Variations with depth of oceanographic properties along the equator in the Pacific

The vertical distribution along the equator in the Pacific of temperature, salinity, density, oxygen, and phosphate, from the sea surface to 1000 meters, and the anomaly of the dynamic height of the sea surface and other isobaric surfaces above the 700‐decibar surface are shown. In each of the figures, the available data have been partitioned according to the date of the observation into two periods, July to December and January to June, which are designated in the text as summer and winter, respectively. The figures include data from stations within one degree of latitude north or south of the equator between 110°W and 135°E longitude. The surface of the sea, relative to the 700‐db surface, slopes upward, east to west, approximately 0.8 dynamic meters; the value for the slope is 5.0 × 10 −8 during both summer and winter. The longitudinal pressure gradient does not extend much below the layer of relatively large vertical density gradient. At the depth of σ = 26.5, 250–300 m, relatively little east‐west slope is evident. In the surface layer (sea surface to top of the thermocline), temperatures along the equator are lower in the eastern Pacific during both periods; the thermocline is comparatively level west of the 180th meridian, sloping upward to the east of this longitude. Temperatures are appreciably lower and concentrations of inorganic phosphate are higher in the surface layer in the eastern Pacific during the summer, both reflecting the temporal and longitudinal variations in divergence and upwelling. The oxygen minimum, centered at a depth of approximately 450 m, is a continuous feature from 100°W longitude (eastern limit of the profiles) to near 170°E longitude, with the lowest concentrations in the east (≤ 0.5 ml/L) increasing to 1.5 to 2.0 at the westward limit. West of 170°E longitude, concentrations at 450 m rapidly increase to 3.0 ml/L.