Re: Fremtidens globus er klar!
: 9. jan 2018, 19:35
God artikel her https://motherboard.vice.com/en_us/arti ... extinction
The biggest extinction event in planetary history was driven by the rapid acidification of our oceans, a new study concludes. So much carbon was released into the atmosphere, and the oceans absorbed so much of it so quickly, that marine life simply died off, from the bottom of the food chain up.
The biggest die-off in history, the Permian Extinction event, aka the Great Dying, extinguished over 90 percent of the planet's species—and 96 percent of marine species. A lot of theories have been put forward about why and how, exactly, the vast majority of Earth life went belly up 252 million years ago, but the new study, published in Science, offers some compelling evidence acidification was a key driver.
So does this study mean we should be especially worried about the phenomenon taking hold today?
"Yes," said Dr. Rachel Wood, a professor of carbonate geoscience at the University of Edinburgh and one of the paper's authors.
"We are concerned about modern ocean acidification," she told me in an email. "Although the amount of carbon added to the atmosphere that triggered the mass extinction was probably greater than today's fossil fuel reserves, the rate at which the carbon was released was at a rate similar to modern emissions."
In other words, the Siberian Traps probably spewed out more carbon in total, but we're spewing out just as fast. And that's overwhelming the planetary equilibrium.
"This fast rate of release was a critical factor driving ocean acidification," Wood said.
Why?
"The rate of release is critical because the oceans absorb a lot of the carbon dioxide (CO2) from the atmosphere, around 30 percent of the carbon dioxide released by humans," Wood said. "To achieve chemical equilibrium, some of this CO2 reacts with the water to form carbonic acid. Some of these molecules react with a water molecule to give a bicarbonate ion and a hydronium ion, thus increasing ocean 'acidity' (H+ ion concentration)."
Marine animals whose skeletons are comprised of calcium carbonate—and that's a lot of them (think snails, coral), which form a crucial part of the food chain—dissolved or couldn't form in the first place. And that is what's happening today.
"Between 1751 and 1994, surface ocean pH is estimated to have decreased from approximately 8.25 to 8.14, representing an increase of almost 30 percent in H+ ion concentration in the world's oceans," Wood said.
In 2013, marine scientists released a "State of the Oceans" report that found that the rate of current acidification was "unprecedented." They noted that the seas were acidifying faster than any point in the last 300 million years.