Award: OCE-1760648

The tropical storms can enhance sediment erosion and transport them to the continental shelf where they can get deposited. In the shallow shelf of the northern Gulf of Mexico, storms can also resuspend sediments from the seafloor and redistribute them. To determine the magnitude of new and resuspended sediment deposited in the continental shelf due to Hurricane Harvey, sediment cores were collected from the Louisiana and Texas shelf immediately after the hurricane from approximately 20 stations. These sediment cores were imaged using X-ray radiographic technique. Radiometric analysis for 7Be and 234Thex in the sediments, as well as grain size analysis were also carried out to estimate the newly deposited and redistributed sediments on those cores. The presence of 7Be and 234Thex indicate that about 6 -10 cm of sediment was deposited up to 50m isobath after the passage of hurricane Harvey. Higher disposition of new and/or resuspended sediment was observed near the coast and along the path of the hurricane. The ratio of 234Thex to 7Be in sediments which reflects new vs redistributed sediment, ranged from 0.1 to 8.4 with a gradual increase from shallow coastal to deeper shelf water. This indicates that new deposition was dominant in the continental shelf with 20 m depth and resuspended sediment was dominant in the deeper and farther stations. Assuming a uniform 4 cm thick post hurricane deposition layer across the shelf upto 50m isobath, we estimate that 8.5x109 metric tons of sediment was mobilized shelf wide after the hurricane. This translates to 4.2x107 metric tons of particulate carbon being ejected into water column using the average sediment total organic carbon content of 0.5%. This estimate is of the same order of magnitude as the total particulate organic carbon delivered by the Mississippi and Atchafalaya river on an annual scale and found to impact water column O2 demand, plankton communities and CO2 dynamics in the region. Last Modified: 03/16/2020 Submitted by: Kanchan Maiti