24 Undergraduate Research – Archeological Geology, Precambrian Geology, Neotectonics, Aqueous Geochemistry and Paleoclimatology (Posters)

DEVELOPMENT OF A MILLENNIAL-LONG TREE-RING-WIDTH CHRONOLOGY FROM COLUMBIA BAY, ALASKA

Paper number: 24-5
Program: Technical Sessions
Time: 1:00 PM – 4:30 PM

Authors

Abstract

Columbia Glacier is one of the largest and the most studied tidewater glaciers in Prince William Sound, Alaska. Over the past 1000 years a near-continuous ice advance culminated in a recent maximum position at the mouth of Columbia Bay. The iceberg-calving margin remained near this position for two centuries prior to its catastrophic 12 kilometer retreat initiated in the early 1980s. This impressive retreat has revealed thousands of buried trees that were previously overrun by the advancing ice. Ring-width data from living and subfossil mountain hemlock (Tsuga mertensiana(Bong.) Carr.) trees provide for a tree-ring chronology spanning the past 1020 years. This composite series is based from over 100 series from more than 50 trees and has been constructed by crossdating the living trees growing along the fjord margin with those killed within the recent glacial limit.

The strong crossdating among the series is likely due to variations in growing season temperature based on comparisons with tree-ring data from other sites in Prince William Sound. The climate signal for the dead and living trees should be coherent because of the similarity in elevation and location of the sample sites. In addition, the mountain hemlocks of the region are from the northernmost latitude of their ecological range, where they should be most sensitive to climatic changes. Ongoing dendroclimatic analysis of the ring-width chronology will better define the potential use of this annually resolved series in reconstructing past temperature variations. Along the Gulf of Alaska such records will contribute to the understanding of the past climate variability of the North Pacific region as well as provide a long ring-width record for tree-ring dating.