A Pacific hydrographic section at 88°W: Water‐property distribution

Abstract

Abstract. Full-depth conductivity-temperature-depth (CTD)/hydrographic measurements with high horizontal and vertical resolution were made in February-April 1993 along a line lying at a nominal longitude of 88øW and extending from southern Chile (54øS) to Guatemala (14øN). It crossed five major deep basins (Southeast Pacific, Chile, Peru, Panama, and Guatemala basins) east of the East Pacific Rise. Vertical sections of potential temperature, salinity, potential density, oxygen, silica, phosphate, nitrate, and nitrite are presented to illustrate the structure of the entire water column. Some features of interest found in the sections are described, and an attempt is made to interpret them in terms of the isopycnal property distributions associated with the large-scMe ocean circulation. These features include: various near-surface waters observed in the tropical and subtropical regions and the fronts that mark the boundaries of these waters; the possible importance of salt fingering to the downward salt transfer from the high-salinity subtropical water; a shallow thermostad (pycnostad) developed at 16ø-18.5ø(2 in the subtropical water; lowsalinity surface water in the subantarctic zone west of southern Chile; large domains of extremely low oxygen in the subpycnocline layer on both sides of the equator and a secondary nitrite maximum associated with a nitrate minimum in these lowoxygen domains; high-salinity, low-oxygen, high-nutrient subpycnocline water that is carried poleward along the eastern boundary by the Peru-Chile Undercurrent; the Subantarctic Mode •nd Antarctic Intermediate waters; middepth isopycnal property extrema observed at the crest of the Sala y Gomez Ridge; influences of the North Pacific and the North Atlantic upon deep waters along the section; and the characteristics and sources of the bottom waters in the five deep basins along the section.

Variations in behavior and condition of a Southern Ocean top predator in relation to in situ oceanographic conditions

“…A smaller cluster was also observed at significantly higher temperatures and lower salinities (5.34 Ϯ 0.12°C and 34.16 Ϯ 0.08, respectively). These characteristics were observed mainly from one seal spending Ϸ2 months in a well defined area at Ϸ20°west of Drake Passage north of the SAF, and are consistent with deep-reaching highly mixed surface waters in late winter indicative of the formation of Subantarctic Mode Water and AAIW in this region (38). Physical water properties encountered by Kerguelen and Macquarie seals were strikingly different from those for South Georgia seals, but were consistent with their geographic distributions.…”

The variability and heat budget of the upper ocean under the Chile-Peru stratus

“…Below the thermocline, with a maximum at about 170-200 m, there exists a strong salinity minimum associated with equatorward flowing, mid-latitude surface water that has been subducted. There follows a slight increase in salinity, and then much deeper, at about 700 m, one finds a secondary salinity minimum associated with Antarctic Intermediate Water (Tsuchiya and Talley, 1998). The temperature profile does not show any clear indication of the water masses that are shown in the salinity profile.…”

Magnetostratigraphic Calibration of the Late Oligocene Climate Transition

“…In its early history, Site 1237 lay in the oligotrophic subtropical gyre, and therefore biologic production and biogenic sedimentation rates were lower. The present-day water depth of Site 1237 lies in a mixing zone of relatively oxygen rich (nutrient depleted) Circumpolar Deep Water that enters the Peru Basin as bottom water through the Peru-Chile Trench and relatively oxygen depleted (nutrient rich) Pacific Central Water (PCW) (Lonsdale, 1976;Tsuchiya and Talley, 1998) (Fig. F3).…”