Observations of deep-water renewal in the Caribbean Sea

Abstract

Observations with bottom-moored current meters in the Jungfern passage show that, contrary to previous conclusions, deep water in the Venezuela basin is being renewed. During a 5-day record, the flow was mainly oscillatory at tidal frequency, with a net inflow by the tidal mechanism of only 6×103 m3 sec−1. During a single 11-hour surge the inflow rate was 50 to 200 × 103 m3 sec−1. Steady-state heat-budget and oxygen-budget calculations require a renewal rate of about 100×103 m3 sec−1. The sill depth is 1860 meters. STD observations near the sill reveal a sharp interface between Caribbean water above and oceanic water below sill depth. The north-south hydrographic sections of IGY data show an abrupt change in vertical temperature gradient near 2600 to 2800 meters. This feature, also found in other basins, is interpreted to result from differences in renewal between tidal inflow and stronger sporadic surges, with the earth's rotation being an important controlling parameter.