Investigation of Eddy - Storm Induced Near Inertial Wave Motions in the Northern Sargasso Sea

James Hilditch1, Maureen H Conte2,3, Rodney J Johnson2, Fernando Pacheco2 and Rut Pedrosa Pamies3, (1)University of Cambridge, Cambridge, United Kingdom, (2)Bermuda Institute of Ocean Sciences, St.George's, Bermuda, (3)Marine Biological Laboratory, The Ecosystems Center, Woods Hole, MA, United States
Near-inertial waves are a very common and well studied occurrence however, investigation of storm induced near-inertial waves is hampered by a lack of synoptic data following storm events. An upward-looking 150 kHz Acoustic Doppler Current Profiler (ADCP) mounted at approximately 300 m depth on the Oceanic Flux Program mooring in the northern Sargasso Sea has surveyed the upper ocean since late 2012, capturing multiple storm events. Here we present a synopsis of the near inertial waves resulting from the passage of four major storms: hurricanes Gonzalo (Oct. 2014, Category 3), Joaquin (Oct. 2015, Category 2), Nicole (Oct. 2016, Category 3) and tropical storm Karl (Sep. 2016). The frequency of these waves varies between events ranging from 1.05 f to 1.2 f, with evidence of a frequency dependence on mesoscale eddy interactions. Vertical wavelengths are in the range of 200-400 m and notably we observe significant shear from the surface down through the upper nutricline capable of inducing deep euphotic and subeuphotic turbulent mixing. We parameterize these inertial dynamics based on the storm forcing characteristics and underlying mesoscale eddy velocities, and further, estimate the consequential diapycnal nutrient fluxes to the euphotic zone.