OCEAN CURRENT MONITORING

The most energetic currents in the Gulf of Mexico are created by the Loop Current, which moves from the Caribbean Sea into the eastern part of the Gulf and exits between southern Florida and Cuba (figure 15).

Figure 15. Loop and eddy currents in the Gulf of Mexico (image courtesy of Horizon Marine, Inc.). (Click on image to enlarge)

It affects the ocean from the surface to approximately 3,000-ft (914-m) water depth with varying speeds. Currents as high as 4 knots (kn) have been observed from the surface to 1,000-ft (305-m) water depths.

These upper currents then taper off between 1,000- and 3,000-ft (305- and 914-m) depths.

The Loop Current path may vary by hundreds of miles while the flow direction generally remains constant.

Once it reaches its most northward position, a portion may break off and form an eddy current, a mass of clockwise-rotating water that traverses westward until it dissipates off the western coast of the Gulf.

Beneath the 3,000-ft (914-m) water depth, other currents migrate around the deep waters of the GOM.

Until recently, these deep currents were thought to be minimal and were not a major consideration in most structure designs. In 1999, industry reported significant currents on the OCS below 3,000 ft (914 m).

This information led to a Safety Alert and subsequent study of deep currents by MMS (Hamilton et al., 2003).

This study revealed significant deep currents of up to 2 kn at some locations.

The effects of all currents must be considered in the design of deepwater floating production facilities, drilling rigs, and their ancillary equipment, such as steel catenary risers and mooring systems.

Recent incidents have revealed the need for more accurate data in hind-casting and forecasting events and in daily operations. As a result, MMS is proposing to issue an NTL titled �Ocean Current Monitoring on Floating Facilities.�

This NTL could establish and implement a program where operators of deepwater offshore production facilities and mobile offshore drilling units (MODU�s) collect data on ocean currents and submit them for publication on an industry-sponsored Internet website.

Data collected on currents will improve fatigue forecast models and establish responsible design criteria, resulting in increased reliability of deepwater structures, thereby reducing risk to human lives, offshore facilities, and the ocean environment.