Dept. of Geosciences Colloquium: Eastern Mediterranean boundary current instability and its role in cross-shore transport

Zoom: https://tau-ac-il.zoom.us/j/83294569872?pwd=WmdPUWRPdGVQejIvcXhsQmFJY094UT09

​Abstract:

Surface currents play a critical role in transporting and dispersing buoyant pollutants, such as oil and plastics, and biogeochemicals throughout the ocean, significantly impacting the marine ecosystems. The Eastern Mediterranean (EMED) boundary current is an important constituent of the general circulation in the basin. Although a basin-scale feature, the boundary current is only tens of kilometers wide and a few hundred meters deep, making it challenging for a numerical model to resolve its dynamics adequately. In this presentation, we discuss a realistic regional model of the EMED, with nested grids, that resolves a wide range of motions, from basin scale down to submesoscale (100 m – 10 km), and enables a detailed investigation of the boundary current, including its seasonal variability, instabilities, and interplay with submesoscale motions. Seasonal changes in the boundary current properties – along-slope velocity, salinity, and temperature – will be discussed. The role of bottom drag in destabilizing the boundary current will be analyzed, and the process of surface intensified anticyclonic spiral formation will be elucidated. A kinetic energy (KE) analysis reveals the instability mechanisms responsible for the spiral formation. Further, a coarse-graining analysis demonstrates that the upscale KE fluxes are spatially localized in the spirals whereas the downscale KE fluxes are confined to fronts and filaments at the spiral peripheries. Finally, the seasonal changes in the cross-shore transport by the boundary current and the spiral system coupled with the interior submesoscale currents is shown to explain the observed spatial variability in the chlorophyll concentration offshore the Nile delta, highlighting the influence of submesoscale horizontal stirring on primary production in a nutrient deficient region.

Event Organizer: Dr. Roy Barkan