Hurricane Harvey, the catastrophic tropical cyclone that caused $125bn in damage in South Texas last August, was powered by record-high ocean temperatures in the Gulf of Mexico, according to new research.
Analysis by the US National Center for Atmospheric Research (NCAR) revealed that the hotter-than-average conditions effectively “supercharged” the hurricane by fuelling it with vast stores of moisture.
The strong winds typical of hurricanes stir up the sea’s surface, making it easier for water to evaporate. The warmer the temperature of the upper ocean, the more energy is available to power the evaporation process.
In the case of Hurricane Harvey, NCAR scientists discovered that so much heat was available in the upper ocean that, even as the storm cooled surface temperatures, heat from below welled up and continued to fuel its destruction.
To reach these conclusions, the team compared temperatures in the upper 160m of the Gulf before and after the hurricane using data collected by a network of autonomous floats. They also used data from a NASA satellite to confirm the quantity of rainfall that the storm brought to shore.
The resulting study has proven, for the first time, that the volume of rain over land is directly connected to the amount of water evaporated from an unusually warm ocean. This means that authorities and policymakers must be prepared to deal with mega storms like Harvey as climate change continues to heat the ocean.
"The implication is that the warmer oceans increased the risk of greater hurricane intensity and duration," says lead author Kevin Trenberth, an NCAR senior scientist. "While we often think of hurricanes as atmospheric phenomena, it's clear that the oceans play a critical role and will shape future storms as the climate changes."