HR: 0830h
AN: C11B-0810    [PDF]
TI: Do Trees Tell the Same Story as Glaciers? Reconstructing Drought in Glacier National Park, Montana Since AD 1540
AU: * Pederson, G T
EM: gpederson@montana.edu
AF: Big Sky Institute - Montana State University, 106 AJM Johnson Hall, Bozeman, MT 59717 United States
AU: Fagre, D B
EM: dan_fagre@usgs.gov
AF: USGS Northern Rocky Mountain Science Center - Glacier Field Station, USGS Science Center c/o Glacier National Park, West Glacier, MT 59936 United States
AU: Graumlich, L J
EM: lisa@montana.edu
AF: Big Sky Institute - Montana State University, 106 AJM Johnson Hall, Bozeman, MT 59717 United States
AB: Glacier National Park has well-documented, extensive glacial recession from the end of the Little Ice Age (LIA) to the present. However, information is lacking on climatic variability and trends prior to the LIA. Since relatively little research on this topic exists, we constructed eight tree-ring chronologies for the examination of natural modes of variability and the influence of climatic drivers on glacial recession since AD 1540. We created a simple water balance model, representative of biological drought, using local climate station data. This model was then reconstructed using tree-ring chronologies. The reconstruction had an R$^{2}$$_{a}$=0.49 when validated with standard statistical procedures. As well, the chronologies also exhibit general correspondence with regional river flow and historically documented patterns of drought, which indicates that our reconstruction effectively reflects climatic variability over the entire 460-year record. The June July August drought reconstruction provides evidence for multi-decadal and centennial modes of variability that are inconsistent throughout the length of the record. In addition, the records of glacial recession indicate rapid retreat and ablation during periods of high summer drought. For instance, the Grinnell, Sperry, Jackson and Agassiz glaciers decreased to 50-68% of their original sizes between 1917-1945, at rates of up to 100 m/yr. During this same period, our reconstructions indicate the most extreme drought, in both duration and severity, of this 460-year period. The reconstruction provides insights into the role of drought as a driver of glacial dynamics during the LIA.
DE: 1812 Drought
DE: 1827 Glaciology (1863)
DE: 3344 Paleoclimatology
SC: Cryosphere [C]
MN: 2003 Fall Meeting