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SOURCE: Yale Environment 360

DATE: October 24, 2019

SNIP: From the deck of a Norwegian research ship, the ravages of climate change in the Arctic are readily apparent. In the Fram Strait, the ocean passageway between Norway’s Arctic islands and the east coast of Greenland, seas that should be ice-covered in early September shimmer in the sunlight. Glaciers that muscled across mountains a decade ago are now in rapid retreat, leaving behind walls of glacial till. Rivers of meltwater gush off the Greenland Ice Sheet.

But some of the biggest changes taking place in these polar seas are invisible. Under disappearing ice cover, these waters are rapidly growing more acidic as decades of soaking up humanity’s carbon emissions take their toll on ocean chemistry.

“Warm, fresh, and sour,” says Colin Stedmon, a chemical oceanographer from the Technical University of Denmark, of the changes sweeping Arctic seas, which, along with the Southern Ocean surrounding Antarctica, are acidifying faster than any other marine waters on the planet. He and the rest of the crew of researchers from across Europe are trying to decipher how a warming Arctic is, as Stedmon puts it, “melting ice, freshening seawater, and reducing its ability to resist acidification.”

The Arctic is a bellwether for acidification, oceanographers say. Since the Industrial Age, the planet’s oceans have stored up to 30 percent of human CO2 output, with cold polar waters, in which the gas is the most soluble, absorbing the lion’s share. Those same cold waters and unique environmental conditions make the Arctic especially susceptible to the rapidly shifting ocean chemistry wrought by that excess carbon. The result: rising acidity, which eats up the minerals vital to shell-building creatures, as well as posing other dangers to Arctic marine life.

Acidification is underway throughout the world’s oceans, according to a new Oceans and Cryosphere report by the Intergovernmental Panel on Climate Change. But the various ocean regions will respond differently to the same amount of carbon dioxide, says Alessandro Tagliabue, a University of Liverpool biogeochemist and one of the lead authors on the ocean changes chapter of the report. As our carbon emissions continue to soar, acidic conditions will race across the high latitudes first, according to the report. And Arctic ecosystems and people — already stressed by rising temperatures, vanishing ice, and the myriad other effects of climate change — are particularly threatened by acidification’s impacts.

“The polar regions are especially vulnerable because of a systemic vulnerability that is linked to their chemical states today, which makes them very, very close to tipping over the edge into extremes of acidification,” says Tagliabue.

Models predict that large parts of the Arctic will cross this threshold as early as 2030, and researchers forecast that most Arctic waters will lack adequate aragonite for shell-building organisms by the 2080s. As the corrosive water spreads, it will spill into neighboring regions such as the North Atlantic, where it could impact the ocean food web and threaten important fisheries. Already, high levels of acidification in the cold waters of the North Pacific have caused some oyster die-offs in the U.S. Pacific Northwest.

Widespread ocean acidification poses a severe threat to the planet. Global acidification of the oceans 252 million years ago, caused by massive volcanic eruptions, is believed to have obliterated marine life in Earth’s largest mass extinction. And a new study suggests that the asteroid impact that wiped out dinosaurs 66 million years ago also set off widespread acidification that devastated marine ecosystems for millennia.