Redfield stoichiometry in Arabian Sea subsurface waters

A linear inverse mixing model is applied to hydrographic, nutrient, and carbon data collected during Joint Global Ocean Flux Study and World Ocean Circulation Experiment cruises in 1995 to estimate the Delta C-org/Delta N/Delta P/Delta Si/-Delta O-2 remineralization ratios within the Arabian Sea between 550 and 4500 m. The observed concentrations are separated into mixing fractions of source water masses and changes caused by remineralization processes, while the effect of denitrification is considered. In contrast to earlier investigations, diapycnal mixing, which plays an important role in dissolved matter fluxes in the Arabian Sea, is accounted for. The ratios are found to be variable with depth, especially in the upper 2000 m of the water column. We suppose that in general nutrients are released faster than carbon dioxide during remineralization. The Delta C-org/Delta C-inorg decrease from similar to 4 +/- 1 at 550 m to 2 +/- 0.2 at 2000 m and 1.2 +/- 0.3 at 4000 m, suggesting that the dissolution of calcium carbonate above the calcite lysocline is a potentially important process within the Arabian Sea.