Hurricane Dean is gone. It left behind a trail of damage across the Caribbean and Mexico -- for a thorough rundown see here -- including several billion dollars in damage to Jamaica and 11 killed in Haiti. Amazingly, no deaths are reported from the Yucatan (though 10 are reported after the storm made its second landfall near Veracruz). We have to give Mexico a tremendous round of applause for its amazing preparedness.
Fascinatingly, though, Dean left behind a different kind of wake as well: A cold wake at the surface of the ocean that it passed over. See here for before-and-after images comparing Caribbean sea surface temperatures on August 17 versus August 22; or see below for a still more pronounced wake on August 23, one that extends all the way into the Bay of Campeche and Gulf of Mexico.
What's going on here? Essentially, powerful hurricanes drive warm ocean surface water downward and mix cooler deep water upwards. So when a storm like Dean goes by, you tend to see a cold anomaly at the surface of the ocean to the right of the storm track. [Why the right, you ask? It's because the right front quadrant of a northern hemisphere hurricane is its most powerful area -- that's where winds have the added speed of the storm's forward motion behind them.]
In the case of Dean, the wake may even have been less pronounced than otherwise due to the lack of open ocean in the Caribbean. For a truly dramatic wake, look at what Supertyphoon Sepat did last week -- and please note that these images come from a truly wonderful resource, Remote Sensing Systems:
The, er, cool thing about hurricane wakes is that some scientists think that they're critical to the redistribution of ocean heat in the direction of the planet's poles. We can see the cold wake at the surface; but there's also a warm anomaly below the surface. In order to restore equilibrium, then, the oceans presumably have to redistribute that additional sub-surface heat pole-ward in the direction of regions where waters are cooler.
What's more, that added heat, transported through the oceans, may be enough to have a significant effect on the climate. That's especially so if hurricanes intensify and so drive more warm water down into the ocean depths -- more heat could then get transported to the poles, leading to a disproportionate warming of the higher latitudes in relation to the equatorial ones.
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