Isotope climatology and paleoclimatology of Western Canada

点击翻译按钮获取中文摘要

The proposed research will determine how changes in the pattern and intensity of atmospheric circulation have affected the climate of western Canada over two important time-periods: (1) the past century and (2) the past millennium. The investigations are based on mapping and modelling of the relative abundances of naturally-occurring heavy isotopes of hydrogen and oxygen in precipitation, which yields fundamental information about temperature, moisture, atmospheric circulation regimes, and other aspects of climate variability and change. Studies of the past century will analyse precipitation isotope fields and climate linkages across the western Canadian Cordillera from the Pacific Coast to Northern Great Plains since the end of the Little Ice Age. The climate of this period (especially the last 50 years) is captured in detail by instrumental climate records, as well as by a newly-developed climate model that can simulate the expected precipitation isotope fields under specified conditions. Isotope fields for selected time-slices will be mapped using a combination of existing isotope data from direct sampling of precipitation over the past ~ 40 years and precipitation oxygen-isotope composition reconstructed from analysis of tree-ring cellulose over the full century. The combination of instrumental climate data and reconstructed and model-generated precipitation isotope fields will afford an unprecedented opportunity to develop physically-based understanding of spatial and temporal isotope-climate relations, which can then be used to interpret the climate of the pre-instrumental period. Studies of pre-instrumental climate will probe climate variability and change and the associated impacts on water resources at key times in the past millennium from extended tree-ring isotope records. One of the most pressing concerns is to develop better understanding of the atmospheric circulation regime that led to widespread drought across western Canada in Medieval times, because of the possibility that climate may be in the process of returning to a similar state.