RAPID: Measuring the distribution and character of sedimentary deposits resulting from Hurricane Ian in Southwest Florida

Tropical cyclones can cause significant change to the coastal zone by eroding and transporting sediments. These sediments can be deposited into coastal sinkholes and offshore blue holes allowing scientists to study long-term hurricane activity. However, it remains poorly understood how sediment transport and deposition can vary due to different storm characteristics. The landfall of Hurricane Ian along the southwest coast of Florida provides an opportunity to study how intense hurricanes move sediments in the coastal zone. Knowing more about storm impacts will help clarify long-term risks associated with hurricanes. This project will study sediment from coastal sinkholes and offshore blue holes in southwest Florida. These data will be used to determine where, how much, and what kind of sediment was deposited from the storm. The results of this study have important implications in terms of coastal response to intense storms. These storms may become more frequent in response to Anthropogenic climate change. More storms may further alter coastal carbon cycling and nutrient flow in marine ecosystems. The Broader Impacts for this project include documenting local flooding patterns and sediment transport pathways that resulted from the storm. This information may be used to identify hazards associated with similar storms in the future. In addition, the project will provide support for an early-career postdoctoral researcher as the lead PI, and students will also participate in the project. Both PIs will work closely with local educators and stakeholders to disseminate the results broadly to the general public. This RAPID response study will examine the geomorphic and sedimentological impacts of the passage of Hurricane Ian on coastal sinkholes and offshore blue holes and the adjacent seafloor. Tropical cyclones can cause significant change to the shorelines and coastal oceans by eroding and transporting sediments. Coastal sinkholes and offshore blue holes can act as natural sediment traps that archive evidence of tropical cyclone sediment transport and have thus been utilized to reconstruct long-term hurricane activity. However, it remains poorly understood how archived deposits vary spatially and how they are expressed in relation to hurricane characteristics (e.g., intensity, translation speed) as relatively few hurricanes have impacted sites with sinkhole reconstructions in recent history. Hurricane Ian presents an exceptional opportunity to assess the sedimentary structure and composition of event deposits in a number of sinkholes and offshore blue holes along the coast most heavily impacted by the storm (Sarasota to Naples). By characterizing recent, minimally reworked or degraded deposits from a hurricane of known characteristics (i.e., intensity, track, translation speed, size), scientists can better constrain how paleo-hurricane deposits are related to local storm intensity. Further, significant offshore particulate organic matter export occurred as a result of Ian based on spatially and temporally constrained plumes captured in satellite imagery. Blue hole sediment records in The Bahamas contain organic rich layers atop coarse sediment beds attributed to hurricane driven transport, but the causality of these organic carbon rich beds has never been directly linked to event deposits in sinkholes and blue holes. Given that the post-Ian organic matter plumes intersect many offshore blue holes and terrestrial sinkholes, this is an ideal place and time to test this hypothesis by assessing transport potential, settling time, and provenance in the wake of hurricanes. The results of this study will improve understanding of hurricane-induced sediment transport, which will provide context for identifying and interpreting event beds deposited in sinkholes and offshore blue holes. This work will also begin to quantify hurricane-induced offshore organic sediment flux and provenance, which has important implications for understanding long-term coastal carbon cycling in coastal areas prone to hurricane strikes. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.