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In this study, we investigate the connection between planetary equatorial waves, modulated by the Indian Ocean dipole (IOD) and El Niño Southern Oscillation (ENSO), and the interannual variabilities of the salinity distribution in the Bay of Bengal (BoB) in October–December (OND), along with its associated dynamics, using satellite and reanalysis datasets. In OND 2010 and 2016 (1994, 1997, 2006, and 2019), positive (negative) sea surface salinity anomalies (SSSAs) were distributed in the eastern equatorial Indian Ocean (EIO) and Andaman Sea. Moreover, the southward movement of negative (positive) SSSAs along the eastern Indian coast was observed. This phenomenon was caused by large-scale anomalous currents associated with zonal wind over the EIO. During OND 2010 and 2016 (1994, 1997, 2006, and 2019), due to anomalous westerlies (easterlies) over the EIO and anomalous downwelling (upwelling) Kelvin waves, the strengthened (weakened) Wyrtki jet and the basin-scale anomalous cyclonic (anticyclonic) circulation in the BoB gave rise to positive (negative) SSSAs within the eastern EIO and Andaman Sea. In addition, the intensified (weakened) eastern Indian coastal currents led to the southward movement of negative (positive) SSSAs. It is worth noting that downwelling Kelvin waves reached the western coast of India during OND 2010 and 2016, while upwelling Kelvin waves were only confined to the eastern coast of India during OND 1994, 1997, 2006, and 2019. Furthermore, westward salinity signals associated with reflected westward Rossby waves could modulate the spatial pattern of salinity. The distribution of salinity anomalies could potentially influence the formation of the barrier layer, thereby impacting the sea surface temperature variability and local convection. [ABSTRACT FROM AUTHOR]

Abstract In this paper, internal solitary waves (ISWs) in the northern South China Sea (NSCS) are investigated with respect to their propagation and evolution processes in different months. To achieve that, environmental parameters associated with ISW are first calculated using climatological datasets derived from the Simple Ocean Data Assimilation 3.3.1 (SODA3.3.1) reanalysis. The environmental parameters are significantly distinct from month to month, especially the quadratic nonlinearity coefficient α. It is negative in the deep basin and turns positive on the shallow continental shelf. A clear dividing line that α equals to zero can be found along the shelf from northeast to southwest from January to February and from October to December. The dividing line is interrupted starting from March and is mostly constrained on the northeast shelf, and from May to September only limited areas can positive α be found. Further simulations based on the variable extended Korteweg-de Vires (veKdV) model indicate that the polarity conversion process of ISWs therefore exhibits significant seasonality. It can be concluded from the simulation results that near the 200-m isobath on the continental shelf the elevation waves are more likely to appear from November to March owing to the positive values of α. The large-scale background current exhibits little effect on the deformation and polarity conversion of ISW in the NSCS although it prominently affects the environmental parameters around the shelf currents from Luzon strait. Highlights • ISWs in the NSCS are investigated with respect to their propagation and evolution processes in different months. • A parametric study and simulation of ISW reveal that elevation waves are more likely to appear in November to March. • The polarity conversion depth of ISW in different months as well as its variation is determined. [ABSTRACT FROM AUTHOR]

Abstract: Satellite observations of sea surface height (SSH) from 1993 to 2010 reveal a decadal variability of summer circulation in the South China Sea (SCS) with three phase changes in 1998, 2001 and 2006, respectively. There appears to be a large rise during 2006–2010 contributing to unprecedented anomalous high sea levels in 2010. The first leading empirical orthogonal function (EOF) mode of SSH exhibits an anomalous anticyclonic circulation pattern in the western central SCS north of 11°N, thus weakening the northern cyclone of the summer dipole during 2006–2010. The negative phase of the Pacific decadal oscillation (PDO) may have contributed to the anomalous high sea levels and disappearance of the summer dipole pattern. These variations reflect a linkage between the circulations of the SCS and Pacific Ocean. [Copyright &y& Elsevier]