The Solomon Sea has long been recognized as a major pathway for the western boundary currents of the western tropical Pacific to redistribute South Pacific thermocline waters from the subtropics to the equator. Recent evidence suggests that oceanic anomalies originating in these South Pacific thermocline waters are responsible for the modulation of ENSO variability on decadal time scales. However, several key aspects of the oceanic circulation in the Solomon Sea remain poorly observed and are not properly depicted by models. Questions remain as to how much water is carried through the Solomon Sea to the equator and in what density range. The Moorings for the Southwest Pacific Circulation Experiment (MoorSPICE) is an international co-operative experiment designed to measure the flow in these boundary currents with simultaneous mooring deployments in the major passages that bound the Solomon Sea: Indispensible Strait, Vitiaz Strait, St. Georges Channel and Solomon Strait.
The measurements span an 18-month period beginning in August 2011. This project is the U.S. component of MoorSPICE. The key motivation for MoorSPICE is to obtain a quantitative view of the mean and variability of the equatorward South Pacific western boundary current flow through the main exit channels of the Solomon Sea to the equatorial Pacific. Each pathway possibly means different water mass combinations, and implies a different time scale for water to reach the equator. The ratio of transport through each of the straits may also vary with time. The partition between the straits could thus be determinant for the thermocline water route to the equator (the longitude at which it joins the Equatorial Undercurrent) with potential consequences for the equatorial response to changes in the southwest Pacific winds and circulation.
Intellectual merit: The simultaneous mooring deployments in each major passage of the Solomon Sea will provide vital information on the partitioning of the South Pacific western boundary flow and how it changes in response to regional and remote wind forcing. Because of the narrow passages and complex topography, at present the numerical models offer little guidance of the flow through each pathway and there are few available observations to constrain the models. The definitive MoorSPICE data set will allow for quantitative evaluation of model simulations of the various thermocline water pathways en route to the equator, including their time-dependent variability. Understanding the transport and property characteristics of the subtropical waters that are transmitted to the tropics will help elucidate the mechanisms that are responsible for the extra-tropical induced ENSO variability.
Broader Impacts: As part of the educational component to advance discovery and understanding, MoorSPICE will support the research project of a graduate student. The results will be broadly disseminated within and beyond the scientific community through workshops, presentations at oceanographic meetings and schools, and a web site. MoorSPICE is a coordinated international research effort that will act to enhance our research infrastructure. The full MoorSPICE data set will be made available to the community two years after the finish of the fieldwork. Validation of models with the MoorSPICE data will provide societal benefit through a wide range of ocean, climate, management and conservation applications.
