A 7000 YEAR OXYGEN ISOTOPE RECORD OF CLIMATE CHANGE IN SOUTHWESTERN BRITISH COLUMBIA, CANADA
We dated the Turquoise Lake record using 210Pb, 137Cs, ten 14C measurements, and one tephra layer and analyzed 293 samples of authigenic carbonate (the <63µm fraction) collected at 2mm intervals. The Turquoise Lake δ18O record exhibits an increasing trend from -17‰ to -16‰ over the last 4000 years. During this time period, five 400-600 year intervals occur in which δ18O values gradually increase then abruptly decrease thereafter. Greater variability in δ18O occurs from 4000 yr BP to 1500 yr BP (between -17.5 and -15‰), while after 1500 yr BP the record is less variable (-17.3 to -16‰). More negative δ18O values occur from 1100 yr BP to 500 yr BP, implying wetter conditions during the Medieval Climate Anomaly, followed by a steady increase until 400 yr BP, which indicates a drier climate early in the Little Ice Age. The results provide insight on the influence of Pacific ocean-atmosphere dynamics including the El Niño Southern Oscillation, Pacific Decadal Oscillation, and the Pacific North American Pattern on climate in the Pacific Northwest, and thus will improve our overall understanding of past hydroclimate changes in North America.