Presenter: James Acker (Adnet Systems Inc. / NASA Goddard Earth Sciences Data and Information Services Center)

Description:
Bellona Plateau is a major Coral Sea carbonate platform about 600 km west of New Caledonia. The bi-lobed plateau’s 180 km long axis is oriented from NW to SE, wider at the NW end than the SE end. Water depths range between 25 to 50m; maximum depths reach 100m at sinkholes. Bellona is about 60% as large as Little Bahama Bank, a well-studied platform for suspension and shedding events driven by atmospheric forcing.  In late March 2006, Cyclone Wati moved W as a Category 2 storm to near the NW lobe of Bellona Plateau. It stalled there March 21-22 as it intensified to Category 4. Wati then moved SE along the long axis of Bellona Plateau, varying between Category 3 and Category 4. Following the transit of Wati, resuspension of benthic carbonate sediments by accelerated bottom currents made the entire plateau observable in visible satellite remote sensing images. A March 25 MODIS-Aqua image clearly shows the plateau, in 100% suspension phase, and several sediment plumes moving off-bank to the NE and SW. Suspended CaCO₃ was visible over Bellona until March 27-28. This event’s areal extent is the largest CaCO₃ suspension/shedding occurrence ever observed, in terms of both total area and total carbonate volume. It holds major implications for CO₂ cycling in the Coral Sea and Western Tropical Pacific. Oceanographic modeling of Wati, using the GLobal Oceans ReanalYsis and Simulation (GLORYS12 v1) model employing the NEMO Ocean General Circulation Model, indicated that induced current velocities on the plateau reached a maximum between 0.2 and 0.3 m/s at 50m depth, and a maximum of ~0.2 m/s at 100m depth. These new data are important for estimating CaCO₃ sediment resuspension and shedding (net shallow-to-deep flux) and transport potential from large sources during major tropical storm system events, in both the tropical Atlantic and Pacific. This is a primary research goal of the Continuous Orbital Remote Sensing of Archipelagic Geochemical Events (CORSAGE) research group.