The Air-Sea Nitrous Oxide Flux along Cruise Tracks to the Arctic Ocean and Southern Ocean

Abstract

Nitrous oxide is a trace gas with two global environmental effects: it depletes stratospheric ozone and contributes to the greenhouse effect. Oceans are one of the most significant nitrous oxide sources; however, there are ocean areas whose contributions to the nitrous oxide budget are not yet well studied. The Southern Ocean and the Arctic Ocean feature strong winds and portions that are covered by sea ice. These intense environmental conditions and the remoteness of these regions hamper fieldwork; hence, very limited data are available on the distributions and the source and sink characteristics of nitrous oxide. Using data from the 4th Chinese National Arctic Research

Interannual variability in methane and nitrous oxide concentrations and sea-air fluxes across the North American Arctic Ocean (2015–2019)

“…Sea-air fluxes of CH4 and N2O integrated over the mixed layer residence time of each gas were calculated, incorporating variability in wind speed, sea ice cover, and sea level atmospheric pressure. This approach contrasts with some previous studies based on Arctic Ocean seawater measurements that have calculated sea-air fluxes of CH4 and N2O using either instantaneous wind speeds (Heo et al, 2021;Hirota et al, 2009;Zhan et al, 2017), or wind speeds averaged over a fixed amount of time, e.g., one month (Li et al, 2017;Lorenson et al, 2016). As gas exchange is a nonlinear function of wind speed, high wind speeds have a disproportionately large impact on the total sea-air flux.…”

A Harmonized Nitrous Oxide (N2O) Ocean Observation Network for the 21st Century

“…The Atlantic Meridional Transect 7 is an example of an annually repeated cruise on which N 2 O measurements have been made over two decades (Forster et al, 2009;Rhee et al, 2009;Grefe and Kaiser, 2014). N 2 O has been repeatedly measured during the annual Chinese Arctic and Antarctic Expeditions (CHINARE) to the Arctic and Southern Oceans, see e.g., (Zhan and Chen, 2009;Zhan et al, 2015Zhan et al, , 2017. Beside these examples, there are few published time-series measurements of open ocean water column N 2 O distributions from repeat hydrographic sections (Nevison et al, 1995;Fenwick and Tortell, 2018).…”

N2O dynamics in the western Arctic Ocean during the summer of 2017

“…The distribution of SC N 2 O exhibited different patterns from the distribution of NC N 2 O within the surface layer. These results are indicators of the effect of the physical solubility, which is mainly determined by T and S 34 , and is dominant in the NC (cold and fresh) compared to the SC (warm and saline) 23 . In addition to the physical solubility, Randall et al 64 reported that the N 2 O of sea-ice meltwater was greatly under-saturated, and several studies 13 , 19 , 21 , 24 have suggested that the under-saturated N 2 O in the NC surface water may be related to the dilution of melting sea ice.…”

“…The positive N 2 O fluxes were estimated by Hirota et al 20 , although their research area was limited to the south of the SC, and the investigation was conducted in few locations. Wu et al 21 and Zhan et al 23 likewise estimated positive N 2 O fluxes in the SC and negative N 2 O fluxes in the NC, although the flux values were calculated using only one model. In addition, Fenwick et al 19 estimated relatively lower fluxes, suggesting that these results may be due to either of the different calculation approaches (e.g., weighted mean wind data over 60 days prior to sampling), varying oceanographic conditions (e.g., dilution by melting of sea ice with low N 2 O concentration) or both.…”