Submesoscale Instability in the Straits of Florida

Abstract

The Florida Current (FC) flows in the Straits of Florida (SoF) and connects the Loop Current in the Gulf of Mexico to the Gulf Stream (GS) in the Western Atlantic Ocean. Its journey through the SoF is at time characterized by the formation and presence of mesoscale but mostly submesoscale frontal eddies on the cyclonic side of the current. The formation of those frontal eddies was investigated in a very high resolution two-way nested simulation using the Regional Oceanic Modeling System (ROMS). Frontal eddies were either locally formed or originated from outside the SoF. The northern front of the incoming eddies was susceptible to superinertial shear instability over the shelf slope when the eddies were pushed up against the slope by the FC. Otherwise, incoming eddies could be advected relatively unaffected by the current, when in the southern part of the straits. In absence of incoming eddies, submesoscale eddies were locally formed by the roll-up of superinertial barotropically unstable vorticity filaments when the FC was pushed up against the shelf slope. The vorticity filaments were intensified by the friction-induced bottom layer vorticity flux as previously demonstrated by Gula et al. (2015b) in the GS. When the FC retreated further south, negative vorticity West Florida Shelf waters overflowed into the SOF and led to the formation of submesocale eddies by baroclinic instability. The instability regimes, hence, the submesoscale frontal eddies formation appear to be controlled by the lateral ‘sloshing’ of the FC in the SoF.

Physical Characteristics and Evolution of a Long-Lasting Mesoscale Cyclonic Eddy in the Straits of Florida

“…In addition to the biological and ecological relevance, the CEs in the SoF have been studied in their physical characteristics (e.g., Chew, 1974;Vukovich, 1988;Lee et al, 1992Lee et al, , 1994Lee et al, , 1995Shay et al, 1998Shay et al, , 2000Hitchcock et al, 2005;Parks et al, 2009;Chérubin et al, 2021), statistical characteristics (Zhang et al, 2019), and their relationship with the LC perturbations (e.g., Fratantoni et al, 1998) and the FC meandering (e.g., Lee et al, 1994;Kourafalou and Kang, 2012). Recently, the complex current dynamics in the SoF were explored using high frequency radar, satellite altimetry data, and numerical model output (Liu et al, 2021).…”

Global coarse-grained mesoscale eddy statistics based on integrated kinetic energy and enstrophy correlations

“…Mesoscale eddies (MEs) at spatial scales from approximately 50 up to 500 km are energetic patterns of ocean surface flow fields. The birth of MEs often occurs along shorelines triggered by shear-driven barotropic instabilities or at the edges of surface currents by density-anomaly-driven baroclinic instabilities (Willett et al, 2006;Chelton et al, 2007;Smith, 2007;Badin et al, 2009;Chelton et al, 2011;Faghmous et al, 2015;Marta and Isachsen, 2018;Brach et al, 2018;Pnyushkov et al, 2018;Cetina-Heredia et al, 2019;van Sebille et al, 2020;Chérubin et al, 2021;Wichmann et al, 2021). The observation of mesoscale vortices on global ocean surfaces is usually based on satellite altimetry, which determines local sea surface heights with respect to the geoid by return time analysis of reflected microwave pulses (Stammer and Cazenave, 2017).…”