Areas off the central coast of California have been identified for development of offshore floating deep-water wind farms by the U.S. Beauro of Energy and Management (BOEM link > https://www.boem.gov/renewable-energy/state-activities/morro-bay-wind-energy-area). The structures will be anchored to the seafloor in more than 500 m water depth and require other infrastructure which will inevitably alter the seafloor. Before 2018, the seafloor in this area was almost unexplored making it impossible to evaluate the impact and feasibility of this potential development. Thus we joined forces with the USGS, BOEM, and NOAA (EXPRESS) in an effort to map and explore the seafloor to provide a baseline characterization of this area. MBARI’s contribution to this effort involves utilizing the technologies associated with our mapping AUVs and ROVs to conduct detailed investigations of particular features AUV Data, ROV Data. From these seafloor observations we have made an account of the existing biological communities in this area now.

A number of geologic features of special interest are clearly revealed in the new regional surface ship maps. This includes the ~5 thousand large seafloor depressions called pockmarks (average 156 m diameter, 5 m depth) in what is North America’s largest pockmark field. In addition to these features, the detailed bathymetry collected with MBARI’s AUV revealed the existence of seafloor pits, previously un-mapped, as they are below the resolution of surface ship mapping techniques. These smaller (average 9 m diameter and 1 m depth) features are ~ three times as abundant as the pockmarks, exist in amongst the pockmarks and extend outside of the pockmark field. We are focused on understanding the origins of all of these features, establishing whether they are geologically active, and determining if they are areas of special biological significance.

Map showing the bathymetry offshore of Central California. The location of the proposed wind farm lease area is indicated in gray. Green lines outline the extent of the Sur Pockmark Field. The Sur Pockmark Field contains over 5,000 pockmarks (outlined in red) that are each larger than a football field. How these curious depressions were formed and are maintained over time are the focus of our research at this site

The continental slope here is also crossed by two submarine channel systems. These channels are conduits that carry sediment from the shelf edge down toward the deep sea. Large volumes of sediments are carried down these channels episodically during powerful turbidity current events (Internal LINK to CCE page), that leave distinctive sand rich layers behind. How frequently these energetic events occur and  whether the turbidity currents also escape from the confinement of these channels is also being investigated.

Team

Collaborators

Linda Kuhnz, Mary McGann (USGS), Guy Cochrane (USGS), Tom Lorenson (USGS), Jason Adison (USGS), Mauree Walton (USGS now NRL), Nora Nieminski (USGS), Lisa Gilbane (BOEM), Jeremey Potter (BOEM), Steve Dobbs (Stanford graduate student), Marianne Coholic (Stanford graduate student)

Publications

Kuhnz, L.A., L. Gilbane, G.R. Cochrane, and C.K. Paull. 2022. Multifactor biotopes as a method for detailed site characterization in diverse benthic megafaunal communities and habitats in deep-water off Morro Bay, California. Deep Sea Research Part I: Oceanographic Research Papers, 190(103872): 1–19. https://doi.org/10.1016/j.dsr.2022.103872

Cochrane, G.R., L.A. Kuhnz, L. Gilbane, P. Dartnell, M.A.L. Walton, and C.K. Paull. California Deepwater Investigations and Groundtruthing (Cal DIG) I, Volume 3—Benthic Habitat Characterization Offshore Morro Bay, California. Reston, VA: 2022. https://doi.org/10.3133/ofr20221035

Walton, M.A.L., C.K. Paull, G. Cochrane, J. Addison, D. Caress, R. Gwiazda, D. Kennedy, E. Lundsten, and A. Papesh. California Deepwater Investigations and Groundtruthing (Cal DIG) I: Fault and Shallow Geohazard Analysis Offshore Morro Bay, Volume 2. Camarillo, CA: US Department of the Interior, Bureau of Ocean Energy Management, 2021. https://espis.boem.gov/final%20reports/BOEM_2021-044.pdf