A case study of the westward transport of Chorophyll-a entrained by ocean eddies during a tropical cyclone

Abstract

During the passage of tropical cyclone (TC) ARB O1, a westward transport of Chlorophyll-a (Chl-a) enhancement was identified south of the Indian Peninsula. The features and underlying dynamics were investigated with high-resolution satellite remote sensing, reanalysis, and Argo buoy data. From January 12 to January 19, 2006, the phytoplankton bloom propagated westward with two ocean anticyclonic eddies, which were enhanced after the passage of the TC. The surface average maximum Chl-a concentration with an inertia period of approximately 4–5 days occurred in the four boxes. The maximum average concentration of Chl-a on January 16 (21) was 0.4 mg•m−3 (0.53 mg•m−3) in Box B, which was caused by a cyclonic eddy and Ekman pumping triggered by the TC (horizontal current transport). However, the maximum average concentration of Chl-a was 0.32 mg•m−3 in Box D, which was caused by an anticyclonic eddy and Ekman pumping triggered by the TC. After passage of the TC, the mixing layer deepened, and the upper ocean stratification weakened, which promoted an uplift of phytoplankton from the deeper layer to the upper layer. In addition to horizontal current transport, westward phytoplankton transport was produced under the joint influence of eddy entrainment and Ekman pumping triggered by the TC. This study can aid with assessing the biological responses of future typhoons.