Modelling new production in the northwest Indian Ocean region

Abstract

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 whlch 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 biogeochernical 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.

Contribution of atmospheric nitrogen deposition to new production in the nitrogen limited photic zone of the northern Indian Ocean

“…More details of this technique are discussed by Kumar and Ramesh [2005]. 15 N tracer technique‐based new and primary production data in the northern Indian Ocean have been obtained from published studies [ McCarthy et al , 1999; Watts et al , 1999; Watts and Owens , 1999; Sambrotto , 2001; Kumar et al , 2004, 2010; Prakash et al , 2008; Gandhi et al , 2010a; N. Gandhi et al, Primary and new production in the thermocline ridge region of the southern Indian Ocean:, submitted to Deep Sea Research, Part I , 2012] (Tables 1 and 2 and Figure 2); as in the case of aerosols, measurements cover most of the Arabian Sea, but are spatially limited in the Bay of Bengal. As for the aerosol deposition fluxes, we have estimated the weighted averages of new and primary production, and the contributions (in %) of aerosol deposition to new production are calculated as the ratios of the sum of dry and wet deposition fluxes to the new production (Tables 1 and 2).…”

Delineation of ecological provinces using ocean colour radiometry

“…The problem was more acute when the sampling stations were located near the boundaries of the putative provinces. This issue has been addressed at global , Longhurst 2006) and basin scales (Hoepffner et al 1999, Watts et al 1999, Gibb et al 2000, Gonzalez-Silvera et al 2004.…”

“…We used these provinces as a template and assigned to them photosynthetic parameters and parameters that describe vertical structure in chl a distribution for computing primary production. The main limitation of the approach, acknowledged by , lies in the static definition of the province boundaries: ocean circulation and therefore water mass location change with seasonal cycles or in response to intense atmospheric events (see also Platt & Sathyendranath 1999).…”

“…This information could be applied to aid in assigning dynamic province boundaries, which would be superior to the static boundaries that have been used so far. Several authors have used satellite data to identify surface water masses and to compute phytoplankton production at basin scales (Dugdale et al 1989, Sathyendranath et al 1991, Watts et al 1999, Fischer et al 2000. These methods are based on SST and chl a concentration.…”

Identification of biophysical regions in the south-western part of the Okhotsk Sea by satellite imagery classification

“…As a result, the effects of ocean circulation, intense atmospheric events and seasonal cycles on changes in water mass location could not be addressed (Platt and Sathyendranath, 1999). With advances in technology, several authors have used satellite data to identify surface water masses to understand biological and physical processes in the ocean ecosystem Saraceno and Provost, 2005;Saraceno et al, 2006) and compute primary production (Watts et al, 1999;Fischer et al, 2000). Longhurst et al (1995) determined the world's ocean provinces using two databases: chlorophyll a from the Coastal Zone Colour Scanner (CZCS) and physical forcing.…”