By the investigation of moisture fluxes into Antarctica and the moisture convergence over Antarctica as a measure of snow accumulation, the deposition of e.g. dust connected with this accumulation in the ice of Antarctica will be interpretated. Results from the Vostok ice core reveal for example that during colder climatic conditions lower greenhouse gas concentrations were accompanied by higher dust concentrations. Focus is laid on the possible reasons for this concentration changes. Did the atmospheric circulation pattern change from the last glacial maximum (LGM, 21 kyr BP) to the recent climate?
In the present paper, two different paleosimulations of the Hamburg climate model, ECHAM3 (T42), are used: the timeslice experiment for the LGM and for the holocene climate optimum (HOL, 6 kyr BP). The ECHAM model is validated against the ECMWF-analyses. For the evaluation of the moisture fluxes, the atmospheric branch of the hydrological cycle was used. Especially, the aerial runoff, Q,
was calculated by integrating the specific humidity from the ground up to the 300 hPa level.
In the observational data (ECMWF-analyses) three regions of preferred moisture transports into Antarctica are identified with a high interannual persistence:
Dronning Maud Land, Wilkes Land and Marie Byrd Land. The model is capable to reproduce the observed patterns very well. Inspite of reduced total moisture transports in the climate of the LGM, the relative contribution of the meridional moisture transports in the LGM is increased. Similar structures of water vapor fluxes between the HOL and the recent climate are identified.
The accumulation in Antarctica (70o-90oS) deduced via the divergence of Q reveals higher values in JJA (186 mm/yr) then in DJF (106 mm/yr). In comparison to the recent climate in the LGM, the accumulation is reduced by nearly 50% but the same patterns are observed. The accumulation in the climate of the HOL do not differ significantly from that of the recent climate.
For further interpretation of the results from ice cores, a trajectory analyses will be provided. For extreme periods of moisture accumulation, five-day isentropic backward trajektories were calculated in the middle troposphere. The results reveal longer transport paths in the LGM (higher wind speed) with a shift in the source areas to more distant ocean basins. In the LGM the percentage of trajectories crossing continental areas increases in comparison
to recent climate conditions. For example, for those trajectories ending at Wilkes Land the percentage of trajectories crossing South America rises from 12 to 18%. In the HOL only small changes occur. From the model simulation it appears that the higher dust concentrations in the LGM can probably be attributed to a more meridional, convergent transport pattern in comparison to the recent climate with a more frequent crossing of southern hemisphere
landmasses, especially South America.