THE GLACIAL HISTORY OF WOLF LAKE VALLEY AND THE DEVELOPMENT OF A 4000 YEAR TREE RING RECORD IN GLACIER BAY NATIONAL PARK AND PRESERVE, ALASKA

Over the past several decades, glacially overrun wood has been useful for developing millennial-scale tree-ring records from Glacier Bay National Park and Preserve, Alaska. Annually dated tree-ring chronologies provide valuable paleoclimate data that is essential to resolving radiocarbon calibration and identifying the calendar year of cosmic events. Glacier Bay has been undergoing ice retreat since ca. CE 1750, leaving behind buried wood, whose crossdating results can extend our chronologies further into the past as well as track past glacial movements. A recent collection of 87 samples of sub fossil wood from Wolf Lake in the East Arm of Glacier Bay adds detail to the regional glacial chronology and has the potential to extend the 2000-year tree-ring record. Tree ring dating of the Wolf Lake collection indicates that the region was either abruptly run over by ice ca. 2,000 years before present (2 ka), or the forests were killed by a highstand of Muir Lake when it was dammed by the advancing West Arm Glacier. Analyses of the spatial pattern of the tree-ring dates along with previous reports in the region will contribute to better understanding the glacial history.

Currently, a ~200-year gap between the ring width calendar-anchored chronology (2.2 ka to present) and a floating ring-width chronology (4.0-2.4 ka) prevents this series from being continuously dated back 4000 years. New samples were collected in the summer of 2021 in order to fill this gap and extend the anchored chronology. In this presentation, we will report on how these new samples have increased the sample size and extended this chronology further into the past, as well discussing the implications these new data provide to the region’s Holocene glacial chronology. Additional work using radiocarbon wiggle-matching and identification of a cosmic event about 2.6 ka may assist in future efforts to calendar date the series.