Nitrous oxide production in the Ocean

Abstract

Examination of vertical profiles of N 2 O, oxygen, and nitrate from the Northeast and Northwest Atlantic, Northeast Pacific and eastern tropical North Pacific reveals a striking consistency in the relationships among them. With the exception of zones of active denitrification, N 2 O is negatively correlated with oxygen and positively correlated with nitrate throughout the water column and it is, therefore, concluded that N 2 O production in the ocean is associated with the oxidative regeneration of nitrate. In both the Atlantic and Pacific Oceans, the difference between the measured N 2 O concentration and its equilibrium solubility is linearly correlated with apparent oxygen utilization and from this relationship and the Redfield plankton decomposition model it is estimated that N 2 O‐nitrogen comprises about 0.1 to 0.4% of the nitrogen regenerated in the ocean. From the ratio of N 2 O to nitrate production during nitrate regeneration and estimates of the overall regeneration of nitrate in the ocean, it is concluded that the total marine production of N 2 O is in the range of 4 to 10 Tg‐N yr −1 (6 to 16 Tg‐N 2 O yr −1 ). This estimate is in good agreement with estimates of the N 2 O loss to the atmosphere derived from N 2 O measurements at the sea surface.