Intraseasonal Variability of Upwelling in the Equatorial Eastern Indian Ocean

  • 30 November 2015
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Intraseasonal Variability of Upwelling in the Equatorial Eastern Indian Ocean

A new CVP-supported study by Chen et al. titled “Intraseasonal Variability of Upwelling in the Equatorial Eastern Indian Ocean” has been published in the Journal of Geophysical Research: Oceans.

By analyzing satellite observations and conducting a series of ocean general circulation model experiments, the researchers examined the physical processes that determine intraseasonal variability of the equatorial eastern Indian Ocean upwelling for the 2001-2011 period.

For both winter-spring and summer-fall seasons, the intraseasonal variability of eastern Indian Ocean sea level and thermocline depth is dominated by remote forcing from the equatorial Indian Ocean wind stress. According to the scientists, this drives Kelvin waves that propagate along the equator and subsequently along the Sumatra–Java coasts.

Local wind forcing within the eastern Indian Ocean plays a secondary role. The intraseasonal variability of sea surface temperature, however, is dominated by upwelling induced by remote equatorial wind only during summer-fall, with less contribution from surface heat fluxes for this season. During winter-spring, the intraseasonal variability of sea surface temperature results primarily from shortwave radiation and turbulent heat flux induced by wind speed associated with intraseasonal oscillations, and local forcing dominates the sea surface temperature variability.

In the season studied by the researchers, the mean thermocline is deep in the warm pool and thus thermocline variability decouples from the instraseasonal variability of sea surface temperature. Only in summer-fall when the mean thermocline is shallow, upwelling has important impact on sea surface temperature.

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