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Oct. 6, 2022

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Study: Cooling ocean won’t help combat hurricanes

Expert: Best strategy is to improve our detection, adaptation

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FORT LAUDERDALE, Fla. — Though it’s a nice idea, artificially cooling ocean surfaces won’t do much to stop the destructive power of a hurricane. The news comes from a recent study by scientists at the University of Miami Rosenstiel School of Marine, Atmospheric and Earth Science.

“Massive amounts of artificially cooled water would be needed for only a modest weakening in hurricane intensity before landfall,” said the study’s lead author James Hlywiak, in a release. He added that weakening would not necessarily decrease inland damages and safety risks.

The idea of using cool water to cut the knees out from under a hurricane makes a lot of sense.

Hurricanes form and strengthen, in part, because of warm ocean water above 79 degrees. And scientists know that slow-moving hurricanes sometimes weaken themselves — they produce so much wind that cool water is pulled up from the deep, and zaps some of the storm’s energy. In theory, if humans could aid this cool upwelling process we could dampen a storm.

The goal of the UM study was to figure out just how much cooler surface water would be needed to cause a noticeable impact on hurricane intensity.

To figure that out, Hlywiak and co-author David Nolan compared two models of hurricane assessment. The simpler of the two, the maximum potential intensity theory, is commonly used to determine the maximum velocity of tropical storms.

The other was a more complex state-of-the-art numerical weather model. “We used this to simulate a more realistic approach featuring a finite region of cooling over a more realistic ocean and land surface,” said Hlywiak. The numerical model also factored in the amount of time a storm would travel over cooled water — something the simpler model could not do.

In the simpler model, fast-moving storms traveling over very hot water could be significantly weakened by technology-induced cooling, the study said, but in the more complex numerical simulations, the artificial cooling would require a massive scale.

Their model simulated an approximately Category 4 hurricane encountering an area of cooled water larger than the state of Oregon — that’s nearly twice the size of Florida.

They set the patch at 3.6 degrees cooler than the surrounding water (the optimal temperature difference, according to models), and found that the hurricane weakened by only 15 percent.

The amount of energy that the numerical model removed from that area of water is 100 times the amount of energy that the entire U.S. used in 2019.

“That would be like taking a Category 4 or 5 storm down to a low Category 3, so it’s still a major hurricane,” said Hlywiak. He cautioned that focusing on category can be deceptive. “We chose not to focus on maximum wind speed — it only describes intensity at one point in storm,” he said.

“Hurricane Sandy is a good example. It was the equivalent of a Category 1 storm, yet it was still one of the most devastating hurricanes on record due to the sheer size. As we say in Miami, there’s more to the story than the category.”

The study found that faster-moving storms could be weakened to a higher degree than slow storms, but would require an even larger field of cooled water, since they would cross the cooled patch faster.

How would technology ever cool that much water? That remains to be seen.

Ideas for actually creating cool water upwellings include running perforated pipes below the thermocline, typically between 50 and 100 feet deep in the South Florida region, and releasing a stream of bubbles from the pipes.

The rising bubbles would create an upwelling of cold water.

Another challenge the study notes is that the path of a hurricane can change dramatically and quickly. Arranging technology to intercept a hurricane would be quite difficult.

The perforated pipe concept suggests running the “bubble curtain” between Cuba and Florida, which would, in theory, weaken storms heading into the Gulf. Once through the curtain, though, they still would encounter warm water.

Some natural forces that inhibit hurricane formation and strengthening include traveling over land, especially mountainous regions, and a phenomenon known as the Saharan air layer, or Saharan dust wave, a 2-mile thick layer of hot, dry dusty air that shoots off North Africa east toward Florida.

It travels about a mile above the water’s surface at 30 mph to 50 mph and can cut into storms, tearing them apart. These winds typically dissipate in mid-August.

Another force that weakens hurricanes is other hurricanes — as they pass through an area, they leave the water cooler. In 2005, hurricanes Katrina and Rita both cooled certain areas of the Gulf of Mexico by 7.2 degrees, according to data from NASA.

NASA research indicates that climate change will result in more available moisture in the atmosphere for hurricanes in the future.

Their models do not suggest more frequent tropical storms, but those that do form will have a great likelihood of becoming destructive and dangerous Category 4 or 5 storms.

The University of Miami study also warns that artificial cooling through upwelling could result in accelerated upper-ocean deoxygenation, since deep water holds less oxygen.

They say the biological consequences are not well understood. “Ample caution must be taken to avoid catastrophic ecological habitat changes,” they wrote.

“We see a lot of attention put towards (the question), ‘Well why can we just use technology to change the oceans?’” said Hlywiak.

Hlywiak suggest that relying on geoengineering, or human intervention in large natural systems, is a mistake.

“What we do could have cascading effects further down the road, or they might not have any effect at all. So the best strategy … is to improve adaptation, improve infrastructure, improve the science around detection of storms. In the grand scheme of things, try to have as low a footprint as possible on our climate and planet.”

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