Ocean observations under Hurricanes Irma (2017) and Florence (2018): Evolution of the response across the storm wakes

Steven R Jayne, Woods Hole Oceanographic Institution, Physical Oceanography, Woods Hole, MA, United States and Elizabeth Sanabia, US Naval Academy, Department of Oceanography, Annapolis, MD, United States
Ocean observations under two major Atlantic hurricanes at unprecedented spatial and temporal resolution shed new light on upper ocean processes before, during, and after hurricane passage. Arrays of ALAMO profiling floats deployed from US Air Force Hurricane Hunter aircraft across the tracks of Hurricanes Irma (2017) and Florence (2018) collected temperature, salinity, and pressure observations to depths near 300 m every two hours. The inter-comparison of upper ocean responses to each storm yields unique insights into common wake characteristics. Responses were both expected: surface cooling and upper-ocean near-inertial oscillations; and unexpected: consistently greater mixed-layer deepening right of the storm track and strong salinity stratification beneath Irma that inhibited mixing, which points to the criticality of these measurements to accurately identify surface fluxes, forecast hurricane intensity change, and understand ocean heat storage on climate time scales. A mixing depth parameterization well approximates the observed mixed layer depths changes, which may enhance predictability of these storm-induced changes and increase accuracy of hurricane intensity forecasts.