Low-salinity pools at Barbados, West Indies: Their origin, frequency, and variability

Abstract

A vertical array of conductivity-temperature recorders moored off the west coast of Barbados, West Indies, from May 1996 to November 1997 revealed a heterogeneous and variable salinity pattern punctuated by five pools of low-salinity water (<34.5 practical salinity units (psu)) entering the region. A typical pool extended to 30-m depth and lasted -25 days, although one pool extended to 47 m and lasted 94 days. Water samples taken from a pool in May 1997 have radium 228/226 activity ratios of-l, consistent with previous measurements in Barbados of water that originated in the Amazon River mixing zone. The Amazon water likely was translated to Barbados in rings spawned from the North Brazil Current. Analysis of sea height anomaly and residual derived from the TOPEX/Poseidon satellite supports this conclusion and reveals that, contrary to previous studies, rings are shed throughout the year, mostly during spring. The pools of low-salinity water and their associated velocities dramatically changed the already variable flow in our study area. We believe the complex salinity and flow we observed represented the disorganized remnants of North Brazil Current rings that were at or near the ends of their lives. The changes we observed in the velocity and water structure are interesting in their own right as evidence of the Barbados region as a mixing zone and for their influence on recruitment of larval fishes to the reef along the island's west coast. Copyright 2000 by the American Geophysical Union.