Assessing the Impact of Various Controlling Factors on Chlorophyll Concentration in the Arabian Sea Using Remotely Sensed Observations

Abstract

Present work examines a long-term trend (2003–2020) of the chlorophyll-a concentration and impact of various controlling factors on it in the Arabian Sea using robust non-parametric Man Kendall analysis, two-way ANOVA statistical test, and two-stage least square regression technique. Climatological means and interannual variations of chlorophyll-a (Chl_a) concentration and other controlling factors viz. Sea surface temperature (SST), Aerosol optical depth (AOD) and sea surface wind (SSW) have been analysed. From the seasonal variation of Chl_a and AOD it is observe that the highest Chl_a (1.4 mg/m³) is observed during July, August, September and October, and the highest AOD (0.8) is observed during June, July, August and September over the Arabian Sea. There was a two-month delay in the peak concentration of Chl_a/AOD, SSW; however, one month delay is observed in the peak concentration of Chl_a/SST in the Arabian Sea. A long-term trend of Chl_a concentration and SSW shows a decreasing trend, whereas SST and AOD show an increasing trend in the Arabian Sea. From ANOVA and two-stage least square regression it is observed that SST plays a significant role in influencing the decreasing trend of Chl_a in comparison to the other two controlling factors (AOD and SSW). A rise of 1% in SST results into a decrease of 0.138 percentage point in Chl_a concentration that is statistically significant at 1% significance level. The present work helps to understand the impact of various controlling factors on the ocean's primary productivity and the effect of climate change on the marine ecosystem.