Ocean Observations Under Two Major Hurricanes: Evolution of the Response Across the Storm Wakes

Abstract

Abstract Hurricanes fundamentally alter the upper ocean thermal structure across millions of square kilometers annually through a medley of complex processes that are not well understood but are critically important to hurricane intensification. High‐resolution, air‐deployed profiling float observations beneath Hurricanes Irma (2017) and Florence (2018) detail storm‐induced changes in upper ocean temperature, salinity, and density structures. This unique and comprehensive data set allows for validation and quantification of results from previous observational and modeling studies, including the time evolution of sea surface cooling and upper ocean near‐inertial oscillations, greater mixed layer deepening right of each storm track, and inhibition of mixing by salinity stratification (beneath Irma). These observations also reveal that storm‐forced upper ocean currents remain remarkably uniform with increasing distance from the radius of maximum winds and result in consistent mixed layer deepening, particularly right of each storm track. These observed ocean mixed layer depth changes are closely approximated by a mixing depth parameterization, which may enhance storm‐forced ocean response predictability and therefore increase hurricane intensity forecast accuracy. Further, these hurricane‐induced upper ocean temperature changes contribute to the evolving nature of hurricanes and ocean heat storage on seasonal and climate time scales.

Keywords

• tropical cyclone
• Hurricane Irma
• Hurricane Florence
• cold wake
• ALAMO observations
• barrier layer