t
•
272
Theory of the Ventilated Thermocline
Fig. 4.12.7a--d. As in Fig. 4. 12.6 except for the fields of a passive tracer and potential vorticity. a
and b are the isolines of tracer concentration and age for the coarse and fine grid resolution
calculations, respectively; c and d are for the potential vorticity
the gyre that originate at the outcrop line. These streamlines flow southward
and pull away from the eastern boundary, leaving exposed there a zone of
weak flow that we recognize as the region of the shadow zone. Further west in
the layer there is a region of streamlines which close through the western
boundary layer, and which we identify with the western pool region of
unventilated fluid.
A passive tracer with a half-life decay equal to that of tritium (12.3 years) is
injected into the surface layer of the model and carried along during the
experiment. Panels a and b of Fig. 4.12. 7 show the isolines of tracer age
(measured from time of injection) on the same density surface as in Fig. 4.12.6.
In both the coarse- and fine-resolution experiments it is easy to distinguish the
ventilated region, by the tongue of fluid in which the tracer age is less than 6.5
years, from the shadow zone and the unventilated western pool where the
•
272
Theory of the Ventilated Thermocline
Fig. 4.12.7a--d. As in Fig. 4. 12.6 except for the fields of a passive tracer and potential vorticity. a
and b are the isolines of tracer concentration and age for the coarse and fine grid resolution
calculations, respectively; c and d are for the potential vorticity
the gyre that originate at the outcrop line. These streamlines flow southward
and pull away from the eastern boundary, leaving exposed there a zone of
weak flow that we recognize as the region of the shadow zone. Further west in
the layer there is a region of streamlines which close through the western
boundary layer, and which we identify with the western pool region of
unventilated fluid.
A passive tracer with a half-life decay equal to that of tritium (12.3 years) is
injected into the surface layer of the model and carried along during the
experiment. Panels a and b of Fig. 4.12. 7 show the isolines of tracer age
(measured from time of injection) on the same density surface as in Fig. 4.12.6.
In both the coarse- and fine-resolution experiments it is easy to distinguish the
ventilated region, by the tongue of fluid in which the tracer age is less than 6.5
years, from the shadow zone and the unventilated western pool where the