The role of spatial and temporal variability of Pan-arctic river discharge and surface

hydrologic processes on climate

Dennis P. LettenmaierDepartment of Civil and Environmental Engineering

University of Washington

Eric F. WoodDepartment of Civil Engineering

Princeton University

Andrew WeaverSchool of Earth and Ocean Sciences

University of Victoria

ARCSS Freshwater Initiative All-investigators MeetingBoulder, CO

February 18, 2003

Science questions: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?

Experimental Design• 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.

Land surface model updates – high latitude processes

Lakes and wetlands

Source: San Diego State University Global Change Research Group

Saturated extent 1999 and 2000

0

100

200

300

400

6/10 6/30 7/20 8/9 8/29Inu

nd

ate

d a

rea

(km

2 )

19992000

2000

= wet = dry

a.

b. c. d. e.

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

Lake energy balance

Lake surface energy balance

Mean daily values, June-August 2000

Mean diurnal values, June-August 2000‘Lake 1’, Arctic

Coastal Plain, Alaska

Lake ice formation and break-upTorne River, Sweden

ice formationice break-up

= area > 20 km2 = area < 20 km2

Wetland Algorithm

soilsaturated

land surface runoff enters

lake

evaporation depletes soil

moisture

lake recharges

soil moisture

Blowing Snow

Günter Eisenhardt 3.31.2002, Iceland

Distribution of terrain slopes

Trail Valley Creek, NWT Imnavait Creek, Alaska

Non-equilibrium Transport

average fetch, f

transport = 0

transport = Qt(x= f)

snow

Estimating average fetch

vegetation type terrain slope terrain st. dev

Simulated annual sublimation from blowing snowSensitivity to fetch

Permafrost

SWE and active layer depth

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

Effect on runoff + baseflow

Preliminary results