Variability in Solomon Sea circulation derived from altimeter sea level data

Abstract

International audienceThe 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

Regional circulation around New Caledonia from two decades of observations

“…We used the altimetric data and assume that thermocline currents and surface geostrophic currents are well correlated. This has indeed been shown to be true north of NC (Kessler and Cravatte, 2013b;Melet et al, 2010;Ridgway et al, 1993) where surface currents were successively used as a proxy to estimate thermocline transports variability. To distinguish between the low-frequency (seasonal and interannual variability) and the high-frequency (intraseasonal) variability, weekly altimetric currents were filtered as described in Section 2.4.…”

Monitoring Sea Level in the Coastal Zone with Satellite Altimetry and Tide Gauges

“…Along-track data from the three datasets were post-processed with various filters to remove the remaining erroneous data, using a strategy similar to that used in Melet et al (2010). As the coastal shelf is narrow off Western Africa (a few tens of km), we selected the sections of the altimetry tracks that are located less than 200 km off the coast (referred to as coastal sections hereafter) to characterize the evolution of sea level trends from the open to the coastal ocean.…”

A 1/36° model of the Solomon Sea embedded into a global ocean model: On the setting up of an interactive open boundary nested model system

“…The impacts of the wind stress formulation, as inferred from the differences between the two simulations, are more evident in terms of variability. The simulated sea level anomalies (SLA) variability and surface EKE from both simulations are compared to these induced from the AVISO altimetric dataset in Fig 6. The SLA variability in the Solomon Sea has been analysed using the AVISO altimetric data in Melet et al 18 , and is large at seasonal and interannual time-scales. Two patches of strong sea level variability are located in the north-eastern and south-eastern parts of the Solomon Sea.…”