New R/V Falkor Multibeam Data from the Papahānaumokuākea Marine National Monument in the Northwestern Hawaiian Islands
Wednesday, 17 December 2014: 5:15 PM
From March to June 2014, the Schmidt Ocean Institute, along with National Marine Sanctuaries and the National Science Foundation, supported 72 days of mapping surveys on two cruises using R/V Falkor in the Papahānaumokuākea Marine National Monument (PMNM) located within the Northwestern Hawaiian Islands (NWHI). PMNM is one of the largest marine protected areas in the world. Approximately 127,000 km2, 35% of the PMNM, were surveyed using dual multibeam systems from less than 30 to >5000 meters water depth, and thus covering the habitat depth ranges for shallow living corals, mesophotic corals, drowned reefs, to deep-sea corals and sponge communities. A total of 18 seamounts, guyots, banks, or atoll flanks (e.g., Midway and Kure) were mapped in the upper northwestern section of the monument, including the generically named Bank 9 Seamount, which appears to be a composite of a younger Hawaiian seamount and an older Cretaceous guyot. The middle segment of the PMNM consists mostly of large volcanic rift zone ridges and broad carbonate platforms. The rift zones located there are comparable in shape and size with those off Maui and the Island of Hawai‘i in the main islands. Likewise, the magnitude of the largest carbonate platform of Gardner Pinnacles suggests its original high island may have met or exceeded the enormity of the Island of Hawai‘i. Furthermore, the new mapping data have revealed the detail of numerous landslides and their deposits all along the chain, including an unusual rift zone flank failure creating a knife-edge ridge off Pioneer Bank. Dives with the Pisces V submersible were previously carried out on this feature, where extensive filter feeding biological communities were discovered. Not to be overlooked, the sidescan backscatter component of the multibeam data proved essential for identifying subtle reef features, numerous carbonate terraces, and debris channels that appear to transport sediment down the edifice flanks to the deep seafloor. Additionally, it was essential in delineating volcanic landforms such as lava flows, fissures, and eruptive cones. In short, the high quality and resolution of Falkor’s bathymetric and backscatter data have exposed second and possibly third order deep-water geomorphologic and structural elements on a regional scale.