Bay of Bengal currents during the northeast monsoon

Abstract

Velocity and property observations were made during February and March 1995 as part of the World Ocean Circulation Experiment (WOCE) Hydrographic Program (WHP) expedition in the Indian Ocean. The observed circulation in the upper 300 m of the ocean during the northeast monsoon is compared to the output of a high-resolution, 3-layer, nonlinear model forced by European Center for Medium Range Weather Forecasting (ECMWF) winds. The data identify several new features in the Bay of Bengal: a shelf-break coastal current in the northeast corner, an eddy and subsurface jet near the South Preparis Channel, and an eastward countercurrent extending from 80°E to the eastern boundary. The countercurrent transports high-salinity surface water from the northwest Indian Ocean into the bay, and separates the historically observed North Equatorial Current into two currents with separate sources and water properties. The data also detail the spatial structure of the South Equatorial Current and Countercurrent, and show the Equatorial Undercurrent in the eastern half of the Indian Ocean. The model compares well enough with the data to suggest that such realistic models may provide a useful temporal context for the WHP snapshot.