Melet A., Gourdeau Lionel, Verron J., Djath B. (2013). Solomon Sea circulation and water mass modifications : response at ENSO timescales. Ocean Dynamics, 63 (1), p. 1-19. ISSN 1616-7341.
Titre du document
Solomon Sea circulation and water mass modifications : response at ENSO timescales
Ocean Dynamics, 2013,
63 (1), p. 1-19 ISSN 1616-7341
The South Pacific low latitude western boundary currents (LLWBCs) carry waters of subtropical origin through the Solomon Sea before joining the equatorial Pacific. Changes in their properties or transport are assumed to impact El Nino Southern Oscillation (ENSO) dynamics. At ENSO timescales, the LLWBCs transport tends to counterbalance the interior geostrophic one. When transiting through the complex geography of the Solomon Sea, the main LLWBC, the New Guinea Coastal Undercurrent, cannot follow a unique simple route to the equator. Instead, its routes and water mass properties are influenced by the circulation occurring in the Solomon Sea. In this study, the response of the Solomon Sea circulation to ENSO is investigated based on a numerical simulation. The transport anomalies entering the Solomon Sea from the south are confined to the top 250 m of the water column, where they represent 7.5 Sv (based on ENSO composites) for a mean transport of 10 Sv. The induced circulation anomalies in the Solomon Sea are not symmetric between the two ENSO states because of (1) a bathymetric control at Vitiaz Strait, which plays a stronger role during El Nino, and (2) an additional inflow through Solomon Strait during La Nina events. In terms of temperature and salinity, modifications are particularly notable for the thermocline water during El Nino conditions, with cooler and fresher waters compared to the climatological mean. The surface water at Vitiaz Strait and the upper thermocline water at Solomon Strait, feeding respectively the equatorial Pacific warm pool and the Equatorial Undercurrent, particularly affect the heat and salt fluxes. These fluxes can change by up to a factor of 2 between extreme El Nino and La Nina conditions.
