Remote sensing and isotopic analysis to determine the contribution of snow- and ice-melt to streamflow in the Nepal Himalaya [Mark Williams]
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Remote sensing and isotopic analysis to determine the contribution of snow- and ice-melt to streamflow in the Nepal Himalaya [Mark Williams]

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Remote sensing and isotopic analysis to determine the contribution of snow- and ice-melt to streamflow in the Nepal Himalaya. Presented by Mark Williams at the "Perth II: Global Change and the......

Remote sensing and isotopic analysis to determine the contribution of snow- and ice-melt to streamflow in the Nepal Himalaya. Presented by Mark Williams at the "Perth II: Global Change and the World's Mountains" conference in Perth, Scotland in September 2010.

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  • 1. The Niwot Ridge Mountain Biosphere Reserve:Tipping points in high-elevation ecosystemsin response to changes in climate andatmospheric deposition Mark Williams, University of Colorado
  • 2. High-elevation areas are important bellwethers of global change: we need long-term research
  • 3. Glaciatedvalley SADDLE
  • 4. External Drivers: Temperature Increasing air temperature since early 1980’s Summer air temps warming fastest Earlier lake ice-out dates 5ºC increase in 25 years
  • 5. External Drivers: Precipitation Greater precipitation with increasing elevation Increases in the winter months (more snow) Summer drought starting in 2000
  • 6. External Drivers: N deposition• Increased rates of N deposition (wetfall)• N loading increases, despite drought
  • 7. ARIKAREE D1 CLIMATE GLACIERROCKGLACIER GREEN LAKE 4 3,600 m
  • 8. Earlier Snowmelt 2-6 days decade-1
  • 9. Precipitation Effects on Streamflow GL4 225-ha MART 8-ha
  • 10. Wet Year vs. Dry Year-Increasing subsurfacepathways.-- Snowmelt peak is notsnow – old, reacted water(talus + baseflow) ispushed out by infiltratingsnow.-- Source of baseflowchanges and volumes arenot significantly different.
  • 11. Arikaree glacier is dying Drought Tipping pointArikaree Glacier: Mass balance (Bn), cm water equivalent.
  • 12. N dep + warming T = N saturation N Critical load: Aquatic 4 Kg N/ ha/ yrAnnual VWM concentrations of nitrate increase at all stream sites
  • 13. Stoichiometric controls on N- cycling Scatterplot of NO3- vs. DOC: NO3- ratio for eight sites in Green Lakes Valley.
  • 14. Saddle site
  • 15. how much N input does it take to produce a change in species composition? (= N critical load using biotic response)Addressed experimentally inspecies rich dry meadow, usingadditions of 2, 4, 6 g N/m2/yr
  • 16. species composition response: 50 treatment x year P < 0.01 Carex rupestris 40projected cover (%) N added: Carex rupestris 30 0 2 20 4 10 6 0 96 98 00 02 04 06 08 19 19 20 20 20 20 20 Treatment specific rate of change in cover similar response for Trisetum spicatum
  • 17. Empirical estimation of N critical load for plant species responses in alpine dry meadows 4 (% projected cover/yr) change in Carex cover 3 2 1 0 -1 0 1 2 3 4 5 6 7 -2 -1 0.0 N input (g N m yr ) N Critical load: score (value /year) Change in DCA1 10-40 Kg N/ ha/ -2.5 yr -5.0 Whole community response -7.5 -1 0 1 2 3 4 5 6 7 -2 -1 N input (g N m yr )
  • 18. Woody Willow Encroachment
  • 19. Willow Encroachment Experiment Factorial manipulation of N (fertilizer), snow (snowfence), summer temperature (open- topped chambers), in all possible combinations + Addition of Salix glauca seedlings
  • 20. Shrub growth benefits fromincreased N, snow, and temperatureSalix growth in height after 2 years (cm)
  • 21. Feedbacks to ecosystem processes Willow encroachment increases litter, N availability, Net N mineralization (mg N/g soil/30 days) and snow depth. These effects may accelerate encroachment Absent Present Willows
  • 22. Summary• Disappearing glaciers• Snowmelt occurring earlier• Drought years little discharge because of groundwater deficit• Increasing N deposition increases nitrate in streamflow• Critical loads for terrestrial veg 10 kg/ha/yr• Shrub invasion of alpine
  • 23. QUESTIONS?