Influence of Windblown Dust on Snowmelt Timing in the Rocky Mountains
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Influence of windblown dust on snowmelt timing in the Rocky Mountains, USA. Presented by David Clow at the "Perth II: Global Change and the World's Mountains" conference in Perth, Scotland in September 2010.
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Influence of Windblown Dust on Snowmelt Timing in the Rocky Mountains
- 1. Influence of Windblown Dust on Snowmelt Timing in the Rocky Mountains, USA Using Calcium as an indicator of dust David W. Clow1 Mark Williams2 George Ingersoll1 1. U.S. Geological Survey 2. University of Colorado, Boulder
- 2. Snowmelt is Occurring Earlier Trend in Snowmelt Onset In Colorado, Snowmelt and Streamflow are Ocurring 2 Weeks Earlier than in the Late 1970s What are the Drivers? Clow (2010), J. Climate
- 3. Dust is One Driver of Early Melt Dust changes snowpack albedo Other Drivers Include: Increasing Air Temperature Decreasing Snowfall Photo from Niwot Ridge, spring 2006
- 4. Key questions: What is the Spatial Pattern of Dust Deposition in the Rocky Mountains? Are there trends in Dust Deposition? What is the Relative Importance of Dust in Controlling Snowmelt Timing?
- 5. Problem: Data are Sparse Little dust data for Rocky Mountains Makes analysis of the influence of dust on snowmelt timing problematic
- 6. Can We Take Advantage of Existing Snow Chemistry Data? Hypothesis: Calcium can be Used as Indicator of Dust Deposition Dust contains Calcite Calcite dissolves readily, releasing Ca and HCO3 (alkalinity) Reflected in precipitation Chemistry
- 7. Rocky Mountain Snowpack has Chemical Signature of Calcite 57 Sites Sampled Annually Principal in Rockies during 1992- Components 2009 1 2 3 Alk 0.77 0.16 0.33 PCA identified the Ca 0.82 -0.27 0.27 following components: Mg 0.79 -0.35 0.23 Alk, Ca, Mg (dust) Na 0.17 -0.15 0.92 K 0.69 -0.02 -0.04 NH4, NO3, SO4 (acids) NH4 -0.13 -0.69 0.13 Na, Cl (salt) Cl 0.21 -0.05 0.90 Explained 75% of NO3 0.24 -0.85 0.08 Variance in Chemistry SO4 0.22 -0.88 -0.01
- 8. Dusty Snow Layers Contain Calcite Major dust event in February 2006 Dust Layer was Sampled at 14 Sites in Colorado Samples Analyzed for Ca, Alkalinity, Dust Concentrations Dust Layers had a Strong Calcite Signature Feb 2006 dust layer, Niwot Ridge
- 9. Dust often Originates in Desert Southwest Feb 14 - 15, 2006 Typical Transport Trajectory
- 10. Spatial Patterns: Wet Deposition of Calcium 2007
- 11. Spatial Patterns: Snowpack Ca Increases from North to South 1992-2009 Winter averages Alk and Mg show same pattern Ca can be used as surrogate for dust
- 12. Trends in Winter Ca during 1992 - 2009 Trends were Analyzed using the Regional Winter Kendall Test (RKT) 60% of groups had significant trends (all up) Trends were Strongest in South-Central Rockies
- 13. Trends in Springtime Ca in Wet Deposition Relatively few Significant trends A few Upward Trends in Northern Colorado
- 14. Climate and Dust Affect Snowmelt Timing Snowmelt Onset Snowmelt Center of Mass
- 15. Conclusions Dust deposition increases from north to south in the Rockies Trends in Dust Deposition were variable Increasing trends in northern Colorado, but magnitude uncertain Major Drivers of Snowmelt Timing in the Rockies include: Increasing Springtime Air Temperatures Decreasing Snowfall Increasing Dust Concentrations
- 16. Acknowledgements Funding Provided by USGS Office of Global Change Water, Energy, and Biogeochemical Budgets program National Science Foundation Long-Term Ecological Research program
- 17. Future Directions Prepare Manuscript Incorporate Dust Effect in Hydrological Models (PRMS)