A Global Oxygen Isotope Model – Semi-Empirical, Zonally Averaged

Abstract

A simple model, which is zonally averaged, for the transport of atmospheric water vapour is presented which uses as input the zonally averaged evaporation field and the mean meridional travel distance of tropospheric water vapour as functions of latitude. The model demonstrates that for polar regions each of the 10° latitude strips poleward of 25° is of equal importance as a moisture source. The model is used to predict zonal averages of δ(¹⁸O) for the present day and 18 ka BP. Both annual average values and seasonal amplitudes are presented and compared to observations. Sea-ice cover is an important factor in determining both annual averages and seasonal amplitudes today and at 18 ka BP. An earlier model (Jouzel and others 1983) linking δ(¹⁸O), the deuterium excess, and sea-salt content in an Antarctic ice core to the relative humidity of the source region is based on a single-source atmospheric water-vapour cycle type model and is re-evaluated using the present model.