C041-07
Glacier Change in the Olympic Mountains, WA over the past and future 100 years

Friday, 11 December 2020: 16:24
Virtual
Andrew G Fountain1, Bryce Glenn2, Christina Gray1 and Brian Menounos3, (1)Portland State University, Department of Geology, Portland, OR, United States, (2)Portland State University, Department of Geography, Portland, OR, United States, (3)University of Northern British Columbia, Natural Resources and Environmental Studies Institute and Geography Program, Prince George, BC, Canada
Recorded Presentation
Abstract:
Glaciers of the Olympic Mountains, Washington, have been studied, scientifically, since the International Geophysical Year in 1957 with most of the effort focused on Blue Glacier, the largest glacier. Here we update the inventory of glaciers, document their area and volume changes, and link their change to sea surface temperatures of the North Pacific Ocean.

Results show that since their initial inventory in 1981 the total glacier-covered area has decreased -36 ± 0.02 % by 2015, and mean glacier area decreased by half from 0.18 km2 to 0.08 km2. Volume loss was about is -0.741 ± 0.164 km3. If we assume that all mass loss from storage occurs during the months of August and September, the period in which seasonal snow is at a minimum and maximum ice is exposed, then the contribution to stream runoff is about 357,000 +/- 79,000 m3 dy-1. Using the time series of Blue Glacier area as an index the estimated total glacier-covered area in 1900 was 55.3 km2, more than twice the area in 2015.

A simple model of Blue Glacier mass balance, based on monthly air temperature and precipitation, showed good correspondence with variations in glacier area. Interrogation of the model showed that century-scale mass loss is caused by warming air temperatures. Winter mass accumulation is equally sensitive to precipitation and air temperature, suggesting the importance of temperature controlling precipitation phase. On decadal time scales air temperature is the dominant influence on glacier mass balance with precipitation playing a secondary role. Changes in the temporal trends of glacier mass balance and area are highly correlated with regime shifts in the North Pacific showing the importance of sea surface temperature on maritime glaciers. Finally, the future of these glaciers is grim. Using a coupled global circulation model (CMiP5) to drive a regional glaciation model shows that the glaciers of the Olympic Mountains should largely disappear by 2070. For comparison, we will present results for glacier change in the Cascade Range of northern Washington, 100 km away and inland from the Olympic Mountains.

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