Influence of windblown dust on snowmelt timing in the Rocky Mountains, USA [David Clow]


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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, USA [David Clow]

  1. 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 Ingersoll11. U.S. Geological Survey2. University of Colorado, Boulder
  2. 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. 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. 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. 5. Problem: Data are Sparse Little dust data for Rocky Mountains Makes analysis of the influence of dust on snowmelt timing problematic
  6. 6. Can We Take Advantage of Existing SnowChemistry 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. 7. Rocky Mountain Snowpack has ChemicalSignature 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. 8. Dusty Snow Layers Contain CalciteMajor dust event in February 2006Dust Layer was Sampled at 14 Sites in ColoradoSamples Analyzed for Ca, Alkalinity, DustConcentrationsDust Layers had a Strong Calcite Signature Feb 2006 dust layer, Niwot Ridge
  9. 9. Dust often Originates in Desert Southwest Feb 14 - 15, 2006 Typical Transport Trajectory
  10. 10. Spatial Patterns: Wet Deposition of Calcium 2007
  11. 11. Spatial Patterns: Snowpack Ca Increasesfrom North to South 1992-2009 Winter averages Alk and Mg show same pattern Ca can be used as surrogate for dust
  12. 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. 13. Trends in Springtime Ca in Wet Deposition Relatively few Significant trends A few Upward Trends in Northern Colorado
  14. 14. Climate and Dust Affect Snowmelt TimingSnowmelt Onset Snowmelt Center of Mass
  15. 15. ConclusionsDust deposition increases from north tosouth in the RockiesTrends in Dust Deposition were variable Increasing trends in northern Colorado, but magnitude uncertainMajor Drivers of Snowmelt Timing in theRockies include: Increasing Springtime Air Temperatures Decreasing Snowfall Increasing Dust Concentrations
  16. 16. AcknowledgementsFunding Provided by USGS Office of Global Change Water, Energy, and Biogeochemical Budgets program National Science Foundation Long-Term Ecological Research program
  17. 17. Future Directions Prepare Manuscript Incorporate Dust Effect in Hydrological Models (PRMS)