Geologic Publications for Mount Rainier

Changes in glacier extents and estimated changes in glacial volume at Mount Rainier National Park, Washington, USA from 1896 to 2021

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Author(s): Scott R. Beason, Taylor R. Kenyon, Robert P. Jost, Lauren J. Walker

Category: PUBLICATION
Document Type: Natural Resource Report NPS/MORA/NRR—2023/2524
Publisher: National Park Service
Published Year: 2023
Volume:
Number:
Pages: 63
DOI Identifier: 10.36967/2299328
ISBN Identifier:
Keywords:

Abstract:
Surface area of glaciers and perennial snow within Mount Rainier National Park were delineated based on 2021 aerial structure-from-motion (SfM) and satellite imagery to document changes to glaciers over the last 125 years. These extents were compared with previously completed databases from 1896, 1913, 1971, 1994, 2009, and 2015. In addition to the glacial features mapped at the park, any snow patches noted in satellite- and fixed-wing-acquired aerial images in September 2021 were mapped as perennial snowfields.

In 2021, Mount Rainier National Park contained a total of 28 named glaciers which covered a total of 75.496 ± 4.109 km² (29.149 ± 1.587 mi²). Perennial snowfields added another 1.938 ± 0.112 km² (0.748 ± 0.043 mi²), bringing the total perennial snow and glacier cover within the park in 2021 to 77.434 ± 4.221 km² (29.897 ± 1.630 mi²). The largest glacier at Mount Rainier was the Emmons Glacier, which encompasses 10.959 ± 0.575 km² (4.231 ± 0.222 mi²).

The change in glacial area from 1896 to 2021 was -53.812 km² (-20.777 mi²), a total reduction of 41.6%. This corresponds to an average rate of -0.430 km² per year (-0.166 mi² × yr^-1) during the 125-year period. Recent changes (between the 6-year period of 2015 to 2021) showed a reduction of -3.262 km² (-1.260 mi²) of glacial area, or a 4.14% reduction at a rate of -0.544 km² per year (-0.210 mi² × yr^-1). This rate is 2.23 times that estimated in 2015 (2009-2015) of -0.244 km² per year (-0.094 mi² × yr^-1).

Changes in ice volume at Mount Rainier and estimates of total volumes were calculated for 1896, 1913, 1971, 1994, 2009, 2015, and 2021. Volume change between 1971 and 2007/8 was -0.65 km³ ( 0.16 mi³; Sisson et al., 2011). We used the 2007/8 LiDAR digital elevation model and our 2021 SfM digital surface model to estimate a further loss of -0.404 km³ (-0.097 mi³). In the 50-year period between 1971 and 2021, the glaciers and perennial snowfields of Mount Rainier lost a total of -1.058 km³ (-0.254 mi³) at a rate of -0.021 km³ per year (-0.005 mi³ × yr^-1).

The calculation of the total volume of the glaciers during various glacier extent inventories at Mount Rainier is not straightforward and various methods are explored in this paper. Using back calculated scaling parameters derived from a single volume measurement in 1971 and estimates completed by other authors, we have developed an estimate of glacial mass during the last 125-years at Mount Rainier that mostly agree with volumetric changes observed in the last 50 years. Because of the high uncertainty with these methods, a relatively modest 35% error is chosen.

In 2021, Mount Rainier's 28 glaciers contain about 3.516 ± 1.231 km³ (0.844 ± 0.295 mi³) of glacial ice, snow, and firn. The change in glacial mass over the 125-year period from 1896 to 2021 was 3.742 km³ (-0.898 mi³), a total reduction of 51.6%, at an average rate of -0.030 km³ per year (-0.007 mi³ × yr^-1). Volume change over the 6-year period of 2015 to 2021 was -0.175 km³ (-0.042 mi³), or a 4.75% reduction, at a rate of -0.029 km³ per year (-0.007 mi³ × yr^-1).

This survey officially removes one glacier from the Park's inventory and highlights several other glaciers in a critical state. The Stevens Glacier, an offshoot of the Paradise Glacier on the Park's south face, was removed due to its lack of features indicating flow, therefore is no longer a glacier, but instead a perennial snowfield. Two other south facing glaciers – the Pyramid and Van Trump glaciers – are in serious peril. In the six-year period between 2015 and 2021, these two glaciers lost 32.9% and 33.6% of their area and 42.0% and 42.9% of their volume, respectively. These glaciers are also becoming exceedingly fragmented and no longer possess what can be called a main body of ice. Continued losses will quickly lead to the demise of these glaciers in the coming decades. Overall, the glaciers on the south face of the mountain have been rapidly shrinking over the last 125 years.

Our data shows a continuation of gradual yet accelerating loss of glacial ice at Mount Rainier, resulting in significant changes in regional ice volume over the last century. The long-term impacts of this loss will be widespread and impact many facets of the park ecosystem. Additionally, rapidly retreating south-facing glaciers are exposing large areas of loose sediment that can be mobilized to proglacial rivers during rainstorms, outburst floods, and debris flows.

Regional climate change is affecting all glaciers at Mount Rainier, but especially those smaller cirque glaciers and discontinuous glaciers on the south side of the volcano. If the regional climate trend continues, further loss in glacial area and volume park-wide is anticipated, as well as the complete loss of small glaciers at lower elevations with surface areas less than 0.2 km² (0.08 mi²) in the next few decades.

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Suggested Citations:
In Text Citation:
Beason and others (2023) or (Beason et al., 2023)

References Citation:
Beason, S.R., T.R. Kenyon, R.P. Jost, and L.J. Walker, 2023, Changes in glacier extents and estimated changes in glacial volume at Mount Rainier National Park, Washington, USA from 1896 to 2021: Natural Resource Report NPS/MORA/NRR—2023/2524, National Park Service, 63 p., doi: 10.36967/2299328.