Modelling new production in the northwest Indian Ocean region

Oceanic new production is a potential avenue for the removal of atmospheric carbon dioxide to the deep abyss. The ability to estimate new production on large, ocean-basin scales has important implications for studies of the greenhouse effect. This paper describes the development of a method which will allow real-time estimates of new production on ocean-basin scales, given real-time data on ocean colour and sea-surface temperature from satellites. This study has concentrated on the northwest Indian Ocean region but the protocol developed could be geographically transportable. Results from a biogeochemical study carried out in the northwest Indian Ocean during a monsoon and an intermonsoon period in 1994 indicate that this region can be partitioned into 6 distinct provinces based on bathymetry, sea-surface temperature and chlorophyll measurements. Parameters that define the vertical structure in the biomass profile and the photosynthesis-light curve have been established for each province and these, in combination with archived satellite data, are used to compute the primary production for each province using an established light-dependent model. From our empirically derived relationship between the f-ratio and primary production, new production for the northwest Indian Ocean over these 2 different seasons is computed.