Abstract
The concentrations of the ozone-depleting greenhouse gas nitrous oxide (N2O) in the upper 300 m of the Subarctic and Arctic Oceans determined during the 5th Chinese National Arctic Research Expedition were studied. The surface water samples revealed that the study area could be divided into three regions according to the distribution of dissolved N2O in the surface water, namely, the Aleutian Basin (52° N–60° N), continental shelf (60° N–73° N) and Canadian Basin (north of 73° N), with N2O in the surface water in equilibrium, oversaturated and undersaturated relative to the atmosphere, respectively. The influences of physical and chemical processes, such as eddy diffusion and sedimentary emissions, beneath the surface layer are discussed. The results of a flux evaluation show that the Aleutian Basin may be a weak N2O source of approximately 0.46 ± 0.1 μmol·m−2·d−1, and the continental shelf acts as a strong N2O source of approximately 8.2 ± 1.4 μmol·m−2·d−1. By contrast, the Chukchi Abyssal Plain (CAP) of the Canadian Basin is at least a temporal N2O sink with a strength of approximately −10.2 ± 1.4 μmol·m−2·d−1.
Highlights
Nitrous oxide (N2 O) is an important atmospheric trace gas that is one of the most powerful greenhouse gases in the troposphere with a radiative forcing efficiency 200–300 times greater per molecule than that of CO2 [1]
South of 60◦ N, the lowest N2 O Saturation Anomaly (SA) in surface water is approximately −2%, which is close to the uncertainty level of our method, suggesting that the surface water in the Aleutian Basin is in equilibrium with the atmosphere since the SA falls within the precision of our method
The N2 O fluxes in the Aleutian Basin, continental shelf and Chukchi Abyssal Plain (CAP) were studied during Chinese National Arctic Research Expedition (CHINARE) 5
Summary
Nitrous oxide (N2 O) is an important atmospheric trace gas that is one of the most powerful greenhouse gases in the troposphere with a radiative forcing efficiency 200–300 times greater per molecule than that of CO2 [1]. The atmospheric concentration of N2 O has been increasing significantly since pre-industrial times [2]. N2 O is considered the most important ozone-depleting substance due to its increased emissions, while the emissions of other major ozone-depleting substances (e.g., chlorofluoro carbon) have decreased over time [3]. For N2 O, the ocean acts as one of the most important sources to the atmosphere, contributing ~4 Tg·N N2 O a−1 , or ~1/3 of the annual natural N2 O source [4,5,6]. Significant N2 O sources have been found in the tropical ocean where upwelling occurs, for example, in the Peruvian upwelling system of the subtropical Pacific Ocean [7] and in the Arabian Sea [8], which contribute
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