Application of an atmospheric tracer model to high southern latitudes

Abstract

We discuss the development of a global three-dimensional tracer model and use it to examine the atmospheric dispersal of passive tracer gases, particularly carbon dioxide, and their transport to Antarctica and the Southern Ocean. The tracer model is based on the University of Melbourne General Circulation Model and includes the effect of convective transport. Our results indicate the importance of a realistic treatment of the effect of convection. The model is applied to the dispersion of idealized distributions of tracer to determine atmospheric transport times. We examine particularly the time taken for the “tracer front” to reach the Antarctic coast and the South Pole in the case of clouds initialized at three latitudinal domains. The transport in all cases is seen to be very rapid south of about 45°S; this is due to the mixing associated with the strong and numerous transient disturbances at these latitudes in the Southern Hemisphere. The model is also used with an inverse technique and an annual mean carbon dioxide type distribution to deduce apparent sources and sinks of this gas. Net sources are found in the Northern Hemisphere and equatorial regions and net sinks in the Southern Hemisphere. This latter result is of considerable interest in view of the uncertainty of the CO₂ uptake by the Southern Hemisphere oceans. DOI: 10.1034/j.1600-0889.1992.00013.x