Glenn Patterson, M.S.
Ph.D. Student
Department of Geosciences
Colorado State University
Fort Collins, Colorado, USA 80523-1482
voice +1.970.491.7113

Seasonal Snowpack Trends about Rocky Mountain National Park

He is interested in snowpack and snowmelt dynamics. He is also interested in water law and policy, and has developed online courses at CSU on this topic.

Glenn earned his BA in biology from the University of Chicago and his MS in watershed management from the University of Arizona. He worked as a hydrologist for the U.S. Geological Survey for 30 years in California, Oregon, South Carolina, Virginia, and Colorado. As a CSU Research Associate, he works part-time with the National Park Service on water issues.

The seasonal snowpack in and near Rocky Mountain National Park is undergoing changes that will pose challenges for water providers, natural resource managers, and winter recreation enthusiasts. Assessing long-term trends in measures of the seasonal snowpack, and in the climatic factors that influence its accumulation and melt, helps to characterize those challenges. In particular, evaluating the patterns of variation in those trends during the snow season provides new understanding as to the causes, specific ramifications, and likely future course of the trends. In addition, placing the current 35-year trends in the longer context of longer-term observational records, and paleoclimate tree-ring reconstructions provides useful comparisons of current and past trends. Finally, projections of future trends provided by linked climate and hydrologic models offer a sense of how these trends are likely to affect the snowpack of the future.

Some factors such as the high elevation of the study area help to preserve conditions favorable to development of the seasonal snowpack, and hence to limit trends toward greater warming-induced melt and less precipitation falling as snow. Nevertheless, traditional measures such as April 1 snow water equivalent (SWE) show consistent declining trends over the 35-year period of record for automated snow monitoring stations in the study area. The trends are not uniform throughout the snow season, but vary significantly by month. As a result, November and March have warming and drying trends that retard the beginning of the winter snow season and reduce the traditional accumulation that formerly characterized the early spring. In contrast, the core winter months of December, January, and February have cooling and wetting trends that have been enhancing SWE during the heart of the winter. Mid-April to early May is another period during which cooling and wetting trends have been enhancing SWE, although these months also show more variability. This oscillating pattern helps to explain why there has not been a pervasive shift to earlier and lower annual peak SWE in the study area.

Tree-ring reconstructions of paleo-climate suggest that trends with similar rates of SWE loss have occurred in past centuries, but generally not of the same duration as the trends observed during 1981-2015. Linked climate and hydrologic models project that the observed trends are likely to continue, and that by 2050 measures such as April 1 SWE in the study area are likely to decrease by 25 percent.

Advisor: Steven Fassnacht
Melinda Laituri (Watershed Science)
William Sanford (Geosciences)
James Pritchett (Agriculture and Resource Economics)

Last update: SRF, 2016-08-02