Mysterious North Atlantic Cold Patch Signals Weakening Ocean Current System

A new climate study says a large area of the northern Atlantic Ocean is cooling even as most of the world’s oceans warm, and that the anomaly is strong evidence that the Atlantic Meridional Overturning Circulation, or AMOC, is weakening sharply. The report, published Saturday by CNN, says the system is now at its weakest point in about 1,000 years.

Researchers used computer models and satellite data to examine the so-called cold blob, a patch of unusually cold water in the North Atlantic. They concluded the cooling is not mainly caused by temporary winds or cloud cover at the surface, but by changes deep in the ocean, where atmospheric effects have little influence. The study links the phenomenon to climate change-driven melting in Greenland, which is sending large amounts of fresh water into the Atlantic. Because fresh water is less dense and less salty, it disrupts the sinking of water that helps power the AMOC and slows the current.

Professor Stefan Rahmstorf of the University of Potsdam, a co-author, said, “All signs point to the direct effect of the AMOC. The system changes the way heat is transported in the ocean, and that is what drives the dramatic cooling of the cold blob.” Scientists warn that a collapse or shutdown of the AMOC would not be a local problem, but a global catastrophe affecting geography and economies.

The reported risks include faster sea-level rise along the U.S. East Coast, severe cooling and harsher winters in Europe that could disrupt agriculture and infrastructure, and major shifts in African monsoons that could bring prolonged drought and widespread famine. Other experts urged caution, however. Rene van Westen of Utrecht University said earlier studies showed cold blobs can be produced by atmospheric conditions alone, though the new work is strengthened by consistent results across multiple datasets. David Thornalley of University College London said sparse real-time measurements from the deep ocean mean existing data should be treated as estimates, not perfect representations. Jonathan Baker of the UK Met Office told CNN the study adds important evidence for AMOC’s role, but is not the final word.