Dendroclimatology in the Canadian Cordillera has focussed on temperature-sensitive upper tree-line sites and few records have been developed from low-elevation sites. At the lower forest border these sites are moisture-sensitive and well suited to provide records that address the question of precipitation variability which may be more closely related to significant changes in atmospheric circulation patterns. Sixteen new tree-ring width chronologies have been developed from open-grown, low-elevation, moisture-sensitive stands of Pseudotsuga menziesii and Pinus ponderosa collected from 13 sites in the Canadian Rockies and southern British Columbia. These chronologies represent the initial phase of the development of a more extensive network covering the southern Canadian Cordillera. This project parallels a network of tree-line sites which is being developed to address temperature variation over the same region and timeframe as part of the IGBP-PEP1 initiatives. Complementary reconstruction of both temperature and precipitation parameters from networks of sites over the same region may provide significantly more information about past climate and circulation patterns than either network alone.
Ring-width chronologies were calibrated with homogenised precipitation records (AES-HCPN Data) and highly significant, well-verified annual (July-June or August-July) precipitation reconstructions (r=0.60-0.79) were developed for Banff, Jasper, Kamloops, Westwold, Penticton and Cranbrook. Over the last 300 years the Banff and Jasper records (200km apart) show synchronous wetter and drier periods indicating strong regional patterns of precipitation variability. The longest reconstruction from Banff (1430-1994) shows slightly drier conditions than the instrumental record (508.4mm, 1896-1994; 486.0mm, 1430-1994) but significantly wetter intervals ca 1515-1550, 1585-1610, 1660-1680, 1870-1885 and 1890-1905 (also seen in the instrumental record). Most of the period ca 1690-1870 was drier than the instrumental record. Comparison of this record with a recent reconstructed summer temperature series (1073-1983, based on tree-ring densitometry) suggests that the glacier advances of the last few centuries occurred during cooler and drier conditions than those of the 20th century.
Reconstructions from the other sites (Kamloops, Westwold, Cranbrook and Penticton) are shorter but show consistent long term trends with each other and recent PDSI reconstructions from the adjacent United States.