Estimating the freshwater budget of high-latitude land surfaces

1. Estimating the freshwater budget of high-latitude land surfaces Laura C. Bowling Ph.D. Defense August 21st, 2002

2. Presentation Outline • Introduction • Dissertation Synopsis • Pan-Arctic model simulation • Hydrologic effects of lakes and wetlands • Sublimation of blowing snow • Exploratory Analysis of Model Sensitivity • Lakes: Runoff hydraulics • Blowing Snow: Relative humidity • Summary and Recommendations

3. Observed cryosphere changeSea ice extent Source: W.M.O. Statement on the Status of Global Climate in 2000

4. Arctic discharge trends Summer Winter Annual

5. Thermohaline Circulation G. Holloway, Institute of Ocean Sciences, Sidney, BC

6. Arctic drainage basin Mackenzie Lena Ob Yenesei

7. Previous studies of macroscale models in arctic environments • Include PILPS 2d, PILPS 2e and Bowling et al. 2000 • Identified limitations in model representations, including: • lakes and wetlands, • permafrost and frozen ground • blowing snow

9. Location Map

10. Focus on regions typical of ungauged areas

11. Meteorological Inputs • Station data interpolated to 1/8o latitude by longitude grid • 1986 - 2001 • Relative humidity, air temperature and wind speed • 8 WERC stations • Hourly data • Precipitation • 2 NRCS gauges with Wyoming wind shields • 2 NCDC stations with NWS 8” gauges • Corrected for wind-induced gauge undercatch • Daily data

12. Annual average precipitation Unadjusted % difference Adjusted

13. Annual average meteorological variables

14. Lakes and wetlands Source: San Diego State University Global Change Research Group

15. Prudhoe Bay Landcover from Landsat MSS images (Muller et al. 1999).

16. Putuligayuk River discharge

17. Spring water balance 1999 2000 2001

18. Saturated extent 1999 and 2000 2000

19. Snow melt water balance 1999 2000 2001

20. Snow melt water balance

21. Predicting the effects of lakes and wetlands • Lake energy balance based on: • Hostetler and Bartlein (1990) • Hostetler (1991) • Assumptions: • One “effective” lake for each grid cell; • Laterally-averaged temperatures; and • Rule curve for release of runoff from grid cell lake.

22. Lake energy balance

23. Mean daily values, June-August 2000 Lake surface energy balance Mean diurnal values, June-August 2000 ‘Lake 1’, Arctic Coastal Plain, Alaska

24. Mean temperature profile (1993-1997)Toolik Lake, Alaska ObservedSimulated

25. Lake ice formation and break-upTorne River, Sweden ice break-up ice formation

26. soil saturated land surface runoff enters lake evaporation depletes soil moisture lake recharges soil moisture Wetland Algorithm

27. Simulated saturated extentPutuligayuk River, Alaska

28. with lake algorithm without lake algorithm Simulated mean annual evaporation • Simulated annual evaporation increases by 60%

29. Blowing Snow Günter Eisenhardt 3.31.2002, Iceland

30. Snow accumulation SWE > 0? Blowing snow sublimation Snow mass and energy balance Yes No Predictive model of the sublimation from blowing snow • Derived from existing small-scale blowing snow models (Pomeroy et al. 1993 and Liston and Sturm 1998). • Mass concentration of suspended transport based on power law relationship (Kind 1992). • Particle sublimation rate proportional to the undersaturation of water vapor. = VIC snow model

31. Overstory? Blowing sublimation = 0 Yes Yes No Percentile wind speed Snow accumulation SWE > 0? Saltation Snow mass and energy balance Fetch adjustment No Total transport and Sublimation Probability of blowing snow Final percentile? Blowing sublimation Yes No

32. Overstory? Blowing sublimation = 0 Yes Yes No Percentile wind speed Snow accumulation SWE > 0? Saltation Snow mass and energy balance Fetch adjustment No Total transport and Sublimation Probability of blowing snow Final percentile? Blowing sublimation Yes No

33. Distribution of terrain slopes Trail Valley Creek, NWT Imnavait Creek, Alaska

34. Sub-grid variability in wind speed • Wind speeds assumed to follow a Laplace distribution • Standard deviation of wind speed proportional to the mean wind speed, standard deviation of terrain slope and gradient autocorrelation of terrain • Total sublimation flux found by summing sublimation for the average wind speed of ten equally-probable intervals

35. Overstory? Blowing sublimation = 0 Yes Yes No Percentile wind speed Snow accumulation SWE > 0? Saltation Snow mass and energy balance Fetch adjustment No Total transport and Sublimation Probability of blowing snow Final percentile? Blowing sublimation Yes No

36. Non-equilibrium Transport

37. Estimating average fetch vegetation type terrain slope terrain st. dev

38. Simulated annual sublimation from blowing snowSensitivity to fetch

39. Model Sensitivity and Limitations • Low-gradient runoff hydraulics

40. SWE and active layer depth

41. Simulated saturated extentPutuligayuk River, Alaska

42. Problems with hydrograph timing

43. Second generation optimization

44. Model runs selected for best area

45. Model Sensitivity and Limitations • Low-gradient runoff hydraulics • Vapor pressure uncertainty

46. Annual average sublimationKuparuk River

47. Sensitivity to vapor pressure Average annual surface sublimation: RH w.r.t. ice -5.3 mm RH w.r.t water -9.2 mm Tdew = Tmin 6.6 mm

48. Summary - water balance of arctic coastal regions lakes and wetlands • 60 to 74% of snow melt water goes into storage and is not immediately available for runoff • Between 50 and 64% of the stored meltwater is depleted by evaporation from open water areas. • Evaporation and drainage result in a seasonal reduction of the extent of surface water bodies of 58 to 73%. • The presence of extensive open water effects the spatial distribution of simulated evaporation. Basin annual evaporation is 60% higher (26 mm) when the lakes are simulated.

49. Summary - water balance of arctic coastal regions Blowing snow • Annual average sublimation from blowing snow varies from 55 mm in the foothills to approximately 25 mm on the coastal plain. • It is impossible to estimate blowing snow transport at large spatial scales without some estimate of the distribution of wind speeds. • The simulated blowing snow sublimation is sensitive to estimates of upwind fetch in regions of complex terrain.

50. Recommendations for further work • Tundra runoff processes and the influence of snow dams in low gradient arctic rivers • Implications of relative humidity on the mid-winter snow pack energy balance • What is to be done about precipitation in regions with sparse data, that is getting sparser?