as permafrost releasing those stores into the atmosphere as carbon dioxide (CO2), accelerating warming; and the disabling of the ocean circulation system.
Researchers’ biggest fear is for the future of the ocean circulation system, which moves heat around the world and may dictate global climate.
The researchers once considered these tipping points to be largely independent of each other. Now they warn that the world faces a “cascade” of abrupt shifts in the planet’s climate system, as global warming takes hold. “We might already have crossed the threshold for a cascade of inter-related tipping points,” they wrote in Nature. This “could trigger a shift in the state of the Earth system as a whole,” one of the authors, Will Steffen of the Australian National University in Canberra, told Yale Environment 360.
Their biggest fear is for the future of the global ocean circulation system, which moves heat around the world and may dictate global climate. They say melting Greenland ice in a warmer Arctic has driven a key component of ocean circulation to a thousand-year low. Further decline, which would lead to a shift in heat distribution around the planet, could trigger forest collapse in the Amazon; cause near-permanent drought in Africa’s Sahel region; disrupt Asian monsoons; rapidly warm the Southern Ocean, which would cause a surge in global sea levels as the West Antarctic Ice Sheet disintegrates; and potentially shift the planet to a new climate regime they call “hothouse Earth.”
One climate scientist, Mike Hulme of the University of Cambridge, dismissed the new analysis as “a speculative opinion from a small group of self-selecting scientists.” He added that “there are no new research findings presented here” and that “many earth systems scientists would challenge the view” that the earth is close to crossing major tipping points. Lenton and his co-authors accept there is speculation involved, but argue that “given its huge impact and irreversible nature… to err on the side of danger is not a responsible option.”
The “climate emergency” is not just political rhetoric, they argue. It is now an identifiable scientific fact. Their message to the latest UN climate negotiations, under way in Madrid this week, is that the world may be almost out of time to prevent what they call an “existential threat to civilization.” Their study was released as a new report said that greenhouse gas emissions have hit a record high, with 40.6 billion tons of CO2 being pumped into the atmosphere in 2019.
The term “climate tipping points” was first coined 15 years ago by Hans Joachim Schellnhuber, former director of the Potsdam Institute for Climate Impact Research in Germany and a co-author of the new analysis, to describe how, under pressure from global warming, parts of the climate system could suddenly collapse or run out of control.
In their new analysis, the researchers conclude that of the 15 potential tipping points they identified in 2008, seven now show signs of being “active,” along with two others they have added to their list.“ That doesn’t mean a tipping point has necessarily been reached,” says Lenton. “But it means the system in question is showing evidence of change, of heading in the wrong direction.”
Four of these nine active tipping points involve thawing ice. Arctic sea ice is rapidly disappearing, and ice loss is accelerating on all three of the planet’s large, land-based ice sheets: Greenland, West Antarctica, and the Wilkes Basin in East Antarctica. Lenton says two of these, the West Antarctic Ice Sheet and Wilkes Basin, “are showing evidence consistent with having passed a tipping point,” meaning further ice loss may be unstoppable.
Greenland may not be far behind.“ Models suggest that the Greenland Ice Sheet could be doomed at 1.5 degrees C [2.7 degrees F] of warming, which could happen as soon as 2030,” the researchers report. Exceeding the three ice sheet tipping points could eventually cause an irreversible rise in sea levels of about 13 meters (43 feet), says Lenton.
Unlike the slowly deteriorating ice sheets, passing biospheric tipping points will produce abrupt, immediate, and obvious changes.
This may take centuries or millennia to play out, as the ice sheets slowly disappear into the ocean. But it will be virtually unstoppable, because once a thaw sets in, the surface of the ice sheet is lowered, exposing it to ever warmer air at lower altitudes.
Four more of the already-active tipping points involve the biosphere and its stores of carbon. The Amazon is suffering recurring droughts and forest dieback. In the boreal forests of the far north, rising temperatures are triggering epidemics of forest fires and pests. Meanwhile, permafrost is thawing and releasing methane, a greenhouse gas; and in the tropics, coral reefs are suffering massive die-offs, threatening wider ocean ecosystems.
Unlike the slowly deteriorating ice sheets, passing biospheric tipping points will often produce abrupt, immediate, and obvious changes, say the researchers. These may also be imminent. For instance, deforestation in the Amazon is already reducing rainfall and lengthening the dry season to a point where the rest of the trees die or are consumed by fires.
Carlos Nobre of the University of Sao Paulo, who was not involved in the present analysis, says that “when the dry season becomes longer than four months, tropical forest turns to savanna.” He puts the Amazon tipping point at 40-percent tree loss, a figure that changing global climate could reduce to between 20 and 25 percent by 2050. That is disturbingly close to the current total loss, reckoned to be approaching 20 percent.
Lenton says abrupt releases of CO2 from these natural carbon stores would drastically reduce the leeway the world has for avoiding global warming above 1.5 degrees, the preferred target set by the 2015 Paris Agreement. That probably requires limiting future CO2 emissions to about 500 billion tons — roughly 12 years’ emissions at current rates. But abrupt forest dieback in the Amazon and boreal forests, coupled with methane emissions from thawing permafrost, could use up 300 billion tons of that emissions budget, Lenton says.
The basic mechanisms behind these tipping points have been well-known for some years, though the predictions of the time it will take before they are activated have become much shorter. But the real new concern, says Lenton, is the identification of the potential for tipping point “cascades,” in which breaching one tipping point triggers breaches of others, leading to a rapid escalation of damage.
Lenton, Steffen, and others argued last year that 2 degrees C of warming “could activate… a domino-like cascade that could take the Earth system to even higher temperatures.” Such a change to what they called “hothouse Earth” would be irreversible, they said, even if greenhouse gas emissions were brought to zero.
The lynchpin of one such cascade, they say, is the ninth tipping point that they have identified to be active — a critical feature of the global ocean circulation system, centered in the North Atlantic and known as the Atlantic Meridional Overturning Circulation (AMOC).
“In our view, the evidence from tipping points alone suggests that we are in a state of planetary emergency,” the scientists wrote.
The AMOC is currently initiated by evaporation of warm water moving north, which leaves behind saltier, denser water that sinks to the sea bed. It is responsible for driving the ocean circulation, distributes heat around the globe, and may be the prime regulator of the climate.
Stefan Rahmstorf, an oceanographer at the University of Potsdam and a co-author of the new analysis, told e360: “The AMOC stands at the center of tipping-point cascades because of its large-scale heat transport.” It is, he says, the main reason why the Northern Hemisphere is warmer than the Southern Hemisphere. But it is being disrupted.
“Arctic warming and Greenland melting are driving an influx of fresh water into the North Atlantic,” he says. The fresher water is less dense and sinks less. Rahmstorf calculates that, as a result, the AMOC has weakened by about 15 percent since global warming took hold in 1975. “It is now at its weakest in the past millennium, or even longer,” he says.
This decline of the ocean circulation threatens to trigger other tipping points elsewhere. “A slowdown of the AMOC reduces rainfall over the Amazon basin, increasing the probability of crossing a tipping point there,” says Steffen. It could also mess with monsoon systems in Asia and West Africa, triggering drought in the Sahel. And by bringing warm waters into the Southern Ocean, it would further destabilize ice in Antarctica, unleashing an acceleration in global sea level rise.
Most climate models predict a continued weakening of the AMOC through the 21st century. It remains unclear how close it might be to a tipping point, the researchers admit. But Lenton says that historically the AMOC appears to jump between different stable states. “The question,” says co-author Johan Rockstrom, who is director of the Potsdam Institute for Climate Impact Research, “is, what are the pressure points where we might cross a threshold and trigger a state change?”
In the face of this threat, the researchers wade into the political debate about whether — as the European Parliament voted last month — the world should declare a climate emergency. “In our view, the evidence from tipping points alone suggests that we are in a state of planetary emergency,” their Nature paper concludes.
They justify this claim by attempting to define a climate emergency in mathematical terms, as a product of the extent of the threat, the probability of it happening, and the urgency, defined as how much time we have left to act. They argue that the current climate crisis fits that definition, with huge risks, increasing likelihood, and time fast running out.
This claim has drawn fire from some scientists. Hulme says such a calculation is “deeply misleading and dangerous… It is a bid by these scientists to place themselves as arbiters of whether or not we are in a climate emergency.” It is for society as a whole to decide what an emergency is, not scientists, he said.
“I am definitely not bidding to be an arbiter of climate emergency,” insists Lenton. “I am just trying to offer some scientific support for the already loud societal claims for climate emergency.” Referring to ongoing global youth protests demanding action to reduce greenhouse gas emissions, Lenton added, “The schoolkids are right.”
“We need to reach a social tipping point,” of low-carbon living, says an expert, “before we reach a planetary one.”
Hulme is also concerned about unintended consequences, such as encouraging politicians to embark on geo-engineering projects like deploying devices to shade us from solar radiation. “Calling a planet-wide emergency,” says Hulme, “can only accelerate the day when solar climate engineering is actively pursued” — something he opposes. Hulme and Lenton signed a joint statement, published in Nature Climate Change in 2015, warning of just such an eventuality.
Lenton says he remains opposed to geo-engineering, which he calls “as risky as the risks we are trying to avoid.” He thinks the threats the world faces are too great for scientists to stand on the political sidelines, especially given the world’s current failure to act to head off climate disaster.
“The current approach of the UN Climate Change Convention is a failure,” says Steffen. But he is not without hope. He believes declining fertility, innovation towards low-carbon energy, and growing movements for “greener” consumption all suggest that human society may be reaching its own tipping point in responding to the crisis. The bottom line, he says, is that “we need to reach a social tipping point, before we reach a planetary one.”
Researchers have produced the first physics-based quantifiable evidence that thinning ice shelves in Antarctica are causing more ice to flow from the land into the ocean.
Their findings have been published in Geophysical Research Letters.
Satellite measurements taken between 1994 and 2017 have detected significant changes in the thickness of the floating ice shelves that surround the Antarctic Ice Sheet. These shelves buttress against the land-based ice, holding them in place like a safety band.
While it has been suggested that the thinning ice shelves were responsible for a direct loss of ice from the land-based ice sheet into the ocean, there was no actual evidence linking data and physics that could demonstrate this, until now.
Researchers in the UK and US have now undertaken the first continent-wide assessment of the impact the thinning ice shelves are having on the flow of ice in Antarctica.
They were particularly interested in seeing how much ice flowed across the ‘grounding line’. This is the point where the land-based ice sheet meets the sea-based ice shelves.
They used a state-of-the-art ice-flow model developed at Northumbria University, UK, and newly available measurements of changes in the geometry of ice shelves to calculate the changes in grounded ice flow.
When the modelled results were compared with those obtained by satellites over the last 25 years, the researchers found what they described as ‘striking and robust’ similarities in the pattern of ice flowing from the ice sheet into the ocean.
The largest impact was found in West Antarctica, which already makes a significant contribution to sea level change. The largest changes are taking place around the Pine Island and Thwaites glaciers. On Pine Island Glacier, evidence of these changes could be seen almost 100 miles (150km) inland, upstream of the grounding line.
Hilmar Gudmundsson, Professor of Glaciology and Extreme Environments at Northumbria University led the study. He said there has been a long-standing question as to what was causing the changes we have observed in land-based ice over the last 25 years, and that while the thinning of the floating ice-shelves had been suggested as a reason, the idea had never been put to the test before now.
“I found it striking how well our modelled changes agree with the pattern of observed mass loss,” he said.
“There are other processes in play as well, but we can now state firmly that the observed changes in ice-shelves do cause significant changes over the grounded ice, speeding up its flow into the ocean.”
A critical element of the findings was the speed at which the ice flowed from the sheet into the ocean as a result of the thinning ice shelves.
“One of the most important lessons from this study is that the impact is felt without any delay,” said Professor Gudmundsson.
“Generally, we distinguish between an instantaneous response or a delayed, transient response. Our study shows the thinning of the ice shelves results in a significant instantaneous response to ice flow and ongoing mass loss. This means that we are not protected against the impact of the Antarctic Ice Sheet on global sea levels by a long response time.”
He added: “This study closes an important hole in our understanding. Lack of data and limitations in modelling previously made it challenging to quantify the importance of ocean-induced changes as a driver for ongoing mass loss, but we have now shown that the observed ice shelf changes do indeed impact on upstream flow significantly.”
The research was led by Northumbria University, Newcastle in the UK, with the NASA Jet Propulsion Laboratory and the Scripps Institution of Oceanography at the University of California San Diego.
Helen Amanda Fricker, Professor at Scripps Institution of Oceanography, said: “Ice shelves are the most vulnerable parts of Antarctica’s ice sheet system and we know that they are shrinking, but what we didn’t know before this work was how that was impacting the grounded ice behind them.”
Fernando Paolo, postdoctoral scholar at Jet Propulsion Laboratory/California Institute of Technology, added: “It is striking how far inland the changes in ice shelves can impact the ice sheet flow. Since we now know that shrinking ice shelves are directly responsible for increases in ice discharge to the ocean, it is important that we keep monitoring them to watch how they evolve.”
It is believed that the ice shelves may be thinning due to changes in ocean heat content, either by ocean warming or from changes in how the ocean circulates around and below the shelves, but further research is needed to establish the specific reasons.
The study, Instantaneous Antarctic ice-sheet mass loss driven by thinning ice shelves is published in Geophysical Research Letters.
The concept of a canary in a coal mine — a sensitive species that provides an alert to danger — originated with British miners, who carried actual canaries underground through the mid-1980s to detect the presence of deadly carbon monoxide gas. Today another bird, the Emperor Penguin, is providing a similar warning about the planetary effects of burning fossil fuels.
Most recently, I worked with colleagues to combine what we know about the life history of Emperor Penguins with different potential climate scenarios outlined in the 2015 Paris Agreement, to combat climate change and adapt to its effects. We wanted to understand how climate change could affect this iconic species, whose unique life habits were documented in the award-winning film “March of the Penguins.”
Our newly published study found that if climate change continues at its current rate, Emperor Penguins could virtually disappear by the year 2100 due to loss of Antarctic sea ice. However, a more aggressive global climate policy can halt the penguins’ march to extinction.
Carbon Dioxide in Earth’s Atmosphere
As many scientific reports have shown, human activities are increasing carbon dioxide concentrations in Earth’s atmosphere, which is warming the planet. Today atmospheric CO2 levels stand at slightly over 410 parts per million, well above anything the planet has experienced in millions of years.
If this trend continues, scientists project that CO2 in the atmosphere could reach 950 parts per million by 2100. These conditions would produce a very different world from today’s.
Emperor Penguins are living indicators whose population trends can illustrate the consequences of these changes. Although they are found in Antarctica, far from human civilization, they live in such delicate balance with their rapidly changing environment that they have become modern-day canaries.
A Fate Tied to Sea Ice
I have spent almost 20 years studying Emperor Penguins’ unique adaptations to the harsh conditions of their sea ice home. Each year, the surface of the ocean around Antarctica freezes over in the winter and melts back in summer. Penguins use the ice as a home base for breeding, feeding and molting, arriving at their colony from ocean waters in March or April after sea ice has formed for the Southern Hemisphere’s winter season.
In mid-May the female lays a single egg. Throughout the winter, males keep the eggs warm while females make a long trek to open water to feed during the most unforgiving weather on Earth.
When female penguins return to their newly hatched chicks with food, the males have fasted for four months and lost almost half their weight. After the egg hatches, both parents take turns feeding and protecting their chick. In September, the adults leave their young so that they can both forage to meet their chick’s growing appetite. In December, everyone leaves the colony and returns to the ocean.
Throughout this annual cycle, the penguins rely on a sea ice “Goldilocks zone” of conditions to thrive. They need openings in the ice that provide access to the water so they can feed, but also a thick, stable platform of ice to raise their chicks.
Penguin Population Trends
For more than 60 years, scientists have extensively studied one Emperor Penguin colony in Antarctica, called Terre Adélie. This research has enabled us to understand how sea ice conditions affect the birds’ population dynamics. In the 1970s, for example, the population experienced a dramatic decline when several consecutive years of low sea ice cover caused widespread deaths among male penguins.
Over the past 10 years, my colleagues and I have combined what we know about these relationships between sea ice and fluctuations in penguin life histories to create a demographic model that allows us to understand how sea ice conditions affect the abundance of Emperor Penguins, and to project their numbers based on forecasts of future sea ice cover in Antarctica.
When we used a climate model linked to our population model to project what is likely to happen to sea ice if greenhouse gas emissions continue on their present trend, we found that all 54 known Emperor Penguin colonies would be in decline by 2100, and 80% of them would be quasi-extinct. Accordingly, we estimate that the total number of Emperor Penguins will decline by 86% relative to its current size of roughly 250,000 if nations fail to reduce their carbon dioxide emissions.
However, if the global community acts to reduce greenhouse gas emissions and succeeds in stabilizing average global temperatures at 1.5 degrees Celsius (3 degrees Faherenheit) above pre-industrial levels, we estimate that Emperor Penguin numbers would decline by 31% — still drastic, but viable.
Less-stringent cuts in greenhouse gas emissions, leading to a global temperature rise of 2°C, would result in a 44% decline.
Our model indicates that these population declines will occur predominately in the first half of this century. Nonetheless, in a scenario in which the world meets the Paris climate targets, we project that the global Emperor Penguin population would nearly stabilize by 2100, and that viable refuges would remain available to support some colonies.
In a changing climate, individual penguins may move to new locations to find more suitable conditions. Our population model included complex dispersal processes to account for these movements. However, we find that these actions are not enough to offset climate-driven global population declines. In short, global climate policy has much more influence over the future of Emperor Penguins than the penguins’ ability to move to better habitat.
Our findings starkly illustrate the far-reaching implications of national climate policy decisions. Curbing carbon dioxide emissions has critical implications for Emperor Penguins and an untold number of other species for which science has yet to document such a plain-spoken warning.
Unusual weather patterns in the upper atmosphere over Antarctica have caused a drastic reduction in ozone depletion, leaving the ozone with the smallest hole seen sin1982, according to NASA and the National Oceanic and Atmospheric Administration.
The government agencies said that the hole had shrunk to 3.9 million square miles for the remainder of September and October, according to satellite data. The peak in the hole was 6.3 million square miles, observed on Sept. 8. During normal weather conditions, the hole is usually around 8 million square miles during this time of year.
“It’s great news for ozone in the Southern Hemisphere,” said Paul Newman, chief scientist for Earth Sciences at NASA’s Goddard Space Flight Center in a statement on NASA’s website. “But it’s important to recognize that what we’re seeing this year is due to warmer stratospheric temperatures. It’s not a sign that atmospheric ozone is suddenly on a fast track to recovery.”
This time-lapse photo from Sept. 9, 2019, shows the flight path of an ozonesonde as it rises into the atmosphere over the South Pole from the Amundsen-Scott South Pole Station. Scientists release these balloon-borne sensors to measure the thickness of the protective ozone layer high up in the atmosphere. Credits: Robert Schwarz/University of Minnesota
A video was posted to NASA’s Goddard YouTube page showing the satellite data in further detail.
The ozone layer is approximately 7 to 25 miles above the Earth’s surface and acts as a “sunscreen” for the planet, NASA added. It keeps out harmful ultraviolet radiation from the Sun that has been linked to skin cancer, cataracts, immune system suppression and can also cause damage to plants.
The hole over the Antarctic forms during the Southern Hemisphere’s late winter as the Sun’s rays start to cause ozone-depleting reactions. This involves chlorine and bromine from man-made objects being released into the stratosphere which then destroys the molecules in the ozone.
Although “measurements at the South Pole did not show any portions of the atmosphere where ozone was completely depleted,” atmospheric scientist Bryan Johnson at NOAA’s Earth System Research Laboratory said, it’s not all good news.
This is just the third time in the past 40 years (September 1998 and 2002 were the others) where the ozone depletion has been limited by unusual weather systems, a phenomena researchers are still trying to figure out.
“It’s a rare event that we’re still trying to understand,” said Susan Strahan, an atmospheric scientist. “If the warming hadn’t happened, we’d likely be looking at a much more typical ozone hole.”
The 1987 Montreal Protocol was enacted after scientists disturbingly found a hole in the ozone over Antarctica and Australia in 1985. It was enacted by the United Nations Environment Program. Former U.N. Secretary-General Kofi Annan said it was “[p]erhaps the single most successful international agreement to date” and it has been widely regarded as successful, with the ozone continuing to recover each year.
Record warm temperatures above Antarctica over the coming weeks are likely to bring above-average spring temperatures and below-average rainfall across large parts of New South Wales and southern Queensland.
The warming began in the last week of August, when temperatures in the stratosphere high above the South Pole began rapidly heating in a phenomenon called “sudden stratospheric warming”.
In the coming weeks the warming is forecast to intensify, and its effects will extend downward to Earth’s surface, affecting much of eastern Australia over the coming months.
The Bureau of Meteorology is predicting the strongest Antarctic warming on record, likely to exceed the previous record of September 2002.
September stratospheric warming from 2002 (left) and 2019 (right). (Australian Bureau of Meteorology)
What’s going on?
Every winter, westerly winds – often up to 200 kilometre per hour (120 miles per hour) – develop in the stratosphere high above the South Pole and circle the polar region.
The winds develop as a result of the difference in temperature over the pole (where there is no sunlight) and the Southern Ocean (where the sun still shines).
As the sun shifts southward during spring, the polar region starts to warm. This warming causes the stratospheric vortex and associated westerly winds to gradually weaken over the period of a few months.
However, in some years this breakdown can happen faster than usual.
Waves of air from the lower atmosphere (from large weather systems or flow over mountains) warm the stratosphere above the South Pole, and weaken or “mix” the high-speed westerly winds.
Very rarely, if the waves are strong enough they can rapidly break down the polar vortex, actually reversing the direction of the winds so they become easterly. This is the technical definition of “sudden stratospheric warming.”
Although we have seen plenty of weak or moderate variations in the polar vortex over the past 60 years, the only other true sudden stratospheric warming event in the Southern Hemisphere was in September 2002.
In contrast, their northern counterpart occurs every other year or so during late winter of the Northern Hemisphere because of stronger and more variable tropospheric wave activity.
What can Australia expect?
Impacts from this stratospheric warming are likely to reach Earth’s surface in the next month and possibly extend through to January.
Apart from warming the Antarctic region, the most notable effect will be a shift of the Southern Ocean westerly winds towards the Equator.
Past stratospheric warming events and associated wind changes have had their strongest effects in NSW and southern Queensland, where springtime temperatures increased, rainfall decreased and heatwaves and fire risk rose.
The influence of the stratospheric warming has been captured by the Bureau’s climate outlooks, along with the influence of other major climate drivers such as the current positive Indian Ocean Dipole, leading to a hot and dry outlook for spring.
Nine anomalous polar vortex years compared to other years between 1979-2016. (Bureau of Meteorology)
Effects on the ozone hole and Antarctic sea ice
One positive note of sudden stratospheric warming is the reduction – or even absence altogether – of the spring Antarctic ozone hole. This is for two reasons.
First, the rapid rise of temperatures in the upper atmosphere means the super cold polar stratospheric ice clouds, which are vital for the chemical process that destroys ozone, may not even form.
Secondly, the disrupted winds carry more ozone-rich air from the tropics to the polar region, helping repair the ozone hole.
Thanks to improvements in modelling and the Bureau’s new supercomputer, these types of events can be forecast better than ever before.
Compared to 2002, when we didn’t know much about the event until after it had happened, this time we’ve had almost three weeks’ notice that a very strong warming event was coming. We also know much more about the process that has been set in train, that will affect our weather over the next one to four months.