Transcript Slide 1

Wind-Forced Baroclinic β-Plumes and
the Hawaiian Lee Counter-Current
A. Belmadani1, N. Maximenko1, O. Melnichenko1, N. Schneider1, and E. Di Lorenzo2
1IPRC, 2Georgia
32°
N
(a)
(b)
30°
N
28°
N 174°E
28°
N
174°
W
162°
W
150°
W
(c)
(d)
20°
N
12°
N
28°
N
140°E
160°E
180°E
160°
W
(e)
20°
N
12°
N
140°E
160°E
180°E
160°
W
Mean Zonal Transport (m2/s) in (a) ROMS and (c) OFES. Mean Zonal
Velocity (cm/s) in (b) ROMS and (d) OFES along vertical sections indicated
by the dashed lines in (a) and (c) respectively. OFES currents were filtered
in space to remove the large-scale flow. (e) Mean Deep Zonal Velocity
(cm/s) derived from trajectories of ARGO floats.
Tech
A study of the vertical structure of β-plumes in
an idealized subtropical ocean forced by
localized wind stress curl using the Regional
Oceanic Modeling System (ROMS) shows the
solution is consistent with a theoretical linear
β-plume: a set of zonal jets forms and the
barotropic flow is conserved west of the forcing
region (a). A fact not commonly known about
such a plume is that the baroclinic flow varies
zonally: the surface eastward current weakens
toward the west together with a deepening of
the lower boundary of the plume and the
formation of a deep eastward flow away from
the forcing region (b).
The Hawaiian Lee Counter-Current is thought
to be a surface current induced by the curl
associated with the blocking of the trade winds
by the tall mountains of the Hawaiian Islands.
Simulation with the high-resolution OGCM for
the Earth Simulator (OFES), however, features
barotropic (c) and baroclinic structures (d)
similar to those of the idealized β-plume. In
particular, it shows a deep eastward flow
thousands of miles west of Hawaii, a finding
supported by ARGO float trajectory data (e).