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- Title
Investigating the effect of El Niño on nitrous oxide distribution in the Eastern Tropical South Pacific.
- Authors
Qixing Ji; Altabet, Mark A.; Bange, Hermann W.; Graco, Michelle I.; Xiao Ma; Arévalo-Martínez, Damian L.; Grundle, Damian S.
- Abstract
The open ocean is a major source of atmospheric warming and ozone depleting gas nitrous oxide (N2O). Intense sea-to-air fluxes of N2O occur in major oceanic upwelling regions such as the Eastern Tropical South Pacific Ocean (ETSP). The ETSP is influenced by the El Niño-Southern Oscillation that leads to inter-annual variations of physical, chemical and biological properties. A strong El Niño was developing in this region in October 2015, during which we investigated the N2O production pathways and, by comparing to previous non-El Niño years, the effects of El Niño on water column N2O distributions and fluxes. Analysis of N2O natural abundance isotopomers suggested that both nitrification and partial denitrification (nitrate and nitrite reduction to N2O) were important N2O production pathways. Higher than normal sea-surface temperatures were associated with a deepening of the oxycline, while the level of sea surface N2O supersaturation on the continental shelf was nearly an order of magnitude lower than those of non-El Niño years. Therefore, a significant reduction of N2O efflux in the ETSP occurred during the 2015 El Niño event. At both offshore and coastal stations, the N2O concentration profiles during El Niño showed moderate N2O concentration gradients, and peak N2O concentrations were deeper than during non-El Niño years; this was likely the result of suppressed upwelling retaining N2O in subsurface waters. The depth-integrated N2O concentrations during El Niño were nearly twice as high as those measured in non-El Niño years, indicating subsurface N2O during El Niño could be a reservoir for intense N2O effluxes when normal upwelling is resumed after El Niño.
- Subjects
NITROUS oxide; SUPERSATURATION; SOLUTION (Chemistry); ISOMERISM; DENITRIFICATION
- Publication
Biogeosciences Discussions, 2018, p1
- ISSN
1810-6277
- Publication type
Article
- DOI
10.5194/bg-2018-453