AUTHOR=Kim Il-Nam 

TITLE=Estimating “Mean-State” July (1985–2007) N2O Fluxes in the Northern Gulf of Mexico Hypoxic Region: Variation, Distribution, and Implication

JOURNAL=Frontiers in Marine Science

VOLUME=5

YEAR=2018

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2018.00249

DOI=10.3389/fmars.2018.00249

ISSN=2296-7745

ABSTRACT=<p>Along the Texas-Louisiana continental shelf in the northern Gulf of Mexico (nGOM) is a region frequently referred to as the “Dead Zone” due to severe oxygen depletion caused by eutrophication. Owing to its characteristics, it is expected to be an oceanic source region for nitrous oxide (N<sub>2</sub>O) emissions to the atmosphere during the hypoxic events. However, there is little known about whether the nGOM is source or sink region for atmospheric N<sub>2</sub>O. Here, we estimate “mean-state” July (1988-2007) N<sub>2</sub>O fluxes from the nGOM, using simple modeling approach. The estimated mean N<sub>2</sub>O fluxes for July across the air-sea interface ranged from +0.9 ± 11.7 to +14.3 ± 15.0 μmol N<sub>2</sub>O m<sup>−2</sup> d<sup>−1</sup> with a mean value of +6.1 ± 9.0 μmol N<sub>2</sub>O m<sup>−2</sup> d<sup>−1</sup> (+: sea → air). Our estimates were in reasonable agreement with the few available summer measurements, and suggested that the nGOM hypoxic region acts as a source of atmospheric N<sub>2</sub>O during the month of July between 1985 and 2007. Local regions influenced by the Mississippi and Atchafalaya Rivers showed higher N<sub>2</sub>O fluxes to the atmosphere than other regions. If the area affected by nutrient loading and the resulting hypoxia expands, the nGOM may become an even stronger oceanic N<sub>2</sub>O “hot spot” source region. Therefore, future study, based on <italic>in-situ</italic> observations, is necessary to elucidate N<sub>2</sub>O dynamics in the nGOM hypoxic region.</p>