Dendroclimatology of the Columbia Bay Region, Prince William Sound, Alaska

Aaron Shear

Department of Geology

The College of Wooster

This material is based upon work supported by the National Science Foundation under Grant No. 9910805. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.

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The Columbia Glacier is a 60km-long, iceberg-calving, piedmont glacier located in Prince William Sound, Alaska. The retreat of this great tidewater glacier from its Little Ice Age maximum began in 1982. Partly buried mountain hemlock forests along a section of the 15km fjord were exposed due to this retreat.

During the past summer (2000), four other scientists and I had the opportunity to travel to this region of southern Alaska to take part in dendrochronologic / dendroclimatic research concerning the Columbia Glacier. The project was funded by a National Science Foundation grant to Parker E. Calkin of the Universirty of Colorado at Boulder, Greg Wiles of The College of Wooster and David Barclay at SUNY-Cortland. The primary objective of this research was to help develop a continuous tree-ring chronology from living and subfossil wood around Prince William Sound that would span the past 2000-years. The 2000 year chronology will be developed by linking and extending existing tree-ring records with new collections of subfossil and living wood. We took samples from subfossil logs either in the form of cores or disks, while living trees were sampled using non-destructive increment borers.

This new record will be used to: reconstruct the Holocene history of the Columbia Glacier, provide calendar-dates to early Medieval (AD 600) glacial advances around the northern Gulf of Alaska, and finally to asssess climate change in the North Pacific region over the past two millennia through calibration with meteorological records and dendroclimatic reconstruction. My area of emphasis on the project will be in the area of dendroclimatology and examining what the tree-ring record tells us about climate.

By comparing the collected tree-ring data with meteorological record I will be able to identify the most important climatic variables that influenced the growth of the mountain hemlocks, and that ultimately lead to the advance or retreat of the Columbia Glacier throughout the past several hundred years. Meteorological records stretching back into the early to mid 1900s can be acquired from stations in Seward, Valdez, and Cordova. Longer records will be used for comparison with regional climate will be taken from stations at Kodiak and Sitka.
Such reconstruction of past climate is accomplished by taking several steps. The first of which is to compare the modern meteorological records with the widths of the collected tree rings that were produced during the same period of time. The second step is to establish a statistical relationship between the meteorological record and tree ring record. Finally by substituting the widths of the dated rings (using them as a proxy). these estimates of climate from tree rings can substitute for meteorological reocords and thus provide valuable information concerning climate for periods and areas where no meteorological data exists.

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