Controlling hurricanes

In a talk presented Monday at the 27th annual meeting of the American Meteorological Society's conference on Hurricanes and Tropical Meteorology, Philip Kithil of Atmocean, Inc. presented a radical idea to reduce the intensity of hurricanes approaching the coast: deploy an array of wave-activated deep ocean pumps in front of an approaching storm. These pumps would each be attached to a 1000 meter long, 1.5 meter diameter flexible tube moored to the ocean bottom. Since the water at 1 kilometer depth is up to 15 degrees C cooler than the surface water, these pumps could quickly pump enough cold water to the surface to significantly cool the surface waters. Assuming a typical 2-meter high wave, the pumps, which operate at 30% efficiency, would be able to able to pump enough cold water to the surface in a day or two to cool a 50 meter deep layer by 1 degree C. In a field test conducted near Bermuda last year, Atmocean lowered the surface temperature of ocean water by 4 degrees C using a test pump attached to a 25 cm wide, 160 meter long tube.


Figure 1. Diagram of the deep ocean pump with flexible tube attached proposed by Atmocean to reduce hurricane intensity.

Could such a scheme work? Yes, but you would need a lot of these pumps. Kithil estimated that 6000 of these units would be needed, deployed in a 100 km wide band stretching across the Gulf of Mexico, each pump spaced 50-100 meters apart. The pumps would all be tethered to each other and anchored to the bottom to slow any drift that might occur from ocean currents. The pumps and flexible tubes cost about $2800 each, so we're talking a total cost of $2.4 billion for a single array stretched across the Gulf of Mexico. Additional arrays located off the Florida Atlantic coast and near the Lesser Antilles Islands would cost $2 billion or more, each. The yearly cost of maintenance and operation would be another 20% of the installation cost.

That's a pretty steep price, and makes this scheme a difficult sell. In addition to the major financial issues to overcome, the plan also has serious technical, environmental, political, and legal problems to consider.

Environmental concerns
Kithil acknowledged that an evaluation of the ecological effects of injecting a large amount of cold water to the surface needs to be done. Such a large change to a significant region of the ocean is bound to have major and possibly negative consequences to fisheries and wildlife. Since the pumps can be turned off when there is no hurricane threat, it is possible that these effects will be minimal.

Technical problems
It is not clear how long the cold water pumped to the surface will stay there--the cold water pumped to the surface is more dense than the water beneath it, and so will tend to sink, allowing warmer water beneath to replace it and warm the surface waters again. Modeling studies and field studies are needed to determine if the cold water can stay at the surface long enough to significantly affect a hurricane. The modeling studies Atmocean did do of a Hurricane Ivan case showed a 10 mb increase in pressure when the storm crossed the cold wake, followed by a re-intensification of the storm after it crossed back into warm waters. In some cases, this will be a worthwhile expenditure of money, since such a reduction in storm strength would save billions. However, in other cases, the storm would simply re-intensify and grow even stronger after encountering the cold pool, and nothing would be gained.

Political issues
The array of pumps will lie across some very busy shipping lanes. Companies that operate deep draft vessels such as oil tankers are not going to be too happy about their ships having to take longer and more costly routes around the array. It will take some considerable political clout to convince Congress into authorizing the money for this project.

Legal problems
Another major obstacle to clear will be a legal one. While Mr. Kithil pointed out that none of their numerical model simulations of hurricanes hitting pools of cold water showed the hurricanes changing course, it is inevitable that sooner or later such a course change would occur, since hurricanes naturally make sudden unpredictable course shifts. Residents on the coast hit by the modified storm will want to sue, and there will be many lawyers more than happy to take their case. I asked Dave Moran, Professor of Law at Wayne State University about this this, and he assured me that those suing would have a very good case. Atmocean would have to get special legislation passed to protect it from lawsuits, such as was recently passed to protect the gun industry from lawsuits.

Despite all these negatives, Atmocean appears to be determined to pull this off. They appear to have some venture capital money to work with, which they are applying this year to the twin tasks of doing more computer model simulations and field tests. I wouldn't be surprised if they hire a lobbyist to work the corridors of power in Washington D.C., as well. I am dubious that given all the obstacles involved that they can pull this off, but I wish them luck in their creative effort to do so.

Jeff Masters