Abstract
Based on the eddy-resolving Four-dimensional variational Ocean Re-Analysis for the Western North Pacific over 30 years (FORA-WNP30) product, this study investigates the seasonal evolution of mesoscale eddy characteristics and underlying mechanisms in the Kuroshio Extension (KE) region. In the upstream region, eddies are stretched in the zonal direction and characterized by higher activity in summer and autumn. Energy analysis illustrates that baroclinic instability associated with the horizontal buoyancy flux is responsible for the seasonal variability. In the downstream region, in comparison, eddies tend to be stretched in the meridional direction. Eddy kinetic energy (EKE) level in this region is mainly regulated by the upstream through pressure work. During 1993–2013, the EKE level does not change in the upstream region but it depicts an increasing trend in the downstream region. This evolution reflects the decadal variability of the KE system associated with the Pacific Decadal Oscillation.
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Data availability
The datasets generated and/or analyzed in the current study are available from the corresponding author on reasonable request. The following datasets are used for the analysis: FORA-WNP30 dataset is downloaded from http://synthesis.jamstec.go.jp/FORA/e/, and JRA-55 is downloaded from https://rda.ucar.edu/datasets/ds628.1/. Satellite data is sourced from https://www.aviso.altimetry.fr/ and ECMWF ERA5 is sourced from https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-single-levels-monthly-means?tab=overview. The climate index of PDO is sourced from https://www.ncei.noaa.gov/pub/data/cmb/ersst/v5/index/ersst.v5.pdo.dat.
Code availability
Codes for the energy budget can be available from the corresponding author.
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Acknowledgements
This work has been carried out at Physical Oceanography Laboratory/Ocean University of China, China. The authors would like to thank the laboratory for providing all the needed support to carry out this research. All the analysis and plotting are done in MATLAB.
Funding
This research is supported by the National Natural Science Foundation of China (42176006, 42076009, and 41922039) and Fundamental Research Funds for the Central Universities (202241006 and 202072001).
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Yang, C., Yang, H., Chen, Z. et al. Seasonal variability of eddy characteristics and energetics in the Kuroshio Extension. Ocean Dynamics 73, 531–544 (2023). https://doi.org/10.1007/s10236-023-01565-9
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DOI: https://doi.org/10.1007/s10236-023-01565-9