Glacial and climatic fluctuations during the Little Ice Age, Mt. Waddington area, southern Coast Mountains of British Columbia, Canada

Waddington area, southern Coast Mountains of British Columbia (Canada). This study establishes 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, dendrochronological, and radiocarbon dating techniques applied to 14 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 the 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 mean temperature (January, July, summer) and snowpack depth (April 1) were developed for the past 300 years. Collectively, the proxy indices indicate that the Mt. Washington 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 northern Washington State. The models of net annual balance for the region show that periods of positive mass balance occurred in the 1750s, 1820s to 1830s, and 1970s. 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 indicate 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.