Satellite-Observed Multi-Scale Variability of Sea Surface Chlorophyll-a Concentration along the South Coast of the Sumatra-Java Islands

Tengfei Xu,Zexun Wei,Chao Yuan,Teguh Agustiadi,Raden Dwi Susanto,Nyoman Radiarta,Anastasia Kuswardani,Mukti Trenggono,Agus Setiawan,Shujiang Li

doi:10.3390/rs13142817

Abstract

The southern coast of Java is known as one of the most productive fishing grounds for tuna, feeding by nutrient-rich water along the coast caused by the subsurface water upwelling. This primary productivity can be evidenced by the high sea surface chlorophyll-a concentration (SSC). Based on satellite remote sensing products, we investigate the multi-scale variability in SSC along the Sumatra-Java coast. The results show that seasonal variability of SSCs is primarily due to monsoon-driven upwelling and rainfall in the Indian Ocean and Indonesian seas sides of the Sumatra and Java Islands, respectively. Local Ekman pumping plays a secondary role, while rainfall input to the ocean has little effect. Coastally trapped Kelvin waves and mesoscale eddies are responsible for the intraseasonal SSC anomalies in regions along the south coast of Java and off the Sunda and Lombok Straits, respectively. The interannual variability in SSC is caused by the anomalous upwelling related to the Indian Ocean Dipole. There was a weak increasing trend of ~0.1–0.2 mg/m3 per decade, above the global averaged trend, which may be related to enhanced local Ekman pumping. These analyses provide an overall description of SSC variations based on satellite observations; however, further investigations based on in situ observations are needed to achieve better quantification.

Highlights

The Chla levels in the open areas of the Java Sea are higher in summer than in winter, which is explained by the fact that offshore Ekman transport favors southward transport of high Chla waters from the south coast of Kalimantan (Figure 3b,d)
The Chla levels are low in the southeastern tropical Indian Ocean and southern Java Sea, suggesting that rainfall input contributes little to Chla increase
Case studies have suggested that El NiñoSouthern Oscillation (ENSO) and Indian Ocean Dipole (IOD) events impact the sea surface chlorophyll-a concentration (SSC) along the Sumatra-Java south coast [12,14,33,34,35,36,37,38]

Summary

Introduction

Marine primary productivity is the fundamental factor that feeds the marine ecosystems and fisheries. Only satellite ocean color sensors can provide coverage of global ocean chlorophyll, which in turn indicating the phytoplankton biomass and marine primary productivity [1,2,3]. High sea surface chlorophyll-a concentration (SSC) areas generally are identified in the upwelling and coastal areas feeding by nutrient-rich water from deeper layer and runoff, respectively (Figure 1a). The global SSC is found subject to multi-scale variability associated with ocean dynamical processes such as upwelling, mesoscale eddies, and sea ice melting [4,5,6,7]. Previous investigations show no significant trend in global

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Discussion

Conclusion