Temporal insights into deep chlorophyll maxima dynamics in the Indian sector of the Southern Ocean: a Bio-Argo float study

This study investigates seasonal variations and influencing factors on the Deep Chlorophyll Maximum (DCM) in the Subtropical Front (STF) and Polar Front (PF) regions of the Indian Sector within the Southern Ocean, utilizing Bio-Argo floats data. Our analysis reveals distinct seasonal and regional patterns in salinity, temperature, and DCM dynamics. The STF region, characterized by warmer, saltier waters and a shallower Mixed Layer Depth (MLD), facilitates stronger stratification and nutrient retention, resulting in an enhanced DCM of 1.55 mg/m 3 . In contrast, the PF’s colder, fresher waters exhibit deeper MLDs and reduced stratification, leading to lower mean DCM concentrations of 0.88 mg/m 3 . The depth of the DCM increased along this gradient, deepening from a median of 42 m at the STF to 78 m at the PF. We identify a robust correlation between DCM, Photosynthetically Active Radiation (PAR), and MLD, highlighting how environmental conditions profoundly influence DCM and its depth in these critical oceanic zones. This study shows that the DCM is present year-round in the STF, while it exhibits seasonal variability in the PF.