Scientists call these moorings "barnys" because they are shaped like barnacles.
The barnys, 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 hourslong enough to record the passage of about 50 waves.
Even though the barnys' 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."
Free E-Mail News Updates
Sign up for our Inside National Geographic newsletter. Every two weeks we'll send you our top stories and pictures (see sample).
SOURCES AND RELATED WEB SITES