Dating stratigraphic variations of ions and oxygen isotopes in a high-altitude snowpack by comparison with daily variations of precipitation chemistry at a low-altitude site

摘要

Daily precipitation at Tustervatn (65°83'N, 13°92'E, 439 m above sea level) was analysed for ions and oxygen isotopes. Seven-day air mass trajectories provided information about the precipitation source and history. The highest Na~+ loads were associated with air masses which had crossed the Norwegian Sea and the highest non-sea-salt SO_4~(2-) loads with trajectories crossing Scandinavia or the United Kingdom; high SO_4~(2-) loads in late April reflected decreasing snow cover. Trajectories from the Arctic basin resulted in the lowest δ ~(18)O values. During the winter, 4.8 m of snow accumulated at 1470 m above sea level on the glacier Austre Okstindbreen, 25 km north-east of Tustervatn. Mean ionic concentrations were lower than at Tustervatn, but loads were higher, as the total precipitation was three times greater. At both sites, ionic loads were closely related to ionic concentrations but not to sample water-equivalent values/precipitation amounts. Dates could be assigned to much of the snowpack on the basis of similarities between its chemical stratigraphy and temporal variations of precipitation chemistry at Tustervatn. Examination of the influence of individual storms on δ ~(18)O variations and the relationship between those variations and atmospheric circulation patterns has potential importance in relation to understanding past, present and possible future climatic conditions.