01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-04-0088 |
| Title of Abstract | Latitudinal patterns of deep chlorophyll maxima (DCM) and their bio-optical response to climate forcing in the north to south Indian Ocean |
| Authors | Sudarsana Rao Pandi*, Sarat Chandra Tripathy, Aneesh A Lotliker, R Chandrasekhar Naik, Sunil Kumar Padhi, Rahul Mohan |
| Organisation | National Centre for Polar and Ocean Research |
| Address | NCPOR, Headland Sada Vasco Da Gama, Goa, India Pincode: 403804 E-mail: sudarsanarao@ncpor.res.in |
| Country | India |
| Presentation | Oral |
| Abstract | The deep chlorophyll maximum (DCM) in the Indian Ocean exhibits distinct latitudinal patterns shaped by regional physical processes and bio-optical conditions. This study utilizes hyperspectral radiometric (Satlantic) profiles of backscattering and chlorophyll-a fluorescence collected during three expeditions⿿SS356 (February⿿March 2017), SWTIO (June 2014), and the Indian Scientific Expedition to the Southern Ocean (January⿿February 2018) covering the northeastern Arabian Sea, Southwestern Tropical Indian Ocean (including the Equatorial and Southern Indian Ocean), and the Indian sector of the Southern Ocean (ISSO). Two types of DCMs were identified from vertical profiles of chlorophyll-a and backscattering at 650nm: deep acclimation maxima (DAM), driven by photoacclimation, and deep biomass maxima (DBM), representing true biomass accumulation. The study examines how salinity and temperature-driven stratification influences DCM characteristics across contrasting oceanic regimes. In the North Indian Ocean (NIO), strong salinity stratification from less-riverine input, and higher optical active substances, and productivity, results in a shallow DCM (~30⿿50m). The Equatorial Indian Ocean (EIO) shows a weaker and more variable DCM (~50⿿70m), shaped by dynamic forcings. In comparison, the SWTIO region exhibits stronger stratification, lower sea level anomaly, higher precipitation, a more stable mixed layer, and elevated buoyancy frequency, with DBM dominant, whereas DAM prevails in the EIO. In the Southern Ocean, the DCM deepens (~80⿿120m) under oligotrophic conditions and strong light limitation. Across frontal zones such as the Subtropical Front (STF) and Subantarctic Front (SAF), eddy-driven mixing and nutrient supply enhance the DCM, while in the Polar Front (PF), freshwater stratification and deep convection modify phytoplankton community structure. These findings highlight that climate-driven ocean warming and surface freshening are likely to significantly alter phytoplankton vertical distribution and community composition across the Indian Ocean, with major implications for biogeochemical cycles and carbon export. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Stratification; Winds and eddies; Sea ice extent; Bio-optical properties; Hyperspectral radiometer. |
| For Awards | no |