I'm sure we've seen this conclusion about the comparative rate of ocean acidification from previous studies, but still:
Some 56 million years ago, a massive pulse of carbon dioxide into the atmosphere sent global temperatures soaring. In the oceans, carbonate sediments dissolved, some
organisms went extinct and others evolved.
Scientists have long suspected that ocean acidification played a part in the crisis—similar to today, as manmade CO2 combines with seawater to change its chemistry. Now, for the first time, scientists have quantified the extent of surface acidification from those ancient days, and the news is not good: the oceans are on track to acidify at least as much as they did then, only at a much faster rate.And the oceans do not fix themselves quickly:
In a study published in the latest issue of Paleoceanography, the scientists estimate that surface ocean acidity increased by about 100 percent in a few thousand years or more, and stayed that way for the next 70,000 years. In this radically changed environment, some creatures died out while others adapted and evolved. The study is the first to use the chemical composition of fossils to reconstruct surface ocean acidity at the Paleocene-Eocene Thermal Maximum (PETM), a period of intense warming on land and throughout the oceans due to high CO2.
"This could be the closest geological analog to modern ocean acidification," said study coauthor Bärbel Hönisch, a paleoceanographer at Columbia University's Lamont-Doherty Earth Observatory. "As massive as it was, it still happened about 10 times more slowly than what we are doing today."
The study confirms that the acidified conditions lasted for 70,000 years or more,
consistent with previous model-based estimates.
"It didn't bounce back right away," said Timothy Bralower, a researcher at Penn State who was not involved in the study. "It took tens of thousands of years to recover."
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