Abstract

The tropical western Pacific has been the subject of increasing attention during the past two decades. Tropical western Pacific currents influence the heat budget of the warm pool, and thereby play a role in the El Nino-Southern Oscillation (ENSO) phenomenon. They also provide waters for the Indonesian Throughflow, a component of the global thermohaline circulation. Despite these motivations, direct current observations have been limited to a few quasi-synoptic shipboard acoustic Doppler current profiler (SADCP) surveys and moorings concentrated in localized areas along the western boundary. These snapshots and point measurements do not provide a reliable, comprehensive description and quantification of the mean flows and their seasonal variability, let alone their year-to-year fluctuations. The numerical simulations of this domain are therefore poorly constrained. Our state of knowledge is especially reduced below 300 m, which until recently was the typical depth range of most SADC Ps. The few observations we have indicate the presence of intense intraseasonal variability at intermediate depth in the western Pacific in general, and along the western boundary in particular. But these observations are inadequate to explore the dynamics of the variability. The present work uses a combination of direct current observations and high resolution state of the art ocean simulations to provide a detailed description of the currents and to identify the sources of intraseasonal variability at the western boundary.