The Lagrangian progression of nitrous oxide within filaments formed in the Mauritanian upwelling

Abstract

Concentrations of dissolved nitrous oxide (N 2 O) and N 2 O flux densities were determined during the Lagrangian investigation of two filaments advected from the Mauritanian upwelling. The ratio between remineralization and N 2 O production, predominantly through nitrification was 0.11 ± 0.01%. This was linked to the hydrodynamic character of each filament, which was determined by the relative proportions of two central water masses from which they originated. Surface waters were saturated with N 2 O up to 150% when first upwelled, but following advective transport offshore and exchange with the atmosphere at rates between 5 and 27 μmol m -2 d -1 were closer to equilibrium with the atmosphere (105%) when the filament was approximately two weeks old. Annual estimates of N 2 O emissions from transient filaments in this area are between 1.3 and 2.1 Gg N, but could be as high as 9.8 Gg N y -1 for the extended upwelling area in the vicinity of Cap Blanc. Copyright 2011 by the American Geophysical Union.