Ocean margin profile

Fig. 10-1 Schematic representation of the physiographic profile at ocean margins.

Figure 11 Depth profiles of (a) N2O concentration and (b) and (c) <5 0 of N2O at station ALOHA in the subtropical North Pacific (22° 45 N, 158° W) during four separate cruises. The solid line in (a) indicates theoretical saturation with atmospheric N2O at in situ temperatures and salinities. The minima in and <5 0 around 200 m are thought to be due to significant in situ production of N2O from nitrification. The broad isotopic maxima at depth are likely due to N2O consumption, perhaps in the denitrifying waters along the eastern Pacific margin. The filled squares at the top of (b) and (c) represent measurements of <5 N and <5 0 of atmospheric N2O during the Hawaii Ocean Time-series 76 cruise, and arrows indicate the range of historical measurements as of the late 1980s. Reprinted from Dore JE, Popp BN, Karl DM, and Sansone FJ (1998) A large source of atmospheric nitrous oxide from subtropical North Pacific surface waters. Nature 396 63-66.

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