Since the 1950s, mass-balance measurements have been systematically collected at USGS Benchmark Glaciers, beginning with South Cascade (WA) and later including Gulkana (AK), Wolverine (AK), and Lemon Creek (AK). Results from this program form the longest continuous record of North American glacier mass balance. Similar measurements began at Sperry Glacier (MT) in 2005, completing the five-glacier USGS Benchmark Glacier network.
Research at these independent sites were unified into a single project in 2013, The USGS Benchmark Glacier Project. Common field methodologies coupled with long-term, consistently analyzed records, are the hallmark of this project. Such uniformity among sites have allowed mass balance records from different climate zones of North America to be directly compared in order to better understand the response of glaciers to changes in climate.
In 2019, historic data from the five benchmark glaciers were reanalyzed with consistent analysis techniques, compared, and published (O'Neel et al, 2019). Each glacier exhibited cumulative mass loss since the mid-20th century, which has been driven primarily by summer warming. Additionally, distance of a glacier from the ocean, known as continentality, was shown to have an impact on the observed mass loss, as does latitude, to a lesser degree. And, similar to elevation, there were times when topographic shading, snow redistribution, and glacier surface features were the biggest influences on mass loss.
Direct field measurements of glacier mass balance (ice melt and snow accumulation) and geodetic calibration, derived from aerial and satellite imagery, were analyzed to understand the processes leading to changes in long-term glacier mass balance. Ongoing efforts of the USGS Benchmark Glacier Project will better link field and satellite records to regional glacier change as the project continues to gain insight into glacier-climate interactions.
O'Neel, S., McNeil, C., Sass, L., Florentine, C., Baker, E., Peitzsch, E., McGrath, D., Fountain, A., and Fagre, D. (2019). Reanalysis of the US Geological Survey Benchmark Glaciers: Long-term insight into climate forcing of glacier mass balance. Journal of Glaciology, 65(253), 850-866. https://pubs.er.usgs.gov/publication/70207167