TY - Generic T1 - Declining Snowpack Depths and Snow Water Equivalent at Snowpack Monitoring Sites in the Rocky Mountain Region, USA, 1993-200 T2 - 77th Annual Western Snow Conference Y1 - 2009 A1 - Ingersoll, G. P. A1 - Mast, M.A. A1 - Campbell, D.H. A1 - Clow, D.W. A1 - Nanus, L. KW - Declining snowpack, snow depth, Rocky Mountains, regional trends AB - Recent studies indicate the widespread decline of snowpack depths and snow-water equivalent in the western USA. Since 1993, the US Geological Survey, National Park Service, and USDA Forest Service have operated a network of up to 62 snowpack-chemistry-monitoring sites at elevations above 1,500 meters in the Rocky Mountain region. Two 8-year periods before and during the 2001-2008 drought indicate significant decreases in both snowpack depth and SWE. Further comparisons of trends in the Northern, Central, and Southern Rockies subregions yielded moderate to highly significant declines in snowpack depth and SWE in only the Central Rockies. Regionally decreasing trends in SWE were more pronounced at lower-elevation sites than at higher-elevation sites, however, trends in both snowpack depths and SWE were decreasing with moderate significance at higher-elevation sites during the study. JF - 77th Annual Western Snow Conference T3 - Proceedings of the 77th Annual Western Snow Conference PB - Western Snow Conference CY - Canmore, AB UR - sites/westernsnowconference.org/PDFs/2009Ingersoll.pdf ER - TY - Generic T1 - Trends in Snowpack Chemistry and Comparison to National Atmospheric Deposition Program Results for the Rocky Mountains, U.S.A. 1993-2004 T2 - 75th Annual Western Snow Conference Y1 - 2007 A1 - Ingersoll, G. P. A1 - Mast, M.A. A1 - Campbell, D.H. A1 - Clow, D.W. A1 - Nanus, L. A1 - Turk, J.T. KW - Snowpack chemistry, Rocky Mountains, NADP, Kendall test, sulfate AB - Seasonal snowpack chemistry data from the Rocky Mountain region for 1993-2004 was examined to identify long-term trends in concentration and chemical deposition in snow, and in snow-water equivalent. Comparisons of trends were made between snowpack data and National Atmospheric Deposition Program wetfall data from nearby sites in the region. We used an innovative, non-parametric correlation method known as the Regional Kendall Test. This technique expressed the slope, direction, and probability of trend for several sites at once in each of the Northern, Central, and Southern Rockies subregions. Seasonal Kendall tests were used to evaluate trends at individual sites. Sulfate deposition decreased with moderate to high significance in all three subregions in both wetfall and snowpack. Precipitation trends consistently were downward for wetfall-, snowpack-, and SNOTEL data for the Central and Southern Rockies subregions (p<0.02), while no trends were noted for the Northern Rockies subregion. JF - 75th Annual Western Snow Conference T3 - Proceedings of the 75th Annual Western Snow Conference PB - Western Snow Conference CY - Kailua-Kona, HI UR - sites/westernsnowconference.org/PDFs/2007Ingersoll.pdf ER - TY - Generic T1 - EFFECTS OF STORM TRAJECTORIES ON SNOWFALL CHEMISTRY IN ROCKY MOUNTAIN NATIONAL PARK, COLORADO T2 - 69th Annual Western Snow Conference Y1 - 2001 A1 - Ingersoll, G. P. A1 - Tonnessen, K. A. A1 - Campbell, D.H. A1 - Glass, B.R. A1 - Torizzo, A.O. KW - Simulation model, SNOTEL, Snow chemistry AB -

Snowfall samples from snowstorms lasting 1 to 4 days were collected near the Bear Lake snow telemetry (SnoTel) site in Rocky Mountain National Park, Colorado (ROMO), during the 1998-99 snowfall season to determine if storms moving in from different directions affect the chemistry of precipitation in the park. Storm pathways to Bear Lake during snowfall events were estimated using the HYSPLIT4 backward-trajectory model developed by the National Oceanic and Atmospheric Administration. Deposition of acidic ions of nitrate and sulfate in snowfall during the study varied substantially (two- to threefold) depending on storm trajectory because air masses traversing the park originated from different surrounding areas, including some having large sources of emissions of nitrate and sulfate. Concentrations of nitrate and sulfate in samples were lowest when storms reached ROMO from north and east of the park and were elevated when air masses traveled from the west where a number of power plants are located. Concentrations were highest in storms reaching ROMO from the south, a region with urban areas including Metropolitan Denver.

JF - 69th Annual Western Snow Conference T3 - Proceedings of the 69th Annual Western Snow Conference PB - Western Snow Conference CY - Sun Valley, Idaho UR - sites/westernsnowconference.org/PDFs/2001Ingersoll.pdf ER - TY - Generic T1 - Rocky Mountain snowpack chemistry relative to El niño effects of water years 1993-97 T2 - 66th Annual Western Snow Conference Y1 - 1998 A1 - Ingersoll, G. P. KW - El niño, Snowpack chemistry, Southern Oscillation Index AB - Snowmelt-dominated runoff is correlated with El Nino-related Southern Oscillation Index events in the Rocky Mountain region. Generally. during El Nino winters, the Rocky Mountains are drier in the north and wetter in the south. Annual snow sampling by the U.S. Geological Survey during water years 1993-97 at 52 sites throughout the Rocky Mountain region near a variety of regional anthropogenic emissions sources revealed strong inverse relations between snow depth and chemical concentrations in the snowpack. The Southern Oscillation Index (SOl) indicates that 1995 was the strongest El Nino year affecting the Rocky Mountains during water years 1993-97. However, neither greater snowfall amounts nor correspondingly lower snowpack concentrations of ammonium, nitrate, or sulfate occurred that year. During water year 1997, the year with the least negative SOl and the weakest El Nino effect, the greatest variance in snow depths among the study sites was observed (p<0.005) relative to the other 4 years. Snow depths as a group in water year 1997 were significantly greater (p