Late Holocene glacier fluctuations in the Wrangell Mountains, Alaska

Four intervals of late Holocene glacier advance are recognized from study of nine valley glaciers in the Wrangell and westernmost St. Elias Mountains of Alaska. The oldest glacial advance is recognized at the Nabesna and Barnard Glaciers where live radiocarbon ages suggest advance as early as 2700 cal. (calibrated) yr B.P. Two additional radiocarbon-dated advances are centered on cal. yr A.D. 300 and the beginning of the Little Ice Age about A.D. 1200. The best-documented Little Ice Age advances occurred during the mid-1600s through the 1800s and are recognized at all nine glaciers. These latter advances are dated by tree rings of trees overrun by glaciers in five glacier valley, by 17 radiocarbon dates, and by tree-ring and lichen ages from 20 moraines that were deposited during the culmination of these advances. The glacial chronology is broadly similar to chronologies from adjoining Alaskan mountain ranges, at both coastal and interior sites for the past 3000 yr. There are, however, differences in timing of advances during the first millennium A.D. The glacial history for the past 2000 yr is also consistent with temperature-sensitive proxy records from interior Alaska and Yukon Territory.