Why We Could Trigger Mass Extinction in the Ocean Within Decades — Oceans Deeply

An MIT scientist’s research links past mass die-offs of marine life to the accumulation of carbon in the sea, finding that the current rapid absorption of CO2 could push the ocean to a tipping point by the end of the century.

The last major marine extinction event occurred 252 million years ago, but the next may be just decades away, according to new research on past extinctions which found that the ocean’s rapid absorption of carbon dioxide could trigger another mass die-off of species by the century’s end.

The study, published on Wednesday in the journal Science Advances, reveals a startling pattern that preceded past mass extinction events: major upward fluctuations of carbon in marine sediment – similar to what scientists are seeing today.

“Once a threshold is breached, the carbon cycle, and the Earth system more generally, are at risk of becoming unstable,” said study author Daniel Rothman, a professor of geophysics at the Massachusetts Institute of Technology. “Looking at past data, crossing the threshold is associated with mass extinction.”

Compared to marine carbon accumulation in the past, Rothman found that marine carbon concentrations are increasing at a much more rapid pace today. He arrived at that conclusion after comparing the amounts of carbonate found at various depths of two deep-sea sediment cores, which contain layers of isotopic carbon. This type of carbon contains a chemical signature that allowed Rothman to calculate when it was deposited on the seafloor.

He said there are two types of thresholds that, when exceeded, appear to trigger mass extinction events: rate for slow carbon increases and magnitude for fast increases. To determine those thresholds, Rothman devised an equation that relates both the rate and amount of carbon change to a geological time scale, allowing him to distinguish fast change from slow.

For the modern era, the “threshold for catastrophic change” is related to the amount of carbon…

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