Hurricane induced spatial and temporal variation in salinity in a semi-enclosed subtropical Estuarine Bay

Hurricane Irma (2017) induced severe flooding in South Florida due to heavy rainfall and storm surge. However, little is known about the spatiotemporal variation of salinity and the fate of the canal water in the semi-enclosed bay along the southeastern Florida coast. The impacts of wind and heavy rainfall on freshwater plume, salinity distribution, and water column stratification during this extreme event also remain poorly understood. Using rigorous numerical simulations and sensitivity tests, we quantified the relative contributions of canal discharge and rainfall to salinity variations in Biscayne Bay. Results show that freshwater released from canals produced salinity changes of up to 20 psu, whereas rainfall caused a maximum reduction of approximately 8 psu. Canals delivered freshwater that accounted for up to 90% of salinity changes near the shoreline, while rainfall contributed more than 90% in deeper depth and in regions closer to open ocean. Lagrangian particle tracking revealed that particles released during strong easterly winds had relatively short residence times in the bay (approximately 1–5 days), whereas particles released during northwesterly winds remained in the bay for longer periods. These results demonstrate that wind forcing associated with Hurricane Irma accelerated canal water flushing and induced spatially variable stratification in the bay.