Well, we’ve got a second named storm in the Northeast Pacific. As NHC forecaster James Franklin notes, this is an unusual (although not un-heard of) occurrence:
THE DEPRESSION IS UPGRADED TO A 35 KT TROPICAL STORM. ONLY TWICE BEFORE…IN 1956 AND 1984…HAVE THERE BEEN TWO EASTERN NORTH PACIFIC NAMED STORMS IN MAY.
Barbara is apparently steadily intensifying–the Wisconsin folks estimate the intensity at 45 knots by now. Because this storm could become a hurricane before striking Mexico, it is going to be watched very closely.
Meanwhile, what is the point of a storm like Barbara, or any other hurricane? Are these storms just random weather? Or are they a critical part of the climate system, one mechanism that the planet “uses” to keep cool around its tropical waistline?
That’s the question investigated in a new paper just published in the journal Nature by Ryan Sriver and Matthew Huber of Purdue University (PDF; subscription only). The paper is entitled “Observational evidence for an ocean heat pump induced by tropical cyclones.” Here’s the freely available editor’s summary of the work:
Tropical cyclones are known to mix the upper layers of the ocean, a process that ‘pumps’ heat downwards and thereby cools the ocean surface on local scales. It has been suggested that they may play an important role in ocean mixing at the global scale, and new calculations suggest that tropical cyclones are indeed responsible for significant cooling and vertical mixing of the surface ocean in tropical regions. Heat pumped downwards must be balanced by heat transport towards the poles, so some 15% of peak poleward oceanic heat transport may be associated with tropical cyclone-induced mixing. The amount of mixing induced by tropical cyclones is also related to sea surface temperature, suggesting that future changes in tropical sea surface temperatures may have significant effects on ocean circulation and ocean heat transport, as both processes are affected by ocean mixing. Climate change models could benefit from taking these effects into account.
This actually doesn’t do full justice to the potential implications of this work. Allow me to quote the authors themselves, who have kindly provided a copy of the paper. From their concluding paragraph:
Our analysis suggests that changes in global cyclone frequency, duration and/or intensity are closely related to the amount of heat pumped into–and available to be subsequently transported by–the oceans. This relationship may have implications for changes in heat transport associated with past and future climate change.
Extrapolation of our results suggests that future increases in tropical temperatures may result in increased dissipation, mixing, heat storage, and eventually heat transport. Moreover, this positive response in transport might feed back on climate by redistributing heat poleward, diminishing the Equator-to-pole temperature gradient, and
raising global mean temperature. We have provided some evidence that cyclone-induced mixing is a fundamental physical mechanism that may act to stabilize tropical temperatures, mix the upper ocean, and cause polar amplification of climate change.
In other words: Tropical cyclones play an essential role in getting heat out of the tropics, which they do by churning up the oceans and “pumping” warm water downward, in turn leading to a net poleward transport of ocean heat. So if the globe warms and hurricanes intensify, they will also send more heat poleward through the oceans–thus further warming the polar regions. The Arctic is already experiencing greatly amplified global warming; this could greatly increase that phenomenon.
The result, as the authors note, could be a considerable lessening of the equator-to-pole temperature gradient. And it could mean that one way the planet responds to global warming is to create dramatically more intense hurricanes.
Food for thought, to say the least. There is much more on this emerging line of scientific thinking in Storm World.