Early Holocene climate at Castle Peak, southern Coast Mountains, British Columbia, Canada

Abstract

New palynological, radiocarbon, and stable isotope data from Castle Peak in the southern Coast Mountains indicate that the early Holocene climate of southern British Columbia was warmer and perhaps drier than today. Fossil wood fragments are common above timberline at Castle Peak and have yielded 13 radiocarbon ages ranging from 9.1 ka to 8.1 ka. This evidence for higher timberline during the early Holocene is in agreement with pollen data indicating a warmer and possibly longer summer growing season in this area during the early Holocene, and is consistent with theoretical considerations based on Milankovitch forcing of climate change. The oxygen and hydrogen stable isotope composition of fossil wood cellulose is similar to that of living trees in the same area. Growing season relative humidity values derived from the isotopic data provide some support for episodes of dryness at times of elevated timberline, although the majority of paleohumidity estimates fall within the range of modern moisture levels.