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Abstract Extreme precipitation during Hurricane Florence, which made landfall in North Carolina in September 2018, led to breaches of hog waste lagoons, coal ash pits, and wastewater facilities. In the weeks following the storm, freshwater discharge carried pollutants, sediment, organic matter, and debris to the coastal ocean, contributing to beach closures, algae blooms, hypoxia, and other ecosystem impacts. Here, the ocean pathways of land‐sourced contaminants following Hurricane Florence are investigated using the Regional Ocean Modeling System (ROMS) with a river point source with fixed water properties from a hydrologic model (WRF‐Hydro) of the Cape Fear River Basin, North Carolina's largest watershed. Patterns of contaminant transport in the coastal ocean are quantified with a finite duration tracer release based on observed flooding of agricultural and industrial facilities. A suite of synthetic events also was simulated to investigate the sensitivity of the river plume transport pathways to river discharge and wind direction. The simulated Hurricane Florence discharge event led to westward (downcoast) transport of contaminants in a coastal current, along with intermittent storage and release of material in an offshore (bulge) or eastward (upcoast) region near the river mouth, modulated by alternating upwelling and downwelling winds. The river plume patterns led to a delayed onset and long duration of contaminants affecting beaches 100 km to the west, days to weeks after the storm. Maps of the onset and duration of hypothetical water quality hazards for a range of weather conditions may provide guidance to managers on the timing of swimming/shellfishing advisories and water quality sampling. 

Abstract This study investigated how ocean optical properties and solar attenuation may affect the upper ocean temperature structure and ocean heat content (OHC). We employed a realistic three‐dimensional ocean circulation model for the northwestern Atlantic to simulate ocean states during the active Atlantic hurricane season of 2017. Sensitivity experiments were performed by coupling the ocean circulation prediction with either a conventional water type‐based solar attenuation model or an inherent optical properties (IOP)‐based model. Validations against in‐situ ocean temperature observations and remote sensing‐derived OHC showed that ocean simulations using the IOP‐based model outperformed simulations using the conventional water type‐based model in predicting sea surface temperature, upper ocean thermal structure, and OHC. An OHC‐hurricane intensity relationship derived for five major hurricanes in 2017 suggests that the ocean optical properties and the application of an appropriate solar attenuation model are important for the forecast of hurricane intensity. 

Changes in marine carbon cycling due to hurricanes with different intensity and translation speeds have not been systematically investigated. This study uses an idealized coupled physical-biogeochemical model and a suite of model sensitivity analyses to better quantify the relationship between hurricane characteristics and marine property changes, including variations in air-sea carbon flux and partial pressure of carbon dioxide in water (pCO2w). We find that strong (category 4–5), mid-speed (5–8 m/s) storms cause the most carbon flux from the atmosphere to the ocean, and that the relationship between air-sea carbon flux and hurricane properties is non-linear. Climate models that do not consider synoptic-scale, storm-induced physical-biogeochemical coupling may underestimate regional carbon sinks.