POLEWARD UNDERCURRENT ALONG THE PERU COAST: 5 TO 15 degree S.

During March to May 1977, two field experiments, ESACAN and JOINT-II, were conducted in Peru coastal waters between 5 and 15 degree S. The combined data set includes current measurements with a common period of 38 days from moorings near 5, 10, 12 and 15 degree S. The mean currents at 40 and 90 m were poleward at all locations, although the mean wind was equatorward at all locations. Offshore arrays at 5 and 15 degree S show similar vertical and offshore structure of the poleward undercurrent when the offshore dimension is scaled by the Coriolis parameter. At both latitudes, the maximum poleward flow was at a depth of about 100 m over the continental slope. The poleward flow was stronger and more persistent at 5 than at 15 degree S. The temperature at the core is apparently higher at 5 than at 15 degree S. An alongshore array showed that poleward flow was at about mid-depth over the shelf all along the coast; thus, the poleward undercurrent supplies the water that upwells along the coast. Refs.