PO Lunch Seminar 19 Jan 2022

Wednesday, January 19, 12:30 PM to 01:30 PM PST

RESCHEDULED TO FEB 23

Glider based turbulence observations in the Gulf of Mexico: hot spots and deep Gulf circulation

Sergey Molodtsov
University of Pennsylvania

12:30 P.M., OSB 425 and via Zoom
https://washington.zoom.us/j/92092614769

Abstract
Glider based microstructure observations combined with ship based CTD profiles were collected in two important “hot spots” of elevated mixing in the Gulf of Mexico (GOM). The first “hot spot” is related to the Loop Current Eddy (LCE) activity. Turbulence parameters have been estimated from microstructure velocity and temperature measurements in an anticyclonic Loop Current eddy in the Gulf of Mexico for the very first time. Measurements were performed during a mission in October, 2016, using a G2 Webb Research Slocum ocean glider instrumented with a microstructure sensors suite. Well defined turbulent kinetic energy dissipation rate patterns in the eddy and the surface mixed layer were clearly identified from both the velocity and temperature microstructure data. Double diffusive thermohaline intrusions were detected on the side of the eddy, while the region below the eddy core was more conducive for salt fingering. Heat and salt fluxes associated with these processes suggest that a life span of such an eddy is ~1.5 years.

The second “hot spot” can be found in regions with rough bathymetry. Dynamical processes associated with the bathymetry were observed and enhanced mixing along the continental slope was detected with diffusivity values up to 10-3 m2/s. Based on our results we suggest that slope regions represent locations for deep waters of the GOM to upwell and therefore facilitate ventilation of the deep GOM. Recent studies (Ochoa et al., 2021) proposed a conceptual model of deep GOM circulation where deep waters, entering the GOM, consisting mainly from NADW, sink and fill the deep GOM through the Yucatan channel. We hypothesize that to retain mass balance this continuously supplied deep water has to upwell and create intermediate waters, which form the outflow of the GOM, ventilating the deep GOM on time scales ~100 years. The western GOM has areas with steep continental slopes, providing a likely candidate for the transformation and upwelling of deep waters. Our findings confirm higher mixing values along the slope around the GOM region in support of the proposed theory.

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