Chlorophyll-A Variability and Its Interrelation with ENSO (El Nino Southern Oscillation) In Northern Waters Of Papua

Abstract

This research aimed to study the variability of surface chlorophyll-a and its interrelation to ENSO (El Nino Southern Oscillation) in the North Papua waters. Monthly averaged data of Nino 3.4 Index from CPC NOAA, sea surface temperature (SST) from ERSL NOAA, and surface chlorophyll-a from Globcolor Project were analyzed using FFT (Fast Fourier Transform) and wavelet methods during September 1997 - April 2009. Referring to temperature anomaly at Nino region 3.4 during the period this study, three El Nino events were taken place in 1997/1998, 2002/2003, and 2004/2005. The 1997/1998 El Nino was the strongest with temperature anomaly reaching +2,69 oC, while from twice La Nina events (1998/1999/2000, 2007/2008), the 2007/2008 La Nina showed the weakest temperature anomaly at -1,89 oC. During 1997/1998 El Nino, SST in the North Papua waters was decreasing to range 29,48 - 29,72 oC, compared to its normal range of 30,05 - 30,33 oC. On the contrary, surface chlorophyll-a was increased to 0,088 – 0,391 mg/m3 during 1997/1998 El Nino, while low range of chlorophyll-a was observed during 2007/2008 La Nina (0,062 – 0,140 mg/m3 Keywords: chlorophyll-a, sea surface temperature, El Nino, inter-annual signal, North Papua ). During El Nino, hotspot of chlorophyll-a was shifted from west to east and following the movement of warm pool. Power spectrum density of chlorophyll-a revealed dominant inter-annual signal compare to annual and semi-annual. Cross-correlation analysis between Nino 3.4 with chlorophyl-a variability showed strong coherence at inter-annual signal which presumed as El Nino, in where the rise of chlorophyll-a was observed 1 - 3 month after El Nino event.