A large dam for hydropower with a 67 km long reservoir is proposed in the Susitna basin, leading to multiple studies of the basin. This study focuses on the response of climate change of the Susitna basin glaciers and the effects on basin discharge

Aubry-Wake, Caroline

Braun, Juliana

Hock, Regine

Liljedahl, Anna

Wolken, Gabriel

Zhang, Jing

English

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  Hock, R., 1999. A distributed temperature index ice and snow melt model including potential direct solar radiation. J. Glaciology 45(149), 101-111. Support by UAF Undergraduate Research and Scholarly Activity (URSA SUgR S1314-2)  and the Alaska Energy Authority is gratefully acknowledged. Field work support by A.C. Beedlow, J. Young and A. Gusmerolli is greatly appreciated.   . RESPONSE OF GLACIER MELT AND DISCHARGE TO FUTURE CLIMATE CHANGE, SUSITNA BASIN, ALASKA Caroline Aubry-Wake 1,2, Regine Hock1, Juliana Braun1, Jing Zhang3, Gabriel Wolken4 , Anna Liljedahl5  1Geophysical Institute, University of Alaska, Fairbanks [UAF], USA; 2McGill University, Montreal, Canada;  3Department of Physics, Department of Energy & Environmental Systems, North Carolina A&T State University 4Alaska Division of Geological & Geophysical Surveys (DGGS); 5Water and Environmental Research Center, UAF     Conclusions / Summary  Reference and Acknowledgements   A large dam for hydropower with a 67 km long reservoir is proposed in the Susitna basin, leading to multiple studies of the basin. This study focuses on the response of climate change of the Susitna basin glaciers and the effects on basin discharge.    Specific goals: - Quantify the glacier mass change until 2100; - Project future runoff; - Analyze the changes in annual runoff,      seasonality and peak flows;  Background and Goals Study area Model Temperature and Precipitation, 1955-2012  Discharge, 1955-2012       1980-81   1981-82   1982-83   2011-12 measured  modeled  Projections 2005-2100 2006 2099  Depending on the climate scenario, runoff in the glacier basins is predicted to increase by 20 to 40% over the period 2005-2100 due to increased temperature of 3 to 5°C and precipitation increase between 20 and 35%.   During the same period the glaciers are projected to lose 10 to 12% of their area.  The future projections show no trend in winter balance but show a trend towards more negative specific summer balances.  The model, despite its simplicity and focus on snow and ice melt, is able to reproduce well the observation in discharge and mass balance.   Downscaling for temperature and precipitation biases of the climate model scenarios yields better results when done on a monthly instead of annual basis. r2 = 0.79 log r2 = 0.91 Proposed dam Susitna basin Area evolution We used the open access distributed temperature index model (DETIM, http://regine.github.io/meltmodel/ , Hock, 1999) which uses daily  precipitation and air temperature as climate forcing  Daily Snow and ice melt, M, is computed using a grid-based temperature-index mass-balance model including daily potential direct solar radiation, Ipot, (Wm-2),  (Hock, 1999):       T = daily mean air temperature (°C),  f = melt factor,   asnow/ice = radiation coefficients.  Snow precipitation is computed from daily precipitation data using a temperature threshold.   Discharge is computed using four parallel linear reservoirs for the firn area, the bare ice area,  the snow-covered area (on and outside of glacier) and the snowfree area outside the glacier. Different storage coefficients are assigned to each reservoir to account for differences in water travel times.  For the future scenarios a simple glacier retreat algorithm is implemented using volume-area scaling.  The model has 9 model parameters (melt factor, radiation coefficient for snow and ice, temperature lapse rate, precipitation correction factor and lapse rate, storage coefficients for each reservoir).  measured  modeled   The model was calibrated over the period 1955-2012.   Daily temperature at AWS1 (1516 m a.s.l.) was extended using the Talkeetna airport NCDC station (907 m a.s.l.) .   Daily precipitation from Talkeetna airport was corrected by a precipitation correction factor calibrated  in DETIM to represent the precipitation at AW1.   Daily mean discharge data from the Susitna river near Denali highway,  covering the period 1957-1966, 1968-1986 and 2012 and 109 mass balance point measurements  for years 1980-1983 and 2011-2012 were used to calibrate the model. The parameters were calibrated maximizing the agreement between measured and modeled discharge and point glacier mass balances.       Discharge, 1983-1984  Calibration AWS 2 AWS 1 Stake Study area Elevation : 740-4000 m a.s.l.  2230 km2 20% glacierized Point mass balances Discharge (m3 s-1) Discharge A1B =  +39%    A2 = +38%   B1 = +22% Change 2005-2100:  Runoff Components  J F M A M J J  A S O N D      J F M A M J J  A S O N D   3500 2500 2000 1500 3000 m a.s.l. Mean 2006-2010 Mean 2095-2099 Discharge (m3 s-1) Runoff from glacier firn area (melt and rain)               “firn reservoir”  Runoff from snow free area outside glacier (only rain)   “ice-free reservoir” Runoff from snow covered area (except firn area)       “snow reservoir” Runoff from glacier bare ice area (melt and rain)           “ice reservoir”  measured AWS 2 AWS 2 AWS 2 AWS 2 AWS 2 Mass Balance Cumulative net balance  2005-2100:  A1B = -100 m w.e.   A2 = -128 m w.e.   B1 = -92 m w.e. Annual Winter Summer Mass balance  (m w.e. yr-1) Precipitation (mm yr-1) Precipitation Change 2005-2100:  A1B = +34%   A2 = +33%   B1 = +23%    Temperature  (°C) Temperature A1B = +4.4 °C    A2 = +4.9 °C     B1 = +3.0 °C Change 2005-2100:   The calibrated model was run for the period 2005-2100 using daily precipitation and temperature data from the Scenarios Network for Alaska & Arctic Planning (SNAP) project based on the Community Climate System Model (CCSM). We use data from 3 emission scenarios (A1B, A2 and B1).   The data series of the grid point closest to AWS 1 was used and bias-corrected using data from Talkeetna and AWS 1.  Gauging station  Susitna river near Denali (weather stations) (Eq. 1) r2 = 0.78 Measured (m w.e. yr-1) Modeled (m w.e. yr-1) Area change: A1B = -11%     A2 = -14%     B1 = -10% A1B scenario Model Results G. Wolken (m3 s-1) Area (km2) °C m3/s 

Response of Glacier Melt and Discharge to Future Climate Change, Susitna Basin, Alaska

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Response of Glacier Melt and Discharge to Future Climate Change, Susitna Basin, Alaska

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