Phytoplankton blooms with sequential cyclonic and anticyclonic eddies during the passage of tropical cyclone Hibaru

Abstract

Two phytoplankton blooms triggered by the tropical cyclone (TC) Hibaru were studied in the Bay of Bengal. Hibaru occurred in southeastern Sri Lanka in January 2005. After the passage of Hibaru, two strong phytoplankton blooms appeared in the study area (3.5° N-6° N, 83.5° E-88.5° E). In this study, the dynamic mechanisms were investigated with remote sensing, multisource reanalysis products and Argo float data. The first bloom on January 19 to 20 was induced by upwelling with the upper cyclonic eddy and mixed entrainment caused by Hibaru, where the maximum chlorophyll a (Chl-a) concentration was 0.235 mg•m–3. Sea surface cooling and heavy rainfall also occurred. The second bloom from January 27 to 28 was triggered by the interaction of the upper cyclonic eddy and submarine anticyclonic eddy after the passage of Hibaru, where the maximum of the Chl-a concentration was 0.124 mg•m–3. With the submarine anticyclonic eddy and weakened barrier layer thickness (BLT), the subsurface horizontally converged chlorophyll and nutrient water was uplifted with upwelling. This study contributes to the assessment of the ecological impact of ocean eddies during the passage of TC in the Bay of Bengal.

Keywords

• tropical cyclone
• ocean eddy
• phytoplankton
• bay of bengal