Climate researchers discover El Nino's fueling effect on intense hurricanes

A press release from the University of Hawaii-Manoa: 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. It has major impacts on society and Earth’s climate – inducing intense droughts and floods in multiple regions of the globe. Further, 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 (TC) activity. This prompted scientists to investigate El Niño’s influence on hurricanes via its remote ability to alter atmospheric conditions such as stability and vertical wind shear rather than the local oceanic environment.

Fei-Fei Jin and Julien Boucharel at the UH Mānoa School of Ocean and Earth Science and Technology (SOEST), and I-I Lin at the National Taiwan University published a paper today in Nature that uncovers what’s behind this “remote control.” Jin and colleagues 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.

El Niño develops as the equatorial Pacific Ocean builds up a huge amount of heat underneath the surface and it turns into La Niña when this heat is discharged out of the equatorial region.  “This recharge/discharge of heat makes El Niño/La Niña evolve somewhat like a swing,” said Jin, lead author of the study.

Prior to Jin's and colleagues’ 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....

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