Satellites Help Offshore Industry Avoid Weather and Water Hazards

Hurricanes have a liquid counterpart in the waters below called ocean eddies. Offshore industries, such as oil and gas companies, have to keep a weather eye on both. Satellite altimetry is helping government and industry manage those risks.

Satellite ocean observations are a standard part of marine operations around the world. Keeping track of local currents is critical for daily operations. And in the Gulf of Mexico, that means knowing the location of the Loop Current and its dangerous eddies.

 The Loop Current, which is part of the Gulf Stream, begins as a large flow of warm water from the Caribbean. It heads up into the eastern part of the Gulf of Mexico, then turns south and finally moves out through the Straits of Florida. Deep and fast moving, the Loop Current often breaks off and forms strong, clockwise rotating eddies called anticyclones that travel westward into the Gulf. The currents along the outer edges of the Loop Current, as well as these eddies, have been clocked at speeds as high as three to four knots (three to five miles per hour), comparable to the fastest ocean currents ever observed.

Because the Loop Current and its eddies are warmer, and thus higher in surface elevation, than the surrounding waters, they are easily spotted by satellite altimeters, such as those aboard the NASA/French Space Agency Jason 1 and Ocean Surface Topography Mission/Jason 2 satellites. To see what the altimeters see, many offshore operators turn to Research Professor Robert Leben and his colleagues at the University of Colorado's Center for Astrodynamics Research in Boulder. They use the latest satellite measurements of sea-surface height from Jason 1 and two other satellite altimeters to create maps showing the location, direction and speed of currents in the Gulf of Mexico.

To plan and design rigs and oil platforms for the future, oil companies would like to be able to anticipate the sea conditions a particular facility may encounter in the Gulf of Mexico over its lifetime. A consortium of about 20 different companies, along with the U.S. Minerals Management Service, has asked Leben and Forristall to develop a model to help determine what the risks from strong currents may be.

"We're constructing a 1,000-year-long statistical simulation of the Loop Current and its eddies," said Leben. "While we have only 20 to 30 years of observations, using computer simulation and the right statistical methods, we can figure out how the current and eddies behave and then simulate a longer period of time."

"The idea," said Forristall, "is to map the Gulf. There are some places where there have only been a few eddies in the past. With our artificial time series, we'll be able to fill in the gaps. We'll be able to see what is the likelihood of an eddy occurring in a particular spot."

Another goal of the effort is to better understand the relationship between the Loop Current and hurricanes, which grow stronger as they pass over warm water. Leben said results of the 1,000-year Loop Current simulation will be combined with simulations of how the Loop Current's warm surface waters and eddies effect hurricane intensification.

"These tandem ocean/atmosphere events are rare, but they do occur," said Leben. "During Hurricane Katrina, when both strong eddy currents and a category-five hurricane hit the oil patch in the north-central Gulf of Mexico, a total of five rigs and 18 platforms were lost and many more were damaged."

Knowing more about the Loop Current and its spinning offspring will help oil companies and other offshore industries plan for the future.