St-George Meko Girardin-2009-The tree-ring record of drought on the Canadian Prairies

Ring-width data from 138 sites in the Canadian Prairie Provinces and adjacent regions are used to estimate
summer drought severity during the past several hundred years. The network was divided into five regional
groups based on geography, tree species, and length of record: the eastern Rockies, northern Saskatchewan,
central Manitoba, southern Manitoba, and northwestern Ontario. Regional tree-ring records are primarily
related to summer moisture and drought conditions, and are less responsive to droughts caused by deficits in
winter precipitation. These summer-sensitive data are not linearly related to major modes of climate
variability, including ENSO and the Pacific decadal oscillation (PDO), which primarily affect the climate of
western Canada during winter. Extended drought records inferred from tree rings indicate that drought on
the Canadian Prairies has exhibited considerable spatial heterogeneity over the last several centuries.