How Modern Multibeam Surveys Can Dramatically Increase Our Understanding of the Seafloor and Waters Above to Support the United Nations Decade of Ocean Science for Sustainable Development

Multibeam echosounder (MBES) technology has been constantly evolving since its commercial introduction in the late 1970s. The early systems were large and designed to efficiently acquire bathymetric data in deep water. As the underlying sonar technologies improved and computing power increased, systems became smaller and capable of operating on a wider range of vessels over a broader range of depths. Modern deep seafloor exploration, and our present understanding of the geomorphological and biophysical processes that shape it, are closely linked to advances in multibeam echosounder technology. Low to mid-frequency (12-30 kHz) acoustic waves generated by MBES sonars can penetrate kilometers of water column and remotely measure the deep seafloor and shallow subsurface. Reflectivity measurements of the seafloor and water column can also be extracted from MBES datasets, but until the last decade of the 20th century, only the bathymetric swath data was being utilized. In the 1990s, scientists began taking advantage of the multibeam acoustic wave's reflected energy, or backscatter, to interpret information on seafloor geometry (slope), physical characteristics (hardness and roughness), and intrinsic properties, such as composition, surficial and volumetric scattering. Analyzing the geophysical signature of reflected acoustic beams has proven an effective quantitative and qualitative tool to remotely characterize the lithologic composition and geologic nature of the seafloor. Analyzing seafloor backscatter and most recently, backscatter intensities in the water column, has been used for a wide range of applications, including fisheries research, marine biomass assessment, benthic habitat mapping, geological classification, subsea engineering and geohazard mitigation, and hydrocarbon seep studies. This presentation will briefly look at the evolution of MBES technology before focusing on how modern MBES surveys, using the latest generation technology, can deliver a comprehensive characterization of the seafloor and the waters above, as opposed to bathymetry data alone. With The Nippon Foundation-GEBCO Seabed 2030 Project now underway, and planning for the United Nations (UN) Decade of Ocean Science for Sustainable Development having recently commenced, modern MBES technology will play a critical role in bridging ocean bathymetry and ocean observation to improve our understanding of the ocean, its seafloor and its processes. One of the key R&D priorities of the Decade is a comprehensive map (digital atlas) of the ocean. Modern multibeam surveys will support not only bathymetric mapping, but also physical, biological, chemical, geologic, ecosystem, cultural and resource mapping of the world's oceans. Such an approach can feed both Seabed 2030 and the Decade to deliver, as the UN has so eloquently stated, “the ocean we want for the future we need.” Keywords- multibeam; sonar; mbes; echosounder; bathymetry; hydrography; marine geology; mapping; ocean mapping; seeps; seabed seeps; hydrocarbon seeps; exploration; ocean exploration; geophysical; survey; geophysical survey; ocean; seafloor; characterization; seafloor characterization; backscatter; multibeam backscatter; water column; observation; ocean observation; Seabed 2030, United Nations Decade of Ocean Science for Sustainable Development; Ocean Decade.