Walsh, Mapping climatological seasonal variations of surface currents in the tropical Atlantic using ship drifts, Journal of Geophysical Research , 91 , Schott, F. Brandt, M. Hamann, J. Fischer, and L. Wilson, W. Johns, and R. Monthly absolute geostrophic currents are calculated using the P-vector inverse method 1 , The P-vector method is under the assumptions of geostrophy, Boussinesq approximation, and conservation of potential density and potential vorticity.
No motionless level is assumed in the geostrophic current calculation. The interannual anomalies of the geostrophic transport are calculated based on the — climatology and low passed by a 4th-order Butterworth filter with a cutoff period of 13 months.
A linear continuously stratified model LCSM of ocean circulation is used to simulate the equatorial circulation in the Pacific Ocean. The model is the same as that used by Yuan and Han 19 and Yuan et al. The eigenfunctions baroclinic mode functions are not sensitive to the density profiles averaged over the different latitudinal bands of the equatorial Pacific Ocean.
The shallow water equations SWEs of each baroclinic mode are solved on a 0. The model is forced by the mean wind stress averaged from the monthly ERA interim data from to The integration starts from a motionless state and is spun-up for years. The horizontal Rayleigh friction and Newtonian cooling coefficients are set at 1.
Li is supported by NSFC He obtained funding to support the cruises and research, designed and implemented the cruise experiments, and oversaw the data analyses. Publisher's note. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
National Center for Biotechnology Information , U. Sci Rep. Published online Jul Author information Article notes Copyright and License information Disclaimer. Dongliang Yuan, Email: nc. Corresponding author. Received Jan 9; Accepted Jun Subject terms: Physical oceanography, Physical oceanography.
Open in a separate window. Figure 1. Geostrophic currents The Argo absolute geostrophic currents based on the P-vector calculation 1 equivalent to beta-spiral under the geostrophy and Bousinessq approximations show the existence of the NESC across the entire basin of the tropical North Pacific Ocean Fig. Figure 2. Figure 3. Figure 4. Figure 5. Conclusion In this paper, the structure, water mass properties, and dynamics of the NESC are investigated. Methods Mooring data Ocean current measurements from a deep mooring are used in this study.
Article Google Scholar. Fleming, J. I- B King, J. Fish Wildlife Serv Spec. Knauss, J. Austin, T. Fish Wildlife Serv. Koninklijk Nederlands Meteorologisch Institut, No. Navy Hydrographic Off.
Download references. You can also search for this author in PubMed Google Scholar. Here, the equatorial countercurrent exists year-round, and is strongest in the fall and winter, with speeds slightly.
In both the Pacific and Atlantic the equatorial countercurrent is located farthest north in the fall, centered near 8 degrees north. In the Indian Ocean, the countercurrent is present only during the winter. There are large month-to-month changes in the strengths of the Pacific and Atlantic equatorial coun-tercurrents.
The changes are most pronounced during fall in the Pacific, and during summer in the Atlantic, and are associated with clockwise rotating eddies centered between the equatorial countercurrent and the South Equatorial Current to the south. The eddies move westward, driven by the contrast in temperature and flow between the equatorial countercurrent and the South Equatorial Current.
Over an entire season, they act to decrease the strength and temperature of the equatorial countercurrent.
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