National Data Buoy Center (NDBC) Processing, Display, and Observation of Near-Bottom Currents Acquired by Oil and Gas Companies in the Northern Gulf of Mexico

Abstract

Under a Notice to Lessees (NTL No. 2005-G05) issued by the Minerals Management Service in April 2005, oil companies operating in the northern Gulf of Mexico in waters deeper than 400 meters are required to collect current profile data to a depth of 1000 meters. These data provide estimates of strong ocean currents, which may affect extreme loads, structural failure, and daily operations on the oil platforms and drilling rigs. Real-time data from near the surface to 1000 meters are reported every 20 minutes to the National Data Buoy Center (NDBC) and displayed on their public website. The oil and gas companies must also measure near- bottom currents at sites deeper than 1100 meters and recover and report these data at least every six months. These delayed-mode data are the subject of this effort. NDBC began accepting real-time current profile data in April 2005 and implemented real-time quality control of the data in March 2006 [1]. In August 2006, NDBC received four files containing the near-bottom, delayed-mode data. The data were processed through the same quality control algorithms and stored along with previously processed near-surface data. Since that time eighty-four additional data sets have been received and processed through the quality control algorithms at NDBC. Tables of these data with quality control flags and current velocity plots with depth are available to the general public on the NDBC website. One of the first delayed-mode data sets was collected from the Na Kika platform, approximately 100 kilometers south-east of the Mississippi River delta, during the active Hurricane season of 2005. The data from August 2005 showed greater than 0.30 cm/s currents at depths greater than 1900 meters to the right of the path of Hurricane Katrina. The currents rotated clockwise in the bottom waters at a period less than 24 hours and decayed over a period of nearly ten days. Although Hurricane Rita passed 360 kilometers to the southwest of the Na Kika platform in late September 2005, the bottom waters were impacted by the passage. The currents were not as strong as those related to Hurricane Katrina, but they were noticeable and lasted for several days. There are no near-surface data sets to corroborate these data because the platforms were evacuated due to the hurricanes. These results indicate a basin-wide response to these two strong hurricanes.