Interannual to Decadal Variations of Submesoscale Motions around the North Pacific Subtropical Countercurrent

Type Article
Date 2020-09
Language English
Author(s) Sasaki Hideharu1, Qiu Bo2, Klein Patrice3, 4, Sasai Yoshikazu5, Nonaka Masami1
Affiliation(s) 1 : Application Laboratory, Japan Agency for Marine-Earth Science and Technology, Yokohama, Kanagawa 236-0001, Japan
2 : Department of Oceanography, University of Hawai‘i at Manoa, Honolulu, HI 96822, USA
3 : California Institute of Technology, Pasadena, CA 91125, USA
4 : Laboratoire d’Océanographie Physique et Spatiale, Centre National de la Recherche Scientifique, Ifremer, Plouzané 29280, France
5 : Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa 237-0061, Japan
Source Fluids (2311-5521) (MDPI AG), 2020-09 , Vol. 5 , N. 3 , P. 116 (15p.)
DOI 10.3390/fluids5030116
Note This article belongs to the Special Issue Submesoscale Processes in the Ocean
Keyword(s) submesoscale motion, interannual to decadal variations, mixed layer instability, North Pacific Subtropical Countercurrent
Abstract

The outputs from a submesoscale permitting hindcast simulation from 1990 to 2016 are used to investigate the interannual to decadal variations of submesoscale motions. The region we focus on is the subtropical Northwestern Pacific including the subtropical countercurrent. The submesoscale kinetic energy (KE) is characterized by strong interannual and decadal variability, displaying larger magnitudes in 1996, 2003, and 2015, and smaller magnitudes in 1999, 2009, 2010, and 2016. These variations are partially explained by those of the available potential energy (APE) release at submesoscale driven by mixed layer instability in winter. Indeed, this APE release depends on the mixed layer depth and horizontal buoyancy gradient, both of them modulated with the Pacific Decadal Oscillation (PDO). As a result of the inverse KE cascade, the submesoscale KE variability possibly leads to interannual to decadal variations of the mesoscale KE (eddy KE (EKE)). These results show that submesoscale motions are a possible pathway to explain the impact associated with the PDO on the decadal EKE variability. The winter APE release estimated from the Argo float observations varies synchronously with that in the simulation on the interannual time scales, which suggests the observation capability to diagnose the submesoscale KE variability.

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