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Related: About this forumOceans' acidic shift may be fastest in 300 million years
Oceans' acidic shift may be fastest in 300 million years
By Deborah Zabarenko | Reuters 14 mins ago
WASHINGTON (Reuters) - The world's oceans are turning acidic at what could be the fastest pace of any time in the past 300 million years, even more rapidly than during a monster emission of planet-warming carbon 56 million years ago, scientists said on Thursday.
Looking back at this bygone warm period in Earth's history could offer help in forecasting the impact of human-spurred climate change, researchers said.
Quickly acidifying seawater eats away at coral reefs, which provide habitat for other animals and plants, and makes it harder for mussels and oysters to form protective shells. It can also interfere with small organisms that feed commercial fish like salmon.
The phenomenon has been a top concern of Jane Lubchenco, the head of the U.S. National Oceanic and Atmospheric Administration, who has conducted demonstrations about acidification during hearings in the U.S. Congress.
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(19,938 posts)[font size=4]Few Parallels in 300-Million Year Geologic Record[/font]
[font size=3]The worlds oceans may be turning acidic faster today from human carbon emissions than they did during four major extinctions in the last 300 million years, when natural pulses of carbon sent global temperatures soaring, says a new study in Science. The study is the first of its kind to survey the geologic record for evidence of ocean acidification over this vast time period.
What were doing today really stands out, said lead author Bärbel Hönisch, a paleoceanographer at Columbia Universitys Lamont-Doherty Earth Observatory. We know that life during past ocean acidification events was not wiped outnew species evolved to replace those that died off. But if industrial carbon emissions continue at the current pace, we may lose organisms we care aboutcoral reefs, oysters, salmon.
The oceans act like a sponge to draw down excess carbon dioxide from the air; the gas reacts with seawater to form carbonic acid, which over time is neutralized by fossil carbonate shells on the seafloor. But if CO2 goes into the oceans too quickly, it can deplete the carbonate ions that corals, mollusks and some plankton need for reef and shell-building.
That is what is happening now. In a review of hundreds of paleoceanographic studies, a team of researchers from five countries found evidence for only one period in the last 300 million years when the oceans changed even remotely as fast as today: the Paleocene-Eocene Thermal Maximum, or PETM, some 56 million years ago. In the early 1990s, scientists extracting sediments from the seafloor off Antarctica found a layer of mud from this period wedged between thick deposits of white plankton fossils. In a span of about 5,000 years, they estimated, a mysterious surge of carbon doubled atmospheric concentrations, pushed average global temperatures up by about 6 degrees C, and dramatically changed the ecological landscape.
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