Spatio-temporal distributions of atmospheric N₂O isotopocules in the Northern mid- and high-latitudes

Abstract

Fixed-point observations were conducted to determine the latitudinal and altitudinal distribution and long-term variations of N₂O isotopocule ratios in the Northern mid- and high-latitudes, and to analyze the dynamics of N₂O production and consumption. The bulk nitrogen isotope ratio (d¹⁵N^bulk) increased by about 0.05 permil/year and the oxygen isotope ratio (d¹⁸O) increased by about 0.03 permil/year, corresponding to the increase in concentration, from 2005 to 2022 at Hateruma Island, Okinawa (47 m altitude) and over Novosibirsk, Russia (500 m and 7000 m altitudes). On the other hand, ¹⁵N-site preference (SP, the difference of d¹⁵N between central and edge N in NNO molecules) showed no significant long-term change. Detailed analysis of the long-term trends showed an increase in the altitudinal difference in N₂O concentrations and short-term variations in isotopocule ratios at each altitude during 2010-2016 in Novosibirsk, suggesting a change in the contribution of surface sources and stratospheric N₂O.