Environment

Warm ocean water is melting Greenland’s ice from below

Warm ocean waters are slipping underneath parts of Greenland, accelerating the country’s already rapid ice melt.

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Massive strips of ice called “ice tongues,” that are up to 50 miles in length, have extended off of Greenland into surrounding ocean waters. Warm water flows underneath the floating tongues and applies warm pressure, intensifying the ice sheet’s overall melt rate.

Previously, scientists studying the region’s decline had focused on the impact of rising atmospheric temperatures and feedback loops, such as ice turning into darker water that then absorbs more sunlight and causes more ice melt.

The new study helps to explain why Greenland is melting seven times faster than it was in 1972, and twice as fast it was a decade ago.

“The reason for the intensified melting is now clear,” Janin Schaffer, an oceanographer from the Alfred Wegener Institute in Germany who led the team of researchers, said in a press release. “Because the warm water current is larger, substantially more warmth now makes its way under the ice tongue, second for second.”

The warm ocean currents affecting the ice tongues appear to be guided by the shape of the seafloor.

“The readings indicate that here, too, a bathymetric sill near the seafloor accelerates warm water toward the glacier,” Schaffer said in the press release. “Apparently, the intensive melting on the underside of the ice at several sites throughout Greenland is largely produced by the form of the seafloor.”

Greenland is melting faster than any other region on Earth, having lost more than 4,976 gigatons of water — enough to fill 16 trillion bath tubs — since scientists began measuring the region’s decline in 1972. During one particularly hot day in 2019, Greenland lost 11 billion tons of surface ice, which is equivalent to 4.4 million Olympic swimming pools.

Greenland’s rapid decline is also the primary driver of sea level rise around the world. If the area becomes ice-free in the decade ahead, then it could cause global sea levels to rise by an estimated 25 feet.

Sea level rise has a range of consequences, the most obvious being eroding coastlines. Coastal communities are already losing land to the ocean, and 187 million people could be displaced by the phenomenon by 2100.

The new study notes that the ice tongues could be accelerating melting in the Arctic and other ice sheets.

As sea levels rise, extreme storms are packing more rainfall simply because winds have more water to gather up. The jet streams are being disrupted by sea level rise, which could lead to more droughts, heat waves, and extreme cold spells.

Climate change affects marine environments in a number of other ways.

The oceans are absorbing the majority of the excess heat from the sun trapped in the atmosphere by greenhouse gas emissions. These warming temperatures are devastating marine ecosystems, especially coral reefs that are highly sensitive to heat waves.

Much of the carbon dioxide accumulating in the atmosphere is dissolving in the ocean, causing a phenomenon known as “ocean acidification” that’s increasingly deadly to marine animals.

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