North Atlantic cold blob signals weakening ocean current nearing tipping point

A stubborn cold patch in the subpolar North Atlantic, just south of Greenland and Iceland, is cooling even as most of the planet heats up. Scientists say that anomaly, known as the Atlantic “cold blob,” points to a weakening of the Atlantic Meridional Overturning Circulation, a current system that helps move heat, salt and carbon through the ocean.

That matters far beyond oceanography. A weaker AMOC has been linked to changes in Europe’s climate, Atlantic hurricane behavior, monsoons, marine ecosystems and rising sea level along the U.S. East Coast, including New England. The concern is not that collapse is imminent on a set date, but that the circulation may be moving toward a tipping point that could lock in long-term disruptions to weather and coastlines.

Newer analyses are sharpening that warning. NOAA’s Atlantic Oceanographic and Meteorological Laboratory said a recent study found extensive weakening in the 2000s, but also that the decline has paused since the early 2010s as natural variability and human-driven forcing have pulled in opposite directions. NOAA also says state-of-the-art climate models suggest anthropogenic weakening may have been underway since the mid-1980s.

The observing record is still short by climate standards, but it points in the same direction. The RAPID 26.5°N array has measured the Atlantic overturning circulation since April 2004, and it showed a major downturn in 2010-11. OSNAP has continuously tracked the subpolar North Atlantic since 2014, adding a second long-running line of evidence in the region where the cold blob is most visible.

The Intergovernmental Panel on Climate Change said observations from 2004 to 2017 and sea-surface temperature reconstructions indicate the AMOC has weakened relative to 1850-1900, with medium confidence. A 2023 study also found that a more positive North Atlantic Oscillation over the past century may have helped drive the cold blob, a reminder that the anomaly is not explained by ocean circulation alone.

Still, the broad pattern has alarmed researchers because independent work is converging on the same answer. A 2025 University of California, Riverside study said only models with a weakened AMOC matched the observed temperature and salinity pattern in the South Greenland anomaly. Another 2025 analysis projected the circulation could weaken by about 18% to 43% by 2100, a drop that would not mean total collapse but could still redraw rainfall, storm tracks, fisheries and the risk of coastal flooding. JPI Climate and JPI Oceans have launched a 2025-2027 AMOC Joint Initiative to focus the next round of assessment on Europe and North America, where the stakes are highest.