NOAA Ship Okeanos Explorer multibeam sonars trackline in the Gulf of Mexico. Click image for larger view and image credit.
NOAA Corp's commissioned officer LTJG Glen Rice works on processing multibeam sonar seep data on board NOAA Ship Okeanos Explorer. Click image for larger view and image credit.
Gulf of Mexico Expedition 2011
Mashkoor Malik
Expedition Coordinator
NOAA Office of Ocean Exploration and Research
Dr. Tom Weber
Science Lead
University of New Hampshire, CCOM
Bill Shedd
BOEMRE
NOAA Ship Okeanos Explorer is outfitted with one of the very few deep water multibeam sonars capable of providing water column backscatter data. The primary purpose of the expedition is to study the feasibility of using this capability to map gasses in the water column.
The northern Gulf of Mexico is an ideal site to achieve our testing objectives because of the large number of naturally-occurring seeps. Underwater gaseous seeps are fed by the natural underground accumulations of oil and natural gas. Once released from the seafloor, the gas bubbles often rise through the water column, creating oil slicks on the sea surface. Scientists have been using satellite imagery of these surface slicks to identify many areas in the Gulf of Mexico where they believe oil is likely seeping from the ocean floor. However, matching a surface slick to a location on the seafloor is often quite difficult due to currents and weather conditions.
If the multibeam system proves capable of mapping hydrocarbon gasses in the water column, localizing the origin of a specific seep on the seafloor should be relatively easy. This capability could also prove valuable in identifying hydrocarbon leaks from manmade underwater structures.
A perspective of the seafloor showing preliminary results of gas seeps detected NOAA Ship Okeanos Explorer multibeam sonar in vicinity of Biloxi Dome in Northern Gulf of Mexico. Gas seep locations are shown as blue dots and are overlaid on the seafloor bathymetry that was collected. Click image for larger view and image credit.
Natural gas seeps overlaid on the background bathymetry (shown here as gray scale sun shaded bathymetry). The white vertical structures rising above the seafloor are the seeps derived from NOAA Ships Gordon Gunter and Thomas Jefferson , 12/18 kHz split-beam echo sounder during their 2010 work in Gulf of Mexico. The blue cylinder shows the location of the Macando Well head. Click image for larger view and image credit.
A view of the multibeam sonar water column backscatter data used to detect gas seeps. Gas seeps derived from the sonar are shown in the foreground. Click image for larger view and image credit.
Schematic diagram showing coverage of single beam and multibeam sonar. Click image for larger view and image credit.
Results will help identify future uses of the multibeam system and other water column imaging-enabled sonars on a larger scale in the Gulf of Mexico. This cruise will rely on collaborations between OER, UNH-CCOM, SEFSC, BOEMRE, and the NOAA Office of Marine and Aviation Operations (OMAO).
Previous collaborative work between UNH-CCOM and NOAA following Deepwater Horizon [1,2] 
demonstrated the capability of single-beam fisheries sonars for accurately mapping gas seeps. Although quite successful, the survey coverage of the single-beam sonar is limited to a narrow swath underneath the vessel. With its increased swath width, the multibeam sonar offers the possibility of greatly increasing the seep survey efficiency. In addition to detection and localization, the sonars on the Okeanos Explorer are being examined for their ability to provide information regarding the seep morphologies, general makeup, and relative densities. To help in these efforts BOEMRE representative, Bill Shedd, is sailing on board and providing the benefit of years of experience working in the Gulf. The BOEMRE-OER collaboration is a natural outcome of an evolving partnership that first started in 2004, focusing on exploring and understanding deepwater Gulf of Mexico habitats.
The overall expedition will also benefit from a few days of collaborative operations with NOAA colleagues on board the NOAA Ship Pisces. Pisces carries a comprehensive suite of standard fisheries sonars. Cross-checking the sonars on both ships will increase the capacity of both vessels to support multi-purpose operations. Assistance from the Pisces will improve Okeanos Explorer capabilities for both gas seep detection and fisheries-relevant data collection. The presence of the Okeanos Explorer will improve Pisces’ sonar operations for hydrographic mapping efforts, increasing the capacity of both vessels for multi-purpose missions.
In addition to the normal ship’s crew, cruise participants include Mashkoor Malik from NOAA OER, Bill Shedd from BOEMRE, Dr. Tom Weber, Dr. Jonathan Beaudoin, Kevin Jerram, and Maddie Schroth-Miller from UNH CCOM, and Lt. Glen Rice from the NOAA Office of Coast Survey. Ship survey staff constitute of SST Colleen Peters, SST Lillian Stuart and Gustav Karl Kågesten (UCAR/OER).
Partners:
- NOAA Ocean Exploration and Research (OER) –
NOAA Ship Okeanos Explorer - University of New Hampshire, Center for Ocean & Coastal Mapping –
UNH-CCOM - NOAA Fisheries Southeast Fisheries Science Center (SEFSC) –
NOAA Ship Pisces - Bureau of Ocean Energy Management, Regulation and Enforcement –
BOEMRE
Expedition Press Releases:
- NOAA News September 15, 2011 -
NOAA and partners demonstrate success of multibeam sonar to detect and map deep-sea gas seeps
