Low Salinity, High Ocean Heat Content, and Warm Core Eddy Effects on the Upper Ocean Response During Hurricane Sally (2020): An Analysis of a Hurricane Glider Observations and Coupled Atmosphere-Ocean Model

Abstract

On 15 September 2020, Hurricane Sally traveled within ∼32 km from the location of Seaglider SG601 of the National Oceanographic and Atmospheric Administration/National Weather Service/National Data Buoy Center (NOAA/NWS/NDBC) in the northern Gulf of Mexico (GoM). Data from SG601 were used to examine the changes in the upper 100 m of the ocean under Hurricane Sally winds. In this study, we show a 0.5–1°C cooling of the surface layer, recorded on the day of closest approach (D_CA) of the glider to Hurricane Sally. We also found that freshwater from river discharge created an upper ocean barrier layer, which reduced the cooling of surface (or mixed) layer temperature by 38.6%. The high barrier layer potential energy (BLPE) together with the high buoyancy frequency squared (N²), prior to 15 September, indicated a very stable water column. Further analysis shows the interaction between SG601, Hurricane Sally, and a warm core Loop Current (LC) eddy in the northern GoM. Findings presented in this study also show that ocean models do not effectively simulate river discharge (plume) in the northern GoM.