Climate-Regulating Ocean Current Is the Weakest It’s Been in 1,500 Years

In the Atlantic Ocean, the current known as the Atlantic Meridional Overturning Circulation (AMOC) ferries warm surface waters northward — where the heat is released into the atmosphere — and carries cold water south in the deeper ocean layers, according to the National Oceanic and Atmospheric Administration. Its circulation transports heat around the globe like a conveyor belt, and if its movement were to stop, that heat would not get distributed, and weather havoc could ensue.

But the AMOC has been getting weaker, and cold, freshwater infusions by the runaway melting of glaciers, sea ice and permafrost are to blame, and the AMOC may weaken even further if temperatures on Earth continue to rise and ice reserves continue to melt, scientists reported in the two studies.

A research team estimated that, since the current began to lose strength in the mid-1800s, it has weakened by about 15 to 20 percent.

Prior research has suggested that a feeble AMOC brings more dryness to the Sahel, a region of Africa bordering the Sahara Desert; spurs sea-level rise in U.S. coastal cities; and encourages patterns of increasingly cold winters in Europe and the northeastern U.S.

New Ocean Current Discovered Off the Coast of Madagascar

A previously unknown ocean current was recently discovered “by accident” off the coast of Madagascar, a rare find in the 21st century.

In oceanic terms, the Southwest Madagascar Coastal Current is fairly small: At only 62 miles (100 kilometers) long and 330 yards (300 meters) deep, it transports about 264 million gallons (1.3 gigaliters) of warm, salty water a second, or the equivalent of more than 500 Olympic swimming pools’ worth of water.

But the current’s location, rather than its size, makes it vital in understanding the world’s oceans, the researchers said. The Mozambique Channel feeds the Agulhas Current, one of the strongest currents in the world. The Agulhas Current affects the path of tropical storms and carries heat toward higher latitudes. The Agulhas is the equivalent of the Gulf Stream, but for [the] Southern Hemisphere.

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