Heightened Temperatures Robbed Our Seas of Oxygen, and Could do it Again

A recent study of the ancient seafloor has revealed some surprising and worrying facts about our oceans' past. Tens-of-thousands of years ago, our oceans suffered from severe oxygen loss just as massive ice sheets started to melt. Now, with sea ice and glaciers fast retreating in the wake of climate change, experts are worried about another instance of mass deoxygenation.

The study, recently published in the journal PLOS One, details how researchers analyzed marine sediment cores from different regions around the world to assess the extent to which low oxygen zones in the ocean have expanded in the past. Core samples were taken from the subarctic Pacific all the way to the Chilean margins.

Evidence was found of widespread hypoxia (oxygen deprivation) stretching nearly 3,000 meters (9,842 feet) deep. In some oceanic regions, such loss took place over a time period of 100 years or less.

The great swath of these events appears to have occurred roughly 10,000-17,000 years ago - the same exact time as the "deglaciation period" when the globe began to naturally warm, resulting in the melting of massive ice sheets

"This is a global story that knits these regions together and shows that when you warm the planet rapidly, whole ocean basins can lose oxygen very abruptly and very extensively," lead author Sarah Moffitt, from the University of California Davis Bodega Marine Laboratory, said in a statement.

"Our modern ocean is moving into a state that has no precedent in human history," she added. "The potential for our oceans to look very, very different in 100-150 years is real. How do you use the best available science to care for these critical resources in the future? Resource managers and conservationists can use science like this to guide a thoughtful, precautionary approach to environmental management."

Interestingly, this isn't the first study to tie a warming world to deoxygenation. Back in December, researchers found a strong connection between an oxygen deprived Baltic Sea and warming temperatures as well.

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