Climate and glacier mass balance trends from ad 1780 to present in the Columbia Mountains,British Columbia,Canada

Abstract

Climate and glacier mass balance trends from 1780 to present within the Columbia Mountains, British Columbia, Canada, were investigated using tree-ring data. Annually resolved ring width, maximum density and maximum cell wall thickness chronologies were constructed from increment core samples of Engelmann spruce (Picea engelmannii), mountain hemlock (Tsuga mertensiana) and subalpine fir (Abies lasiocarpa) trees collected in Glacier and Revelstoke national parks. Proxy records of maximum June–August temperature, August precipitation and February snowpack provide insight into long-term seasonal climate changes. The intervals 1790–1810, 1850–1870 and 1930–1950 were characterized by warm summer temperatures. While overall August precipitation totals decrease over the period of record, the late 1700s, 1805–1835, the 1880s, 1960–1975 and the mid 1980s were notably wetter. February snowpacks have generally decreased in depth since 1873. The reconstructed winter, summer and net mass balance records indicate that glacier cover in the Columbia Mountains has varied primarily in response to decreased snowfall since the mid 1700s. Intervals of terminus advance and retreat were shown to reflect glaciological responses to relatively short-duration variations in summer temperature and winter snowfall. The rate of cumulative mass balance decline within the last 30 years exceeds that observed at any time over the last 250 years.