HOLOCENE GLACIER ACTIVITY IN THE BRITISH COLUMBIA COAST MOUNTAINS, CANADA

The Coast Mountains lie between the Pacific Ocean and Interior Plateau on the western periphery of British Columbia, Canada. The majority of glaciers in this region reached their Holocene maximum positions during the Little Ice Age, after which climatic amelioration led to persistent negative mass balance conditions. The resultant down wasting and terminus retreat has revealed the remains of glacially-overridden and buried forests below till and outwash deposits at over 60 investigated glaciers. Forest remains dating to the mid-Holocene have recently been exposed at sites close to the contemporary ice surface, offering the opportunity to better understand the regional character of glacier activity following the early Holocene warm period. Following ice expansion during the Younger Dryas, glaciers in the region retreated to positions close or below those at present by 10.6 ka. A brief interval of glacier expansion in 8.2 ka preceded widespread intervals of expansion from 6.7-5.6, 5.1- 4.6 and 4.4-4.0 ka. By 3.8-3.4 ka glaciers were again expanding down valley into mature forests, before retreating and then advancing into standing trees 3.2-2.8 ka. Regional ice expansion 1.8-1.1 ka preceded Little Ice Age terminus fluctuations 0.9 to 0.1 ka. Linking the emerging record of mid-Holocene glacier activity in the Coast Mountains to late Holocene glacier dynamics emphasizes the persistent significance the Aleutian low pressure center on glacial dynamics in the Coast Mountains.