While the world’s oceans have generally been heating up, one patch of the Atlantic located south of Greenland has been dropping in temperature. Dubbed the “cold blob,” the region’s cooling is likely tied to the growing unsteadiness of one ocean current system due to climate change. The collapse of the system could lead to disruptions in global weather patterns.
Current problems
The Atlantic cold blob has cooled by nearly one degree Celsius (1.8 degrees Fahrenheit) since 1900. The region is also the “only part of the world” that has “cooled significantly since the 19th century, both in the atmosphere and ocean,” said a study published in the journal Geophysical Research Letters. Scientists believe that the climate anomaly is happening because of shifts in a network of ocean currents called the Atlantic Meridional Overturning Circulation (AMOC).
Researchers analyzed decades of North Atlantic temperature and heat flux data going back as far as 1870. They found that the cold blob had “shown a marked decrease in the amount of heat escaping to the atmosphere over the last half-century, especially since 1993” and that the “largest drop in heat content has been in the top 1,000 meters — coinciding with the AMOC’s location,” said Science News. The decrease in heat content indicates that the heat supply provided by the AMOC has been declining over the past few decades.
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The AMOC “works like a vast ocean conveyor belt, pulling warm water from the tropics to the Northern Hemisphere, where it cools, sinks and flows back south,” said CNN. Over time, the system has been “weakening as human-driven global warming melts ice and causes a surge of freshwater into the ocean, disrupting the AMOC’s delicate balance of heat and salinity.” Eventually, the current system may “become so weak” that it can “no longer distribute heat around the world,” said USA Today. The collapse of the AMOC has been deemed a climate tipping point after which there will be irreversible ecological damage.
Future problems
The cold blob and resulting disruption of the AMOC have been taking a toll on various regions of the planet. The Indian summer monsoon rainfall pattern has “shifted dramatically since 1999,” said a study published in the journal AGU Advances. “Northwest India receives 24.6% more rain during the monsoon season, while the Indo-Gangetic Plain has decreased by 4.4%, experiencing drought conditions.” Upon investigation, researchers found that the cold blob had “shifted the Indian monsoon by creating a strong temperature gradient over the North Atlantic,” which affected “jet stream winds and pressure systems in the atmosphere above Eurasia,” said Live Science, a sister site of The Week.
Similar effects are likely to occur around the world. While scientists do not know when the AMOC tipping point will be reached, it could “trigger dramatically cold winters in northern Europe” when it does, said Euronews. An AMOC collapse would also cause sea levels on the east coast of the U.S. to “rise rapidly since the current normally drives water away from the land,” and “storms in the Atlantic would increase in intensity.”
