Earth’s oceans are heating up. But since the 19th century, one patch in the North Atlantic has cooled by about 1 degree Celsius (1.8 degrees Fahrenheit). Scientists now think they know why. The “cold blob” is the result of a heat-carrying current moving more slowly across the Atlantic.
The cooling spot is just south of Greenland. Experts have thought that the patch was getting colder because less heat was coming into that area through ocean currents. Specifically, less heat was carried by the Atlantic Meridional Overturning Circulation, or AMOC. This massive current brings heat from the tropics northward toward Europe. It shapes temperature and precipitation in Europe, North Africa and beyond.
But a weaker AMOC wasn’t the only possible explanation for the cold spot. Another option was that the area might be losing lots of heat to the atmosphere. That heat escaping the ocean’s surface would leave colder waters behind.
To sort out what was happening, researchers looked a...
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