Glacier Monitoring Program
Glaciers are one of the most valuable resources in the North Cascades National Park Service Complex (NOCA). Approximately one-third of all the glaciers in the lower 48 states are within the park (Post et al. 1971). The 312 glaciers in NOCA are a vital component of hydrologic systems and aquatic ecosystems. They also influence soil development, the distribution of vegetation, flooding and are dramatic indicators of climate change. The glacial resource is also central to the region's hydroelectric industry and our efforts to sustain endangered salmon and trout. Perhaps the most critical role of glaciers is providing fresh water during the summer drought. This role is becoming more important as snow-pack and glaciers decline. Since the end of the Little Ice Age in the late 1800's, glaciers have retreated throughout NOCA and we estimate that approximately 40% of the park's ice cover was lost in the past 150 years (Figure 21). In the Thunder Creek watershed this has resulted in a 30% reduction in summer streamflow. To understand climate change, the glacier resource, and the effect of glaciers on other resources at NOCA, long-term monitoring of glaciers is needed. South Cascade Glacier, located just outside NOCA, has been monitored by the U.S.G.S. Water Resources Division since the mid-1950s. When we began this program in 1993 it was not known how representative South Cascade Glacier was of NOCA glaciers because of the influence of non-climatic factors such as geographic position, aspect and elevation. Since that time we have learned that each glacier in the North Cascades has a unique response to climate, but that all of the glaciers are retreating (Riedel and Larrabee 2011).
Four broad goals are identified to monitor glaciers as important vital signs of the ecological health of NOCA:
Changes to glaciers, measured in water equivalents or water contents of snow, ice, and firn, are monitored annually and analyzed as mass balance. Mass balance is the difference between winter accumulation (growth) and summer melt (loss). Four glaciers in NOCA have had a negative mass balance over seven consecutive years (2003-2009) (Riedel and Larrabee 2011), showing clear evidence of global warming which translates to changes in stream flows and increased challenges for aquatic life and ecosystems.
Riedel, J. and M. A. Larrabee. 2011. North Cascades National Park Complex glacier mass balance monitoring annual report, water year 2009: North Coast and Cascades Network. Natural Resource Technical Report NPS/NCCN/NRTR--2011/483. National Park Service, Fort Collins, Colorado.