Trend lines from single variable analysis indicated that a linear relationship was most supported by the data. As a result, multiple linear regressions were chosen to conduct analysis of the dual variable relationships between lake width, year, and average recession rate for periods 1698-2016 and 1948-2016. The models were not significantly improved when both variables were considered as explanatory for the annual terminal recession rate of Shakes Glacier.
Discussion The data points from 1948 to 2016 provide a comprehensive record of terminus recession. The small number of data points (3) during the period of 1698–1909 (and the possible effect of increased accumulation during the Little Ice Age 1300–1850 [Fagan 2001] on recession rate calculations) limited the ability of statistical analyses to identify relationships when considering the entire period. Regarding the effect of average decadal temperature and lake width at the terminus on the recession of Shakes Glacier, it is possible that the relationships are obscured by other variables, such as the bathymetry (underwater topography) of Shakes Lake, glacial bed slope, and actual glacial lag time. The effect of these variables may also be apparent in ice volume loss rather than terminus retreat. It would be necessary to evaluate these additional variables directly; however, many of them have yet to be measured for Shakes Glacier. Lag time of Shakes Glacier may also have influenced the results of this study. If the lag time is 50 years or more, the full effects of anthropogenic climate change, which was first prominent in temperature models in the late 1970s, have yet to occur. Volumetric discharge and terminus recession could increase soon. Even if the rate of terminus recession remains stable at 107 meters (351 ft.) per year, Shakes Glacier will recede to a point of separation between its dual sources, dividing into two glaciers and possibly retracting from the lake, in approximately 15 years (2032). This could limit access to the glacier by locals who rely on glacier ice to keep their subsistence salmon catch fresh, as well as inhibit tourism related to the glacier, a major source of income for many Wrangell residents.
“In addition to an increased understanding and data on the trends of the Shakes Glacier, the Shakes Glacier Survey Team’s monitoring project is an exemplary model of citizen science.”
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International Journal of Wilderness | April 2018 | Volume 24, Number 1
