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El Niño’s discharged heat fuels intense hurricanes. Historical tracks in black. (credit: Jin/SOEST)

El Niño, the abnormal warming of sea surface temperatures in the Pacific Ocean, is a well-studied tropical climate phenomenon that occurs every few years. Scientists have observed that El Niño greatly influences the yearly variations of tropical cyclones (a general term that includes hurricanes, typhoons and cyclones) in the Pacific and Atlantic Oceans.

However, there is a mismatch in both timing and location between this climate disturbance and the Northern Hemisphere hurricane season—El Niño peaks in winter and its surface ocean warming occurs mostly along the equator, i.e., a season and region without tropical cyclone activity. This prompted scientists to investigate El Niño’s influence on hurricanes via its remote ability to alter atmospheric conditions.

Fei-Fei Jin and Julien Boucharel at the University of Hawaiʻi at Mānoa’s School of Ocean and Earth Science and Technology (SOEST), and I-I Lin at the National Taiwan University recently published a paper in Nature“Eastern Pacific tropical cyclones intensified by El Niño delivery of subsurface ocean heat”—that uncovers what’s behind this “remote control.”

The researchers uncovered an oceanic pathway that brings El Niño’s heat into the Northeastern Pacific basin two or three seasons after its winter peak—right in time to directly fuel intense hurricanes in that region.

Warm, deep water also fuels hurricanes

Prior to Jin’s and colleagues’s recent work, researchers had largely ignored the huge accumulation of heat occurring underneath the ocean surface during every El Niño event as a potential culprit for fueling hurricane activity.

“We did not connect the discharged heat of El Niño to the fueling of hurricanes until recently, when we noticed another line of active research in the tropical cyclone community that clearly demonstrated that a strong hurricane is able to get its energy not only from the warm surface water, but also by causing warm, deep water—up to 100 meters deep—to upwell to the surface,” said Jin.

“The Northeastern Pacific is a region normally without abundant subsurface heat,” said Boucharel, a post-doctoral researcher at SOEST. “El Niño’s heat discharged into this region provides conditions to generate abnormal amount of intense hurricanes that may threaten Mexico, the southwest of the U.S. and the Hawaiian islands.”

Read the SOEST news release for more information.

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