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ocean currents
'Serious Risk' of Vital Ocean Current Collapse by 2100, Warn Scientists
"A string of scientific studies in the past few years suggests that this risk has so far been greatly underestimated," wrote scientists in a letter to Nordic governments.
Oct 24, 2024
A group of 44 climate scientists from 15 different countries warn there is a "serious risk" that soaring global temperatures will trigger the "catastrophic" collapse of a crucial system of ocean currents—and possibly sooner than established estimates considered likely.
The Atlantic Meridional Overturning Circulation, or AMOC, moves warm water up from the tropics to the North Atlantic, where it sinks and cools before returning south. It is, as letter signatory and oceanographer Stefan Rahmstorf told The Guardian, "one of our planet's largest heat transport systems." If it collapsed, it could lower temperatures in some parts of Europe by up to 30°C.
That's why the scientists sent a letter to the Council of Nordic Ministers over the weekend urging them to take action to understand and prevent a potential collapse.
"A string of scientific studies in the past few years suggests that this risk has so far been greatly underestimated," the scientists wrote. "Such an ocean circulation change would have devastating and irreversible impacts especially for Nordic countries, but also for other parts of the world."
In the letter, the scientists detailed some of the potential "catastrophic" impacts of such a collapse, including "major cooling" in northern Europe, extreme weather, and changes that would "potentially threaten the viability of agriculture in northwestern Europe."
One study cited in the letter shows that London could cool by 10°C and Bergen, Norway by 15°C.
"If Britain and Ireland become like northern Norway, (that) has tremendous consequences. Our finding is that this is not a low probability," Peter Ditlevsen, a University of Copenhagen professor who signed the letter, told Reuters. "This is not something you easily adapt to."
Globally, the scientists said, the end of AMOC could cause the ocean to absorb less carbon dioxide, thereby increasing its presence in the atmosphere. It could also further augment sea-level rise along the U.S. Atlantic coast and alter tropical rainfall patterns.
The most recent synthesis report from the Intergovernmental Panel on Climate Change (IPCC) expressed "medium confidence" that the current would not cease functioning before 2100. Since its publication in March 2023, however, a rash of studies have come out upping the risk.
"Given that the outcome would be catastrophic and impacting the entire world for centuries to come, we believe more needs to be done to minimize this risk."
A Nature Communications study, also published last year, looked at 150 years of temperature data and determined with 95% confidence that AMOC would collapse between 2025 and 2095 if greenhouse gas emissions continue to rise as currently predicted.
Another, published in Science Advances in February, concluded that AMOC was currently "on route to tipping."
There are already signs that AMOC has begun to stall over the last six to seven decades, Rahmstorf told The Guardian, such as the cold blob in the North Atlantic that is defying global warming trends. The water in North Atlantic is also becoming less salty due to meltwater from the Greenland ice sheets and increased precipitation due to climate change. Less salty water is lighter and does not sink, interrupting the process that makes AMOC flow.
"It is an amplifying feedback: As AMOC gets weaker, the subpolar oceans gets less salty, and as the oceans gets less salty then AMOC gets weaker," Rahmstorf explained. "At a certain point this becomes a vicious circle which continues by itself until AMOC has died, even if we stop pushing the system with further emissions."
"The big unknown here—the billion-dollar question—is how far away this tipping point is," Rahmstorf said.
The scientists acknowledged that the chance of the AMOC tipping "remains highly uncertain."
They continued:
The purpose of this letter is to draw attention to the fact that only 'medium confidence' in the AMOC not collapsing is not reassuring, and clearly leaves open the possibility of an AMOC collapse during this century. And there is even greater likelihood that a collapse is triggered this century but only fully plays out in the next.
Given the increasing evidence for a higher risk of an AMOC collapse, we believe it is of critical importance that Arctic tipping point risks, in particular the AMOC risk, are taken seriously in governance and policy. Even with a medium likelihood of occurrence, given that the outcome would be catastrophic and impacting the entire world for centuries to come, we believe more needs to be done to minimize this risk.
To respond to this threat, the scientists urged the council—a group that includes Denmark, Finland, Iceland, Norway, Sweden, Greenland, the Faroe Islands, and Åland—to launch a study of the risk posed to these countries by an AMOC collapse and to take measures to counter that risk.
"This could involve leveraging the strong international standing of the Nordic countries to increase pressure for greater urgency and priority in the global effort to reduce emissions as quickly as possible, in order to stay close to the 1.5°C target set by the Paris agreement," they wrote.
Johan Rockström, a letter signatory who leads the Potsdam Institute for Climate Impact Research, wrote on social media that global politics, "particularly in [the] Nordic region, can no longer exclude [the] risk of AMOC collapse."
And there is one way that political leaders can stave off such a collapse, as well as other climate tipping points, according to Rahmstorf.
"This is all driven mainly by fossil fuel emissions and also deforestation, so both must be stopped," he told The Guardian. "We must stick to the Paris agreement and limit global heating as close to 1.5°C as possible."
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'Omen of the Future': Off-The-Charts Hot Oceans Scare Scientists
After 2023 was the hottest year in human history, experts warn that 2024 "has strong potential to be another record-breaking year."
Feb 27, 2024
While global policymakers continue to drag their feet on phasing out planet-heating fossil fuels, scientists around the world "are freaking out" about high ocean temperatures, as they told The New York Times in reporting published Tuesday.
A "super El Niño" has expectedly heated up the Pacific, but Times reporter David Gelles spoke with ocean experts from Miami to Cambridge to Sydney about record heat in the North Atlantic as well as conditions around the poles.
"The sea ice around the Antarctic is just not growing," said Matthew England, a University of New South Wales professor who studies ocean currents. "The temperature's just going off the charts. It's like an omen of the future."
Rob Larter, a marine geophysicist with the British Antarctic Survey who watches polar ice levels, told the paper that "we're used to having a fairly good handle on things. But the impression at the moment is that things have gone further and faster than we expected. That's an uncomfortable place as a scientist to be."
\u2026for almost a year now,\u201d McNoldy said. \u201cIt\u2019s just astonishing. Like, it doesn\u2019t seem real.\u201d Across the unusually warm Atlantic, in Cambridge, England, @rdlarter , a marine scientist who tracks polar ice levels, is equally perplexed. \u201cIt\u2019s quite scary, partly because\u2026— (@)
Last week, Jeff Berardelli, WFLA's chief meteorologist and climate specialist, also highlighted the warm North Atlantic and that "all signs are pointing to a busy hurricane season" later this year.
Noting that in the middle of this month, sea surface temperatures in the North Atlantic were around 2°F higher than the 1990-2020 normal and nearly 3°F above the 1980s, Berardelli explained:
That may not sound like a lot, but consider this is averaged over the majority of the basin shown in the red outline in the image above. A deviation like that is unheard of... until now.
To put it into more relatable terms, considering what's been normal for the most recent 30 years, the statistical chance that any February day would be as warm as it is right now is 1-in-280,000. That's not a typo. This is according to University of Miami researcher Brian McNoldy...
And that 1-in-280,000 is compared against a recent climate, which had already been warmed substantially by climate change. If you tried to compare it against a climate considered normal around the year 1900, the math would become nonsensical. Meaning an occurrence like this simply would not be possible.
McNoldy also stressed the shocking nature of current conditions to the Times, telling Gelles that "the North Atlantic has been record-breakingly warm for almost a year now... It's just astonishing. Like, it doesn't seem real."
The new comments from McNoldy and other scientists come on the heels of various institutions and experts worldwide recently confirming that 2023 was the hottest year in human history. Research also showed that it was the warmest year on record for the oceans, which capture about 91% of excess heat from greenhouse gases.
As Common Dreams reported last month, Adam Scaife, a principal fellow at the United Kingdom's Met Office, said that "it is striking that the temperature record for 2023 has broken the previous record set in 2016 by so much because the main effect of the current El Niño will come in 2024."
That's the warm phase of the El Niño Southern Oscillation, a climate phenomenon that also has a cool phase called La Niña expected later this year. Still, Scaife warned that "the Met Office's 2024 temperature forecast shows this year has strong potential to be another record-breaking year."
Throughout the record-shattering 2023, experts also expressed alarm. After an April study showed that the ocean is heating up faster than previously thought, the BBC revealed that some scientists declined to speak about it on the record, reporting that "one spoke of being 'extremely worried and completely stressed.'"
In July, when a buoy roughly 40 miles south of Miami recorded a sea surface temperature of 101.1°F just after a "100% coral mortality" event at a restoration site, Florida State University associate professor Mariana Fuentes told NPR that "if you have several species that are being impacted at the same time by an increase in temperature, there's going to be a general collapse of the whole ecosystem."
The following month, the European Union's Copernicus Climate Change Service announced that the average daily global ocean surface temperature hit 69.7°F, and deputy director Samantha Burgess said, "The fact that we've seen the record now makes me nervous about how much warmer the ocean may get between now and next March."
"The more we burn fossil fuels, the more excess heat will be taken out by the oceans, which means the longer it will take to stabilize them and get them back to where they were," Burgess emphasized at the time.
Last year ended with a United Nations climate summit that scientists called "a tragedy for the planet," because the final deal out of the conference—led by an Emirati oil CEO—did not demand a global phaseout of fossil fuels.
Azerbaijan, which is set to host this year's U.N. conference in November, has similarly selected a former fossil fuel executive to lead the event. The country also plans to increase its gas production by a third during the next decade.
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'Cliff-Like' Collapse of Critical Current System More Likely Than Thought: Study
"The new study adds significantly to the rising concern about an AMOC collapse in the not-too-distant future," said one scientist. "We will ignore this at our peril."
Feb 10, 2024
A study published Friday warned that a systemic collapse of the Atlantic Ocean currents driving warm water from the tropics toward Europe could be more likely than researchers previously estimated—an event that would send temperatures plummeting in much of the continent.
The Atlantic Meridional Overturning Circulation (AMOC), which includes the Gulf Stream, could be headed for a relatively sudden shutdown that René Van Western, who led the Dutch study published in Science Advances, called "cliff-like."
"We are heading towards a tipping point."
For many millennia, the Gulf Stream has carried warm waters from the Gulf of Mexico northward along the eastern North American seaboard and across the Atlantic to Europe. As human-caused global heating melts the Greenland ice sheet, massive quantities of fresh water are released into the North Atlantic, cooling the AMOC—which delivers the bulk of the Gulf Stream's heat—toward a "tipping point" that could stop the current in its tracks.
An AMOC shutdown would cause temperatures to rise in the Southern Hemisphere but plunge dramatically in Europe. In the study's model, London cools by an average of 18°F and Bergen, Norway by 27°F. An AMOC failure would also cause sea levels to rise along North America's east coast.
"We are moving closer [to the collapse], but we we're not sure how much closer," van Westen told The Associated Press. "We are heading towards a tipping point."
According to the study:
Although AMOC collapses have been induced in complex global climate models by strong freshwater forcing, the processes of an AMOC tipping event have so far not been investigated. Here, we show results of the first tipping event in the Community Earth System Model, including the large climate impacts of the collapse. Using these results, we develop a physics-based and observable early warning signal of AMOC tipping: the minimum of the AMOC-induced freshwater transport at the southern boundary of the Atlantic. Reanalysis products indicate that the present-day AMOC is on route to tipping. The early warning signal is a useful alternative to classical statistical ones, which, when applied to our simulated tipping event, turn out to be sensitive to the analyzed time interval before tipping.
"The research makes a convincing case that the AMOC is approaching a tipping point based on a robust, physically based early warning indicator," said Tim Lenton, director of the University of Exeter's Global Systems Institute. "What it cannot and does not say is how close the tipping point, because... there is insufficient data to make a statistically reliable estimate of that.
"We have to plan for the worst," added Lenton, who was not involved in the Dutch study. "We should invest in collecting relevant data and improving estimation of how close a tipping point is, improving assessment of what its impacts would be, and getting pre-prepared for how we could best manage and adapt to those impacts if they start to unfold."
Stefan Rahmstorf—who leads the Earth Systems Analysis department at the Potsdam Institute for Climate Research in Germany and was not part of the new study—called the research "a major advance in AMOC stability science."
"The new study adds significantly to the rising concern about an AMOC collapse in the not-too-distant future," Rahmstorf told The Associated Press. "We will ignore this at our peril."
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