Coexistence of nitrous oxide undersaturation and oversaturation in the surface and subsurface of the western Arctic Ocean

Abstract

AbstractThe nitrous oxide (N2O) distributions in a shelf‐slope‐basin section from the Chukchi Sea shelf to the Chukchi Abyssal Plain (CAP) in the western Arctic Ocean were observed for the first time during the fourth Chinese National Arctic Research Expedition (4th CHINARE) in late August 2010. The N2O concentrations were 11.4–16.9 nmol L−1, corresponding to saturation values of 92–118% in the surface water. In the surface, biological factor was negligible to N2O production, and physical process dominated the surface N2O distribution. The N2O undersaturation may be the result of dilution by sea ice meltwater. The oversaturation may be caused by the diffusing of N2O‐rich shelf bottom water. Below the surface, N2O concentrations ranged from 11.4 to 21.4 nmol L−1. On the Chukchi Sea shelf, N2O concentrations increased from the surface to the near‐bottom water, indicating sediment N2O produced by nitrification or denitrification emission may be a significant source. The subsurface maxima in the upper halocline layer (UHL) may receive partial contribution from nitrification production but was primarily caused by the spreading of shelf water.