Study of primary productivity on indian ocean dipole mode event and its relationships to pelagic fish catch abundance in Western Part of Sumatera Waters

Abstract

The Indian Ocean Dipole Mode (IOD/IODM) is an oscillation of the interaction between atmosphere and ocean system. IODM comprises of bipolar structure that characterized by the difference of sea surface temperature to normal. This phenomenon provides important influence to the several parameters of oceanographyc. While the positive event of IODM, during southeast munsoon (June to October), southeasterly wind from Australia generates upwelling, bringing cooler waters and increased nutrients to the surface along the southern coast of Java and Sumatera and its condition has been increasing chlorophyll-a concentration. The objectives of this study is to know the variability of chlorophyll-a along the southern coast of Java and Sumatera on positive IODM event. The sea surface temperature (SST) images taken from thermal sensor of Advanced Very High Resolution Radiometer-National Oceanic and Atmospheric Administration (AVHRR-NOAA) has been used to detect the cooler water as upwelling indicator. We investigated the spasial and temporal variability of chlorophyll-a along the south coasts of West Java and Sumatera from September 1997 to December 2009, by using the data of the Sea-viewing Wide-field of view sensor (SeaWiFS) of Sea Star satellite. The results shown that formation phase of IODM in transitional season I (May), while the strengthening of the South Equatorial Current followed by early cooling of the SST. The maturation phase in the southeast monsoon (June to August) and decay phase in November was followed by warming of the SST. At the Southeast monsoon (June to August), there is a visible presence of upwelling in the south of Java and western coast of Sumatera. Upwelling with highly intensity was founded in the southern coast of Java and western part of Sumatera on strong positive IODM event assosiated with intermediate of El Niño event, 1994. Higer chlorophyll-a concentration corresponds very well with monsoon-generated upwelling during the Southeast monsoon cycle. During the peak of anomalous easterly winds on strong positive IODM event (1997 and 2006) were induced strong upwelling. This event produced higher chlorophyll-a concentration that extended further northwest-ward along the Sumatera coast. The impact of upwelling while the IODM positive event on pelagic fish catch, likely follow the temporal variability in chlorophyll.