Wind, Water and Warming

Ignoring the interaction between wind and ocean currents can have consequences if you’re trying to predict global warming.

Specifically, it can cause climate models to underestimate warming by as much as 17%.

“The ocean plays a huge role in global warming – its currents can redistribute heat from warmer to colder regions, for instance, by moving warm water from the equator to the poles,” says Kay McMonigal, a postdoctoral research scholar at NC State and corresponding author of a recent study on wind, currents and warming which was highlighted by Science.

McMonigal’s study focused on shallow ocean currents, which stretch from the ocean surface to 1,000 to 2,000 meters below the surface. Unlike other ocean currents, these shallower currents are susceptible to the effect of wind.

“The currents change as the winds change, and move heat into different places,” McMonigal says. “Climate models haven’t traditionally been looking at this interaction as a potential contributor to warming, so I wanted to find out if changing shallow currents can impact warming.”

McMonigal and the research team utilized standard international climate models and climate data from 1850 – 2014 to run the experiment. They created two models. In one version, shallow ocean currents were allowed to change with the changing climate; in the other, the shallow ocean currents ran in a repeating, seasonal pattern.

The researchers saw that the model where shallow ocean currents shifted with the changing climate warmed 17% more than the model where winds and currents did not change.

Why do shallow ocean currents have this significant impact on warming?

“When the ocean moves heat around, the warmer ocean surface can, in turn, cause the air over that part of the ocean to get warmer,” McMonigal says. “Depending on the location, this extra warming can have different effects; for example, in places considered ‘sensitive’ like the tropical Pacific, warmer oceans reduce cloud cover. Clouds burn off, more sunlight enters the system, and warming is amplified.

“In the interest of more accurate climate models, our study shows that we need to take shallow currents and the winds that drive them into consideration.”