URI oceanographer helps ocean swimmer navigate currents, tides for fundraising swim

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NARRAGANSETT, R.I. – August 1, 2012 – University of Rhode Island oceanographer David Ullman usually spends his time at the Graduate School of Oceanography studying field observations and numerical models to understand how coastal waters circulate and mix and how those forces affect the health of water bodies.

When he heard that Rhode Islander Trent Theroux was planning to swim from Point Judith to Block Island this fall to raise $50,000 to help those with spinal cord injuries, Ullman volunteered to use his expertise to help Theroux navigate the strong currents in Block Island Sound.

“It has been a really interesting exercise helping Trent,” said Ullman, a resident of Peace Dale. “I wouldn’t want the guy to get swept out to Portugal.”

While there is hardly a chance of that happening, Ullman said the strong tidal currents at the northern tip of Block Island could force Theroux to swim several extra miles out of his way or abandon his swim entirely if he didn’t factor in the tides and currents along his route.

“Trent says he can swim about two miles per hour, but the currents can be stronger than that at certain times, and if he’s not aware of that, he could be swimming against the current and end up going backwards,” Ullman said.

According to the URI oceanographer, Theroux’s first important decision was what date to make the crossing. Ullman suggested making the swim during neap tide, a period when the tidal range – the difference in elevation between high and low tide — is the least. Since tides are controlled by a combination of the moon and the sun, the largest tidal range occurs during full and new moon phases. Therefore, the best time to make the swim would be on a day half way between full and new moon. Based on this information, Theroux chose to plan his swim for Sept. 8, a date when the tides will be at a minimum.

The direction of tidal currents in Block Island Sound is largely controlled by the eastward and westward flows of water moving into and out of Long Island Sound. With this in mind, Ullman recommended that Theroux begin his swim at Point Judith at the beginning of the flood tide, around 6 a.m., when the currents are starting to flow westward, and he should swim toward a stagnant area about a mile west of the tip of Block Island. By the time he gets there 6-7 hours later, the tide will reverse and Theroux should be able to ride the eastward currents to the island.

“It’s a little tricky at the north tip of Block Island,” noted Ullman. “There is a very large current there and it’s a treacherous area where the water can be moving at two or two-and-a-half knots. There’s no way he’ll be able to swim against that.”

Ullman has sent Theroux some tidal current maps and a recommended route. The swimmer’s support team will be able to use GPS to ensure that Theroux remains on course.

“I’m looking forward to monitoring his progress and celebrating with him when he completes the swim,” Ullman said.

“I am grateful that Dr. Ullman and the GSO staff accepted my request of support for this charity event,” said Theroux, who will swim the backstroke on the entire route. “Navigating the waters of Block Island Sound was of paramount concern for my team. Dr. Ullman’s models clearly identify the correct path to follow during the swim. I thank him for his time and efforts.”

For more information about Theroux’s plan to swim from Point Judith to Block Island, or to support his campaign to raise funds for RISE Above Paralysis, visit www.backtoblock.org.

URI Office of Communications & Marketing photo by Michael Salerno Photography.