Variability in Solomon Sea circulation derived from altimeter sea level data
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The Solomon Sea is a key region in the Pacific Ocean where equatorial and subtropical circulations are connected. The region exhibits the highest levels in sea level variability in the entire south tropical Pacific Ocean. Altimeter data was utilized to explore sea level and western boundary currents in this poorly understood portion of the ocean. Since the geography of the region is extremely intricate, with numerous islands and complex bathymetry, specifically reprocessed along-track data in addition to standard gridded data were utilized in this study. Sea level anomalies (SLA) in the Solomon Sea principally evolve at seasonal and interannual time scales. The annual cycle is phased by Rossby waves arriving in the Solomon Strait, whereas the interannual signature corresponds to the basin-scale ENSO mode. The highest SLA variability are concentrated in the eastern Solomon Sea, particularly at the mouth of the Solomon Strait, where they are associated with a high eddy kinetic energy signal that was particularly active during the phase transition during the 1997–1998 ENSO event. Track data appear especially helpful for documenting the fine structure of surface coastal currents. The annual variability of the boundary currents that emerged from altimetry compared quite well with the variability seen at the thermocline level, as based on numerical simulations. At interannual time scales, western boundary current transport anomalies counterbalance changes in western equatorial Pacific warm water volume, confirming the phasing of South Pacific western boundary currents to ENSO. Altimetry appears to be a valuable source of information for variability in low latitude western boundary currents and their associated transport in the South Pacific.
KeywordsSouthwest tropical Pacific Ocean Solomon Sea Altimetry Low latitude western boundary currents ENSO Annual cycle
This work was supported by the Centre National d'Etudes Spatiales (CNES). It is a contribution to the INSU/LEFE national programme and to the CLIVAR/SPICE International programme. Gridded altimeter products were produced by Ssalto/Duacs and distributed by AVISO, with support from Cnes (http://www.aviso.oceanobs.com/duacs). The original T/P data were reprocessed at the Center for Topographic studies of the Oceans and Hydrosphere (CTOH/LEGOS, http://www.legos.obs-mip.fr/fr/observations/ctoh). We thank Florence Birol for her help reprocessing the altimeter data, Billy Kessler, Sophie Cravatte, and Patrick Marchesiello for their helpful comments. WWV time series were obtained from the TAO Project Office at NOAA/PMEL (http://www.pmel.noaa.gov/tao/elnino/wwv/).
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