Based upon a suite of satellite and hydrology data along with numerical model simulations, the Kuroshio is found to be separated into two branches. The two branches are located on the western and eastern sides of the Batanes Islands. The western branch, which is the main branch of the Kuroshio, is estimated to carry roughly 68% of the transport, while the eastern branch, which has not been reported before, carries the remainder. Both branches bring warmer water northward, producing two separate warm tongues east of the Luzon Strait. The western warm tongue has an obvious seasonal variation due to the seasonal variation of the Kuroshio in the northern Luzon Strait, while the eastern warm tongue is associated with Pacific mesoscale eddies. As an anticyclonic (a cyclonic) eddy approaches the Batanes Islands from the east, the eastern branch of the Kuroshio is strongly intensified (weakened), and a more (less) pronounced warm tongue is induced. Consequently, interannual variability of Pacific mesoscale eddies affects the strength of the eastern branch.

No abstract

No abstract

No abstract

No abstract

Based on the self-organizing map (SOM) method, a suite of satellite measurement data, and Hybrid Coordinate Ocean Model (HYCOM) reanalysis data, the east branch of the Kuroshio bifurcation is found to have four coherent patterns associated with mesoscale eddies in the Pacific Ocean: anomalous southward, anomalous eastward, anomalous northward, and anomalous westward. The robust clockwise cycle of the four patterns causes significant intraseasonal variation of 62.2 days for the east branch. Furthermore, the study shows that the four patterns of the east branch of the Kuroshio bifurcation can influence the horizontal and vertical distribution of local sea temperature.

The Greenland Sea, Iceland Sea, and Norwegian Sea (GIN seas) form the main channel connecting the Arctic Ocean with other Oceans, where significant water and energy exchange take place, and play an important role in global climate change. In this study steric sea level, associated with temperature and salinity, in the GIN seas is examined based on analysis of the monthly temperature and salinity fields from Polar science center Hydrographic Climatology (PHC3.0). A method proposed by Tabata et al. is used to calculate steric sea level, in which, steric sea level change due to thermal expansion and haline contraction is termed as the thermosteric component (TC) and the halosteric component (SC), recpectively. Total steric sea level (TSSL) change is the sum of TC and SC. The study shows that SC is making more contributions than TC to the seasonal change of TSSL in the Greenland Sea, whereas TC contributes more in the Norwegian and the Iceland Seas. Annual variation of TSSL is larger than 50 mm over most regions of the GIN Seas, and can be larger than 200 mm at some locations such as 308 mm at 76.5˚N, 12.5˚E and 246 mm at 77.5˚N, 17.5˚W.

Abstract. Based on satellite remote-sensing observation data and Hybrid Coordinate Ocean Model (HYCOM) re-analysis data, we studied the counter-rotating eddy pair in the Luzon Strait (LS). Statistical analysis reveals that when an anti-cyclonic mesoscale eddy (AE) (cyclonic mesoscale eddy [CE]) in the Northwest Pacific (NWP) gradually approaches the east side of the LS, a CE (an AE) gradually forms on the west side of the LS, and it is defined as the AE (CE) mode of the counter-rotating eddy pair in the LS. The counter-rotating eddy pair exhibits obvious seasonal variation: the AE mode mainly occurs in the summer half of the year, while the CE mode mainly occurs in the winter half of the year. The mean durations of the AE and CE modes are both approximately 70 d. Based on the vorticity budget equation and energy analysis, the dynamic mechanism of counter-rotating eddy-pair occurrence is determined to be as follows: the AE (CE) on the east side of the LS causes a positive (negative) vorticity anomaly through horizontal velocity shear on the west side of the LS, and the positive (negative) vorticity anomaly is transported westward by the zonal advection of the vorticity, finally leading to the formation of the CE (AE) on the west side of the LS.