Glider and altimetric data assimilation in the Solomon Sea

Abstract : n the southwest Pacific, thermocline waters connecting the tropics to the equator via western boundary currents (WBC) transit through the Solomon Sea. Therefore, they may impact the equatorial Pacific heat and transport budgets and play a role in the climate system. As available observations of the region are sparse, modeling provides a useful complementary tool to describe the detailed time and space features of the Solomon Sea circulation. The Solomon Sea has indeed been depicted as a region of high variability from both modeling and altimetric sea level data analysis. An integrated view of the circulation combining numerical simulation and available observations, through data assimilation, is probably the way to provide a realistic description of this highly variable region. This is the motivation of this work which focuses on the control of the Solomon Sea WBC, the New Guinea Coastal Undercurrent, through assimilation of glider and other in situ data supplemented by altimetric sea level anomalies data. At this stage, the objective is rather to assess the capability of existing or expected observing system than to perform realistic data assimilation experiments per se. An observing system simulation experiments (OSSE) strategy is implemented in a twin experiment context to study the ability of glider observations to constrain the Solomon Sea New Guinea Coastal Undercurrent as well as the complementarity of gliders and sea level anomalies observations to do so. From a methodological point of view, we performed original data assimilation in a multigrid model through a local reduced order analysis, based on a sequential scheme derived from the SEEK filter. Observations are located in a 1/12° model of the Solomon Sea which is interactively nested in a 1/4° southwest Pacific model, itself embedded through open boundary conditions in a global 1/4° OGCM. Glider monitoring of the Solomon Sea circulation has been operated since 2007. Those autonomous underwater vehicles provide high temporal and along-trajectory resolution temperature and salinity data down to about 600 m, which are of interest for the control of meso-scale variability of the Solomon Sea WBC. However, this work suggests that a reasonably realistic number of synthetic glider observations alone are not sufficient to constrain the New Guinea Coastal Undercurrent. Altimetry provides a complementary and valuable surface source of information in this region of strong currents flowing through an intricate bathymetry, with numerous islands. This study will discuss the complementarity of localised 3-D glider and synoptic sea level anomalies data to constrain the New Guinea Coastal Undercurrent.
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Submitted on : Tuesday, May 3, 2011 - 11:09:23 AM
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  • HAL Id : hal-00590327, version 1




Angélique Mélet, Jacques Verron, Jean-Michel Brankart. Glider and altimetric data assimilation in the Solomon Sea. OSTST Meeting, Oct 2010, Lisbon, Portugal. ⟨hal-00590327⟩



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