1. Model-Based Estimation of River Flows
to the Arctic Ocean
Dennis P. Lettenmaier
Jennifer C. Adam
Fengge Su
Theodore J. Bohn
Department of Civil and Environmental Engineering
University of Washington
AGU Spring Meeting
Montreal, Canada
May, 2004

2. Outline
Background
Model Description
Calibration
Validation
Pan-Arctic Discharge Estimate and Trends
Multi-Model Project
Conclusions

3. Background
The importance of freshwater inflow to the ocean systems .
The unique features of arctic land-surface hydrology.
The potential effects of climate change on the runoff of northern rivers.
The need of appropriate hydrologic models for runoff prediction from Pan-Arctic terrestrial domain.

4. Modeling Framework Features specific to Cold-Land Processes:
Pan-Arctic Domain per ArcticRIMS
100 km by 100 km EASE
runs: ,
Features specific to Cold-Land Processes:
Two-layer energy balance snow model (Storck et al. 1999)
Frozen soil/permafrost algorithm (Cherkauer et al. 1999, 2003)
Lakes and wetlands model (Bowling et al. 2004)
Blowing snow algorithm (Bowling et al. 2004)

5. 2810 cells routed to 643 outlets Contributing Area: 25 million km2
Routing Model
2810 cells routed to 643 outlets Contributing Area: 25 million km2

6. Model Calibration
Eleven Regions were calibrated separately (not including Greenland)
Calibration was focused on matching the shape of the monthly hydrograph.
Parameter transfer to un-gauged basins was based on the hydro-climatology of the region.

7. Two Eurasian Basins Lena Yenisei Lena at Kusur
Lena at Kusur (Area: km2)
Mean monthly hydrograph ( )
Yenisei at Igarka (Area: km2)
Yenisei

8. Two North American Basins
Mackenzie
Mean monthly hydrograph ( )
Mackenzie at Arctic Red River (Area: km2)
Yukon R NR Stevens Village AK (Area: km2)
Yukon R NR Stevens Village AK
Yukon
Observed
Simulated

9. Model Validation
Snow Cover Extent via comparison to NOAA-NESDIS weekly snow charts
Snow Water Equivalent via comparison to station observations in Eurasia
Permafrost active layer depth via comparison to CALM network observations (ongoing)
Lake algorithm validation via comparison of lake freeze and thaw dates to observed (ongoing)

10. Snow Cover Extent Comparison
NOAA-NESDIS weekly snow charts
VIC

11. Permafrost Active Layer Depth
Snow Water Equivalent
SWE (mm)
Simulated
Station Observations
Grid Cell: 55.65°N, 84.84°E
Permafrost Active Layer Depth

12. Recent Results for the 46-Year (1950-1995) Simulations
Pan-Arctic Discharge Estimates
Trends in Runoff and Precipitation
Changes in Snow Cover Extent
Changes in Active Layer Depth (TBD)

13. Freshwater Discharge to Arctic Ocean/Hudson Bay
Varies between 6950 and 7900 km3/year between 1960 and 1995
Discharge
Trend = 7.3 km3/year2
Precipitation
Trend = 8.7 km3/year2

14. Individual Basins
Lena (at Kusur): 2,430,000 km2
Comparisons of trends for observed and simulated streamflow for major basins suggest that simulated trends are not believable: more work is needed for temporally homogenous precipitation forcings

15. Changes in Snow Cover Extent
Change in number of snow days per year between the 1950’s and the 1990’s.
Increasing # of Days
Decreasing # of Days

16. Multi-Model Project
Collaborative project between the University of Washington and the University of Colorado (Mark Serreze, PI).
Objective is to get best possible time-series of pan-arctic states and fluxes using ensemble average.
Ensemble consists of five models: VIC, CLM, ECMWF, NOAH, and CHASM
All five models were included in the PILPS 2e experiment.

17. Forcing Data (NetCDF, ALMA)
VIC
CLM
ECMWF
NOAH
CHASM
Translate (VIC format)
Translate (CLM format)
Translate (ECMWF fmt)
Translate (NOAH format)
Translate (CHASM fmt)
Translate
Results (NetCDF, ALMA)
Compare CU UW

18. SWE, 1981
Thaw Depth, 1981

19. Evaporation, 1981
Total Runoff, 1981

20. Conclusions
The simulated results for the Arctic’s five largest basins show good agreement with observed values of discharge, SWE and snow cover extent (given the variability in each 10,000 km2 grid cell).
The simulated discharge of freshwater to the Arctic Ocean varies between 0.20 and 0.25 million m3/s (6950 and 7900 km3/year) between 1960 and 1995.
The inferred trend in discharge to the Arctic Ocean is 7.3 km3/year2, although comparisons of observed and simulated streamflow trends for the major basins suggest that this estimate may be incorrect.
For the multi-model project, the different LSMs agree in general output behavior, but some individual variables, notably evaporation and runoff, exhibit significant variation.