AUTHOR=Trusenkova Olga , Kaplunenko Dmitry 

TITLE=Intra-Annual Sea Level Fluctuations and Variability of Mesoscale Processes in the Northern Japan/East Sea From Satellite Altimetry Data

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 9 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.866328

DOI=10.3389/fmars.2022.866328

ISSN=2296-7745

ABSTRACT=Intra-annual sea level fluctuations and variability of mesoscale processes based on eddy kinetic energy (EKE) were studied in the northern (northward of 41 N) Japan/East Sea using data from satellite altimetry for 1993–2020. Decomposition to empirical orthogonal functions (EOF) was performed of the high-pass filtered, with the cut-off period of 250 days, sea level anomalies. The leading mode accounting for the major fraction of the variance yielded sea level fluctuations which were simultaneous in the entire sea, occurred in the range from 70 to 250 days without any preferable timescale, and manifested clear seasonal signal. EKE in the northern sea was also expanded to EOF and yielded the leading mode capturing mesoscale variability within the Primorye (Liman) Current and the Tsushima Warm Current. The seasonal signal of the simultaneous intra-annual sea level fluctuations matches that of EKE, and, as found in the earlier studies, of the mean currents. The sea level rises, the mean currents intensify and EKE increases in summer and fall and the opposite changes occur in winter and spring, with the seasonal extremes in October/November and March/April, respectively. This implies that EKE is generated by instability of the mean currents. The intra-annual sea level fluctuations and EKE manifest rich variability on quasi-biennial, interannual and decadal timescales. However, in contrast with the seasonal signal, the low-frequency variability does not match, implying different kinds of forcing, probably by local wind in the northern JES and the KTS transport variations in the southern JES. However, the relationship of intra-annual simultaneous SLA with the KTS transport interannual variation seems inconclusive.