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A system of meridional ridges in the western South Pacific Ocean frame the Lau Basin and Havre Trough, and form a barrier to direct communication between the far western South Pacific basins and the interior South Pacific Ocean. The eastern side of this system comprises the Tonga and Kermadec Ridges, the location of the main deep western boundary current entering the Pacific Ocean. Observations from floats released in the Lau Basin as part of the RIDGE2000 program suggested the presence of a western boundary current along the Lau Ridge exiting into the North Fiji Basin. Those observations, together with Argo sub-surface float data and repeat hydrographic sections, confirm and expand the boundary current observations along the Lau Ridge throughout the Lau Basin and into the Havre Trough, along the Colville Ridge. The observations also reveal two previously unrecognized westward flowing jets bisecting the Lau Basin and Havre Trough. Using an extension to the classic Stommel-Arons abyssal circulation model, the predicted strength and location of these boundary currents and their bifurcation is compared with the float observations. The model provides a simplified view of the dynamics controlling the boundary current structure in the deep basins. A comparison of transport within the western boundary current derived from float data, hydrographic sections, and the idealized analytical model indicates that roughly 4 Sv (below 1,000 db) is transported northward through the Lau Basin, exiting into the North Fiji Basin.
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A Deep Eastern Boundary Current in the Chile Basin
Abstract Hydrographic data and tracers from several ship‐based sections show the location and structure of a deep eastern boundary current in the Chile Basin. The current is centered above the Peru‐Chile Trench at 2,500–3,400 m and transports up to 6 Sv of low‐potential vorticity, high‐silicate water south toward Drake Passage. Deep current velocities from direct Lowered Acoustic Doppler Current Profiler measurements are up to about 15 cm/s southward. The hydrographic data, as well as potential vorticity and silicate distributions, show that the current is comprised to a large extent of flow from the west moving along the southern flank of the Sala y Gomez Ridge and Nazca Ridge, and to a lesser extent from a flow along the eastern boundary entering directly from the Panama Basin. At the southern edge of the Chile Trench, the current weakens and partly turns offshore to cross the Chile Ridge through a complex region of passages. Above the southern flank of the Chile Rise the flow joins a broader eastward flow; together, these waters return to the eastern boundary before entering Drake Passage.
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- Award ID(s):
- 1658479
- PAR ID:
- 10459947
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Oceans
- Volume:
- 124
- Issue:
- 1
- ISSN:
- 2169-9275
- Page Range / eLocation ID:
- p. 27-40
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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