Hurricanes are among the major natural disasters facing the coastal United States. Hurricane waves, their associated surges and coastal inundations can be studied and monitored using wave models. The choice of wind forcing, numerical schemes, and grid configuration could significantly affect the accuracy of the model prediction and hinder our understanding of these extreme events. A spectral wave model (WAVEWATCH III) was used to study Hurricane Ida (2021) to reveal how applied wind forcing, grid resolution, and boundary conditions affect model fidelity. To properly resolve coastal geometrics and hydrodynamics, we set up three unstructured grids for the Gulf of Mexico (GOM) with different configurations ranging from 260,000 to 90,000 grid nodes. We used two wind forcings, European Center for Medium-Range Weather Forecasts (ECMWF) (9km-resolution), and ECMWF Reanalysis (ERA5) (28km-resolution). The simulations were run with and without incorporating boundary conditions around the open boundaries of the GOM. The results were validated against several buoys data in the GOM. Our sensitivity analysis showed that the model is most sensitive to wind forcing and least sensitive to grid resolution. The differences in simulation results were mostly found in the wave period and direction. Simulations without boundary conditions showed some relatively poor performance in predicting the peak period and mean wave direction but predict the mean wave period better than those with boundary conditions. While simulations forced by ECMWF overestimated the significant wave height (SWH) and mean period as Ida passes, those forced by ERA5 underestimated the SWH.

Animals living in sediments (infauna) drastically modify the physical characteristics of their sediment habitats through ingestion and egestion, locomotion and tube and burrow formation. Infauna can secrete mucus that compacts sediment leading to an increase in sediment strength. Infauna can also increase localized porosity by excavating sediment, burrowing and disrupting sediment structure, or pumping water into the sediment. The accumulation of these activities can change sediment stability, making it more or less resistant to erosion from hydrodynamic stress or compaction or failure under loads, e.g., from objects or structures on the seafloor. This study aims to analyze how the benthic community influences sediment stability by sampling sediment communities with differing sediment physical properties. The York River Estuary, Chesapeake Bay, has a natural gradient in salinity and physical forcings. Historically, the less saline, high flow regions of the York River Estuary contain mostly burrowing bivalves that pump water to the surface. Saltier areas closer to the Chesapeake Bay with less river flow but more waves have more infauna that create burrows and rework the sediment. We predict that the pumping and burrowing activity of burrowing bivalves will increase porosity and destabilize the sediment. More sediment compaction by burrowers will result in increased cohesion resulting in greater stability. We also expect sites with more infaunal activity to have greater variability in sediment properties. The sediment community will be compared with measures of sediment physical properties and the impacts of fauna will be integrated into a framework for characterizing the stability of sediments.

The refractive index (RI) of microbes is determined through its cellular composition. Knowledge of the internal variability of RI not only reveals the structure within these organisms but is also essential to optically modeling them as well interpreting these models. Due to technical limitations, current knowledge of the RI of these microbes is very limited. The Nanolive 3D Cell Explorer is a high precision tomographic microscope that maps the internal structures through their RI based on a rotational interferometric technique to create holographic images. The instrument was calibrated and validated in the lab using materials with known RI values. We measured the RI of marine microbes in near surface waters collected during two experiments, NASA EXPORTS in the North Atlantic in May of 2021 and a pre-PACE cruise in the GoM in March of 2022. In the collected samples, several microbial groups were identified, including Dinoflagellates, Diatoms, and Cilliates. The internal structures can be clearly differentiated based on RI and a general trend in terms of RI values was observed (chloroplast > membrane). For the external membrane, we were able to identify their composition (Calcium Carbonate vs Silica) based on their measured RI values. We were able to differentiate zooplankton, bacteria, and flocculates composed of sediment and oil as well. To the best of our knowledge, this is the first time that the internal variations of refractive index within microbes is being directly measured. These results will allow us to better model the optical properties of these marine particles.