Antarctic currents, which supply 40% of the world’s deep oceans with nutrients and oxygen, are slowing dramatically. These deep ocean tides supply nearly half the world’s oceans with vital nutrients and oxygen, but melting ice shelves are slowing them. Currents in the Atlantic Ocean are also weakening — which could make the climate in some regions unrecognizable. And a newly discovered body of water called Atlantic Equatorial Water stretches from Brazil to West Africa.
Deep-sea currents around Antarctica that are vital to marine life have slowed by 30% since the 1990s and could soon stop altogether, according to a new study.
These currents, known as Antarctic Bottom Water, are fed by dense, cold water from Antarctica’s continental shelf that descends to depths below 10,000 feet (3,000 meters). The water then spreads north into the Pacific Ocean and eastern Indian Ocean, feeding a network of currents called the Global Meridional Overturning Circulation and supplying 40 percent of the world’s deep ocean with fresh nutrients and oxygen.
However, global warming is releasing large volumes of less dense fresh water from Antarctic ice shelves, slowing this circulation.
“If the oceans had lungs, this would be one of them,” Matthew England, a professor of ocean dynamics and climate at the University of New South Wales in Sydney, Australia, who contributed to the study, said in a statement. Scientists from the U.K. and Australia collaborated on a study published in March in the journal Nature that predicted a 40% decline in the strength of Antarctic bottom waters by 2050.
He also warned that the currents could eventually cease entirely. “We’re talking about the potential long-term disappearance of an iconic water mass,” England said.
In a study published in the journal Nature Climate Change, England and his colleagues say they have confirmed these predictions with real-world observations in the Australian Antarctic Basin, which spans the polar waters between Australia and Antarctica.
The researchers looked at changes in the amount of bottom water entering the basin between 1994 and 2017 and found a 30% decrease in speed, suggesting that these deep-sea currents, or abyssal currents, are starting to stagnate.
Weakening circulation around Antarctica could slow the global network of deep currents and lead to a build-up of nutrients and oxygen in the deep ocean, negatively impacting marine life and productivity.
Antarctica. perunica.ru
“The thing is, all the marine life that we have on the surface, when it dies, it sinks to the bottom of the ocean, so there’s a lot of nutrient-rich water in the deep ocean,” England said in a video produced by the Australian Academy of Science. “If we slow down the overturning circulation that brings that bottom water back to the surface, we cut off the pathway for nutrients to come back to the surface to restore marine life.”
According to a new study, about 276 trillion tons (250 trillion metric tons) of cold, salty, oxygen-rich water sinks around Antarctica each year. In a warming climate, fresh meltwater reduces the density of this sinking mass, meaning more of it remains in the upper ocean. “These regions supply deep water to the entire Pacific and East Indian basins, so the changes quantified here are likely to affect much of the global abyssal ocean,” the researchers wrote.
Scientists have warned that the influx of freshwater into Antarctic waters is likely to continue and accelerate in the coming decades, meaning these vital currents could soon collapse. “Such profound changes in the ocean’s exchange of heat, freshwater, oxygen, carbon and nutrients will have significant impacts on the oceans for centuries,” England said.
The new findings confirm dramatic estimates made by researchers earlier this year, said Ariaan Purich, a research fellow at Monash University’s School of Earth, Atmosphere and Environment in Australia who was not involved in the study.
“This new research is important because, along with a recent landmark modelling study, it provides further evidence, including observational data, that melting of the Antarctic ice sheet and shelves will affect global ocean circulation, which will have a significant impact on how the ocean absorbs heat and carbon,” Purich told Australia’s Science Media Exchange.
A mysterious patch of water in the North Atlantic has puzzled scientists for decades. Located southeast of Greenland, the patch of seawater was colder between 1901 and 2021 than it was in the late 1800s, even as the seas around it grew warmer.
Some scientists attribute the “heat hole” to an influx of cold meltwater from the Arctic; others blame pollution from shipping, which can reflect sunlight back into space. But mounting evidence suggests the hole has a more sinister origin — one whose effects, if released, would spread far beyond the small region of the North Atlantic.
The heating hole could be a sign that the Atlantic Ocean currents are slowing down. This network of currents regulates Earth’s climate by moving heat from the tropics to the Northern Hemisphere. The currents, including the Gulf Stream, form a huge and seemingly permanent loop known as the Atlantic Meridional Overturning Circulation (AMOC), Live Science reports.
The AMOC has weakened before, ancient sediments show, and some past circulation changes have been extremely abrupt. But human societies will struggle to adapt to the rapid pace of change that many researchers predict over the coming century, said Robert Marsh, a professor of oceanography and climate at the University of Southampton in the U.K. Weaker currents could cause freezes in parts of Europe, worsen sea-level rise along the U.S. east coast, and cause droughts around the equator in ways that scientists are racing to predict.
The AMOC is part of Earth’s largest conveyor belt, the thermohaline circulation, which pushes water across the world’s oceans. Waters flowing north from the tip of South Africa skim the ocean’s surface, absorbing heat from the atmosphere as they glide through the tropics and subtropics. They release that heat into the North Atlantic near Greenland, leading to a warming effect that is particularly strong in northwestern Europe.
Melting ice on the Greek ice sheet is affecting ocean currents across the Atlantic. Ashley Cooper/Getty Images
The Northern Hemisphere is currently warmer than it would be if the currents that make up the AMOC were weaker. For example, the AMOC makes air temperatures in countries like Norway, on average, 18 to 27 degrees Fahrenheit (10 to 15 degrees Celsius) warmer than they would otherwise be.
To return south, surface water in the North Atlantic must sink further down the water column and merge with bottom currents. Climate scientists say that at this stage of sinking, circulation slows down because surface water must be very salty, and therefore very dense, to sink. But rising rivers of meltwater from the Greenland Ice Sheet and the Arctic dilute the salt concentration of surface water, preventing it from sinking to the seafloor.
The warming hole that worries scientists is located where the AMOC is releasing heat. Ocean temperatures there are cooler than researchers would expect to see given current global temperatures if the AMOC were still strong. This suggests that the transport of heat from south to north has already slowed.
And with climate change frying the planet, there’s a risk that more freshwater will enter the North Atlantic, causing a feedback loop that will accelerate the weakening of the AMOC. As ocean currents slow, the amount of salt reaching the North Atlantic could decrease, making it harder for already diluted surface waters to sink.
“When you have a strong AMOC, it pulls in salt water,” David Thornalley, an oceanographer and climate scientist at University College London, told Live Science. “If you start to weaken the AMOC, you’re going to have less salt water coming into the North Atlantic, and that’s going to weaken the AMOC, and then it’s going to be a runaway process.”
The problem is that direct measurements of the AMOC’s strength only go back to 2004, so researchers rely on indirect “fingerprints” — climate parameters they think are related to the AMOC — to determine long-term trends in the Atlantic’s circulation.
The problem with fingerprints is that they produce variable — and sometimes contradictory — results. For example, a 2018 study suggested a weakening, while a study published in January suggested that the Atlantic currents had not weakened in the past 60 years, although some scientists criticized the January study.
Whether or not the Atlantic currents have slowed down already, most scientists believe they will in the future.
If the circulation weakens significantly, “there will be some pretty dramatic changes, and they will happen gradually over the 21st century,” Thornalley said.
First, weakening ocean currents will carry less heat to countries like Norway, Sweden, and the UK, leading to cooler temperatures in those regions. The extent of the cooling will depend on how much the AMOC loses its strength.
Climate models generate different predictions depending on what assumptions they make, how sensitive they are to certain climate factors, and what data researchers feed into the models. Some show a 10% decline in AMOC strength, while others predict declines closer to 50%, Marsh said.
“A 50% decline would have a much more significant impact on our regional climate,” Marsh said, adding that the subsequent drop in temperatures would disrupt weather-dependent industries like agriculture. By comparison, “a 10% weakening of the AMOC would be noticeable but manageable,” he said. “It would probably make our weather a little less mild, especially in the winter.”
A complete collapse is unlikely, the study says. Even if surface waters stop sinking in the North Atlantic, there are relatively constant factors, such as wind, that control the movement of water, Marsh said.
“A collapse that is a hypothetical 100% failure of AMOC just doesn’t seem plausible to me,” Marsh said. But AMOC doesn’t have to collapse to throw human lives and systems into chaos, he added.
Cooling in the North Atlantic and northwestern Europe could offset some of the warming from climate change — but that could be bad, Marsh said. The drop in temperatures could change the atmospheric processes that drive storms and other weather in those regions, he said.
A cold snap in the North Atlantic won’t directly make the East Coast of the U.S. colder, Marsh said. That’s because the weather in the Northeast is dictated more by the Arctic polar vortex, a ring of cold wind that circles the North Pole and traps cold air near the Arctic. If that band warps or widens, as it sometimes does in the winter, cold air escapes and sweeps over the Midwest and south to the Gulf.
But a weaker AMOC could change the Arctic polar vortex, which in turn would affect the Northeast, Marsh said. The vortex is vulnerable to climate change, and recent data suggests the structure is already behaving strangely.
Direct impacts on the East Coast and northwestern Europe could also result from rising sea levels. Sea levels in parts of the North Atlantic are currently 2.3 feet (70 centimeters) lower than they would be if the AMOC were weaker, as strong currents create uneven sea levels. If the AMOC were to weaken, water could redistribute and amplify the sea level rise caused directly by global warming.
As the Northern Hemisphere cools, tropical and subtropical regions could also be thrown into chaos. Research suggests that a colder North Atlantic will change the Earth’s energy balance and cause a southward shift of the Intertropical Convergence Zone (ITCZ), a band of clouds that circles the globe near the equator.
The wet ITCZ oscillates up and down depending on the Earth’s position relative to the sun, bringing heavy rains and storms. It is responsible for monsoons—weather patterns with distinct wet and dry seasons—in South America, West Africa, India, and East Asia.
If the ITCZ shifts south, research suggests it would disrupt monsoons for at least 100 years. “Right now, we have regions that are used to receiving very intense rainfall during the rainy season,” said Ben-Yami, the study’s lead author. Ecosystems are adapted to these downpours, and people depend on the rainfall for agriculture, she said.
The southward shift of the ITCZ will lead to shorter, drier rainy seasons in places like West Africa. Those effects could last for decades and seriously disrupt life around the equator, Ben-Yami said. “Farmers anywhere in sub-Saharan Africa need that rainfall,” she said.
A map of ocean currents in the Atlantic. These ocean currents are weakened by a “heat hole” in the waters southeast of Greenland. PeterHermesFurian/Getty Images
Changes in rainfall will also affect the Amazon rainforest. The effects could differ in the northern and southern parts because the rainforest is so large that the southern part will still receive significant rainfall even if the ITCZ shifts south, Ben-Yami said.
However, the northern Amazon rainforest, including parts of Colombia, Peru, Ecuador, Venezuela, Suriname, Guyana, French Guiana and Brazil, will experience longer and more intense dry seasons, which will have devastating consequences for the region, she said.
Moreover, North Atlantic sediments from the last glacial period (120,000–11,500 years ago) indicate that abrupt climate changes associated with AMOC have occurred in the past.
Researchers say the AMOC will weaken significantly before 2100, but it’s difficult to pinpoint exactly when the biggest changes will occur.
Because direct measurements go back only 20 years, scientists often extrapolate historical data to estimate when Atlantic currents might reach a tipping point. Tipping points are thresholds in some Earth systems that, if exceeded, could shift those systems from one stable state to a completely different one.
A noteworthy 2023 study concluded that the AMOC could reach a tipping point as early as this year. The authors used sea surface temperatures in the North Atlantic subpolar gyre between 1870 and 2020 to calculate variations in the stability and strength of the AMOC. Their model suggested that the Atlantic currents were becoming less stable and weaker, possibly leading to a tipping point before mid-century.
But in a 2024 paper, Ben-Yami and other experts argued that there was too much uncertainty in the data before 2004 to predict when the AMOC might collapse. “If you take all these uncertainties into account, you don’t get a practical forecast,” she said.
Not having reliable forecasts may be worse than knowing when the system will fail because the future is so uncertain, Ben-Yami said. “We have to be even more careful” in the face of that uncertainty, she warned.
While some researchers look to the past for answers, others are looking for early warning signals that hold clues about future changes in the AMOC. One such signal is the amount of freshwater flowing into the Atlantic at 34 degrees south latitude, near the tip of South Africa. Models suggest that freshwater transport there will reach a minimum about 25 years before the AMOC reaches the point of no return, meaning experts can accurately predict shifts in the AMOC before the biggest changes occur.
But knowing this minimum won’t help anyone prevent a significant weakening of the AMOC, because by the time the minimum is reached, it will be too late to reverse the driving force – anthropogenic climate change, says E.J.W. (Emma) Smolders, a doctoral student specializing in AMOC early warning signals at Utrecht University in the Netherlands.
A newly discovered body of water called Atlantic Equatorial Water stretches from Brazil to West Africa. Scientists have discovered a previously undiscovered body of water in the middle of the Atlantic Ocean: a giant body of water that stretches across the Atlantic from the tip of Brazil to the Gulf of Guinea, near West Africa.
Employees of the P.P. Shirshov Institute of Oceanology of the Russian Academy of Sciences have made a world-class discovery. They have established that in the Atlantic Ocean, as well as in the Indian and Pacific Oceans, there is an equatorial water mass with unique characteristics.
A water mass called Atlantic Equatorial Water forms along the Earth’s equator when ocean currents mix separate bodies of water in the north and south.
Before the discovery of Atlantic Equatorial Water, scientists had noticed water mixing along the equator in the Pacific and Indian oceans, but never in the Atlantic. The researchers published their findings on October 28, 2024, in the journal Geophysical Research Letters.
It seemed controversial that an equatorial water mass is present in the Pacific and Indian Oceans but absent from the Atlantic Ocean, since the equatorial circulation and mixing in all three oceans have common features. The discovery of a new water mass made it possible to complete (or at least more accurately describe) the phenomenological picture of the main water masses of the World Ocean.
From Brazil to West Africa: Russian Scientists Discover Atlantic Equatorial Water Mass. Tsargrad
Ocean water is not the same everywhere, but is a vast mosaic of interconnected masses and layers that mix and separate again by currents, eddies, and changes in temperature and salinity.
Water masses are individual parts of this motley structure; each body of water shares a common geography, formation history, and common physical properties such as density and dissolved isotopes of oxygen, nitrate, and phosphate.
To distinguish between water masses, oceanographers map the relationship between temperature and salinity across the ocean—two measurements that together determine the density of seawater.
In 1942, this temperature-salinity mapping led to the discovery of equatorial waters in the Pacific and Indian Oceans. Formed by the mixing of waters to the north and south, both the Indian and Pacific equatorial waters have temperature and salinity curves along lines of constant density that are easily distinguishable from the surrounding water. However, no such connection could be found in the Atlantic.
Volumetric TS diagram of the Atlantic Ocean, obtained from Argo data; SACW — South Atlantic Central Water mass, AECW — Atlantic Equatorial Water mass, WNACW and EACNW — Western and Eastern branches of the North Atlantic Central Water mass. Fig. (b): TS diagram of the Atlantic water masses according to Sverdrup et al. (1942). P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences
To find the missing mass of water, scientists analyzed data collected by the Argo program, an international network of robotic self-submersible floats scattered throughout the world’s oceans.
By analyzing the data collected by this floating mass, the researchers discovered an overlooked curve of temperature and salinity that parallels the curves dividing the North Atlantic and South Atlantic waters to the north and south: the Atlantic Equatorial Waters.
“It was easy to confuse the Atlantic Equatorial Waters with the South Atlantic Central Waters, and to distinguish them required a fairly dense network of vertical temperature and salinity profiles covering the entire Atlantic Ocean,” the researchers reported.
Now that the water mass has been identified, it will allow scientists to better understand ocean mixing processes, which are vital for the oceans to transport heat, oxygen and nutrients around the world.
Scientists thought La Niña was coming. But it hasn’t — at least not yet. What might that mean for this year’s hurricane season, and how might long-term climate change affect El Niño and La Niña patterns?
After one of the strongest El Niños on record ended in 2024, meteorologists predicted that La Niña, the climate model’s equivalent, would follow. Signals of the slow-moving and “unusual” La Niña grew stronger over the winter but began to weaken in recent months. By March, it had died.
So what happened and how might it affect the weather this summer and the upcoming Atlantic hurricane season?
A graph showing observed and predicted temperatures that will indicate whether El Niño, La Niña, or neutral conditions will occur this fall. OAA Climate.gov, based on data provided by the Climate Prediction Center
El Niño is a seasonal shift in Pacific Ocean temperatures that can suppress hurricanes, alter rainfall patterns, and bend the jet stream. Its cold-water counterpart, La Niña, tends to do the opposite: fuel Atlantic hurricanes and increase wildfire risk in the West. Together, they form the El Niño-Southern Oscillation (ENSO).
ENSO refers to seasonal climate shifts caused by changes in the surface temperature of the Pacific Ocean. Changes in winds and currents can draw cold water from the deep ocean, where it interacts with the atmosphere in complex ways. Even small shifts in sea surface temperatures can shift global weather in the coming months toward hot and dry — or wet and cool — depending on the region.
Scientists are monitoring a narrow band of the Pacific Ocean near the equator. A rise or fall in average surface temperature of 0.9 degrees Fahrenheit (0.5 degrees Celsius) over five overlapping three-month periods can signal the onset of an El Niño or La Niña, respectively.
Graph showing ENSO occurrences for three-month periods through November, December, and January. NOAA Climate Prediction Center
ENSO-neutral patterns occur when surface temperatures hover around the long-term norm. But neutrality doesn’t mean good—it may just mean the forecast is more complex.
Rather than asking why La Niña was short-lived, it’s better to ask whether it happened at all. Although sea surface temperatures dropped below normal this winter of 2024-25, they didn’t last that long: By mid-April, NOAA forecasters reported that a full-fledged La Niña had not occurred.
But the story may not end there. When the 30-year baseline temperature is revised to account for more recent, warmer years, future analysts may reclassify this winter’s La Niña in the historical record, even if it was not qualified in real time.
La Niña. nplus1
Without El Niño or La Niña to tip the scales, forecasting becomes more difficult. These patterns sharpen the fuzziness of seasonal forecasts, adding important information about how weather might deviate from the usual scenario. Without them, when ENSO is neutral, they are left squinting into the future with little more than historical averages and climate trends.
El Niño tends to suppress hurricanes, while La Niña and neutral conditions allow them to run wild. With a warm Atlantic and ENSO expected to be neutral, this could mean a busy season.
In an April 10, 2025 statement, NOAA officials wrote that El Niño or La Niña conditions are unlikely to occur this summer and that ENSO-neutral conditions are expected to persist through October.
