Is the Atlantic's Most Important Ocean Current on the Verge of Collapse?

While ocean temperatures around the world continue to climb, a large patch of water south of Greenland and Iceland has been quietly doing the opposite. It's been cooling. Researchers have called it the "cold blob" or "warming hole" and for years scientists have debated what's causing it.

A new study says it has the answer — and it's not good news.

The cold blob has cooled by nearly 1 degree Celsius since 1900. New research concludes that this isn't just a surface phenomenon driven by wind patterns and cloud cover. The cooling is happening deep in the ocean too — far below where atmospheric conditions have much influence. That points to one explanation: the weakening of the Atlantic Meridional Overturning Circulation, or AMOC.

"It is changing ocean heat transport," said Stefan Rahmstorf, a study author and physics and oceans professor at Potsdam University in Germany. "That is what is driving the cooling of the cold blob."

What AMOC Is and Why It Matters