Missions and Data

Applying the criteria in Article 76 of the Law of the Sea Convention requires data on the morphology of the seafloor and, in some areas, the thickness of the underlying sediment. For this reason, the ECS Project has conducted field programs necessary to collect bathymetric and seismic data. The data collected by the ECS Project can be downloaded from NOAA’s National Centers for Environmental Information.

Bathymetric Data

Bathymetric data are collected using state-of-the-art multibeam echosounders that provide a three-dimensional map of the surface of the seafloor. These data are important for applying the criteria in Article 76, including identifying the foot of slope and 2,500 meter (m) isobaths (i.e., depth contours).

Bathymetric data collection for the ECS Project is coordinated through the Center for Coastal and Ocean Mapping/Joint Hydrographic Center (CCOM/JHC), a cooperative partnership between NOAA and the University of New Hampshire. Since 2002, CCOM/JHC has mapped more than two and a half million square kilometers of the ocean floor, an area the size of Alaska and Texas combined. These data were collected on thirty-one cruises in ten regions totaling nearly two-and-a-half years of sea time (Table 1.1).

Seismic Data

The second primary dataset is seismic data, which provides information on the depth, thickness, geometry, and other characteristics of the sediments lying on the seafloor.  The ECS Project requires seismic data to derive the thickness of the sediment for those regions where the sediment thickness formula in Article 76 applies.

Seismic data is collected by a sound source towed behind the ship which emits acoustic energy at constant time or distance intervals. The transmitted energy is reflected or refracted from boundaries between various geologic layers (such as sedimentary horizons) and received in an array of hydrophones towed behind the ship called a seismic streamer or in a self-contained instrument deployed in the water behind the vessel (sonobuoy) or resting on the seafloor (ocean bottom seismometer).  The signals are recorded in digital form and stored on high-speed computers for subsequent processing, analysis, mapping, interpretation, and display.

Seismic data collection for the ECS Project is coordinated through the U.S. Geological Survey.  Seismic data collection has been completed in the Arctic, Atlantic, Bering Sea, and Gulf of Alaska (Table 1.2).  USGS made significant efforts to minimize the impact of seismic data collection on living resources through careful planning, obtaining the applicable authorizations, and following mitigation strategies.

Seismic data in the Arctic Ocean was conducted in a cooperative effort with Canada.  The U.S. Coast Guard Cutter (USCGC) Healy collected multibeam bathymetric data and created a straight and open path through the ice for the Canadian Coast Guard ship Louis S. Saint Laurent, which followed collecting seismic reflection and refraction data with sensors towed behind the stern of the ship.