(CNN)Friday is the statistical peak of hurricane season, yet a monster named Larry is forecast to transform into a winter storm that will deliver feet of snow in Greenland.Yes, you read that correctly. A hurricane producing feet of snow. It’s been a crazy year for tropical systems already, so why not?This year is already ahead of pace in terms of storms, with 13 named. On average, we don’t see 13 named storms until the end of the season.
Hurricane-force winds are not uncommon in Greenland, but hurricanes that bring significant snow are.
Feet of snow for Greenland
Hurricane Larry is forecast to slide up the east coast of Greenland this weekend. When it gets there, it will have sustained winds around 60 to 70 mph, with gusts as high as 85 mph. Larry’s hurricane-force wind likely will produce blizzard conditions across Greenland, although Larry might lose the tropical aspects of a hurricane by then.Enter your email to sign up for CNN’s “Meanwhile in China” Newsletter.close dialog
The term extratropical has to do with the storm’s core. A hurricane has a warm core, while an extratropical (or post-tropical) has a cold core.Cold core systems produce weather features like cold fronts and warm fronts — terms people are more familiar with. Warm core systems produce weather features such as eyes, eyewalls and outer-bands.As Larry interacts with this other system, it will be able to pull in a tremendous amount of moisture leading to significant snowfall in Greenland.Widespread totals of 12 to 18 inches are expected in the eastern half of the island nation. Higher elevations along the east coast could get 2 to 4 feet or higher.Hurricane Larry could bring feet of snow to Greenland.While it is rare for tropical systems to help trigger snow, it’s not unheard of. In fact, just last year Hurricane Zeta brought snow to the Northeast US, including several inches to Massachusetts.What makes Larry a bit more unusual is the timing. Zeta hit in late October. So did Superstorm Sandy, which also helped produce snowfall in October 2012.
Larry is a large hurricane with hurricane-force winds extending outward up to 90 miles from the center. Even after it transitions to extratropical, Larry is expected to stay big in size.The Canadian Hurricane Centre has extended the Tropical Storm Warning along the southern coast of southeastern Newfoundland westward to Francois and along the northern coast of southeastern Newfoundland to Fogo Island.
CNN meteorologists Chad Myers and Brandon Miller contributed to this story.
Estimates of ‘just’ 90 centimeters sea level rise by 2100 ignore Antarctica’s slower but hefty contribution, warns oceanographer John EnglanderShare in FacebookShare in TwitterSend in e-mailSend in e-mailZen ReadPrint article
Glacier on west Greenland in August 2007, as it bends in its normal descent to the sea. Due to warming the melting glacier has retreated far inlandCredit: John EnglanderRuth SchusterGet email notification for articles from Ruth SchusterFollowPublished at 23:48
The vast ice sheet on Greenland has become unstable and technology isn’t storming to the rescue. The world is not on a trajectory to “curb” global warming at 1.5 degrees Celsius – we’re almost there already. “Everybody is asleep. It’s like the Titanic,” wails sea level rise guru John Englander, an oceanographer and author who has made it his life’s mission to shake the world awake before it’s too late.
Too late for what? To secure coastlines all over the world ahead of the rising sea, which is pushing coastlines farther inland. To protect property values, to strategize and reorganize economic priorities, to move seaside nuclear reactors, you name it. Life as we know it.
Part of the reason for the global somnolescence is that scientific reports by nature err on the side of caution. Thus, the current sea level rise estimates for 2050 or 2100 (which distract from the fact that sea level rise will continue afterward) are typically conservative, which in this case means they understate the real rise. It’s also considered rude to conclude that the world is careening toward hell in a handbasket.- Advertisment –
But the world is not on a minimalist trajectory. It is not heading for a “mere” 40-centimeter (16-inch) increase by 2100 based on the optimistic scenario, which is losing credence. The official (UN-IPCC) high end of forecasts is around 90 centimeters by 2100 – but even that is too optimistic in Englander’s view, as he warned in a joint paper with other academics in December: “Twenty-first century sea level rise could exceed IPCC projections for strong-warming futures.”
Sea level rise by 2100 could be 2 meters. It could be 3, or 4 meters, he says. The only thing we know is that we don’t know: the situation is fluid, you should excuse the expression. And we know that a lot of the water will come from Greenland.
To warn the general population, however, Englander feels science’s kid gloves are inappropriate at this point. Mounting evidence indicates climate change is accelerating and creating vicious circles that quicken it even more. The destabilization of Greenland’s ice sheet is a case in point.
It is hard to reconcile reports of its accelerated melting and destabilization with estimates that it will, nonetheless, take maybe five to six centuries for all Greenland’s ice to melt. Englander explains this seeming incongruity.
“I’ve been there several times, leading expeditions,” he tells Haaretz. “It’s hard to comprehend how vast Greenland is. It’s 2,500 kilometers north to south and about 1,000 kilometers east to west, literally from east of the Mississippi in the U.S., and from Maine to Florida” – i.e., nearly 2.2 million square kilometers.- Advertisment –
In Middle Eastern terms, Greenland is about the size of Saudi Arabia. (Israel is about 22,000 square kilometers in area – about twice the size of B-15, the biggest-ever iceberg caught on camera, which calved off the Ross Ice Shelf. )https://www.youtube.com/embed/lBfzFt_kgNU?start=0&controls=1&loop=0&modestbranding=1&rel=1&autoplay=false&enablejsapi=1&mute=undefined
Greenland is covered by a layer of ice 1 to 3 kilometers thick; if it all melts, it will raise global sea levels by over 7 meters. No one thinks that can happen quickly. It will take centuries, at least. “The question is what will happen by 2050 and 2100,” Englander drives home the point.
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Asked if the Greenlandic ice sheet’s recently reported destabilization could change his vague expectation that the melt should take centuries, Englander offers the only answer he can: maybe. Which is all the more reason to wake up.- Advertisment –
Sea level rise cannot be stopped
Even if carbon dioxide emissions were to screen to a halt today, even if cows were to start farting flowers instead of methane, even if every car were to suddenly morph into a tree, further sea level rise is inevitable. Like the Titanic, its direction cannot be diverted anymore, though its momentum might be influenced.
It is time to glance again at John Englander’s famous graph of historic correlations between atmospheric carbon dioxide levels, global mean temperatures, and sea level over the last 400,000 years. The graph shows exactly what the problem is:
Atmospheric carbon dioxide has risen to levels last seen millions of years ago, approximately speaking (neither Donald Trump nor the coronavirus changed the trajectory in any meaningful sense). Atmospheric carbon dioxide concentrations and temperature are correlated: if the one rises, so does the other. The higher the CO2, the higher the global mean temperature – at a lag. Again: at a lag. Temperature has yet to proportionately react to the increase in carbon dioxide levels.
Yes, after CO2 rises, temperature will too – but how long the reaction will take depends on a practically infinite array of parameters, so it cannot be predicted with any meaningful accuracy. All we can say is it will happen, and the fact that the globe has experienced year after year of “record heat” is just the start. Oceans, being vast and dense and saline, take longer to react than the air or shallow lakes, but as the air warms, so does their surface and then their depths. The Arctic has been among the worst affected – there are days parts of it are hotter than in Tel Aviv.
Apropos of which, forecasting the future of Israel’s coast is tricky.
“The coastline has moved kilometers inland over the last 50 years,” says Dr. (emeritus) John K. Hall of the Geological Survey of Israel, adding that this conundrum tends to be met with massive denial. “The beaches are eroding, the cliffs are coming down,” he adds. At sea rise levels of 20 to 30 centimeters, it is difficult to draw lines with any accuracy, to say which neighborhoods will be affected and which spared – but the key issue is the likelihood of increasingly violent storms smashing into the beaches and cliffs. “If sea levels come up, storms will beat the hell out of the coast,” Hall predicts.
Anyway, there is a growing unease in global scientific circles about simultaneously warning and reassuring the public. More and more scientists are warning that sea level will rise faster “than previously thought.” Which means what?
The Greenland ice sheet alone locks up 7 meters of sea level rise, which is bad enough, but Antarctica locks up 65 meters more, Englander explains. All the other glaciers in the world add just 1 more meter. “Looking at glaciers from Mount Kilimanjaro [in Kenya] to the Alps, it’s pocket change” he says.
Ergo: the Arctic island of Greenland and southern continent of Antarctica contain about 98 percent of the ice on land, by volume. Yet modelers have been ignoring Antarctica’s contribution.
This is why? For one thing, because the dynamics and precise timing of Antarctica’s melting ice remain profoundly unclear. As we said, scientists tend to err on the side of caution, lest they be perceived as a pack of yowling Cassandras scorned by policymakers. If you stand on a soapbox shrieking “The end is nigh,” precious few will listen even as avenging angels begin to arrive.
But the result is that projections of half a meter to just-under-a-meter of sea level rise by the century’s end don’t factor in Antarctica, nor do they factor in Greenland’s destabilization, Englander explains.
That is bound to end about as well as the Euripides play performed in 408 B.C.E., where the actor Hegelochus meant to say, “After the storm I see again a calm sea,” but wound up saying, “After the storm I see again a weasel.” Well, 2,500 years belatedly, the unfortunate thespian may have had a point. Those are not calm seas on our horizon.
The Greenlandic irony
What does “Greenland has destabilized” even mean? That parts of the ice sheet and major glaciers are already exhibiting sudden break up and collapse. In 2012, the documentary “Chasing Ice” captured one huge collapse using time-lapse cameras. Meanwhile, Greenland is already the chief contributor to sea level rise today, and it has started to dawn on coastal residents and insurance companies and the like that “something” will have to be done.
Part of Englander’s book due out on April 6, “Moving to Higher Ground” (The Science Bookshelf), discusses exactly these conundrums.
Why is it only an issue now? The science of climate change has been around for decades. Why is anybody still buying a beachside home?
Englander blames a failure of imagination. At the height of the Ice Age, the average sea level was 120 meters lower than it is now. As the latest Ice Age waned and the ice sheets melted, sea levels gradually rose – sometimes more abruptly than at other times. But none of that happened during recorded history.
Civilization as we could recognize it – a gradual transition from hunting-gathering to a settled lifestyle – seems to have begun around 12,000 years ago, some places earlier, some places later, well after the Last Glacial Maximum 22,000 years ago. People adore living by the coast and always have. Even Neanderthals are thought to have frolicked in the water and dived for shellfish. And the first villages on low-lying shoreland were indeed inundated. Israeli archaeologists, for example, have found the remains of Neolithic villages off today’s coast, under the waves of the Mediterranean.
But for the last 7,000 or 8,000 years, sea levels have been stable, near present-day heights, and we are not capable of imagining the situation otherwise, Englander postulates.
Sea levels have been creeping up since the industrial revolution began and some cities have noticed – think of Miami and its sunny-day floods. But that is why we simply cannot fathom what a meter or two even mean. It’s beyond our scope of experience.
The last time sea level was above present-day levels was 122,000 years ago, when it was some 7 meters above present, he explains.
“Even at the accelerated warming rate, most people don’t think we’ll get more than a meter out of sea level rise from Greenland this century. But a meter of global sea level rise would be devastating, flooding literally thousands of coastal communities,” he points out the obvious.
Three of the biggest cities in the world are in acute danger: Shanghai, Mumbai and Jakarta, and so are hundreds more from Alexandria to Boston to London.
Ironically, Greenland’s own coastlines are probably safe. This is because as its ice cover melts, the land is rising, as land does when an enormous weight is lifted. It is the obverse of the situation in Jakarta, where the land is sinking because of groundwater depletion, the heavy buildings and sea level rise. Never mind 2100: the city is expected to be 95 percent underwater by 2050.
“The human instinct is to be optimistic, [to hope] technology will come to the rescue. But it doesn’t make sense in this context,” Englander sums up. “The oceans have been warmed almost a degree already and we’re going to warm them 2 degrees more. The ice is going to melt.”
Frozen Greenland is on track to become significantly less frozen before the 21st century is over. By 2055, winter snowfall on the Greenland Ice Sheet will no longer be enough to replenish the ice that Greenland loses each summer, new research finds.
Rising global temperatures are driving this dramatic change. If Earth continues to heat up at its present pace, average global temperatures should climb by nearly 5 degrees Fahrenheit (2.7 degrees Celsius) by 2055. Regional averages in Greenland become even hotter, rising by about 8 F (4.5 C), scientists reported in a new study.
Under those conditions, Greenland’s annual ice loss could increase sea levels by up to 5 inches (13 centimeters) by 2100 — unless drastic steps are taken, starting now, to curb greenhouse gas emissions and slow global warming trends.
Ice sheets are any thick masses of ice that cover more than 20,000 square miles (50,000 square kilometers) of land, and they grow their icy layers from snow that builds up over thousands of years, according to the National Snow and Ice Data Center (NSIDC). During the last ice age (around 115,000 to 11,700 years ago), ice sheets blanketed much of North America and Scandinavia. But today, only two ice sheets remain — in Greenland and in Antarctica — holding around 99% of Earth’s freshwater reserves, NSIDC says.
Ice sheets aren’t static — their own weight pushes them slowly toward the ocean, where they discharge ice and meltwater from ice shelves, streams and glaciers. An ice sheet can remain stable only so long as its lost ice is replenished seasonally by winter snowfall.
The Greenland Ice Sheet is roughly three times the size of Texas, measuring approximately 656,000 square miles (1.7 million square km), according to NSIDC. If all of Greenland’s ice were to melt at once, sea levels would rise by about 20 feet (6 meters). While that catastrophic scenario is unlikely to happen anytime soon, Greenland has been steadily losing ice for decades, at a rate of about 500 gigatons per year since 1999, another study published in August 2020 found.
Those scientists said that Greenland was already losing more ice than it gained every winter. Their models factored in ice loss from iceberg calving, which can be substantial; a massive iceberg that separated and drifted alarmingly close to a Greenland village in 2018 was thought to weigh more than 12 million tons (11 million metric tons), Live Science previously reported.
However, the processes that drive icebergs to separate from the ice sheet are complex and unpredictable, said Brice Noël, lead author of the new study and a researcher with the Institute for Marine and Atmospheric research (IMAU) at Utrecht University in the Netherlands. For the new study, the researchers analyzed the Greenland Ice Sheet’s surface to determine when melt would surpass snowfall, Noël told Live Science in an email.
“We explore the sensitivity of the Greenland Ice Sheet mass loss to atmospheric warming using a much higher resolution climate model — 1 km — compared to previous work (20 to 100 km),” Noël said. “Higher spatial resolution means that we can now better capture the high mass loss rates of small outlet glaciers;” this source of melt runoff was previously excluded from models, but contributes significantly to the total mass of ice lost, he explained.
“As a result, we can more accurately project the future evolution of the Greenland Ice Sheet mass loss and its contribution to sea-level rise,” Noël said.
Stability of the ice sheet began to slip after the 1990s, as atmospheric warming boosted meltwater runoff during warm summer months, according to the study. Models showed that most of the runoff was produced at the margins of the ice sheet, in a narrow band called the ablation zone. As Earth warms, it melts the ablation zone’s protective layer of tightly compressed snow. Once this layer is gone, the ice underneath — which is much less reflective than the bright snow — absorbs more sunlight, leading to more melt.
“The accelerating exposure of bare ice amplifies the runoff production, and thus the surface mass loss,” Noël said.
In a scenario where humans don’t lower greenhouse gas emissions and present warming continues, ice loss in Greenland will cross a new threshold — in which the ice sheet gets smaller each year — within just a few decades, according to the study. And that’s a conservative estimate; that threshold could be crossed even earlier, depending on how much additional ice is lost annually from calving icebergs, the authors reported.
It could then take thousands of years for the ice sheet to melt completely, but saving Greenland’s ice from disappearing would require halting or reversing global warming sooner rather than later — “during this century,” Noël said.
That’s why the dark zone is so worrisome. During the summer months, part of the western section of the ice sheet turns from brilliant white to inky gray as algae bloom across the surface. Since 2000, these blooms have gotten bigger, causing the dark zone to expand, according to a statement by the researchers.
The darker color of the ice reduces its albedo — the amount of sunlight it reflects back to space — and causes the ice sheet to absorb more heat. However, until now, what triggers these algal blooms has remained a mystery.
“We see a lot of variability in the blooms that form on the ice-sheet surface,” said Jenine McCutcheon, a microbiologist at the University of Waterloo in Ontario and lead author of the new study describing the findings. “We wanted to better understand what causes their growth,” she told Live Science.
Understanding the algal blooms
During the Arctic’s sunless winter months, the ice algae — primarily made up of Ancylonema nordenskioeldii and species in the Mesotaenium genus — remain in a dormant state deep within the ice. During spring, as the ice melts, these algae slowly migrate to the surface. When they reach the surface, the Arctic summer provides 24-hour sunlight for photosynthesis and growth. The algae are normally green, but when exposed to constant sunlight, they create dark-colored sunscreens to protect themselves from damaging ultraviolet rays. This is what darkens the ice and, ironically, causes it to absorb more sunlight.(Image credit: Jim McQuaid)
But sunlight alone didn’t seem enough to cause the expansive blooms the researchers were seeing.
After the researchers analyzed samples they collected from the surface, “it became clear phosphorus was the most important nutrient to the algae,” study co-author Jim McQuaid, a climate scientist at the University of Leeds in England, told Live Science. “We then found that it was originating locally.”
In Greenland, the phosphorus comes from hydroxylapatite — a phosphate mineral that also contains calcium, oxygen and hydrogen — that gets blown across the ice as dust from exposed rocky outcrops.
“As the atmosphere gets warmer due to climate change, the exposed rock becomes drier and winds get stronger,” McQuaid said. “This means more dust is transported across the ice.”
Melting ice in the area also uncovers more hydroxylapatite-rich rocks, thus increasing the available phosphorus. So the algal blooms are part of a positive feedback loop: The increased ice melting leads to a higher phosphorus input, which spurs the algal growth that, in turn, further increases the ice melting.
“This type of thing will continue to happen in the future; there’s no doubt in my mind,” McQuaid said, referring to the accelerated melting.RELATED CONTENT
However, now that scientists fully understand the dark zone phenomenon, they can more accurately predict how fast the Greenland ice sheet will melt.
“If we can measure the amount of phosphorus that’s in the environment, it may be possible to translate that to an estimate of algal growth and allow us to better monitor the rate of ice melting,” McCutcheon said.
On the heels of thehottest summer the Northern Hemisphere has ever seen, U.N. researchers digging through the climate record have reported a chilling discovery: On Dec. 22, 1991, a remote weather station atop the Greenland ice sheet recorded a temperature of minus 93.3 degrees Fahrenheit (minus 69.6 degrees Celsius) — the coldest temperature ever recorded in the Northern Hemisphere.
The frigid new record, announced Wednesday (Sept. 23) in a statement from the U.N.’s World Meteorological Organization (WMO), shivers past the previous record of minus 90.4 F (minus 67.8 C) set in two different towns in the Siberian Arctic, first in 1892 and the other in 1933. For comparison, all three of those extreme lows sneak past the average temperature on Mars, which is roughly minus 81 F (minus 63 C), according to NASA.
“In the era of climate change … this newly recognized cold record is an important reminder about the stark contrasts that exist on this planet,” WMO Secretary-General Petteri Taalas said in the statement.
Contrasting those lows, of course, are extreme highs that continue to set scorching new records year after year, thanks to global warming. In Verkhoyansk, for example — one of the Siberian towns that witnessed the former record-low in 1892 — temperatures reached 100 F (38 C) this June for the first time in recorded history, setting a new record-high temperature for the Arctic Circle.
Meanwhile, Antarctica — which still holds the world record for coldest temperature on Earth (minus 128.6 F, or minus 89.2 C, recorded in 1983) — saw a new all-time high this February, when temperatures reached 69.35 F (20.75 C) during the Southern Hemisphere’s summer.
Greenland’s new record low was discovered by a team of so-called “climate detectives” working at the WMO’s Archive of Weather and Climate Extremes in Geneva. The temperature was recorded by the Klinck automatic weather station, which was active from 1990 to 1992 near the highest peak of the Greenland ice sheet, according to AP News. The WMO detectives confirmed these results with the original Klinck researchers before making their announcement on Wednesday. Formed in 2007, the WMO Archive has uncovered a slew of similar meteorological records over the years. In June 2020, Archive researchers announced the discovery of the longest lightning bolt ever recorded — a 440-mile-long (700 kilometers) bolt that stretched across Brazil and Argentina on Halloween, 2018. What could be spookier than that?
Many parts of the Earth’s climate system have been destabilised by warming, from ice sheets and ocean currents to the Amazon rainforest – and scientists believe that if one collapses others could follow
The warning signs are flashing red. The California wildfires were surely made worse by the impacts of global heating. A study published in July warned that the Arctic is undergoing “an abrupt climate change event” that will probably lead to dramatic changes. As if to underline the point, on 14 September it was reported that a huge ice shelf in northeast Greenland had torn itself apart, worn away by warm waters lapping in from beneath.
That same day, a study of satellite data revealed growing cracks and crevasses in the ice shelves protecting two of Antarctica’s largest glaciers – indicating that those shelves could also break apart, leaving the glaciers exposed and liable to melt, contributing to sea-level rise. The ice losses are already following our worst-case scenarios.
These developments show that the harmful impacts of global heating are mounting, and should be a prompt to urgent action to cut greenhouse gas emissions. But the case for emissions cuts is actually even stronger. That is because scientists are increasingly concerned that the global climate might lurch from its current state into something wholly new – which humans have no experience dealing with. Many parts of the Earth system are unstable. Once one falls, it could trigger a cascade like falling dominoes.
We have known for years that many parts of the climate have so-called tipping points. That means a gentle push, like a slow and steady warming, can cause them to change in a big way that is wholly disproportionate to the trigger. If we hit one of these tipping points, we may not have any practical way to stop the unfolding consequences.
The Greenland ice sheet is one example of a tipping point. It contains enough ice to raise global sea levels by seven metres, if it were all to melt. And it is prone to runaway melting.
This is because the top surface of the ice sheet is gradually getting lower as more of the ice melts, says Ricarda Winkelmann of the Potsdam Institute for Climate Impact Research in Germany. The result is familiar to anyone who has walked in mountains. “If we climb down the mountain, the temperature around us warms up,” she says. As the ice sheet gets lower, the temperatures at the surface get higher, leading to even more melting. “That’s one of these self-reinforcing or accelerating feedbacks.”
The collapse would take centuries, which is some comfort, but such collapses are difficult to turn off. Perhaps we could swiftly cool the planet to below the 1.6C threshold, but that would not suffice, as Greenland would be melting uncontrollably. Instead, says Winkelmann, we would have to cool things down much more – it’s not clear by how much. Tipping points that behave like this are sometimes described as “irreversible”, which is confusing; in reality they can be reversed, but it takes a much bigger push than the one that set them off in the first place.
In 2008, researchers led by Timothy Lenton, now at the University of Exeter, catalogued the climate’s main “tipping elements”. As well as the Greenland ice sheet, the Antarctic ice sheet is also prone to unstoppable collapse – as is the Amazon rainforest, which could die back and be replaced with grasslands.
A particularly important tipping element is the vast ocean current known as the Atlantic meridional overturning circulation (AMOC), which carries warm equatorial water north to the Arctic, and cool Arctic water south to the equator. The AMOC has collapsed in the past and many scientists fear it is close to collapsing again – an event that was depicted (in ridiculously exaggerated and accelerated form) in the 2004 film The Day After Tomorrow. If the AMOC collapses, it will transform weather patterns around the globe – leading to cooler climates in Europe, or at least less warming, and changing where and when monsoon rains fall in the tropics. For the UK, this could mean the end of most arable farming, according to a paper Lenton and others published in January.
For instance, the melting of the Greenland ice sheet is releasing huge volumes of cold, fresh water into the north Atlantic. This weakens the AMOC – so it is distinctly possible that if Greenland passes its tipping point, the resulting melt will push the AMOC past its own threshold.
“It’s the same exact principles that we know happen at smaller scales,” says Katharine Suding of the University of Colorado, Boulder, who has studied similar shifts in ecosystems. The key point is that processes exist that can amplify a small initial change. This can be true on the scale of a single meadow or the whole planet.
However, the tipping point cascade is very difficult to simulate. In many cases the feedbacks go both ways – and sometimes one tipping point can make it less likely that another will be triggered, not more. For example, the AMOC brings warm water from equator up into the north Atlantic, contributing to the melting of Greenland. So if the AMOC were to collapse, that northward flow of warm water would cease – and Greenland’s ice would be less likely to start collapsing. Depending whether Greenland or the AMOC hit its tipping point first, the resulting cascade would be very different.
What’s more, dozens of such linkages are now known, and some of them span huge distances. “Melting the ice sheet on one pole raises sea level,” says Lenton, and the rise is greatest at the opposite pole. “Say you’re melting Greenland and you raise the sea level under the ice shelves of Antarctica,” he says. That would send ever more warm water lapping around Antarctica. “You’re going to weaken those ice shelves.”
“Even if the distance is quite far, a larger domino might still be able to cause the next one to tip over,” says Winkelmann.
In 2018, Juan Rocha of the Stockholm Resilience Centre in Sweden and his colleagues mapped out all the known links between tipping points. However, Rocha says the strengths of the interconnections are still largely unknown. This, combined with the sheer number of them, and the interactions between the climate and the biosphere, means predicting the Earth’s overall response to our greenhouse gas emissions is very tricky.
Into the hothouse
The most worrying possibility is that setting off one tipping point could unleash several of the others, pushing Earth’s climate into a new state that it has not experienced for millions of years.
Since before humans existed, Earth has had an “icehouse” climate, meaning there is permanent ice at both poles. But millions of years ago, the climate was in a “hothouse” state: there was no permanent polar ice, and the planet was many degrees warmer.
If it has happened before, could it happen again? In 2018, researchers including Lenton and Winkelmann explored the question in a much-discussed study. “The Earth System may be approaching a planetary threshold that could lock in a continuing rapid pathway toward much hotter conditions – Hothouse Earth,” they wrote. The danger threshold might be only decades away at current rates of warming.
Lenton says the jury is still out on whether this global threshold exists, let alone how close it is, but that it is not something that should be dismissed out of hand.
“For me, the strongest evidence base at the moment is for the idea that we could be committing to a ‘wethouse’, rather than a hothouse,” says Lenton. “We could see a cascade of ice sheet collapses.” This would lead to “a world that has no substantive ice in the northern hemisphere and a lot less over Antarctica, and the sea level is 10 to 20 metres higher”. Such a rise would be enough to swamp many coastal megacities, unless they were protected. The destruction of both the polar ice sheets would be mediated by the weakening or collapse of the AMOC, which would also weaken the Indian monsoon and disrupt the west African one.
Winkelmann’s team studied a similar scenario in a study published online in April, which has not yet been peer-reviewed. They simulated the interactions between the Greenland and west Antarctic ice sheets, the AMOC, the Amazon rainforest and another major weather system called the El Niño southern oscillation. They found that the two ice sheets were the most likely to trigger cascades, and the AMOC then transmitted their effects around the globe.
What to do?
Everyone who studies tipping point cascades agrees on two key points. The first is that it is crucial not to become disheartened by the magnitude of the risks; it is still possible to avoid knocking over the dominoes. Second, we should not wait for precise knowledge of exactly where the tipping points lie – which has proved difficult to determine, and might not come until it’s too late.
Rocha compares it to smoking. “Smoking causes cancer,” he says, “but it’s very difficult for a doctor to nail down how many cigarettes you need to smoke to get cancer.” Some people are more susceptible than others, based on a range of factors from genetics to the level of air pollution where they live. But this does not mean it is a good idea to play chicken with your lungs by continuing to smoke. “Don’t smoke long-term, because you might be committing to something you don’t want to,” says Rocha. The same logic applies to the climate dominoes. “If it happens, it’s going to be really costly and hard to recover, therefore we should not disturb those thresholds.”
“I think a precautionary principle probably is the best step forward for us, especially when we’re dealing with a system that we know has a lot of feedbacks and interconnections,” agrees Suding.
“These are huge risks we’re playing with, in their potential impacts,” says Lenton. “This is yet another compulsion to get ourselves weaned off fossil fuels as fast as possible and on to clean energy, and sort out some other sources of greenhouse gases like diets and land use,” says Lenton. He emphasises that the tipping points for the two great ice sheets may well lie between 1C and 2C of warming.
“We actually do need the Paris climate accord,” says Winkelmann. The 2016 agreement committed most countries to limit warming to 1.5 to 2C, although the US president, Donald Trump, has since chosen to pull the US out of it. Winkelmann argues that 1.5C is the right target, because it takes into account the existence of the tipping points and gives the best chance of avoiding them. “For some of these tipping elements,” she says, “we’re already in that danger zone.”
Cutting greenhouse gas emissions is not a surprising or original solution. But it is our best chance to stop the warning signs flashing red.
The ice feature was already heavily fractured in 2019; this summer’s warmth has been its final undoing. Spalte Glacier has become a flotilla of icebergs.
Look closely at the satellite pictures and the higher air temperatures recorded in the region are obvious from the large number of melt ponds that sit on top of the shelf ice.
The presence of such liquid water is often problematic for ice platforms. If it fills crevasses, it can help to open them up. The water will push down on the fissures, driving them through to the base of the shelf in a process known as hydrofracturing. This will weaken an ice shelf.
Oceanographers have also documented warmer sea temperatures which mean the shelf ice is almost certainly being melted from beneath as well.
“79N became ‘the largest remaining Arctic ice shelf’ only fairly recently, after the Petermann Glacier in northwest Greenland lost a lot of area in 2010 and 2012,” explained Prof Jason Box from the Geological Survey of Denmark and Greenland (GEUS).
“What makes 79N so important is the way it’s attached to the interior ice sheet, and that means that one day – if the climate warms as we expect – this region will probably become one of the major centres of action for the deglaciation of Greenland.”
The Northeast Greenland Ice Stream drains about 15% of the interior ice sheet. The stream funnels its ice either down N79 or the glacial member just to the south, Zachariae Isstrom. Zachariae has already lost most of its floating ice shelf area.
Prof Box said N79 could resist longer because it was penned in right at its forward end by some islands. This lends a degree of stability. But, he added, the shelf continues to thin, albeit mostly further back along the trunk.
“This will likely lead to N79 disintegrating from the middle, which is kind of unique. I guess, though, that won’t happen for another 10 or 20 years. Who knows?” he told BBC News.
July witnessed another large ice shelf structure in the Arctic lose significant area. This was Milne Ice Shelf on the northern margin of Canada’s Ellesmere Island.
Eighty sq km broke free from Milne, leaving a still secure segment just 106 sq km in size. Milne was the largest intact remnant from a wider shelf feature that covered 8,600 sq km at the start of the 20th Century.
The fast pace of melting in Greenland was underlined in a study last month that analysed data from the US-German Grace-FO satellites. These spacecraft are able to track changes in ice mass by sensing shifts in the pull of local gravity. They essentially weigh the ice sheet.
The Grace mission found 2019 to have been a record-breaking year, with the ice sheet shedding some 530 billion tonnes. That’s enough meltwater running off the land into the ocean to raise global sea-levels by 1.5mm.
The melting Greenland ice sheet is already one of the largest contributors to sea level rise. But now, scientists have confirmed that the region saw a record amount of ice melt last year — shattering previous records with 532 billion metric tons of ice lost.
Researchers compared data from satellites with regional climate models to make their calculations. The two satellite missions, GRACE and GRACE-FO, which monitor the Earth’s gravitational field, play key roles in the observations of the ice sheet.
Greenland’s ice melt is a major concern among scientists — if it were to entirely melt, it would raise global sea levels by at least 20 feet. The previous record for ice melt for a single year was 464 billion metric tons in 2012.
“Not only is the Greenland ice sheet melting, but it’s melting at a faster and faster pace,” study lead author Ingo Sasgen, a geoscientist at the Alfred Wegener Institute in Germany, told The Associated Press.
Last year’s melt in Greenland added .06 inches to global sea level rise. Study co-author Alex Gardner, a NASA ice scientist, called that amount “huge” and “astounding.”
Melting ice sheets and glaciers all over the world, in addition to oceans expanding as they warm, are leading to rising sea levels, coastal flooding and extreme weather events globally.
Scientists say 2017 and 2018 saw unusually low ice melt due to colder summers and a high amount of snowfall, but 2019 data reveals a return to extremely high melt rates.
The new satellite data accounts for snowfall, allowing a more precise net loss calculation. Snowfall in 2019 was below average, contributing to the record figure.
Researchers said a number of factors have contributed to an increase in surface melting, including, perhaps most prominently, a phenomenon they call “blocking,” which keeps warm air over the region for longer periods of time.
“After a two-year ‘breather’, in 2019 the mass loss increased steeply and exceeded all annual losses since 1948, and probably for more than 100 years,” Sasgen said in a news release. “There are increasingly frequent, stable high-pressure areas over the ice sheet, which promote the influx of warm air from the middle latitudes. We saw a similar pattern in the previous record year 2012.”
That’s one of the most aggressive timelines for this threshold to be reached and, if correct, is one of the more direct signs that humans are warming the Earth’s climate at an even more dramatic pace than expected.
“We see substantial variations from year to year,” Sasgen said. “But the five years with the highest losses since 1948 were all in the last decade.”
The Greenland Ice Sheet has reached a point of rapid retreat that it couldn’t recover from even if global temperatures stopped rising instantly.
This Arctic ice sheet is the second-largest ice sheet in the world, after the one that blankets Antarctica. It covers the majority of Greenland and melts into the seas via outlet glaciers, which have been rapidly losing ice for decades. Now, new research finds that today’s glacial ice loss is 14% greater than it was between 1985 and 1999. The ice sheet is losing approximately 500 gigatons of ice each year, more than is replenished by annual snowfall.
“Glacier retreat has knocked the dynamics of the whole ice sheet into a constant state of loss,” study co-author Ian Howat, an Earth scientist at The Ohio State University, said in a statement. “Even if the climate were to stay the same or even get a little colder, the ice sheet would still be losing mass.”
Greenland’s ice sheet has long been in peril. In January 2019, researchers reported in the journal Proceedings of the National Academy of Sciences that the ice sheet was losing ice at four times the rate it was in 2003. Other researchers have found that the ice sheet is sliding on its underlying bedrock faster than expected. This sliding can move ice from the cold interior of Greenland to the warmer edges, where it melts faster.
The new study combined three decades of satellite imagery with data from airplane surveys from Operation IceBridge,providing a detailed timeline of ice thickness, ice flow, ice elevation and the location of the calving front of the ice sheet — the line where the glaciers hit the sea and lose ice through the calving of icebergs. This method allowed the researchers to look at both seasonal changes in ice discharge as well as longer trends.
What they found was an increase of about 60 gigatons of ice loss a year between 2007 and 2018 compared with the period between 1985 and 1999. All told, the ice sheet has lost 4,200 gigatons of ice since 1985.
There are regional differences, with some of the accelerating ice retreat between 2001 and 2005 driven by glaciers in the southeastern part of Greenland moving from relatively shallow parts of the seafloor into deeper sections, where warm water can more easily circulate beneath them and melt them.
But regardless of the region of Greenland, the retreat of a glacier by 0.6 miles (1 kilometer) is consistently associated with a 4% to 5% increase in the rate of ice discharge from that glacier. Because these sheets are already retreating, further ice loss is baked in, even in a hypothetical situation in which temperatures stop rising.
“Glaciers have been sensitive to seasonal melt for as long as we’ve been able to observe it, with spikes in ice discharge in the summer,” study lead author Michalea King, a researcher at The Ohio State University’s Byrd Polar and Climate Research Center, said in the statement. “But starting in 2000, you start superimposing that seasonal melt on a higher baseline — so you’re going to get even more losses.”
With the ice sheet set to lose more ice than it gains each year, it might seem like the end of the Greenland Ice Sheet. But that future has yet to be written, Potsdam University physicist and climate scientist Stegan Rahmstorf noted on Twitter. Eventually, he said, the ice retreat will pull the ice sheet away from the ocean. At that point, warm ocean waters will stop melting the ice, and the glaciers will stop calving. The Greenland Ice Sheet will become an entirely land-based entity. When that occurs, a new dynamic will set in: It will be a race between the rate of the surface melt of the ice and the annual snowfall that decides when and whether the ice sheet disappears.
“Thus, Greenland ice loss is a real concern — already today it contributes a lot to sea-level rise,” Rahmstorf wrote. “And Greenland does have a tipping point where the ice sheet becomes doomed to total loss. But the new paper by King et al. does not say anything about whether this has been crossed.”
A significant melt event is unfolding in Greenland this week.
With temperatures nearly 20 degrees Fahrenheit higher than usual in some areas, the southern part of the ice sheet is melting at its highest rate this season. Forecasts suggest that the melting on Greenland’s South Dome—one of the highest elevations on the ice sheet—may be the strongest for early June since 1950.
It worries experts that Greenland could be priming for another big melt season.
Early melting this spring, low snowpack in some areas and the potential for strong high-pressure weather systems later this summer have all raised red flags. Scientists are paying close attention after last summer’s record-breaking ice loss—an event scientists expect to occur more frequently as the Arctic continues to warm.
Scientists typically define the beginning of melt season as the first three-day period in which melting is observed across at least 5% of the ice sheet. This year, that period began on May 13—nearly two weeks earlier on average over the last few decades.
The melting coincided with a heat wave across much of the Arctic. Siberia and the central Arctic were some of the hardest-hit regions. But temperatures skyrocketed in parts of Greenland, as well, after an otherwise chilly start to the month.
At the same time, snow began rapidly disappearing along the margins of the ice sheet, exposing bare rock and ice. The lack of snow is one factor increasing the possibility of an above-average melt year, according to Jason Box, an ice expert with the Geological Survey of Denmark and Greenland.
Snow plays an important role in the Arctic. Its bright surface helps to reflect sunlight away from the Earth. When snow disappears, more heat is able to get through and warm the surface. That, in turn, can cause faster melting.
The exposure of bare ice is happening earlier than usual this year, according to Box.
“Like last year, a dearth of snow along the western ice sheet preconditioned stronger than normal ice loss because the seasonal snow shields the dark bare ice with a bright reflective cover,” he told E&E News by email. “So, all else equal, we can expect more melt this year.”
Xavier Fettweis, a polar climate scientist at the University of Liège in Belgium, agreed that the lack of snow can pose a risk. He added that warm events are also necessary to kick-start the feedback process.
The ice sheet is in the midst of one now. And the fact that melting is happening at such high elevations, where snowpack tends to be stronger, may be cause for some concern.
The melting at South Dome, for instance, is likely to make the snow wetter and denser, according to Fettweis. That will diminish its ability to reflect sunlight and to absorb meltwater that forms on the surface of the ice sheet.
“Such an event so early in the season will certainly favour an above-average melt season this year,” he told E&E News in an email.
It’s possible that more heat waves are on the way.
According to Judah Cohen, director of seasonal forecasting at the analytics firm Atmospheric and Environmental Research, model forecasts suggest strong high-pressure events over Greenland this summer. High-pressure systems are often associated with warming on the ice sheet.
In fact, a recent study concluded that last summer’s extreme melting was linked to abnormally persistent high-pressure systems over Greenland (Climatewire, April 16). Greenland’s melt rates last year were second only to those in 2012—and the total amount of ice lost was actually the highest on record.
This summer’s forecasts seem to suggest the high-pressure systems will be most intense in July. And they may affect larger swaths of the ice sheet than the current melt event, which is mainly limited to the southern part of the ice sheet.
Cohen cautions that there’s still considerable uncertainty about forecasts this far in advance. It’s too early, for now, to say whether these events will definitely occur.
But if the forecast is accurate, he said, it’s “definitely suggestive of high melt over the ice sheet.”
In general, he added, the forecast is in keeping with research indicating that these high-pressure systems are becoming more frequent over Greenland. Some scientists believe that climate change, which can alter the structure and flow of the atmosphere, is partly to blame.
“Nothing is impossible; there’s always variability,” Cohen said of this summer’s forecasts. “But I think just the background would support a continuation of this pattern of high pressure in and around Greenland.”
None of the events this spring necessarily promises a melt season like last year. But put together, with the threat of more heat events this summer, they do suggest cause for a watchful eye on Greenland this season.