Transient Quasi-Zonal Jets Impact Transport and Mixing Processes in the Ocean

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Transient Quasi-Zonal Jets Impact Transport and
Mixing Processes in the Ocean
O. Melnichenko1, N. Maximenko1, and H.
Sasaki2 1IPRC, 2JAMSTEC
Low-frequency motions in the eastern part of the
Pacific Ocean include distinct multiple,
alternating quasi-zonal jet-like features
(striations), which propagate slowly at about 0.3
km/day toward the equator (Fig.1). While
satellite observations of the striations (Fig.
1a) are limited to the sea surface,
high-resolution ocean models, such as the Ocean
General Circulation Model for the Earth Simulator
or OFES (Fig.1b), provide a unique opportunity to
explore their vertical structure. The composite
cross-section of propagating striations in the
eastern North Pacific, constructed from the OFES
solution, reveals the signature of baroclinically
growing disturbances, tapping energy from the
large-scale flow (Fig. 2). Zonal fluxes of water
properties, induced by such features, are
fundamentally different from and may largely
exceed traditional mixing by mesoscale eddies,
and therefore must be incorporated in
parameterizations of mixing processes in
coarse-resolution climate models.
Fig. 1. Latitude-time diagram of the zonal sea
surface velocity anomaly (cm/s) in the eastern
Pacific from (a) satellite data and (b) OFES
hindcast. Zonal average over 150130W and
130110W is applied in the Northern and Southern
Hemispheres, respectively.
Fig. 2. Vertical structure and energetics of
transient striations in the eastern North Pacific
according to the OFES solution (a) Zonal
velocity (cm/s, color) and potential density
(contours contour interval 0.01 kg/m3). Solid
(dashed) contours correspond to positive
(negative) potential density anomaly. (b)
Baroclinic energy conversion from the mean
density field to the zonal striations (10-7
kg/m/s3).