Tropical Cyclones Warm Ocean, May Cause Positive Feedback Cycle

Sea surface height evidence for long-term warming effects of tropical cyclones on the ocean

Authors:

1. Wei Mei (a)
2. François Primeau (a)
3. James C. McWilliams (b)
4. Claudia Pasquero (c)

Affiliations:

a. Department of Earth System Science, University of California, Irvine, CA 92697;

b. Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095; and

c. Department of Earth and Environmental Sciences, University of Milan-Bicocca, I-20126 Milan, Italy

Abstract:

Tropical cyclones have been hypothesized to influence climate by pumping heat into the ocean, but a direct measure of this warming effect is still lacking. We quantified cyclone-induced ocean warming by directly monitoring the thermal expansion of water in the wake of cyclones, using satellite-based sea surface height data that provide a unique way of tracking the changes in ocean heat content on seasonal and longer timescales. We find that the long-term effect of cyclones is to warm the ocean at a rate of 0.32 ± 0.15 PW between 1993 and 2009, i.e., ∼23 times more efficiently per unit area than the background equatorial warming, making cyclones potentially important modulators of the climate by affecting heat transport in the ocean–atmosphere system. Furthermore, our analysis reveals that the rate of warming increases with cyclone intensity. This, together with a predicted shift in the distribution of cyclones toward higher intensities as climate warms, suggests the ocean will get even warmer, possibly leading to a positive feedback.