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Observed intraseasonal thermocline variability in the Bay of Bengal
Author(s) -
Girishkumar M. S.,
Ravichandran M.,
Han W.
Publication year - 2013
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/jgrc.20245
Subject(s) - thermocline , ekman transport , climatology , buoy , wind stress , sea surface height , geology , kelvin wave , bay , rossby wave , forcing (mathematics) , baroclinity , oceanography , ekman layer , sea surface temperature , atmospheric sciences , upwelling , boundary layer , physics , thermodynamics
The time series of temperature data obtained from moored buoys deployed at 8°N, 12°N, and 15°N along 90°E in the Bay of Bengal (BoB) shows a persistent intraseasonal variability on 30–120 day time scale in three distinct periods 30–70 day, near 90 day, and near 120 day in the thermocline region. The standard deviation of moored buoy temperature data shows that half of the variability in the thermocline region is contributed from the 30–120 day variability. The relative contribution of local Ekman pumping velocity and remote wind forcing from equatorial Indian Ocean (EIO) to the intraseasonal thermocline variability in the BoB is examined using satellite‐derived sea surface height anomaly (SSHA), wind and depths of 23° isotherm (D23, proxy for thermocline depth) derived from moored buoys temperature data. The analysis shows that large amplitude intraseasonal oscillations of thermocline—particularly the near 90 day and 120 day variability—could not be explained by local Ekman pumping velocity alone. The SSHA, D23, and wind fields reveal that the first and second baroclinic mode Kelvin and Rossby waves, which are generated remotely by winds from the EIO and eastern BoB, can significantly influence the thermocline variability in the BoB. The near 90 day and 120 day thermocline variability is driven primarily by the variability of equatorial zonal wind stress. While the 30–70 day thermocline variability is affected most by interior Ekman pumping over the Bay, it also appears to be influenced by zonal wind stress in the EIO and alongshore wind stress in the eastern BoB.