E. Zambianchi et al.
46
a
Fig. 5. a Subsurface float trajectories in the PSSO March 1994 through August 1996. Dots
represent surfacing locations (every 30 days). b Lagrangian velocities estimated from subsurface float observations, c Surface and subsurface Lagrangian velocities averaged over
méridional bins of 5 degrees
subsurface data can be that of méridional averages as shown in Fig. 5c, which
again confirms the strong coupling between surface and subsurface fields.
To compare our findings with published data, it has to be kept in mind that the
area in the Southern Océan where the vertical structure of the velocity in correspondence of the ACC has been most extensively investigated is the Drake Passage
([12, 31, 32]; for a review, see [4]). In current meter data a significant corrélation
has been found down to depths of 2000 m and more [12]. This is also mirrored in
the global analysis carried out in [8] on historical hydrographie data, as well as in
[7]. In particular, Fig. 5a of [8] shows normalized geostrophic velocities relative to
3000 dbar for different station pairs in the southeastern PSSO, from which
geostrophic velocities around 1000 m resuit of the order of a 0.2-0.4 fraction of
those at the surface; this ratio is of the same order as our comparison between
surface and subsurface Lagrangian measurements of the flow field.
46
a
Fig. 5. a Subsurface float trajectories in the PSSO March 1994 through August 1996. Dots
represent surfacing locations (every 30 days). b Lagrangian velocities estimated from subsurface float observations, c Surface and subsurface Lagrangian velocities averaged over
méridional bins of 5 degrees
subsurface data can be that of méridional averages as shown in Fig. 5c, which
again confirms the strong coupling between surface and subsurface fields.
To compare our findings with published data, it has to be kept in mind that the
area in the Southern Océan where the vertical structure of the velocity in correspondence of the ACC has been most extensively investigated is the Drake Passage
([12, 31, 32]; for a review, see [4]). In current meter data a significant corrélation
has been found down to depths of 2000 m and more [12]. This is also mirrored in
the global analysis carried out in [8] on historical hydrographie data, as well as in
[7]. In particular, Fig. 5a of [8] shows normalized geostrophic velocities relative to
3000 dbar for different station pairs in the southeastern PSSO, from which
geostrophic velocities around 1000 m resuit of the order of a 0.2-0.4 fraction of
those at the surface; this ratio is of the same order as our comparison between
surface and subsurface Lagrangian measurements of the flow field.