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

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.

Modulation of the Intraseasonal Chlorophyll‐a Concentration in the Tropical Indian Ocean by the Central Indian Ocean Mode

“…Our results verify the role of the oceanic process related to the CIO mode in the intraseasonal variability of mixed layer Chl concentration, and underscores the differences compared to the processes of Chl responses during the MJO season (Jin et al, 2012). Xu et al (2021) reported a high Chl concentration with significant intraseasonal variability along the south coast of the Sumatra-Java Islands, which is well captured by this model (Figure 1). However, the correlation coefficient between the projected CIO mode index and intraseasonal Chl concentration averaged in the south coast of Java (10°-6°S, 105°-115°E) is only 0.23 (not significant at the 95% confidence level).…”

“…Xu et al. (2021) reported a high Chl concentration with significant intraseasonal variability along the south coast of the Sumatra‐Java Islands, which is well captured by this model (Figure 1). However, the correlation coefficient between the projected CIO mode index and intraseasonal Chl concentration averaged in the south coast of Java (10°–6°S, 105°–115°E) is only 0.23 (not significant at the 95% confidence level).…”

Can Coastal Upwelling Trigger a Climate Mode? A Study on Intraseasonal‐Scale Coastal Upwelling Off Java and the Indian Ocean Dipole

“…Recently, Xu et al. (2021) used daily interpolated data and outlined the intraseasonal and interannual surface Chl‐a variations in the southeastern Indian Ocean.…”

“…Satellite-based Chl-a data could be a proxy for the coastal upwelling (Siswanto et al, 2020), but because of the large missing values, most previous studies used monthly averages (e.g., Iskandar et al, 2009;Susanto & Marra, 2005). Recently, Xu et al (2021) used daily interpolated data and outlined the intraseasonal and interannual surface Chl-a variations in the southeastern Indian Ocean. The present study makes daily time series for the coastal upwelling signals based on the satellite-based Chl-a data.…”

Seasonal Variability in Chlorophyll and Air-Sea CO2 Flux in the Sri Lanka Dome: Hydrodynamic Implications

“…In the eastern boundary of the Arabian Sea, the southwesterly winds turn mainly into onshore equatorward winds along the southwest coast of India, generating offshore Ekman transport and coastal upwelling [10,11]. In the eastern equatorial Indian Ocean, the southeasterlies along the southern coast of Java and Sumatra islands induces upwelling off the coast [12,13]. These boundary upwelling systems are mainly characterized as offshore transport of surface water where the subsurface water upwells to the surface.…”