Climate Change in the Western United States: Observed and Potential Impacts to Unique Hydrologic Systems

Unique geographic areas in the western United States (US) that include glaciers in the Wind River Range (WRR) of Wyoming and the 4th largest terminal lake in the world (Great Salt Lake (GSL), Utah) are particularly susceptible to ongoing and future impacts of climate change. Significant attention has been given to the melting of relatively small glaciers in Glacier National Park (GNP), Montana; however, the less visited melting glaciers in the WRR of Wyoming represent the largest accumulation of glacial ice in the Rocky Mountains of the continental US. Melting of these alpine glaciers represents larger impacts and hydrologic hazards than their more popular counterparts in GNP. Delta oxygen-18 (?180) records from WRR glaciers spanning the last - 270 years have indicated an increase in average air temperature (TA) of approximately 2.1 oC since the end of the Little Ice Age. A likely consequence of this warming was the recent failure of a natural ice dam at the head of Grasshopper Glacier, resulting in the instantaneous release of approximately 3.2 million m3 of water that had accumulated in a periglacial lake. Additional periglacial lakes have been observed in the WRR, occurring in steep topography and increasingly destabilized environments, presenting a potential threat to backcountry users on these Federally-managed lands. Increasing atmospheric C02 has been linked to increasing oceanic acidity (Royal Society, 2005). Furthermore, acidic riverine discharge in coastal areas has impacted the formation of shell material associated with shellfish growth as evidenced by depressions in the saturation index (SI) of biogenic mineral phases (Salisbury et al., 2008). Biogenic carbonates (biostromes) in the near-shore areas of GSL represent an important habitat for brine fly (Ephydra cinerea) larvae and pupae, which in turn provide a critical food source for nesting and migratory waterfowl. Geochemical modeling using the U.S. Geological Survey software PHREEQC with the Pitzer thermodynamic database indicates a significant depression in the SI of the aragonite mineral phase (CaC03) in near-shore mixing zones associated with riverine discharge to GSL. The C02 charged water associated with high soil respiration rates during longer growing seasons in the extensive perimeter wetlands surrounding GSL could further impact the future formation of biostromes in this system. Royal Society, 2005, Ocean acidification due to increasing atmospheric carbon dioxide, Policy Doc. 12/05, London. (Available at http:// www.royalsoc.ac.uk) Salisbury, J., Green, M., Campbell, J., 2008, Coastal acidification by rivers: A threat to shellfish?: Eos, Transactions, American Geophysical Union, vol. 18, no. 50, p. 513-514