Observations of the upper ocean from autonomous platforms during the passage of extratropical Cyclone Epsilon (2020)

Abstract

Hurricane Epsilon (2020) was a late-season, category-3 tropical cyclone that underwent extratropical transition and became Extratropical Cyclone Epsilon on October 26. The upper ocean response to the passage of the storm was observed by three types of autonomous platforms: an eXpendable Spar buoy, an Air-Launched Autonomous Micro-Observer profiling float, and two Seagliders. Taken together, this array enabled the rare collection of contemporaneous observations of the upper ocean, air-sea interface, and atmospheric boundary layer before, during, and after the passage of the storm. The evidence presented suggests that Extratropical Cyclone Epsilon contributed to breaking down the residual North Atlantic summer stratification regime and accelerated the shift to the prolonged ocean cooling associated with winter. The synergistic capabilities of the observational array are significant for two reasons: (1) by enabling the comparison of complementary atmosphere and ocean observations, taken from different platforms, they permit a comprehensive approach to better understand how storm-induced momentum, heat, and moisture fluxes alter upper ocean structure, and (2) they demonstrate the ability of future, targeted deployments of similar observational arrays to assess the fidelity of coupled ocean-atmosphere-wave numerical prediction models.