Unlocking the Deep Secrets of a River That Flows Through the Gulf of Mexico

The atmospheric impact of the Loop Current has been studied intensely because its heat energy can fuel killer hurricanes. SAIC has been given the job of probing its deeper secrets so that oil and gas activities in the deepest parts of the Gulf are environmentally compliant and safe.

Until about 10 years ago, most of the drilling in the Gulf of Mexico was in relatively shallow water on the continental shelf and its upper slope. Now, however, the oil industry has begun exploration and production in deeper water. That deeper water, particularly in the Gulf of Mexico, presents unique challenges. For SAIC's oceanographers, deep water in the Gulf is where the ocean gets interesting.

That's because the physics of the underwater currents and processes in the deep waters of the Gulf of Mexico are not particularly well understood, even as the technology for "ultradeep-sea" drilling makes it possible to drill several miles below the seabed in water at depths of 10,000 feet. Because of the Gulf Loop Current and the complexity of its physics, the consequences for ultradeep-water drilling may be profound.

The Department of Interior's Minerals Management Service (MMS) recently awarded SAIC a five-year contract to study the Loop Current and associated processes.

The Loop Current itself is relatively constrained to the eastern part of the Gulf. However, large-scale eddies separate from it and drift westward toward the Mississippi Delta and the Mexican continental shelf. That's why, said Field Operations Manager Jim Singer, "MMS needs SAIC's team to determine why these eddies are formed and whether they can be predicted months and seasons ahead of time."

Spin Cycle

The Loop Current originates in the Equatorial Current between West Africa and the Americas. This westward flowing stream of warm water presses into the Gulf of Mexico from the Caribbean Sea through the Yucatan Channel, creating a loop that flows north into the Gulf and turns in a clockwise motion, then moves southward along the west coast of Florida, and finally streams eastward through the narrow passage between Key West and Cuba. Along the eastern shore of Florida it has the name Gulf Stream as it heads into the vast Atlantic.

Periodically, however, "the northern portion of the Loop Current separates," said Peter Hamilton, an SAIC senior scientist. Hamilton is a 30-year SAIC veteran who has a Ph.D. in physical oceanography and is considered one of the foremost experts in the field of Gulf oceanography and physics.

That separation from the larger current creates "a closed, clockwise-rotating eddy that initially retains many of the velocity and water characteristics of the Loop Current." Such "large-scale eddies" can reach nearly 200 miles in diameter. A second separation can occur before the first eddy has decayed. Hamilton said he's seen as many as three eddies at a time existing in the broad Gulf.

The Loop Current extends down to about 3,000 feet. Below this depth, there are deep energetic eddies and waves. According to Hamilton, "typical current speeds of these deep disturbances are one-third to half a knot, but speeds of greater than one and a half knots (about 2 miles per hour) have been measured on occasion." That is a significant amount of energy when you're talking about a water column thousands of feet in depth.

Indeed, said Hamilton, "speeds of these magnitudes spanning the lower 3,000 feet of the water column generate considerable stresses on drilling platforms, anchoring systems, and risers, particularly when coupled with high-speed, near-surface currents of the Loop Current."

Although the pipe from the well to the platform itself is rigid, a 10,000-foot section of pipe suspended below a platform becomes quite flexible, proportionately, a very thin strand that can be bent in any direction by the horizontal currents, even broken altogether if the current forces are strong and opposing at different depths in the water column.

Why MMS Wants to Know

MMS is responsible for, among other things, granting lease sales for offshore drilling on the sea floor throughout U.S. federal waters (offshore of the three-mile state jurisdiction). MMS needs to be able to gauge the risk of an oil spill on a particular tract of sea floor well in advance of any lease sales to the oil industry.

Engineers stationed on oil platforms can't see these subsurface currents although they can feel the forces of the currents as they put pressure on the rig. At times crews have to shut down operations if the pipe below them is pushed too much from a vertical orientation. For an operation that can cost hundreds of thousands to millions of dollars per day, downtime gets very expensive.

While oil companies use very sophisticated oceanographic technology to measure currents below and adjacent to their platforms, they have not undertaken a large-scale study of Gulf ocean physics that is necessary to advance knowledge and enable predictions of deep currents and processes.

In-Depth Study

The project team, consisting of scientists and technicians from SAIC in Raleigh, N.C., the University of Colorado, the University of Rhode Island, and Princeton University, will make field measurements, use satellite remote sensing of the sea surface to track the location of the Loop Current and eddies, and employ numerical modeling of the physics throughout the region and in the very deep waters.

During this spring, the SAIC field team assembled sets of current meters, which are thick-walled aluminum cylinders, each about 3 feet long and 8 inches in diameter. These are loaded with a sophisticated computer, clock, data storage capabilities, and enough long-life batteries to keep them operational during a long deployment.

The computer in each meter is connected to special sensors on the outside of the cylinder for measuring currents, temperature, and the salinity of the water passing by. These devices take samples every hour for a year during a single deployment in the cold, deep ocean. Each costs in the range of $15,000-$20,000.

Dozens of these current meters are now in the Gulf, attached to a cable that stands vertically in the water column above a large anchor. Special floatation devices are attached at intervals along the wire to keep the array taut and vertical. The top floatation device in each mooring is deep enough to avoid shipping traffic and fishermen.

During the spring and early summer, SAIC placed 29 of these moorings at various locations "that were selected to optimize the likelihood of taking a coherent set of measurements in a region where an eddy separation might be expected to occur," Hamilton said, adding that the "sensors will be used to measure directly, or estimate with documented accuracy, vertical profiles of velocity, temperature and salinity." The moorings are intended to stay in place for 15 months.

At the end of that period, the field team, led by Singer, plans to visit each of the mooring sites, retrieve the equipment, download all the data, replace the batteries, and then put them all back in the water for another 15 months of measurements. Simultaneously during the measurement program, scientists at the University of Colorado will be watching Loop Current behavior using satellite surveillance. When the measurement program is complete, in fall of 2011, the major task of data processing and scientific analysis begins.

Two years later, all of the scientific findings are scheduled to be presented in a massive report written by the team of ocean physicists. This tome is not for the average reader. Rather, it will be slowly digested by Ph.D. oceanographers from MMS and panels of physicists retained by MMS to glean the key results from the report. The database that will result from the study is seen by the MMS as an unprecedented asset to all of the Gulf oceanographic community.

All of the 29 mooring locations have water depths to 10,000 feet. Just to build the large anchors, the team needed 270 railroad wheels or 93 tons. Reusing railroad wheels as anchor weights is the most cost-effective way to moor the vertical arrays.

Study Expected to Increase Safety, Improve Forecasts

According to MMS, the study will help understand how currents could interrupt oil production operations, and change or affect the movement of oil spills, including natural seeps from the ocean floor. Human activities in the Gulf and its coastal areas can also be made safer with an increased understanding of the Loop Current, MMS officials said in a press release.

In addition to collaboration with the University of Colorado, SAIC will establish subcontracts with ocean physicists from Princeton University who will conduct numerical modeling of the current, and with oceanographers from the University of Rhode Island who will participate in the current measurement program and data analyses. SAIC will also coordinate the study with a similar study, partially funded by MMS, by scientists from Centro de Investigación Cientifica y Educación Superior de Ensenada, Mexico, within that country's Exclusive Economic Zone, commonly known as the 200-mile limit.

SAIC will also get an assist in the study of the thermal structure of the Loop Current from the University of Miami and the National Oceanographic and Atmospheric Administration Atlantic Oceanographic and Meteorological Lab in Miami, Fla. That organization hopes to use the data and their own measurements to forecast more accurately the intensification of hurricanes entering or lingering in the Gulf of Mexico. Several recent hurricanes, including Katrina, have gathered considerable strength as they passed over the warm surface water of the Loop Current or its eddies in the eastern Gulf. Understanding those dynamics could significantly improve modeling and prediction of hurricanes approaching the U.S. coastline.

A Satisfying Win for SAIC

Federal funding for ocean research has been cut back over the last 10 years, with organizations like the National Science Foundation, the Office of Naval Research and other agencies having significantly fewer research dollars to award as grants. For that reason, academic institutions that otherwise might have been the recipients of such research money — the Scripps Institute of Oceanography, Woods Hole Oceanographic Institution, Texas A&M University and others — have begun to pursue the types of contracts that have typically been the livelihood of companies like SAIC.

The study is the most extensive oceanographic project being conducted today in U.S. waters for a non-Department of Defense agency, and winning the contract against such storied competition, say those involved, is especially satisfying for the study team.