Spatiotemporal variations of the surface Kuroshio east of Taiwan Island derived from satellite altimetry data

Spatiotemporal variation of the surface Kuroshio east of Taiwan Island is investigated by quantitatively analyzing 23-year(1993–2015)sea surface Absolute Dynamic Topography data.The annual mean state of the Kuroshio is shown,with a flow width ~136 km and surface transport ~7.75×10~4 m^2/s.The corresponding standard deviations of these are 28 km and 2.14×10~4 m^2/s.Results of power spectrum analysis indicate that the primary periods of Kuroshio surface transport east of Taiwan Island are 1 and 2.8 years,respectively.Spatially,the Kuroshio surface transport southeast of Taiwan Island has greater variability than that to its northeast.That transport showed strong seasonality,with a maximum 8.8×104 m^2/s in summer and minimum 7.5×10~4 m^2/s in winter,which was mainly caused by local monsoon winds.A linear long-term upward trend of Kuroshio surface transport during 1993–2015 was found,during which the mean,southeast,and northeast of the Kuroshio east of Taiwan Island increased by 0.30×10~4,0.22×10~4 and 0.36×104 m^2/s,respectively.Correlation and composite analysis show that the Philippines-Taiwan Oscillation(PTO)is important in the interannual variability of the Kuroshio.PTO-induced relative intensity of anticyclonic and cyclonic eddies is the dominant influence on the interannual variability of the Kuroshio east of Taiwan Island.

Variability in upper-ocean salinity stratification in the tropical Pacific Ocean

Using a gridded array for real-time geostrophic oceanography(Argo)program float dataset,the features of upperocean salinity stratification in the tropical Pacific Ocean are studied.The salinity component of the squared Brunt-V?is?l?frequency N2(NS2)is used to represent salinity stratification.Layer-max NS2(LMN),defined as the NS2 maximum over the upper 300 m depth,and halocline depth(HD),defined as the depth where the NS2 maximum is located,are used to specifically describe the intensity of salinity stratification.Salinity stratification in the Topical Pacific Ocean has both spatial and temporal variability.Over the western and eastern equatorial Pacific,the LMN has a large magnitude with a shallow HD,and both have completely opposite distributions outside of the equatorial region.An obvious seasonal cycle in the LMN occurs in the north side of eastern equatorial Pacific and freshwater flux forcing dominates the seasonal variations,followed by subsurface forcing.At the eastern edge of the western Pacific warm pool around the dateline,significant interannual variation of salinity stratification occurs and is closely related to the El Ni?o Southern Oscillation event.When an El Ni?o event occurs,the precipitation anomaly freshens sea surface and the thermocline shoaling induced by the westerly wind anomaly lifts salty water upward,together contribute to the positive salinity stratification anomaly over the eastern edge of the warm pool.The interannual variations in ocean stratification can slightly affect the propagation of first baroclinic gravity waves.