Seasonal Difference of Biological Activity in the East China Sea using Satellite-derived Chlorophyll-a

Abstract

The purpose of this study is to investigate climatological variations from the temporal and spatial surface satellite-driven chlorophyll concentration and to understand the physical mechanism that affect the distribution of chlorophyll in the East China Sea (ECS) during 1998-2014. A linear trend analysis of chlorophyll data reveals that, during recent 17 years, the spring bloom was enhanced in the most of the ECS, while summer and fall blooms were weakened. The increased spring (Mar. - May) chlorophyll was associated with strengthened winter (Dec. - Feb.) wind that probably provided more nutrient into the upper ocean from the deep. The causes of decreased summer (Jun. - Aug.) chlorophyll in the northern ECS were related one or more factors such as river runoff, wind pattern, SST (stratification of the water column), and limited nutrient supply. First, although 17-year summer chlorophyll variations were well correlated with the area influenced by the Changjiang River discharge, their variations was not linearly correlated with the river discharge after 2003. Second, spatially different patterns of chlorophyll were better related to spatial variations of wind-direction that the amount of river discharge during the summer season. Third, the decreased summer chlorophyll seemed to be related with the nutrient limitation. However, the decreased fall (Sep. - Nov.) chlorophyll was associated with weakened wind that tends to he East China Sea (ECS) during 1998-2014. A linear trend analysis of chlorophyll data reveals that, during recent 17 years, the spring bloom was enhanced in the most of the ECS, while summer and fall blooms were weakened. The increased spring (Mar. - May) chlorophyll was associated with strengthened winter (Dec. - Feb.) wind that probably provided more nutrient into the upper ocean from the deep. The causes of decreased summer (Jun. - Aug.) chlorophyll in the northern ECS were related one or more factors such as river runoff, wind pattern, SST (stratification of the water column), and limited nutrient supply. First, although 17-year summer chlorophyll variations were well correlated with the area influenced by the Changjiang River discharge, their variations was not linearly correlated with the river discharge after 2003. Second, spatially different patterns of chlorophyll were better related to spatial variations of wind-direction that the amount of river discharge during the summer season. Third, the decreased summer chlorophyll seemed to be related with the nutrient limitation. However, the decreased fall (Sep. - Nov.) chlorophyll was associated with weakened wind that tends to