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There is no way to ignore global warming unless you live on another planet, but how can a mysterious cold blob form in an ocean that is slowly heating up?
This phenomenon seems ironic in a planet humans have sabotaged. While anthropogenic climate change has raised ocean temperatures by 2 degrees Fahrenheit in the last 120 years, there is a blob (also called a warming hole) just south of Greenland whose surface temps have cooled by 1.6 degrees in that stretch of time. The cold water also acts as a built in AC for the air right above it. Now a team of scientists have been able to simulate the past in what are called digital “hindcasts” that let them go back in time to see the long-term influence of global warming on the blob.
“Its emergence has been linked to…reduced ocean heat transport into the warming hole region,” said Paul Keil, who led a study recently published in Nature Climate Change, adding that “increased ocean heat transport out of the region into higher latitudes and a shortwave cloud feedback dominate the formation and temporal evolution of the warming hole under greenhouse gas forcing.”
Just to give you an idea of how much heat Earth’s oceans have taken just in the past 10 years, it’s as if the most powerful nuclear weapon ever created was set off every ten minutes — for the entire decade.
So what lets the blob keep its cool? Change in the Atlantic Meridionic Overturning Circulation (AMOC), a major ocean current, has had an impact. AMOC sends warm saltwater gushing north in the shallower layers of the Atlantic, and cold water southward in its deeper reaches. Meaning, it circulates tropical heat north, where it is then released into the atmosphere.
There can be disastrous consequences if this circulation is disrupted — think monsoons and hurricanes. Glaciers melting way too fast on the Greenland ice sheet are now sending freshwater into the North Atlantic and AMOC.
Because freshwater was definitely not meant to flow into AMOC, it dilutes the oceanic saltwater, whose density goes down. This screws up the entire current. Less cold water sinks down, and that cold water sticking around holds back the warmer waters on their way up. That explains the lower surface temperatures of the blob — incoming heat is being held back. AMOC is expected to keep slowing down as glacier melt continues. That isn’t even as bad as it gets. The subpolar gyre is a loop of water flowing counterclockwise around the North Atlantic, is supposed to transport heat south, but now it’s taking warmer water even further north (as if the Arctic Ocean didn’t have enough issues with disappearing glaciers already). That water is just more heat being taken away from the blob.
The blob’s lack of heat also leads to the formation of thick, low clouds that reflect sunlight and keep it even cooler. More clouds keep forming and bouncing back more heat as it keeps cooling, and on and on it goes.
“Both the overturning and the gyre circulation contribute to the increased high-latitude ocean heat transport, and therefore are critical to understand the past and future evolutions of the warming hole,” Keil said. Hindcasts will also give insight into how Earth compares to other planets which have gone unaffected by phenomena like global warming.
Humans need to watch out before the North Pole turns into a hot tub, because this is definitely not cool.