Storm-Reverse Weathering

Hurricane Ida moved through the Mississippi Delta and adjacent Louisiana shelf at the end of August 2021. The storm was similar in magnitude, areal extent, and landfall position (Cocodrie, LA) to the category 4 Hurricane Gustav in September 2008. Ida, a much stronger storm than either Hurricanes Harvey or Nate in 2017, likely introduced a significant quantity of oxygen into the sediment of the proximal coastal zone, perhaps enough to turn most of the top ~1 m of the sediment column oxic. We hypothesize that the change in redox and diagenetic conditions initially favored burial of bSi as unaltered opal rather than an authigenic aluminosilicate. Thirteen days prior to Ida’s landfall in Port Fourchon, LA (~45 km east of Cocodrie), we collected sediment cores at three sites in the topset delta sediment between the Southwest Pass (major Mississippi River distributary) and Cocodrie, LA aboard the R/V Pelican; all sites experienced Category 4 hurricane conditions from Ida with maximum sustained winds of 130 knots (67 m/s). The timing of our prior cruise provides a unique opportunity, which is near impossible to plan for with a traditional project, to revisit these sites and quantify the impact of Hurricane Ida on the fate of sediment biogenic silica (i.e., modality between sequestration types) as the system resets in the following months (e.g., single-day cruises in fall 2021, and winter, spring 2022) .