Historical cooling periods are still playing out in the deep Pacific

January 04, 2019

The ocean has a long memory. When the water in today's deep Pacific Ocean last saw sunlight, Charlemagne was the Holy Roman Emperor, the Song Dynasty ruled China and Oxford University had just held its very first class. During that time, between the 9th and 12th centuries, the earth's climate was generally warmer before the cold of the Little Ice Age settled in around the 16th century. Now, ocean surface temperatures are back on the rise but the question is, do the deepest parts of the ocean know that?

Researchers from the Woods Hole Oceanographic Institution and Harvard University have found that the deep Pacific Ocean lags a few centuries behind in terms of temperature and is still adjusting to the advent of the Little Ice Age. Whereas most of the ocean is responding to modern warming, the deep Pacific may be cooling.

The research is published in Science.

"Climate varies across all timescales," said Peter Huybers, Professor of Earth and Planetary Sciences in the Department of Earth and Planetary Sciences and of Environmental Science and Engineering at the Harvard John A. Paulson School of Engineering and Applied Sciences and co-author of the paper. "Some regional warming and cooling patterns, like the Little Ice Age and the Medieval Warm Period, are well known. Our goal was to develop a model of how the interior properties of the ocean respond to changes in surface climate."

What that model showed was surprising.

"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," said Jake Gebbie, a physical oceanographer at Woods Hole Oceanographic Institution and lead author of the study.

More:
https://www.brightsurf.com/news/article/010419473325/historical-cooling-periods-are-still-playing-out-in-the-deep-pacific.html