Sack Lunch Seminar (SLS) – Leif Thomas (Stanford)

Enhanced vertical exchange and mixing driven by the interaction of near-inertial motions and baroclinic currents

Wind-driven inertial motions and baroclinic currents are ubiquitous features of the ocean circulation that often interact. These interactions involve fascinating physics with implications for the transport and mixing of tracers. In this seminar, I will describe theoretical, numerical, and observational work focusing on two particular interactions.

The first involves a study of inertial motions with surface fronts, motivated by observations of freshwater fronts on the Texas-Louisiana shelf forced by diurnal sea breezes, which are near-resonant with respect to the local inertial frequency. The interaction between the two types of motion results in inertially-modulated frontogenesis and secondary circulations that enhance the exchange of surface and bottom waters, with potential impacts on the evolution and spatial structure of the hypoxic waters that can be found in the region.

The second study focuses on mixing in bottom boundary layers caused by the trapping of near-inertial waves (NIWs) in baroclinic currents under certain conditions. In particular, when isopycnals run parallel to the bottom slope, a slantwise critical layer is formed where downward-propagating NIWs are trapped, amplified, and generate turbulence. It is not unusual to find flows in the ocean that satisfy these conditions (examples include dense overflows or currents that experience Ekman arrest and upwelling). I will describe two such examples, one on the Texas-Louisiana shelf, the other in the Straits of Florida, and discuss the impacts on mixing of bottom waters.

About this series: The Atmosphere, Ocean and Climate Sack Lunch Seminar Series is an informal seminar series within PAOC that focuses on more specialized topics than the PAOC Colloquium. Seminar topics include all research concerning the science of atmosphere, ocean and climate. The seminars usually take place on Wednesdays from 12-1pm. The presentations are either given by an invited speaker or by a member of PAOC and can focus on new research or discussion of a paper of particular interest. Contact: sacklunch-committee@mit.edu