The influence of precipitation origin on the δ18O–Trelationship at Neumayer station, Ekstrmisen, Antarctica

The relationship between δ 18 O and air temperature at Neumayer station, Ekstrmisen, Antarctica, was investigated using fresh-snow samples from the time period 1981–2000. A trajectory model that calculated 5 day-backward trajectories was used to study the influence of different synoptic weather situations and thus of different moisture sources on this correlation. Generally a high correlation between air temperature and δ 18 O was found, but the quality of the δ 18 O– T relationship varied with the different trajectory classes. Additionally, the sea-ice coverage on the travel path of the moist air was considered. The amount of open ocean water underneath the trajectory has a large influence on the δ 18 O– T relationship. For trajectories that lead completely above open water, no significant correlation between δ 18 O and T was found, because mixing with air masses containing additionally evaporated water vapour from the ocean influences the isotope ratio of precipitation. A very high correlation, however, was found for transports over the completely ice-covered Weddell Sea.