Gravitational separation suggested by O2/N2, δ15N of N2, δ18O of O2, Ar/N2 observed in the lowermost part of the stratosphere at northern middle and high latitudes in the early spring of 2002

Abstract

Lower stratospheric O2/N2 ratios (δ(O2/N2)) at northern middle and high latitudes were measured by analyzing aircraft air samples collected between Nagoya, Japan and Svalbard Islands in the Arctic during the early spring of 2002. The measured values of δ(O2/N2) are relatively uniform horizontally in the lowermost part of the stratosphere but increase with height. Vertical distributions of δ(O2/N2) and the CO2 concentration observed over Svalbard Islands and Barrow, Alaska are negatively correlated. By examining the rates of change in δ(O2/N2) and δ13C of CO2 relative to the CO2 concentration, such a correlation observed is mainly attributable to upward propagation of their seasonal cycles produced on the ground surface for the troposphere and height‐dependent air age for the stratosphere. However, from the vertical profiles of δ15N of N2, δ18O of O2 and δ(Ar/N2) measured in the lowermost part of the stratosphere over Svalbard Islands, it is suggested that the relationship between δ(O2/N2) and the CO2 concentration is affected by the gravitational separation. By correcting the measured δ(O2/N2) and δ13C values for this gravitational separation, the relationships of δ(O2/N2) and δ13C with the CO2 concentration are consistent with those expected from their secular trends in the troposphere.