USGS

 

Mass Balance, Meteorology, Area Altitude Distribution, Glacier-Surface Altitude, Ice Motion, Terminus Position, and Runoff at Gulkana Glacier, Alaska, 1996 Balance Year

U.S. Geological Survey Open File Report 03-4095

Jan 2004

 

By Rod S. March

Abstract

The 1996 measured winter snow, maximum winter snow, net, and annual balances in the Gulkana Glacier Basin were evaluated on the basis of meteorological, hydrological, and glaciological data. Averaged over the glacier, the measured winter snow balance was 0.87 meter on April 18, 1996, 1.1 standard deviation below the long-term average; the maximum winter snow balance, 1.06 meters, was reached on May 28, 1996; and the net balance (from August 30, 1995, to August 24, 1996) was -0.53 meter, 0.53 standard deviation below the long-term average. The annual balance (October 1, 1995, to September 30, 1996) was -0.37 meter. Area-averaged balances were reported using both the 1967 and 1993 area altitude distributions (the numbers previously given in this abstract use the 1993 area altitude distribution). Net balance was about 25 percent less negative using the 1993 area altitude distribution than the 1967 distribution.

Annual average air temperature was 0.9 degree Celsius warmer than that recorded with the analog sensor used since 1966. Total precipitation catch for the year was 0.78 meter, 0.8 standard deviations below normal. The annual average wind speed was 3.5 meters per second in the first year of measuring wind speed. Annual runoff averaged 1.50 meters over the basin, 1.0 standard deviation below the long-term average.

Glacier-surface altitude and ice-motion changes measured at three index sites document seasonal ice-speed and glacier-thickness changes. Both showed a continuation of a slowing and thinning trend present in the 1990s.

The glacier terminus and lower ablation area were defined for 1996 with a handheld Global Positioning System survey of 126 locations spread out over about 4 kilometers on the lower glacier margin. From 1949 to 1996, the terminus retreated about 1,650 meters for an average retreat rate of 35 meters per year.

CONTENTS

Abstract

Introduction

Description of Gulkana Glacier Basin and Its Climate

Measurement System and Terminology

Data Collection

Meteorology

Air Temperature

Precipitation Catch

Wind Speed

Area Altitude Distribution

Glacier Mass Balance

Balance at Specific Sites

Area-Averaged Balances

Measured and Maximum Winter Snow Balances

Net Balance

Summer Balance

Annual Mass Balance

Accumulation Area Ratio and Equilibrium Line Altitude

Glacier-Surface Altitude

Ice Motion

Terminus Position

Runoff

Summary

References Cited

 

Citation for this report:

 

March, R.S., 2003, Mass Balance, Meteorology, Area Altitude Distribution, Glacier-Surface Altitude, Ice Motion, Terminus Position, and Runoff at Gulkana Glacier, Alaska, 1996 Balance Year: U.S. Geological Survey Water-Resources Investigations Report 03-4095, 33 p.

 

For additional information contact:

 

Rod March

U.S. Geological Survey

3400 Shell Street

Fairbanks, AK 99701-7245

Telephone: (907) 479-5645

Email: rsmarch@usgs.gov


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