1. O. Melnichenko1, N. Maximenko1, and H. Sasaki2
Transient Quasi-Zonal Jets Impact Transport and Mixing Processes in the Ocean
O. Melnichenko1, N. Maximenko1, and H. Sasaki2
1IPRC, 2JAMSTEC
Latitude
(a)
(b)
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.
Meridional distance, km
Depth, m
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(b)
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.
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).