Climate change is accelerating the decline of mountain ice worldwide. Over the past 35 years, North American glaciers have lost substantial mass, alongside more variable precipitation and declining seasonal snowpack. Subsurface ice features like rock glaciers—mixtures of rock and ice insulated by debris—are expected to persist even as surface glaciers disappear.
Meltwater sources strongly influence biogeochemical and physical processes in headwater streams. Surface and rock glaciers sustain streamflow during the melt season, regulate temperatures, supply key nutrients (nitrogen, phosphorus, carbon), and release trace elements into aquatic ecosystems. Further, headwater streams are the source of 75% of the drinking water in the western United States and serve as important habitat for sensitive mountain species. However, meltwater from glaciers can also contain elevated trace elements that may occur naturally in bedrock or be added to the system through atmospheric deposition. Our research aims to understand how meltwater sources, including seasonal snow, groundwater, surface glaciers, and rock glaciers, influence key physical and biogeochemical processes in mountain streams. In the summers of 2024 and 2025, we surveyed mountain streams along a latitudinal gradient in the western U.S. from Glacier National Park (MT) to the Teton Range (WY) and the Wasatch (UT).
We sampled 18 streams fed by varying meltwater sources and visited each stream three times during the summer (early-, mid-, and late-season) to capture intra-seasonal variations. We collected water samples for analysis of key nutrients (nitrogen, phosphorus, and carbon), major ions, and trace elements, and measured physical site conditions. Our results demonstrate key differences in stream physical and chemical properties across locations as a product of the meltwater source. These findings will inform conservation efforts for sensitive aquatic species and water management strategies (i.e., downstream water quality treatment and flow management) to address the impacts of changing meltwater sources.