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

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 88 degrees W and extending from southern Chile (54 degrees S) to Guatemala (14 degrees N). 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-scale 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 16 degrees-18.5 degrees C in the subtropical water; low-salinity 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 low-oxygen 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 and 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.