Session 3

Wednesday, 18 May 2016, 9:00 AM to 10:30 AM

20 minutes per talk, 10 minutes for questions and speaker change

From	To	Name	Affiliation	Title
9:00am	9:30am	Igor Kamenkovich	RSMAS - University of Miami	Properties and Origins of the Anisotropic Eddy- Induced Transport in the Oceans
9:30am	10:00am	Anthony Kirincich	Woods Hole Oceanographic Institution	The Effects of Submesocale Eddies on Exchange Across the Inner Shelf.
10:00am	10:30am	Irina Rypina	Woods Hole Oceanographic Institution	Investigating the eddy diffusivity concept in the coastal ocean

 

Session 3 Abstracts

Properties and Origins of the Anisotropic Eddy-Induced Transport in the Oceans

Igor Kamenkovich (RSMAS - University of Miami)
This study examines properties and origins of the eddy-induced transport in oceanic flows, using idealized
models of the double-gyre oceanic circulation and altimetry-derived velocities. The transport due to the
time-dependent flow ("eddies") is quantified by a two-dimensional, location-dependent diffusivity tensor,
taking into account modulations by the stationary ("mean") flow. This transport is highly anisotropic, that
is, it has a well-defined direction of the maximum transport. The anisotropy is only partly explained by the
effects of the mean advection, and is in large part due to the eddying field. One component of the timedependent
flow, zonally-elongated large-scale transients (ZELTs), is particularly important for the
anisotropy, as it corresponds to primarily zonal material transport and long correlation time scales. The
mechanism is analogous to shear dispersion, as is further illustrated by idealized simulations of an eddying
zonal flow. The importance of ZELTs is further confirmed by simulations of idealized color dye tracers,
which has important implications for parameterizations of the eddy-induced transport in non-eddyresolving
models.

The Effects of Submesocale Eddies on Exchange Across the Inner Shelf

Anthony Kirincich (Woods Hole Oceanographic Institution)
This work investigates the characteristics and implications of sub-mesoscale variability over the
continental shelf in order to understand the relative importance of lateral mechanisms of exchange and
stirring on the total across-shelf transport. Within the study area south of Martha's Vineyard, USA,
observations of high-resolution HF radar surface currents allow lateral scales as small as 1.5 km to be
resolved within a 30x30 km domain. Coupled with dense observations of subsurface velocity and
hydrography for a 6-month period spanning both stratified and weakly stratified conditions, these
observations were used to document horizontal and vertical scales, occurrences, and drivers of spatiallyvariable
circulation. Coherent vortices, or eddies, driven both by density intrusions and tidal processes
were observed at rates up to 4 per day during the stratified period, with locations and length scales
dependent on wind forcing. Despite being temporally short, with mean durations of 5 hours, based on
volumetric transport rates, these features caused exchange equivalent to the wind-driven depthdependent
exchange.

Investigating the eddy diffusivity concept in the coastal ocean

Irina Rypina (Woods Hole Oceanographic Institution)
We test the validity, utility, and limitations of the lateral eddy diffusivity concept in a coastal environment
through analyzing data from coupled drifter and dye releases within the footprint of a high-resolution (800
m) high-frequency radar south of Martha's Vineyard MA. Specifically, we investigate how well a
combination of radar-based velocities and drifter-derived diffusivities can reproduce observed dye
spreading over an 8-hour time interval. A drifter-based estimate of an anisotropic diffusivity tensor is used
to parameterize small-scale motions that are un- and under-resolved by the radar system. This leads to a
significant improvement in the ability of the radar to reproduce the observed dye spreading.