Acoustic doppler current profiling in the Western Pacific during the WOCE P10 cruise, November/December 1993
01 Apr 1997-
TL;DR: In this paper, the authors describe the processing of shipboard acoustic Doppler current profiler (ADCP) data that were collected during a WOCE survey of the Pacific Ocean, line P10.
Abstract: : The objective of this cruise was to occupy a hydrographic section nominally along 149E from Papua New Guinea to the shelf off the coast of Japan near Yokohama as part of the one-time WOCE Hydrographic Programmed survey of the Pacific Ocean, line P10. This report describes the processing of shipboard acoustic Doppler current profiler (ADCP) data that were collected during this cruise. New GPS-based heading measurements (Ashtech heading), which increase the accuracy of the ADCP, are covered in detail. A subset of the processed data from the New Guinea Coastal Undercurrent and from the Kuroshio is presented.
Citations
More filters
TL;DR: The top to bottom large-scale ocean circulation in the northwest Pacific is described using a World Ocean Circulation Experiment (WOCE) onetime hydrographic section along 149°E between Papua New Guinea and Japan as discussed by the authors.
Abstract: The top to bottom large-scale ocean circulation in the northwest Pacific is described using a World Ocean Circulation Experiment (WOCE) onetime hydrographic section along 149°E between Papua New Guinea and Japan. The circulation is quantified using a combination of geostrophic and lowered acoustic Doppler current profiler velocity estimates. At the northern end of the section the flow regime is distinct in that the deep flow largely reflects that at the surface: the Kuroshio jet and its northern and southern recirculations have deep expressions. South of 25°N, the deep and bottom water flows do not mirror the surface flows, and the circulation assumes a highly baroclinic structure. Below the depth of local North Pacific ventilation the flow in the upper deep waters (800-2500 m) alternates in sign roughly every 10° of latitude revealing a set of deep clockwise gyres with significant transports of 40 Sv (1 Sv = 10 6 m 3 s -1 ) for a tropical gyre (south of 6°N) and 20 Sv in a subtropical gyre (6° - 24°N). These gyres provide a pathway for South Pacific influences to reach 22°N (the location of a strong water mass front) through exchange along the western boundary. Maps of properties on density surfaces suggest that the zonal extent of the upper deep water gyres found along 149°E is basin wide. Below 2500 m, flow across the section is isolated from the Philippine Sea by the Izu-Ogasawara-Mariana Ridge and the flow regime and property distribution reflect this: Lower Circumpolar Water flows west in a deep western boundary current near 10°N and coalesces at the Izu-Ogasawara-Mariana Ridge with a tongue of North Pacific Deep Water also flowing west near 15°N. About 4 Sv of a mixture of these waters flows east again near 25°N, associated with an abyssal water mass front. North of the front, the water properties are laterally homogeneous on density surfaces in the strongly recirculating gyres associated with the deep Kuroshio system.
78 citations
TL;DR: The FLUPAC cruise of 1994 as discussed by the authors carried out a zonal transect along the equator, from 170"E to 150"W. Physical and nutrient data from that section presented unusual features: zonal currents in the upper layer were mostly found in opposition to local forcing, i.e. westerly winds and westward flow west of 180°, easterly trade winds and weakly eastward flow elsewhere; east of 170"W strong oscillations of the meridional flow (0.8 m s-' peak to peak) extended from the surface
Abstract: In September-October. 1994, the FLUPAC cruise was carried out in the western equatorial Pacific as a French contribution to the JGOFS programme. One leg of that cruise included a zonal transect along the equator, from 170"E to 150"W. Physical and nutrient data from that section presented unusual features: zonal currents in the upper layer were mostly found in opposition to local forcing, i.e. westerly winds and westward flow west of 180°, easterly trade winds and weakly eastward flow elsewhere; east of 170"W strong oscillations of the meridional flow (0.8 m s-' peak to peak) extended from the surface to the thermocline; a warm (higher than 30°C), fresh (S<34.8) and salinity-stratified surface water mass spread out from 170"E to 172"W, where it ended through a salinity front; east of that limit a deep homogeneous layer was found, but with relatively low vertical mixing; the thermocline deepened steadily from 170"E eastward to a depth of 16v mat 160"W; the boundary of nutrient enriched waters was displaced by about 2800 km eastward as compared with climatology, with 1 pM surface NO3 concentration at 165"W; a relative nutrient minimum (less than 3 pM Nos) was found embedded in the enriched area east of that longitude. These observations are explained with the help of large-scale data from the TAO mooring array: 61 days of westerly winds in the western Pacific before the cruise had triggered a 0.4 m s-' current jet that advected surface waters to the east; a downwelling Kelvin wave propagated east of that wind patch, depressed the thermocline, and changed geostrophic surface current to eastward; tropical instability wave activity caused localized nutrient depletion by meridional advection; west of 180", propagation of an upwelling Rossby wave from the east may have contributed to westward flow. These results stress the importance of intraseasonal variability on physical and nutrient content data obtained during a cruise, and the usefulness of concurrent large-scale observations. ,a 1998 Elsevier Science Ltd. All rights reserved
66 citations