ISOTOPIC VARIABILITY IN ARCTIC PRECIPITATION AS A CLIMATIC INDICATOR

Preliminary data are examined from a project in which the variability in the isotopic composition of precipitation across northern Canada an d the implications for paleoclimatic reconstruction are examined. The data set shows a geographic variability of about 6 parts per thousand in isotopic composition of precipitation across the Canadian Arctic, r oughly double the temporal variability seen in the ice core records fr om the last 10,000 years. The seasonal variability in average monthly delta(18)O values from the arctic stations in 1991 was as much as 26 p arts per thousand. A snow and firn core collected on Bylot Island had a range of 14.8 parts per thousand, compared to the range in average m onthly precipitation of 25.6 parts per thousand covering the same time period. This difference in the observed seasonal range of values is t he result of processes operating in the snow pack, such as vapor movem ent and molecular diffusion, and the strategy used in sampling the cor e. The results indicate that a much better understanding of the geogra phic and seasonal variation in the delta(18)O values of precipitation is required before a direct linkage between the isotope records in ice cores and global climate change can be determined. Using recently dev eloped radiocarbon dating techniques, buried glacier ice that has been preserved in permafrost may be able to provide the greater spatial an d temporal detail required.