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which struck U.S. shores September 15, 2004, kicked up the tallest, most
extreme waves ever measured, scientists announced.
At more than 90 feet (27 meters) tall from crest to trough and
600 feet (183 meters) long, the massive waves would "wipe out" a commercial
fishing boat, said Douglas Mitchell. Mitchell is an oceanographer with the
U.S. Naval Research Laboratory at the Stennis Space Center in Mississippi.
The researchers estimated the wave heights using water pressure data from
undersea sensors that had been placed in the Gulf of Mexico for a separate
project. "Have you seen The Perfect Storm?" Mitchell said when asked to
describe the extreme waves. The reference is to the Hollywood movie based on
Sebastian Junger's best-selling book about an October 1991 storm in the
Atlantic Ocean. In the movie, waves the size of ten-story buildings swamp a
70-foot long-liner (a type of fishing boat) and its six-person crew.
Mitchell and Naval Research Laboratory colleagues David Wang, William
Teague, Ewa Jarosz, and Mark Hulbert reported their findings in the journal
The tallest measured wave was 91 feet (28 meters). The
researchers believe they likely missed even larger waves because their
sensors shut down before the most powerful region of the storm passed over
them. "If we had been fortunate enough to sample the waves when peak winds
were overhead, we'd expect to have seen waves in excess of 130 feet [40
meters] from crest to trough," team member William Teague said. At its peak
intensity, the hurricane was a Category Five storm—the most powerful—with
sustained winds of 161 miles an hour (259 kilometers an hour). Hurricane
Ivan tore a deadly path across the Caribbean and Gulf of Mexico in 2004. It
struck the Gulf Coast on September 15 with 130 mile an hour (209 kilometer
an hour) winds and was directly responsible for 92 deaths. But the extreme
waves disintegrated in the choppy waters of the Gulf of Mexico, never making
The Naval Research Laboratory team obtained their wave
measurements when Ivan passed directly over a series of six concrete-ringed
instrument packages deployed on the ocean floor about 75 miles (121
kilometers) south of Gulfport, Mississippi. Scientists call these moorings "barnys"
because they are shaped like barnacles. The barneys, which sat at depths
between 196 and 295 feet (60 and 90 meters), collect current and water
pressure data. They were placed in the gulf for a six-month-long project to
form a comprehensive profile of the region's currents, Mitchell said. The
timing and passage of the hurricane directly over the sensors was a
fortuitous coincidence, Teague said.
An added bonus is that all the instruments survived the storm.
The scientists calculated the wave heights from the changes in water
pressure recorded by the sensors as waves passed overhead. "As waves go by,
the pressure rises and falls," Teague said. To last for the six-month ocean
current project, the barnys' batteries were designed to turn on for 8.5
minutes every 8 hours—long enough to record the passage of about 50 waves.
Even though the barneys' operational time was staggered, none of the sensors
were on when the strongest part of Ivan passed overhead.
Scientists know little about the biggest ocean waves because
most attempts to measure them have failed. For example, wave-measuring
equipment attached to oil-drilling platforms often snaps off before a storm
peaks. Prior to Ivan, computer models of wave formation during a hurricane
suggested that monster waves topping 90 feet (27 meters) tall were rare.
Thanks to the fortuitous placement of the barnys, this assumption is
beginning to change. "The implication is waves generated by hurricanes are
much larger than previously suspected.
Waves in excess of 90 feet aren't rogue but are fairly common
during hurricanes," Teague said. According to team member David Wang, these
insights will allow scientists to create better computer models of hurricane
impacts. Such models, for example, could prompt engineers to build sturdier
oil-drilling platforms. "The models can only be as good as the data
provided," Wang said. "And we always want more [data]. There's more to be
learned about how waves do form under hurricanes."
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