Circluation of the Lau Basin

The tropical South Pacific is a highly studied area and its circulation is characterized by large gyres that extend from just north of the Antarctic Circumpolar Current (ACC) to the equator, as well as several Western Boundary Currents (WBCs). The flow, however, is complicated by the extensive island chains and persistent breaks that result along the bounding walls. The largest gyre lies east of the Tonga-Kermadec Ridge, which is the eastern boundary of the Lau Basin.

The Lau Basin is a back-arc basin that is situated between the remaining Lau Ridge volcanic arc on the west and the Tofua arc to the east. Since the basin sits on top of a Wadati-Benioff zone, it is seismically active on a regular basis. The basin itself is trapezoidally shaped, stretching from 15S to about 37S and centered around the antimeridian. Though there has been ample research into the geomorphology and the geochemistry of the basin, there has been very little comment on the circulation of the basin and the origin of the waters found within. From ARGO float data, unexploited hydrographic data, established repeat transects, and process model runs this question is being explored. The basic flow pattern in the Lau Basin consists of chaotic, topographically affected flow in the interior and a short northward boundary current along the northern edge of the Lau- Colville Ridge.