Ancient Waters In The Pacific Are Getting Colder, Not Warmer Thanks To The Ocean's 'Long Memory'

Tuesday, 08 January 2019 - 12:42PM
Earth
Tuesday, 08 January 2019 - 12:42PM
Ancient Waters In The Pacific Are Getting Colder, Not Warmer Thanks To The Ocean's 'Long Memory'
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The verdict has been in for quite some time that global warming is real. While data shows that ocean surface temperatures are rising, scientists have discovered waters near the bottom of the Pacific that are centuries behind the trend – in fact, they're actually getting colder thanks to the ocean's "long memory."

In an article recently published in Science, researchers from Harvard University and the Woods Hole Oceanographic Institution (WHOI) discuss using ocean circulation models as well as observations from the 19th and 20th centuries to detect a 700-year-old cooling pattern deep in the Pacific Ocean. It is an understatement to say that there is a lot of water in the Pacific Ocean. The scientists predicted that, because of the water's circulation rate, surface water from long ago would now be many miles away from the sun and would not have experienced more recent warming trends. "If the surface ocean was generally cooling for the better part of the last millennium, those parts of the ocean most isolated from modern warming may still be cooling," WHOI physical oceanographer and lead author Jake Gebbie said in a statement.

By comparing data from a late 19th century HMS Challenger expedition with modern data collected in the 1990s by the World Ocean Circulation Experiment, Gebbie and his colleagues found that while waters in many parts of the world are in fact heating up, there is a patch of the Pacific around 2km (1.2 miles) deep that is moving the thermometer in the opposite direction. "These waters are so old and haven't been near the surface in so long, they still 'remember' what was going on hundreds of years ago when Europe experienced some of its coldest winters in history," said Gebbie.

The findings may change what researchers believe about what the ocean's temperatures were like before global warming because it suggests that the surface climate was already varied and that there was not a state of "equilibrium" before us humans threw everything off with our factories and pollution. "Part of the heat needed to bring the ocean into equilibrium with an atmosphere having more greenhouse gases was apparently already present in the deep Pacific," said co-author Peter Huybers. "These findings increase the impetus for understanding the causes of the Medieval Warm Period and Little Ice Age as a way for better understanding modern warming trends."
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