Event-scale blooms drive enhanced primary productivity at the Subtropical Convergence

• Published in: Geophysical Research Letters
• Main Authors: Llido, J., Garçon, V., Lutjeharms, J. R.E., Sudre, J.
• Other Authors: Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2005
• Subjects: [SDU]Sciences of the Universe [physics]; Southern Ocean
• Online Access: https://hal.science/hal-00282583; https://hal.science/hal-00282583/document; https://hal.science/hal-00282583/file/2005GL022880.pdf; https://doi.org/10.1029/2005GL022880

Frontal systems in the Southern Ocean are known for their enhanced biological activity, with some tantalising suggestions that this enhancement may be intermittent. We have used frequent satellite ocean colour observations to investigate the Subtropical Convergence south of Africa. We demonstrate that the biological enhancement takes place as episodic chlorophyll bloom events with limited spatial and temporal scales. Most of the events appear in austral spring-summer. Two typical lifetimes, 8-24 and 40-60 days, emerge unambiguously during these seasons. A similar analysis has been carried out on modelled chlorophyll fields to investigate the physical-biogeochemical causes for such events. Strong and swift stratification, alleviating the light limitation on growth of phytoplankton, causes the appearance of a bloom. A mixed layer depth expansion subsequently leads to a rapid disappearance of the simulated event. Phytoplankton horizontal transport, either zonal or meridional, also plays a key role on the lifetime of the bloom events.