PNAS - Study Provides New Detail About Methane Hydrate Release During Eemian (125K YA)
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Still, the new findings, published in the Proceedings of the National Academy of Sciences, underscore how little we still know about how the planet will respond to our uncontrolled greenhouse gas emissions — and how unpredictable that response may be.
The new sample of sediment unearthed from the seafloor paints a picture of tumultuous events during a period of Earth’s history around 125,000 years ago, called the Eemian. The era has often stirred scientists’ fears about the future, for while the Earth was not much warmer than it is today, seas were 20 feet or more higher. Some suspect the West Antarctic ice sheet may have collapsed at that time — and a few have even postulated superstorms powerful enough to lift boulders atop cliffs in the Bahamas.
The new research suggests another Eemian climate cascade. It would have begun with large pulses of meltwater from the Greenland ice sheet, which slowed down the circulation of the North Atlantic Ocean — a change that would have reverberated around the globe. As the ocean’s so-called conveyor belt slowed and less cold water made its way into its middle depths, the paper’s authors contend, the continental shelf of the Gulf of Guinea along the coast of Africa was bathed in sudden, strong warmth. This, in turn, destabilized methane that had previously been suspended beneath the seafloor.
The warming of the middle layer of the ocean during the era was “much stronger than previous model studies have assumed,” said Syee Weldeab, a paleoclimatologist at the University of California at Santa Barbara, who led the research along with colleagues at institutions in Germany, China and Australia. “And then, the release of methane is strong and persistent over a longer time, to make it basically noticeable through the sediment, through the water column, and potentially, to the atmosphere,” Weldeab added.
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https://www.washingtonpost.com/climate-environment/2022/08/24/methane-hydrates-ocean-global-warming/