Water-column denitrification open-ocean

Nearly all quantitative estimates of open-ocean water column denitrification are based on some type of nitrate deficit calculation. In the Arabian Sea, Naqvi (1987) have used nutrient-potential temperature relationships to estimate a denitrification rate of 30 Tg/y. In a later study Naqvi and Shailaja (1993) arrived at a... 

Figure 34-4 Water column profiles of nitrate concentration (open symbols) and c5 N itrate (filled symbols) in the Eastern Tropical North Pacific (ETNP, coastal Baja California), Southern Ocean and North Atlantic (Sargasso Sea). The ETNP shows a large increase in c5 N i ate in the thermocline owing to local water column denitrification. The Southern Ocean shows little deviation from the global deep mean c5 N it te except at the surface, where partial NO3 assimilation leaves residual nitrate enriched in N. The North Atlantic profile shows low c5 N itrate in the thermocline owing to the nitrification of locally fixed N. Note that the ETNP profile also includes deep measurements from near Hawaii (diamonds) the smooth transition between samples at distant locations emphasizes the homogeneity of the deep Pacific.

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