Two hundred years of terminus retreat at Exit Glacier: 1815 to 2015
Kurtz D and Baker E. 2016. Two hundred years of terminus retreat at Exit Glacier: 1815 to 2015. Natural Resource Report. NPS/KEFJ/NRR—2016/1341. National Park Service. Fort Collins, Colorado
In this paper we present dated historical terminus positions for Exit Glacier compiled from previously published moraine data, georeferenced historical aerial photos and direct measurements recorded with mapping-grade GPS. We test two methods for measuring the rate of retreat, a centerline method and a box method. Overall retreat is the same using both methods but some interannual differences are highlighted. We present the results and explain the differences of each method. For simplicity and consistency in future measurements, we recommend continuing measurements using the centerline method. Results of the centerline method indicate that over the last 200 years, Exit Glacier retreated 2.5 km from its 1815 Little Ice Age maximum to its position in September 2015. As it retreated, the terminus also became narrower and transformed from a piedmont glacier to a wide valley glacier to a narrow valley glacier as it appears today. The terminus remained stable at its 1815 maximum position until approximately 1889; over that period only, a small retreat of 14 meters occurred. During the period of retreat from 1889 to 2015, the average rate was 19.7 m/yr. In the most recent 5-year period from 2011 to 2015, the average rate of retreat was 44.5 m/yr. Over the previous 5-year period from 2006-2010, the rate of retreat was slightly slower, 29.4 m/yr. Beginning in 2010, mapping of the terminus was performed in both fall and spring, allowing for separation of retreat occurring in summer and winter months. Retreat in summer months occurs a median of 6.7 times faster than during the winter.
- Type
- Published Report
- Authors
- Kurtz, Deborah; Baker, Emily
- Date of Issue
- 2016-11
- Publisher
- National Park Service
- Units
- KEFJ , NRSS
- Keywords
- climate, Exit Glacier, geomorphology, glacial retreat, KEFJ, Kenai Fjords National Park
- Subjects
- Ecological Framework: Geology and Soils | Geomorphology | Glacial Features and Processes , Ecological Framework: Geology and Soils | Geomorphology | Stream/River Channel Characteristics , Ecological Framework: Human Use | Visitor and Recreation Use | Visitor Use