Author : Larocque, S.J. Date : 2003. Title : Glacier and Climate Fluctuations During the Little Ice Age, Mt. Waddington Area, Southern Coast Mountains of British Columbia. Publication : Unpublished PhD dissertation. University of Victoria, Victoria. Issue : Page(s) :
Little is known of the Little Ice Age (LIA) glacial activity in the Mt. Waddington area, southern Coast Mountains of British Columbia (Canada). This study aims to establish a detailed LIA chronology of glacier ice front positions and glacier mass balance fluctuations linked to a better understanding of their interaction and relative significance to climate. Lichenometric, dendrochronologic, and radiocarbon dating techniques applied to fourteen glacier sites were used to develop a history of moraine-building events. A calibrated Rhizocarpon geographicum lichen growth curve was developed for the Mt. Waddington area applicable to surfaces up to 680 years in age. Subfossil wood samples located in situ beneath moraines were either crossdated with local living chronologies or radiocarbon dated. Constraining dates on moraine stabilization were also derived from oldest trees found growing on the moraines surfaces. Moraine-building episodes were found to have occurred prior to AD 620, and in AD 925-933, 1203-1226, 1260-1275, 1344-1362, 1443-1458, 1506-1524, 1562-1575, 1597-1621, 1657-1660, 1767-1784, 1821-1837, 1871-1900, 1915-1928, and 1942-1946. Although synchronicity between periods of glacial activity was common, local factors such as aspect and size were shown to play an important role in individual glacial response. Fifteen living tree-ring chronologies from five conifer species (Douglas-fir, whitebark pine, mountain hemlock, yellow-cedar, and subalpine fir) were sampled on valley slopes, close to glacial termini. The chronologies were used to determine the nature of growth-climate relationships and form the basis for a set of dendroclimatological models. After validating the relationships, models of temperature (January, July, summer) and snowpack (April 1) were developed for the past 300 years. Collectively, these proxy indices suggest that the Mt. Waddington area was characterized by cool-wet conditions from 1701-1708, 1716-1727, 1735, 1742-1765, 1787-1792, 1813-1823, 1848-1851, 1867-1902, 1926, and 1973-1994. The tree-ring chronologies also led to the reconstruction of glacier mass balance for the past 450 years. Regression analyses were applied to local tree-ring chronologies in order to predict glacier mass balance at local and regional scales for glaciers located in southwestern British Columbia and Washington state. The models of net annual balance for the region show that periods of positive mass balance occurred in AD 1749-1753, 1827-1832, and 1976-1980. Peaks of winter balance correspond closely to these periods, showing a sharp drop in winter mass balance totals by the end of the 19th century. Wavelet analyses suggest that glaciers in this region respond synchronously to climate forcing mechanisms driven by the El Nino Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and solar forcing.