IMPACT OF ENSO AND INDIAN OCEAN DIPOLE MODE (IODM) ON VARIABILITY OF THE OCEANOGRAPHIC PROCESSES IN THE EASTERN TROPICAL INDIAN OCEAN.

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In 1999, Indian Ocean Dipole Mode (IODM) was discovered in the Indian Ocean. This phenomenon co-occurred with a strong El Nino event and transformed eastern half of the Indian Ocean equatorial region into an upwelling regime for several months. Such findings made the eastern tropical Indian Ocean region an area of major climatic importance. The purpose of this project is to understand the seasonal evolution and interannual variability of the upwelling phenomena in the eastern tropical Indian Ocean using multi-sensor remote sensing time series data i.e. sea-surface height (SSH), ocean surface winds, sea-surface temperature (SST) and phytoplankton pigment concentration (chlorophyll a) from September 1997 to December 2003. The focus of our research is to monitor impact of the IODM and ENSO on mesoscale physical-biological oceanographic processes in the region. Our results indicated that the eastern tropical Indian Ocean exhibits the largest SST variability, SSH anomaly and the strongest w … More inds during simultaneous occurrence of a strong El Nino and IODM events in 1997-98. Furthermore, there was a significant departure from the 7-year monthly chlorophyll climatology in both magnitude and timing of seasonal response to the SE monsoon. During the peak of the 1997-98 El Nino and IODM, anomalous easterly wind induced strong upwelling and lifted the thermocline to depths much shallower than the climatological mean along the coast of Java resulting higher chlorophyll a concentration and subsequently the high chlorophyll a area extended northwestward along the Sumatra coast. Sequential occurrence of anomalous ocean condition during late-1997, early-1998 and late-1999 was found to be consistent with the evolutionary pattern of the IODM reported earlier. Our results highlight usefulness of multi-sensor remote sensing data in providing significant insight into strong interplay between climatological events and biological oceanographic processes and contribute to furtherance of our understanding of biological production mechanism and pelagic fisheries in the region. Less