Circulation in the Archipiélago de Colón (Galapagos Islands), November, 1993

DCP and CTD data are used to investigate the circulation pattern in the region of the Archipiélago de Colón during the period 8–21 November 1993. Surface flow was dominated by the westward flowing South Equatorial Current except in a small region to the west of Isla Fernandina, where eastward flow associated with the shoaling of the Equatorial Undercurrent was observed. The Equatorial Undercurrent was observed to the west of the Archipelago, centered along 0.5°S at 70 m with peak velocities ∼0.6 m s -1 and, at 92°W, a transport of 6.6 Sv. Between 92°W and the Archipiélago, a distance of only 40 km, the Undercurrent surfaced, the eastward flow decelerated, and meridional flow diverged on either side of 0.5°S, the southward flow appearing to be stronger and better developed than the northward flow. At 89°W the Undercurrent and its associated salinity maximum were observed at 50 m depth at 1°S, with greatly reduced speed, 0.2 m s -1; subsurface eastward flow also appeared in the northern hemisphere, but this flow was at greater depth, 140 m. The interaction of the Undercurrent and the Archipielago appeared to enhance the thickness of the 16°C thermostad.