Tropospheric transport of continental tracers towards Antarctica under varying climatic conditions

We present a method to analyse tracer transit time climatologies based on the concept of tracer age, The method consists of introducing idealized, short-lived radioactively decaying tracers in a general circulation model of the atmospheric. Tracer age since emission is calculated at any given place in the atmosphere from the ratio of the concentrations of tracers with different lifetimes emitted over the same source area. An obvious use of this method is the analysis of transport of real tracers with similar lifetime, (such as dust particles) during different climatic periods. Here, this method is applied to transport from southern hemisphere continental source areas towards Antarctica at the present, the last glacial maximum (21 kyr BP) and the last glacial inception (115 kyr BP). It is found that the variation over time of atmospheric transport efficiency towards Antarctica depends on the tracer source region: changes for Patagonian tracers differ from those for tracers originating over Australia and southern Africa. Transport towards Antarctica during the last glacial maximum (LGM) is faster for Patagonian. but not for Australian and Southern African tracers. It is shown that for the time of the last glacial inception, tracer transit time towards Antarctica is not different from the present, although signs of a more vigorous atmospheric circulation can be seen in the simulation.