Fiorani Luca, Roberto Barbini, Francesco Colao, Roberta Fantoni and Antonio Palucci

ENEA, FIS-LAS, Via Fermi 45, 00044 Frascati, Italy, Tel: +39(06)94005861, Fax: +39(06) 233227077, E-mail: fiorani@frascati.enea.it

Remote sensing by laser and satellite for the biogeochemical characterization of the Southern Ocean during Austral summer

Scientific investigations in the Southern Ocean are part of the Italian National Programme for Antarctic Research (PNRA). These surveys are performed in order to supply information on physical, chemical and biological processes affecting the investigated area, where a high spatial and temporal variability has prevented accurate and comprehensive estimates of the contribution to the carbon cycle of the Southern Ocean and, consequently, of its importance as a food source for higher trophic levels. Ocean color satellites have proven to be powerful tools in gaining a synoptic view of the phytoplankton dynamics. Nevertheless, their estimates of primary production in Antarctic surface seawaters should be taken with care: some authors found a value 4-5 times higher than previous estimates, made from extrapolated ¹⁴C measurements. This could be in part ascribed to the persistent cloud coverage that makes it difficult to get continuous imagery from space. The development of new algorithms, able to track the seasonal and interannual variability of primary production in the regional scale, requires an improvement in accuracy and coverage of the chlorophyll measurements in the Antarctic polynya: this aim can be achieved by means of data from laser remote sensors. In this paper, after a description of instruments and methods, a biogeochemical characterization of the Southern Ocean during Austral summer is given. In particular, the chlorophyll-a data gathered by the ENEA lidar fluorosensor during the Italian Antarctic Oceanographic Campaigns are used to improve the SeaWiFS estimates of primary production.