Marine Heat Wave Returns to the Northeast Pacific

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#Mers & Oceans , #Changements climatiques , #Météo

Publié le 16 septembre 2019

From 2014-2016, a marine heat wave spread across the northeastern Pacific Ocean—an ocean weather event that researchers coined “the blob.” In the summer of 2019, an expanse of warm surface water returned to the region.

The unusual conditions are visible in the maps above and below, which shows sea surface temperature anomalies across the northeastern Pacific in August 2019. Red colors depict areas that were hotter than average for the same month from 1985-2012; blues were colder than average. Data for the map were compiled by Coral Reef Watch, blending observations from the Suomi NPP, MTSAT, Meteosat, POES, Terra, Aqua, and GOES satellites with computer models.

According to Nicholas Bond, Washington’s state climatologist and a research meteorologist at the University of Washington, the warm surface water in August 2019 was caused by an unusual and persistent weather pattern. An atmospheric ridge of high pressure set up off the coast of North America, extending from the Bering Sea to the Pacific Northwest. High pressure systems bring gentle winds—not nearly strong enough to stir the ocean and cause the rise of deeper cold water. There may have been less cloud cover than normal, as well as anomalous poleward currents in the upper ocean that bring warm water north.

The result was a marine heat wave rivaling the magnitude and extent of the 2014-2016 event. Still, Bond noted: “It remains to be seen if it will approach that of 2014-16 in terms of how long it lasts, how deep it reaches, and its impacts.”

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