From heat waves to severe storms and wildfires, the effects of climate change are visible all around us — and new research suggests that the impact of a warming world extends all the way to the bottom of the ocean.
A study published Oct. 29 in the journal Proceedings of the National Academy of Sciences shows that high levels of carbon dioxide — the heat-trapping greenhouse gas that is a key contributor to Earth's warming climate — have made parts of the North Atlantic Ocean and the Southern Ocean so acidic that the chalky white mineral that makes up the seafloor is dissolving.
No one ventured to the seafloor to conduct the study. Instead, researchers led by Olivier Sulpis, a graduate student at McGill University in Montreal, simulated seafloor conditions in a laboratory. The simulations showed that the mineral, a form of calcium carbonate known as calcite, is being replaced by murky brown sediments.
Calcite is made of the skeletons and shells of marine organisms laid down over millions of years, and its loss would represent more than an aesthetic matter. The mineral acts as a chemical buffer, neutralizing the carbonic acid that forms when carbon dioxide seeps from the atmosphere into the ocean. The reaction helps prevent runaway acidification of seawater.
But with cars and factories spewing so much carbon dioxide spewing into the atmosphere, the scientists say, the calcite can't keep up. As a result, the oceans are becoming more acidic.
Ocean acidification is bad news for sea creatures. Roughly 250 million years ago, during the Permian-Triassic Extinction Event, unusually acidic oceans drove more than 90 percent of marine species to extinction. “It seems that we are at the dawn of one of these catastrophic events, and we don’t need to look far to find the cause of it,” Sulpis told NBC News MACH in an email.
Not everyone is particularly worried about the depletion of calcite.
Wallace Broecker, a Columbia University climate scientist who was not involved in the new study, said in an email that it “greatly overplays” the calcite problem. The dissolving of calcite “occurs naturally on a large scale in the deep sea,” he said. “A tiny bit more will have no consequence.”
Sulpis said the slow depletion of calcite matters, in part because it's unlikely to end anytime soon. Even if emissions of carbon dioxide ended today, he said, it would take centuries for the excess CO2 to stop dissolving the seafloor.
Then there's the stark realization that humanity's effect on our environment is disturbingly pervasive. As Sulpis put it, "Even at places on our planet where we have never set foot, or that have never been seen by human eyes, such as the deep sea, there is a trace of human activity."
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