INSTABILITY AND MIXING OF ZONAL JETS ALONG THE WEST ANTARCTIC PENINSULAR CONTINENTAL SHELF BREAK
Alon A Stern, New York University, New York, NY, United States, David Holland, New York University, Courant Institute of Mathematical Sciences, New York, NY, United States and Louis-Philippe Nadeau, Université du Québec à Rimouski, Institut des sciences de la mer de Rimouski, Rimouski, QC, Canada
Abstract:
The interaction between the Antarctic Circumpolar Current and the West Antarctic Peninsula continental shelf break is considered using eddy-permitting simulations of a quasi geostrophic and a primitive equation model with an idealized experimental setup. Results show the development of a zonal jet which forms over the sloping topography of the continental shelf break. The exchange of water across the continental shelf break displays a low frequency variability which is intrinsically linked to the dynamics of this shelf-break jet. At statistical equilibrium, an aperiodic jet life cycle is observed: Initially, over a long stable period, an upper-layer jet develops over the shelf break. Once the vertical shear reaches the critical condition for baroclinic instability, the jet becomes unstable, which gives rise to a strong meridional flux of potential vorticity. Most of the cross shelf exchange occurs during these instability events. Once the jet instability occurs, a strong Reynolds stress divergence inversion is observe across the jet center. This inversion causes an acceleration of the one flank of the jet and deceleration of the other, which causes the jet to drift away from the shelf break. After the jet has moved away from the shelf break center, a new jet forms over the shelf break, and the aperiodic cycle repeats.
