Spatial distribution of phytoplankton along the Sunda Islands: The monsoon anomaly in 1998

Abstract

Recent ocean color and microwave observations are used to assess the spatial distribution of phytoplankton blooming relative to monsoons along the Sunda Islands. In 1997 and 1999, during the northwest monsoon the eastward South Java Current (SJC) along the Sunda Islands restrained the flows from the straits along the Sunda Islands and ceased blooming. During the southeast monsoon the westward South Equatorial Current (SEC) and the southeasterly wind generated cyclonic eddies along the Sunda Islands. The blooming was observed over those cyclonic eddies, where nutrients were entrained to the surface. In 1998, through the northwest to the southeast monsoon the eastward currents were flowing away from the coast. During the southeast monsoon the SEC was not observed. Through 1998, cyclonic eddies were observed along the Sunda Islands in consequence of these anomalies. The distribution of currents is defined for the monsoon anomaly in 1998. (1) The eastward SJC flowed away from the coast in the northwest monsoon. (2) No westward SEC was observed in the southeast monsoon. (3) The eastward SJC restrained the flow from the straits in the southeast monsoon. (4) Chlorophyll a ∼1 mg m−3 were observed along the Sunda Islands through the year. This monsoon anomaly is hypothesized as a result of anomalies in the distribution of pressure systems between the Pacific and the Indian Ocean following to the El Niño.