Streamflow Simulations of the Terrestrial Arctic Regime Fengge Su, Jennifer C. Adam, Laura C. Bowling and Dennis P. Lettenmaier Department of Civil and Environmental Engineering University of Washington, Seattle, WA 98195 E-mail: fgsu@hydro.washington.edu 2018/11/9

Outline Background Model description Data sources Streamflow simulations Conclusion and discussion 2018/11/9

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. 2018/11/9

Model description Model features: multiple vegetation classes in each cell; energy and water budget closure at each time step; subgrid infiltration and runoff variability; and non-linear baseflow generation. The VIC (Liang et al, 1994;1996) model is a grid-based land surface scheme designed both for inclusion in GCMs, and for use as a stand-alone macro-scale hydrological model. 2018/11/9

Cold land processes in VIC A two-layer energy balance snow model (Storck et al, 1999) A frozen soil/permafrost algorithm (Cherkauer et al, 1999; 2003, JGR) A lakes and wetlands model (Bowling et al, 2003,WRR) A blowing snow model (Bowling et al, 2003, in review) All of these have been tested at points or catchments scale, but not ever been applied over the entire Pan-Arctic domain . 2018/11/9

Daily time series (1979-1999) of precipitation, maximum Data sources Meteorological forcings Daily time series (1979-1999) of precipitation, maximum temperature, minimum temperature, wind speed Land surface characteristics Soil parameters: from the FAO global soil map. Land cover characterization: based on University of Maryland 1-km global vegetation classifications. Observed data Discharge data : R-ActicNet V 3.0 (Lammers et al, 2001) Snow cover extent: NOAA Northern Hemisphere EASE-Grid Weekly Snow Cover and Sea Ice Extent Version 2 2018/11/9

Streamflow simulations Study area: Whole Pan-Arctic Model version: VIC4.1.0 (Release data: 7/31/2003) Model options: with full energy balance, frozen soil, lake model, and blowing snow Model resolution: 100 km Time step: 3-hour 2018/11/9

Pan-Arctic Drainage Basins / mask file Yukon Lena Lena Mackenzie Yenisei Ob 2018/11/9

Arctic river network over 100km grid system 2018/11/9

Calibration The most sensitive soil parameters in the model were infiltration capacity curve (bi), and upper and lower soil depths (d1, d2). Calibration was performed manually and focused on matching the shape of the monthly hydrograph, and also based on the hydro-climatology of different basins, including surface air temperature, land cover, permafrost extent and runoff ratio. 2018/11/9

Infiltration parameter bi Model Soil Parameters Lena Yenesei Yukon Ob Mackenzie Infiltration parameter bi 0.5 0.05~0.1 0.1 Top layer depth (m) 0.1~0.5 Lower layer depth (m) 0.1 ~ 0.3 0.2 ~0.3 0.2~0.25 2.0~2.5 1.0~2.0 Bottom layer depth (m) 0.2 ~ 0.3 0.2~0.3 1 Basin Soil parameter 2018/11/9

Lena Observed Simulated Aldan at Verhoyanski Perevoz (Area:696000.00 km2) Mean monthly hydrograph (1979-1999) Lena at Kusur (Area:2430000.00 km2) Lena at Kusur Observed Simulated 2018/11/9

Yenisei Observed Simulated Nizhnyaya Tunguska at Bol’shoy Porog, Yenisei (Area: 447000.00 km2) Mean monthly hydrograph (1979-1990) Yenisei at Igarka (Area: 2440000.00 km2) Mean monthly hydrograph (1979-1998) Observed Simulated 2018/11/9

Ob Observed Simulated Mean monthly hydrograph (1979-1994) Ob at Prokhorkino (Area: 738000.00 km2) Ob at Salekhard (Area: 2430000.00 km2) Mean monthly hydrograph (1979-1998) Observed Simulated 2018/11/9

Mackenzie Yukon Observed Simulated Mackenzie at Arctic Red River (Area: 738000.00 km2) Mean monthly hydrograph (1979-1991) Yukon Yukon R NR Stevens Village AK (Area:508417.50 km2) Yukon R NR Stevens Village AK Observed Simulated 2018/11/9

Indigirka Yana Observed Simulated Indigirka at Vorontsovo, Lena (Area: 305000.00 km2) Yana Yana at Ubileinaya, Lena (Area: 224000.00 km2) Observed Simulated 2018/11/9

Mean number of days with snow 1980-1999 1980-1989 1990-1999 2018/11/9

Fraction of area covered by snow Lena Ob Observed Simulated 2018/11/9

Mean monthly fraction of area covered by snow Lena Lena Mackenzie Mackenzie Ob Ob Yenisei Yenisei Yukon Yukon 1980-1989 1990-1999 Observed Simulated 2018/11/9

Conclusion and discussion The VIC model with the recent upgrades to its representation of cold land processes was used to simulate streamflow from the pan-Arctic land area from 1979 to 1999. The simulated results for the Arctic’s five largest basins show reasonable agreements with the observed values of discharge and snow cover extent. We currently run the model over the entire Pan-Arctic domain to estimate the fresh water inflow to the Arctic ocean . The model is further validated in energy fluxes, snow water equivalent, and soil freezing/thawing depth using the observed data. 2018/11/9

Thank you! 2018/11/9