Bottom Mixing Enhanced by Tropical Storm-Generated Near-Inertial Waves Entering Critical Layers in the Straits of Florida

Lixin Qu , Leif Thomas , Jonathan Gula (1, 2)

1 IUF - Institut universitaire de France
2 LOPS - Laboratoire d'Océanographie Physique et Spatiale

Tropical storms and hurricanes frequently pass over the Straits of Florida, energizing the near-inertial wave (NIW) field in the strait. Two ship-based surveys, which were launched shortly after storms, observed velocity shear bands over the western slope of the strait—clear signatures of NIWs. Also, the hydrographic measurements demonstrate the formation of a slantwise critical layer (where isopycnals are parallel with bathymetry) over the western slope, which is known to be a trapping zone for NIWs. A realistic simulation of the Straits confirms the emergence of NIWs under a tropical storm, which is accompanied by inertially modulated bottom-enhanced mixing over the western slope. The mechanism driving the mixing is that the storm-generated NIWs radiate downward from the core of the Florida Current, reflect off the eastern slope, and enter the slantwise critical layer over the western slope; upon entering, wave trapping, and amplification lead to the enhanced mixing.

Domaines: Planète et Univers [physics]; Sciences de la Terre

Lixin Qu, Leif Thomas, Jonathan Gula. Bottom Mixing Enhanced by Tropical Storm-Generated Near-Inertial Waves Entering Critical Layers in the Straits of Florida. Geophysical Research Letters, 2021, 48, ⟨10.1029/2021GL093773⟩. ⟨insu-03683260⟩