Sat, Dec 08, 2018 - Page 4 News List

Extinction due to warmer oceans: study

SIMULATIONS:A study in the journal ‘Science’ said that massive volcanic activity in the ancient past warmed oceans and starved water of oxygen, killing many species

AP, WASHINGTON

Scientists said they might have discovered the cause of a mass extinction in the distant past and added that climate change might be putting the planet on a vaguely similar path.

Ninety percent of sea life and 70 percent of land life is said to have gone extinct in what scientists call the “Great Dying.”

Scientists have long speculated that massive volcanic outbursts triggered the cataclysmic event — said to have happened about 250 million years ago — but how that worked was still a bit fuzzy. It was not the lava itself.

A study in the journal Science published on Thursday used computer simulations to plot out what might have happened with volcanic activity on such a scale.

Ocean temperatures rose by about 11°C, which then starved the seawater of oxygen, the study said.

That warmer, oxygen-starved water caused a mass marine die-off, especially farther from the equator, the study said.

After the volcanoes blew, the level of heat-trapping carbon dioxide soared to a level more than 12 times what it is today, said lead author Justin Penn, an Earth sciences researcher at the University of Washington.

Water loses oxygen when it warms, much like a warm can of cola goes flat, Penn said.

Scientists looked at dozens of modern species to see what happens to them in warmer, oxygen-starved water to give them ideas about such an extinction event.

One of the keys in the research was that more species died off away from the equator. That is because tropical species were more acclimated to low oxygen levels, Penn said.

While people are not warming the Earth anywhere close to as much as what happened naturally back then, “this puts our future into the category of contenders for true catastrophe,” said study coauthor Curtis Deutsch, an Earth scientist at the University of Washington.

The ancient die-off “shows almost exactly what lies at the end of the road we’re on,” Deutsch said.

“We’re really doing the same thing to Earth’s climate and oceans,” he said.

The study said that if carbon dioxide emissions continue on current levels, by the year 2300, the globe will experience 35 to 50 percent of the extinction level seen in the Great Dying.

University of Leeds paleontologist Paul Wignall said that no current global warming scenario envisions 11°C of warming in the next few centuries.

However, even an event 10 percent as bad as the Great Dying “would be dreadful,” said Wignall, who was not part of the study.

Other outside scientists said the study provided a glimpse into Earth’s possible future.

“Because we are warming up the Earth at a rapid rate, results from this study could prove to very useful in understanding” what happens to life in future oceans, University of Southern California Earth scientist David Bottjer said.

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