In May, a team of researchers announced that hurricanes play an underappreciated role in how heat is regulated in the oceans. Their study adds to the existing model of heat dispersion in which water cools as the Gulf Stream moves toward the North Atlantic, becoming denser and eventually sinking below the surface. This creates a deep underwater current of cold water that flows south, finally surfacing in the Indian, Pacific, and Southern Oceans.
However, in their wake, hurricanes set up large-amplitude waves that mingle warm surface water with colder deep water, says climate scientist Matthew Huber of Purdue University. His research shows that such mixing could account for up to 15 percent of the heat transport in the oceans.
Hurricanes have such a big impact because they occur in the tropics, where the temperature difference between the surface water and the underwater current is greatest. “You essentially want to take the coldest water and mix it with the warmest water,” Huber says.
Because a hurricane cools surface water, it discourages the formation of later storms in its wake, providing a form of negative feedback that limits the hurricane merging effect. Although that seems to be good news for now, hurricanes may end up warming, not cooling, oceans. Huber says we may reach a point, with rising water temperatures from global warming and mingling, where “we will have gotten rid of [the] cold water to mix up.” At that point the blending might produce warmer temperatures—and even stronger storms.