TY - JOUR
T1 - Instability and mixing of zonal jets along an idealized continental shelf break
AU - Stern, Alon
AU - Nadeau, Louis Philippe
AU - Holland, David
N1 - Publisher Copyright:
© 2015 American Meteorological Society.
PY - 2015
Y1 - 2015
N2 - The interaction between an Antarctic Circumpolar Current-like channel flow and a continental shelf break is considered using eddy-permitting simulations of a quasigeostrophic and a primitive equation model. The experimental setup is motivated by the continental shelf of the West Antarctic Peninsula. Numerical experiments are performed to study how the width and slope of an idealized continental shelf topography affect the characteristics of the flow. The main focus is on the regime where the shelfbreak width is slightly greater than the eddy scale. In this regime, a strong baroclinic jet develops on the shelf break because of the locally stabilizing effect of the topographic slope. The velocity of this jet is set at first order by the gradient of the background barotropic geostrophic contours, which is dominated by the slope of the topography. At statistical equilibrium, an aperiodic 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 and drifts away from the shelf break. The cross-shelf mixing is intrinsically linked with the jet drifting, as most of the meridional flux occurs during this instability period. Investigation of the zonal momentum budget reveals that a strong Reynolds stress divergence inversion across the jet is associated with a drifting event, accelerating one flank of the jet and decelerating the other. The hypothesis that jet drifting may be due to one flank of the jet being more baroclinically unstable than the other is tested using topographic profiles with variable curvatures.
AB - The interaction between an Antarctic Circumpolar Current-like channel flow and a continental shelf break is considered using eddy-permitting simulations of a quasigeostrophic and a primitive equation model. The experimental setup is motivated by the continental shelf of the West Antarctic Peninsula. Numerical experiments are performed to study how the width and slope of an idealized continental shelf topography affect the characteristics of the flow. The main focus is on the regime where the shelfbreak width is slightly greater than the eddy scale. In this regime, a strong baroclinic jet develops on the shelf break because of the locally stabilizing effect of the topographic slope. The velocity of this jet is set at first order by the gradient of the background barotropic geostrophic contours, which is dominated by the slope of the topography. At statistical equilibrium, an aperiodic 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 and drifts away from the shelf break. The cross-shelf mixing is intrinsically linked with the jet drifting, as most of the meridional flux occurs during this instability period. Investigation of the zonal momentum budget reveals that a strong Reynolds stress divergence inversion across the jet is associated with a drifting event, accelerating one flank of the jet and decelerating the other. The hypothesis that jet drifting may be due to one flank of the jet being more baroclinically unstable than the other is tested using topographic profiles with variable curvatures.
KW - Atm/Ocean Structure/Phenomena
KW - Circulation/Dynamics
KW - Geographic location/entity
KW - Instability
KW - Mixing
KW - Models and modeling
KW - Ocean dynamics
KW - Potential vorticity
KW - Quasigeostrophic models
KW - Southern Ocean
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U2 - 10.1175/JPO-D-14-0213.1
DO - 10.1175/JPO-D-14-0213.1
M3 - Article
AN - SCOPUS:84945915836
SN - 0022-3670
VL - 45
SP - 2315
EP - 2338
JO - Journal of Physical Oceanography
JF - Journal of Physical Oceanography
IS - 9
ER -