An unusual ‘cold blob’ in the Atlantic is a warning sign for our future weather, researchers say
Recent studies are showing the weakening of a key Atlantic Ocean current system that helps regulate the planet’s climate.Recent studies are showing the weakening of a key Atlantic Ocean current system that helps regulate the planet’s climate.Bob Edme/Associated PressWhen
most of us think about climate change, we picture rising temperatures
and sea levels, stronger storms, and melting glaciers. But deep beneath
the surface of the Atlantic Ocean, another major climate story is
unfolding — one that scientists say could have far-reaching consequences
for weather patterns around the globe, including right here in New
England.
The
concern focuses on the Atlantic Meridional Overturning Circulation,
better known as the AMOC, a vast system of ocean currents. Think of it
as a massive ocean conveyor belt that transports warm, salty tropical
water toward the North Atlantic. The water cools when it reaches the
northern latitudes, becomes dense and sinks, eventually flowing back
south at deeper depths. This process helps regulate climate on both
sides of the Atlantic and plays a critical role in distributing heat
around the planet.The AMOC is a system of ocean currents that overturns (cools and sinks) when reaching the ocean near Iceland and Greenland.NOAA
Scientists have known for years that the AMOC is weakening; this isn’t new. But new research suggests an earlier and more dramatic deceleration or slowdown of the system than many climate models had previously projected.
The
authors of the study call it a “very concerning result,” noting that
they feel more confident than ever that we may reach the tipping point
for a shuttering AMOC maybe by the middle of the century, and a collapse
or shutdown by 2100.
“The
AMOC shutdown is not a low-probability event anymore,” said Stefan
Rahmstorf, a physical oceanographer at the Potsdam Institute for Climate
Impact Research in Germany, who led the research team.
During his
30-year career studying these critical ocean influences, Rahmstorf said
he had always considered the “AMOC tipping risk” to be fairly low. And
now? “It starts to look likely, maybe even very likely,” he said. By
combining real-world ocean observations with climate simulations,
researchers have found that the models showing the greatest decline are
more accurate and significant.
“And
even though a shutdown isn’t reached fully until after 2100 (according
to the latest research), the impacts are already going to be felt pretty
soon in the next few decades unless the (carbon) emissions are reduced
very fast,” Rahmstorf noted. Models show a ”cooling starting in the late
2030s, 2040s," he said, “and that actually is a big concern.”
Another study published in April supports these findings, indicating a sharp AMOC decline (roughly 50 percent) by the end of the century.
One
clue that the AMOC is already weakening can be found in a curious patch
of ocean just south of Greenland and Iceland. While much of the world’s
oceans have been warming, this region has actually cooled over the last
century. Scientists often refer to this unusual swath of ocean as the
Atlantic “cold blob” or “warming hole.”=1440 240w" id="img-GBOEOOHWEFHQZKF5AMJH45QMZM-image" src="https://bostonglobe-prod.cdn.arcpublishing.com/resizer/v2/GBOEOOHWEFHQZKF5AMJH45QMZM.png?auth=13669870148c12faf6e726519f3e0a2b0c57a104fef47ae911ab26b22b24301d&width=1440" />The "cold blob" is seen over the Northern Atlantic Ocean early in 2026.S. Rahmstorf
This
latest research suggests that this cooling is not simply the result of
sea surface heat loss or changing winds or cloud patterns, but a
declining or weakening AMOC. Climate change is the main driver, as
warming seas, melting ice, and increased rainfall have disrupted the
temperature and salt balance of the North Atlantic.
Other
researchers have also explored the cold blob’s connection to the
sweltering heat wave overtaking Europe, finding that it could alter
atmospheric circulation and create conditions for heat domes. “That cold
isn’t a kind of a get-out-of-jail-free card in terms of global warming.
Some of the hot extremes can actually be exacerbated by this cold blob
in the Atlantic,” Gerard McCarthy, an oceanographer at Ireland’s
Maynooth University, told AFP.
But what does all this mean for the Northeast US?
First,
it’s important to note that a weakening AMOC is not the same thing as a
complete collapse. However, a continued slowdown could have major
consequences.
Along
the East Coast, a weaker AMOC will contribute to already rising sea
levels. That is especially important for Boston and other coastal
communities in New England, where even modest increases in sea level can
worsen tidal flooding, coastal erosion, and storm surge impacts. In
places like Boston and along the Maine coast, higher water levels can
turn routine high tides into more frequent flooding.
There
is another possible effect that may seem counterintuitive — cooler
conditions. Because the AMOC helps transport warm water northward, a
weaker current could mean less ocean heat reaching the North Atlantic.
That could influence sea surface temperatures and, over time, help keep
parts of New England cooler than they otherwise would be in a warming
world. It would not cancel out climate change, but it could alter
regional patterns in ways that affect marine ecosystems, fisheries, and
even seasonal weather.
The
AMOC remains one of the most important — and closely watched —
components of Earth’s climate system. This latest research serves as
another reminder that changes happening far out in the ocean can
eventually ripple across the globe, reaching all the way to New
England’s shores.
“The
strong evidence for a weakening AMOC is a serious concern for society
and policy,” Rahmstorf said, “...that requires urgent attention.”
Ken Mahan can be reached at ken.mahan@globe.com. Follow him on Instagram @kenmahantheweatherman.
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