Forcing Mechanisms of Sea Level Interannual Variability in the Bay of Bengal

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Abstract
A nonlinear, 4½-layer reduced-gravity ocean model with active thermodynamics and mixed layer physics is used to investigate the causes of sea level interannual variability in the Bay of Bengal, which may contribute to flooding and cholera outbreaks in Bangladesh. Forcing by NCEP–NCAR reanalysis fields from 1958 to 1998 yields realistic solutions in the Indian Ocean basin north of 29°S. Controlled experiments elucidate the roles of the following forcing mechanisms: interannual variability of the Bay of Bengal wind, equatorial wind, river discharges into the bay, and surface buoyancy flux including precipitation minus evaporation (heat fluxes + P − E). Sea level changes in the bay result largely from wind variability, with a typical amplitude of 10 cm and occasionally 10–25 cm at an interannual timescale. Near the eastern and northern boundaries, sea level anomalies (SLAs) are predominantly caused by equatorial wind variability, which generates coastal Kelvin waves that propagate into the bay along... Abstract A nonlinear, 4½-layer reduced-gravity ocean model with active thermodynamics and mixed layer physics is used to investigate the causes of sea level interannual variability in the Bay of Bengal, which may contribute to flooding and cholera outbreaks in Bangladesh. Forcing by NCEP–NCAR reanalysis fields from 1958 to 1998 yields realistic solutions in the Indian Ocean basin north of 29°S. Controlled experiments elucidate the roles of the following forcing mechanisms: interannual variability of the Bay of Bengal wind, equatorial wind, river discharges into the bay, and surface buoyancy flux including precipitation minus evaporation (heat fluxes + P − E). Sea level changes in the bay result largely from wind variability, with a typical amplitude of 10 cm and occasionally 10–25 cm at an interannual timescale. Near the eastern and northern boundaries, sea level anomalies (SLAs) are predominantly caused by equatorial wind variability, which generates coastal Kelvin waves that propagate into the bay along...