U.S. Department of the Interior U.S. Geological Survey Mass Balance, Meteorology, Area Altitude Distribution, Glacier-Surface Altitude, Ice Motion, Terminus Position, and Runoff at Gulkana Glacier, Alaska, 1996 Balance Year Water-Resources Investigations Report 03–4095 Cover: View looking north-northwest at the middle ablation zone of the main branch of Gulkana Glacier on August 8, 2002. The 1,480-meter weather station appears in the foreground. The main branch of the glacier starts out of the image to the right, then flows from right to left across the image, and finally terminates out of the image on the left. The icefall in the left center of the image is fed by the large western tributary of Gulkana Glacier, not visible here. Index site A lies just barely out of the image to the left; index site B lies in the right center of the image. U.S. Department of the Interior U.S. Geological Survey Mass Balance, Meteorology, Area Altitude Distribution, Glacier-Surface Altitude, Ice Motion, Terminus Position, and Runoff at Gulkana Glacier, Alaska, 1996 Balance Year By ROD S. MARCH Water-Resources Investigations Report 03–4095 Fairbanks, Alaska 2003 U.S. Department of the Interior Gale A. Norton, Secretary U.S. Geological Survey Charles G. Groat, Director Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. For additional information write to: Copies of this report can be purchased from: Alaska Science Center U.S. Geological Survey Chief, Water Resources Office Information Services U.S. Geological Survey Building 810 4320 University Drive, Suite 201 Box 25286, Federal Center Anchorage, AK 99508–4664 Denver, CO 80225–0286 http://ak.water.usgs.gov/glaciology/ CONTENTS Abstract.................................................................................................................................................................................. 1 Introduction ........................................................................................................................................................................... 1 Description of Gulkana Glacier Basin and Its Climate ............................................................................................... 2 Measurement System and Terminology ...................................................................................................................... 3 Data Collection...................................................................................................................................................................... 6 Meteorology........................................................................................................................................................................... 6 Air Temperature........................................................................................................................................................... 6 Precipitation Catch ...................................................................................................................................................... 8 Wind Speed.................................................................................................................................................................. 10 Area Altitude Distribution ..................................................................................................................................................... 13 Glacier Mass Balance ............................................................................................................................................................ 14 Balance at Specific Sites.............................................................................................................................................. 14 Area-Averaged Balances ............................................................................................................................................. 18 Measured and Maximum Winter Snow Balances........................................................................................................ 20 Net Balance.................................................................................................................................................................. 20 Summer Balance.......................................................................................................................................................... 20 Annual Mass Balance .................................................................................................................................................. 20 Accumulation Area Ratio and Equilibrium Line Altitude........................................................................................... 21 Glacier-Surface Altitude........................................................................................................................................................ 21 Ice Motion.............................................................................................................................................................................. 24 Terminus Position .................................................................................................................................................................. 24 Runoff.................................................................................................................................................................................... 28 Summary................................................................................................................................................................................ 29 References Cited.................................................................................................................................................................... 30 FIGURES 1. Diagram showing the cause and effect relationships for the data presented in this report .................................... 2 2. Maps of Gulkana Glacier and vicinity .................................................................................................................... 3 3. Composite vertical photograph of Gulkana Glacier and its basin showing index-measurement sites, stream- gaging station, weather station, and basin boundary, July 11, 1993 ....................................................................... 4 4–12. Graphs showing: 4. Time distribution of index-site mass balances for Gulkana Glacier, 1996 hydrologic year .................................. 5 5. Time distribution of glacier-averaged mass balance of Gulkana Glacier, 1996 hydrologic year .......................... 6 6. Daily mean air temperature recorded at 1,480-meter weather station, Gulkana Glacier Basin, 1996 hydrologic year.............................................................................................................................................. 7 7. Daily precipitation catch recorded at 1,480-meter weather station, Gulkana Glacier Basin, 1996 hydrologic year......................................................................................................................................................................... 10 8. Daily average wind speed recorded at 1,480-meter weather station in Gulkana Glacier Basin, 1996 hydrologic year.............................................................................................................................................. 11 9. Monthly average wind speed recorded at 1,480-meter weather station in Gulkana Glacier Basin for 1996 hydrologic year.............................................................................................................................................. 12 10. Area altitude distribution of Gulkana Glacier in 1967 and 1993 ........................................................................... 13 11. Glacier-averaged measured winter balance, net balance, and summer balance, 1966–96, and smoothed data..... 21 12. Glacier-surface altitudes at index sites A, B, and D............................................................................................... 22 Contents III FIGURES—Continued 13. Map of glacier terminus positions from Global Positioning System surveys on August 31 and September 1, 1996, and from U.S. Geological Survey 1:63,360-scale Mt. Hayes A3 and B3 quadrangle digital raster graphic files ......................................................................................................................................................................... 26 14. Graph showing daily runoff from Phelan Creek near Paxson, 1996 hydrologic year ............................................ 29 15. Graph showing estimated daily runoff from Phelan Creek near Paxson, 1996 hydrologic year, with measured values for both 1996 hydrologic year and entire period of record ......................................................................... 31 TABLES 1. Summary of data collection in Gulkana Glacier Basin for the 1996 balance year analysis................................... 7 2. Daily, monthly, and annual average air temperatures from analog sensor recorded at 1,480-meter weather station, Gulkana Glacier Basin, 1996 hydrologic year........................................................................................... 8 3. Daily, monthly, and annual average air temperatures from digital sensor recorded at 1,480-meter weather station, Gulkana