.
Weekly Seminar

Home
Weekly Seminar

Annual Symposium

CEAFM Dual Degree Program
Members

Contact

Weekly Seminar: Fall 2017

Speaker: Dr. Navid Constantinou (Scripps Institution of Oceanography, UCSD)
Title:
"Eddy Saturation in a Barotropic Model"
Hosted By: Thomas Haine (EPS)

Date: Friday, October 13, 2017
Time: 11:00 a.m.
Location: Hodson Hall 210


Abstract

‘Eddy saturation’ refers to a regime in which the total zonal volume transport of an ocean current is insensitive to the wind stress strength; the Antarctic Circumpolar Current (ACC) is the most prominent example. Baroclinicity is currently believed to be key to the development of an eddy-saturated state. Here, we show that eddy saturation can occur in a barotropic flow over topography, without baroclinic- ity. We demonstrate that in this model the main factor controlling the appearance or not of eddy saturated states is the structure of geostrophic contours, that is the contours of f/H, with f the Coriolis parame- ter and H the depth. Eddy saturated states occur when the geostrophic contours are open, that is when the geostrophic contours span the whole zonal extent of the domain. We demonstrate this minimal requirement for eddy saturated states in a scenario relevant to the ACC using numerical integrations of a single-layer quasi-geostrophic flow over two different topographies characterized by either open or closed geostrophic contours. With open geostrophic contours we find a turbulent regime with impres- sive eddy saturation: only 4-fold transport increase over 60-fold wind stress increase. Furthermore, in the eddy saturation regime (i) the eddy kinetic energy increases linearly with wind stress and also (ii) the mean transport increases with increasing Ekman drag. Both these feature are further ‘symptoms’ of eddy saturation seen in comprehensive models of the ACC. Finally, we extend the stability method of Hart [J. Atmos. Sci., 36, 1736–1746, (1979)] to explain the flow transitions that occur in the solutions with open geostrophic contours.

Bio

Navid Constantinou studied physics at the National and Kapodistrian University of Athens in Greece. He obtained his Ph.D. in March 2015 under the supervision of Prof. Petros J. Ioannou on the formation of large-scale structures in planetary atmospheres. Since September 2015, he is a NOAA Climate & Global Change postdoctoral fellow working with Prof. Bill Young at Scripps Institution of Oceanography, UC San Diego.



Upcoming Seminar

Speaker: Prof. Amy Shen (Okinawa Institute of Technology)
Title: "Viscoelastic and Inertial Instabilities in Microfluidic Flows"

Date: October 27, 2017
Time: 11:00 a.m.
Location: Hodson Hall 210

» More information »