Dennis P. Lettenmaier Department of Civil and Environmental Engineering University of Washington

1. Dennis P. Lettenmaier Department of Civil and Environmental Engineering University of Washington Eric F. WoodDepartment of Civil EngineeringPrinceton University Andrew WeaverSchool of Earth and Ocean SciencesUniversity of Victoria ARCSS Freshwater Initiative All-investigators Meeting Boulder, CO February 18, 2003 The role of spatial and temporal variability of Pan-arctic river discharge and surface hydrologic processes on climate

2. Overarching: How will the coupled arctic climate system respond to changes in riverine discharge of freshwater, and how do the temporal and spatial variability of freshwater discharge, and changes therein, interact with the dynamics of high latitude climate? Specific: What is the uncertainty in the discharge of ungaged areas draining to the Arctic, especially the Canadian Archipelago, and how can this uncertainty best be reduced? What are the relative effects of seasonal albedo changes over ocean and land associated with transitions from sea ice to open water, and snow cover to bare vegetation, respectively, and how are the relative sensitivities likely to change over the next century? How well do current coupled land-atmosphere-sea ice-ocean models represent the processes controlling the dominant modes of climate variability in the Arctic system, and where are the greatest weaknesses? Science questions:

3. The project experimental design is based on a series of uncoupled, partially coupled, and fully coupled simulations with a combination of sea ice, atmosphere, land, and ocean models Sea ice, atmosphere, and ocean models are components of the University of Victoria’s Earth System Climate Model Land model is University of Washington/ Princeton University Variable Infiltration Capacity (VIC) land surface model. The science questions will be posed through a combination of model runs in which sea ice, ocean, and land surface models are run in off-line mode, and various aspects of the off-line climatologies will be prescribed in partially coupled ensemble runs of the fully coupled model system. Partially coupled model results will be compared with results of fully coupled ensemble climate simulations to isolate the effects of interactions among the land, sea ice/ocean, and atmosphere. Experimental Design

4. Land surface model updates – high latitude processes

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

7. 2000 = wet = dry Saturated extent 1999 and 2000 a. b. c. d. e.

8. 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

9. Lake energy balance

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

11. Lake ice formation and break-upTorne River, Sweden ice break-up ice formation = area > 20 km2 = area < 20 km2

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

13. Blowing Snow Günter Eisenhardt 3.31.2002, Iceland

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

15. transport = 0 transport = Qt(x= f) average fetch, f Non-equilibrium Transport snow

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

17. Simulated annual sublimation from blowing snowSensitivity to fetch

18. Permafrost

19. SWE and active layer depth

20. Spatially-distributed frozen soils • Soil node temperatures solved via heat diffusion equation • Ice content, infiltration rate and heat capacity calculated at nodes • Assumed uniform temperature distribution across the grid cell allows spatial variation of infiltration capacity

21. Effect on runoff + baseflow

22. Preliminary results