Transient Quasi-Zonal Jets Impact Transport and
Mixing Processes in the Ocean
O. Melnichenko1, N. Maximenko1, and H. Sasaki2
1IPRC, 2JAMSTEC
Latitude
(b)
Depth, m
(a)
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, highresolution 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.
(b)
(a)
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 150–130W and 130–110W is applied
in the Northern and Southern
Hemispheres, respectively.
Meridional distance, km
Meridional distance, km
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).