| Summary: | Preliminary data are examined from a project in which the variability in the isotopic composition of precipitation across northern Canada and the implications for paleoclimatic reconstruction are examined. The data set shows a geographic variability of about 6%o in isotopic composition of precipitation across the Canadian Arctic, roughly double the temporal variability seen in the ice core records from the last 10,000 years. The seasonal variability in average monthly δ18O values from the arctic stations in 1991 was as much as 26%o. A snow and firn core collected on Bylot Island had arange of 14.8%o, compared to the range in average monthly precipitation of 25.6%o covering the same time period. This difference in the observed seasonal range of values is the result of processes operating in the snow pack, such as vapor movement and molecular diffusion, and the strategy used in sampling the core. The results indicate that a much better understanding of the geographic and seasonal variation in the δ18O 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 developed radiocarbon dating techniques, buried glacier ice that has been preserved in permafrost may be able to provide the greater spatial and temporal detail required. Résumé Dans le présent article, on étudie des données préliminaires d'un projet de la variation de la composition isotopique des précipitations dans le nord du Canada et où, on s'intéresse à l'applicabilité de telles mesures dans les reconstiutions paléoclimatiques. Le jeu de données indique qu'il existe une variabilité géographique de 6 %o dans la composition isotopique des précipitations à travers l'Arctique canadien, ce qui est le double environ de la variabilité temporelle observée dans le carottes de glace des derniers 10,000 ans. La variabilité saisonnière des valeurs moyennes mensuelles de 18O mesurée en 1991 à partir de stations arctiques atteint 26 %o. Une ...
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