Journal Article

Rapid Intensification of Hurricane Ian in Relation to Anomalously Warm Subsurface Water on the Wide Continental Shelf

Law, Jason A., Nickerson, Alexander K., Liu, Yonggang, Weisberg, Robert H., Sorinas, Luis

2025

Overview

Hurricane Ian rapidly intensified from Category 3 to 5 as it transited the wide West Florida Shelf (WFS). This is ascribed to heating by the anomalously warm shelf waters, despite the water depth being shallow when compared to the thicker, mixed layer areas of the deeper ocean. By examining temperature from long‐term moorings, we found that the sea surface and subsurface temperatures exceeded the climatologies by 1–2°C and 2–3°C, respectively. Additionally, these anomalously high temperatures in summer/fall of 2022 were related to the absence of Gulf of Mexico Loop Current interactions with the WFS slope at its “pressure point”. Without such offshore forcing to induce an upwelling circulation, the warmer waters on the shelf were not flushed and replaced by colder waters of deeper ocean origin. This work highlights the importance of subsurface temperature and ocean circulation monitoring on shallow continental shelves, which are largely overlooked in hurricane‐related ocean heat content observational programs. Plain Language Summary Rapid intensification of tropical cyclones can be fueled by upper ocean warm water. The favorable environment of high ocean heat potential is thought to be more likely during marine heatwaves. However, both the hurricane heat potential and marine heatwaves are primarily calculated from satellite‐derived sea surface data, with subsurface data largely overlooked due to lack of in situ measurements, particularly in coastal oceans where hurricanes may rapidly intensify before making landfall. Here we examine an unprecedented set of coastal ocean temperature records from long‐term (26 years) moorings on the wide West Florida Shelf for the cause of Hurricane Ian's rapid intensification to a Category 5 hurricane in 2022. We found that while sea surface temperatures exceeded their climatological mean values by 1–2°C in summer/fall of 2022, the subsurface temperature exceedances were even higher (2–3°C). These anomalously warm waters were further ascribed to a lack of a coastal ocean upwelling circulation due to the absence of offshore forcing by the Gulf of Mexico Loop Current. This work highlights the importance of subsurface temperature and current monitoring on shallow continental shelves, which are largely overlooked in hurricane‐related ocean heat content observing programs. Key Points Hurricane Ian (2022) rapidly intensified over a wide continental shelf with subsurface water 2–3°C warmer than climatology The anomalously warm water was related to the absence of Gulf of Mexico Loop Current interactions with the shelf slope Coastal ocean circulation and subsurface temperature monitoring is important for future hurricane intensification forecasts

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Circulation / Climatological means / Coastal circulation / coastal ocean observing ststem / Coastal waters / Continental shelves / Cyclones / Enthalpy / Gulf of Mexico Loop current / Heat / Heat content / Heat waves / High temperature / Hurricane Ian / Hurricanes / In situ measurement / Loop Current / Marine heatwaves / Mixed layer / Monitoring / Mooring / Ocean circulation / Ocean currents / Ocean temperature / Oceans / Offshore / rapid intensification / Satellites / Sea surface temperature / Subsurface temperatures / Subsurface water / subsurface water temperature / Summer / Temperature / Tropical cyclones / Upper ocean / Upwelling / Warm water / Water circulation / Water depth / Water temperature / West Florida Shelf