Reconstructing Glacial History from Forests Preserved in the Wake of the Catastrophic Retreating Columbia and Wooster Glaciers, Prince William Sound, Alaska

• Main Author: Starr, Kaitlin N
• Format: Text
• Language: English
• Published: Open Works 2016
• Subjects: glaciers; alaska; holocene; Geology; Gulf of Alaska; glacier; Tidewater; Alaska
• Online Access: https://openworks.wooster.edu/independentstudy/7079; https://openworks.wooster.edu/cgi/viewcontent.cgi?article=8339&context=independentstudy

Columbia Glacier, the largest tidewater glacier in Prince William Sound, has undergone a drastic 20 km retreat within the past 36 years. In the wake of this catastrophic retreat, previously overrun and partially buried mountain hemlock forests along the banks of the fjord and within tributary valleys have been uncovered. Tree-ring dating of these recovered logs provide calendar dates of the glacial advance of Columbia Glacier. These tree-ring records extend back to approximately 1000 CE. As a result of the recent glacial retreat, thousands of new logs have been uncovered. During the summers of 2014 and 2015, College of Wooster students and faculty traveled to Columbia Bay collecting approximately 400 samples of these exposed logs. From those samples collected, 104 of them underwent tree-ring analysis and calendar dating. These new calendar dates expand and extend the established glacial advance history of both Columbia Glacier and its land terminating distributary glacier, once referred to as the Land Lobe (unofficial name), here referred to as the Wooster Glacier (unofficial name). These new samples help replicate data and strengthen the established chronologies for both the Columbia and Wooster Glaciers. The 2014 sampling of the East Branch site (the closest sample site to the current calving margin of the glacier) provided new kill dates that extend the glacial advance records from 1020 CE to as early as 1000 CE. This study also provided additional kill dates for the Wooster Glacier ranging from the years 1770 CE -1784 CE. Furthermore, these additional tree-ring dates allows for the calculation of advance and thickening rates within Columbia Bay. The 2014 collection indicated the Columbia Glacier was advancing at a rate of 45 meters per year. The 2014 data shows that Columbia Glacier was thickening at a rate of 8 meters per year opposed to the 1.5 meters per year thickening rate of the Wooster Glacier determined by the 2015 data. Comparison of other land terminating glacial records and the Gulf of Alaska temperature reconstructions conclude that the timing of the Wooster Glacier’s advance and retreat are influenced by the dynamics of the Columbia Glacier rather than being controlled exclusively by climate.