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Airborne Surface Profiling of Alaskan Glaciers

Summary

This data set consists of glacier outline, laser altimetry profile, and surface elevation change data for 46 glaciers in Alaska and British Columbia, Canada, measured with an airborne laser altimetry system. Six glaciers in the Alaska Range of central Alaska, two glaciers in the Wrangell Mountains of southcentral Alaska, 11 glaciers in the Chugach Mountains of southcentral Alaska, five glaciers in the Chigmit Mountains of southcentral Alaska, 13 glaciers in the Kenai Mountains of southcentral Alaska (comprising the Harding Icefield), one glacier in the St. Elias Mountains of southeast Alaska, one glacier in the Takhinsha Mountains of southeast Alaska, and seven glaciers in the Coast Mountains of southeast Alaska and British Columbia were profiled between 1994 and 2001. Surface elevation profiles are accurate to about 0.3 m. Long-term elevation changes can be estimated by comparison of these profiles with existing maps.

Citing These Data:

Echelmeyer, K.A., V.B. Valentine, and S.L. Zirnheld. 2002, updated 2004. Airborne surface profiling of Alaskan glaciers. Boulder, CO: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5RF5RZJ

Overview Table

Category Description
data format Fixed width-separated, comma-delimited, or tab-delimited files
spatial coverage Central, southcentral, and southeast Alaska
temporal coverage 1994 - 2001
file size 1 KB to 5.2 MB
Metadata access View metadata
Data access ftp://sidads.colorado.edu/pub/DATASETS/NOAA/G01378/

Table of Contents

1. Contacts
2. Detailed Data Description
3. Data Access
4. References and Related Publications
5. Document Information

1. Contacts

Investigators

Keith A. Echelmeyer
Geophysical Institute
University of Alaska, Fairbanks
Fairbanks, AK 99775

Virginia B. Valentine
Geophysical Institute
University of Alaska, Fairbanks
Fairbanks, AK 99775 USA

Sandra L. Zirnheld
Geophysical Institute
University of Alaska, Fairbanks
Fairbanks, AK 99775 USA

Technical Contact:

NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449  USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org

2. Detailed Data Description

Data are stored in ASCII text files. See individual data sections below for descriptions of formats.

Glacier Outline Data
Laser Altimetry Profile Data
Glacier Surface Elevation Change Data
Glacier Outline and Profile Trackline Plot

Glacier Outline Data

xxxOUTL.hdr is a Glacier Outline Header file, where "xxx" is the abbreviated name of the glacier. (E.g., BaiOUTL.hdr is the header file for the Baird Glacier outline data.) The glacier outline header files contain the following information:

Glacier Name
World Glacier Inventory (WGI) Glacier Number
Glacier Location
Approximate Center of Glacier
Approximate Length
Glacier Type
Included Tributaries/Regions
Maps used to Generate Outline
Data Fields in File (e.g., easting, northing)
File Name

xxxOUTL.dat is a Glacier Outline Data file, where "xxx" is the abbreviated name of the glacier (e.g., BaiOUTL.dat is the data file for the Baird Glacier outline data). The glacier outline is given in UTM coordinates. The data files contain two fields, either comma-delimited or tab-delimited:

Easting (NAD27, in meters)
Northing (NAD27, in meters)

NAD27 refers to the datum used (the datum is a system of measurement based on earth ellipsoids).

Sample Data Record for BaiOUTL.dat:

BAIRD GLACIER OUTLINE

EASTING(NAD27),NORTHING(NAD27)
661274.2091,6338096.646
661323.4619,6338027.883
661371.6796,6337988.571

Laser Altimetry Profile Data

xxxPROF.hdr is a Laser Altimetry Profile Header file, where "xxx" is the abbreviated name of the glacier. For example, BaiPROF.hdr is the header file for the Baird Glacier laser altimetry data. The laser altimetry profile header files contain the following information:

Glacier Name
World Glacier Inventory (WGI) Glacier Number
Glacier Location
Approximate Center of Glacier
Approximate Length
Glacier Type
Geographic Datum
UTM Zone
Profiles
Data Fields in Profile
GPS Processing
Reference
Contact Information
File Names

xxxJDNp.83a is a Laser Altimetry Profile Data file, where "xxx" is the abbreviated name of the glacier, JDN is the Julian day number on which data were collected, and p is the altimetry pass number (e.g., Bai1651.83a is a data file for the Baird Glacier laser altimetry profile data for pass number 1 collected on Julian day number 165). The data files contain four fields, either tab-delimited or fixed-width separated:

Easting (WGS84, in meters)
Northing (WGS84, in meters)
HAE (height above ellipsoid, in meters)
Error (in meters)

WGS84 refers to the datum used (the datum is a system of measurement based on earth ellipsoids).

Sample Data Record for Bai1651.83a:

BAIRD GLACIER LASER ALTIMETRY PROFILE  PASS 1

EASTING(m, WGS84)	NORTHING(m, WGS84) 	HAE(m, ht above ellipsoid)	ERROR(m)
6.315543600000000e+5	6.330853800000000e+6	4.400000000000000e+0	3.600000000000000e-1
6.315572200000000e+5	6.330860450000000e+6	4.710000000000000e+0	4.300000000000000e-1
6.315578800000000e+5	6.330862100000000e+6	4.500000000000000e+0	1.100000000000000e-1
6.315586800000000e+5	6.330863770000000e+6	4.690000000000000e+0	6.200000000000000e-1

Glacier Surface Elevation Change Data

xxxDZ.hdr is a Glacier Surface Elevation Change Header file, where "xxx" is the abbreviated name of the glacier. For example, BaiDZ.hdr is the header file for the Baird Glacier surface elevation change data.) The glacier surface elevation change header files contain the following information:

Glacier Name
World Glacier Inventory (WGI) Glacier Number
Glacier Location
Approximate Center of Glacier
Approximate Length
Glacier Type
Method For Determining Glacier Elevation Changes
Profiles
Geographic Datum
UTM Zone
Maps Used
Range of Geoid Height
Time Span For Elevation Change
Contact Information
Data Fields
File Name

xxxDZ.dat is a Glacier Surface Elevation Change Data file, where "xxx" is the abbreviated name of the glacier. For example, BaiDZ.dat is the data file for the Baird Glacier surface elevation change data. The data files contain five fields (either tab-delimited or fixed width separated):

Easting (NAD27, in meters)
Northing (NAD27, in meters)
Map Elevation (NGVD29, in meters)
Profile Elevation (NGVD29, in meters)
Elevation Change (in meters)

NAD27 and NGVD29 refer to the datums used (these datums are systems of measurement based on different earth ellipsoids).

Note: The Hubbard glacier surface elevation change data consist of three files:

For more information about the Hubbard Glacier DZ files, please refer to the Hubbard Glacier Notes.

Glacier Outline and Profile Trackline Plot

xxxPLOT.jpg is an image file, where "xxx" is the abbreviated name of the glacier. For example, BaiPLOT.jpg is the image file for the Baird Glacier. The image file contains a geographic plot of the glacier outline and the laser altimetry profile tracklines in the NAD27 datum.

Sample Data Record for BaiDZ.dat

BAIRD GLACIER SURFACE ELEVATION CHANGES

EASTING(m,NAD27)	NORTHING(m,NAD27)	MAP ELEVATION(m,NGVD29)	PROFILE ELEVATION(m,NGVD29)	ELEVATION CHANGE(m)
6.422415500000000e+5	6.337055800000000e+6	6.096000000000000e+2	5.428180300000000e+2	-6.678000000000000e+1
6.417041100000000e+5	6.336794900000000e+6	5.791200000000000e+2	5.170471300000000e+2	-6.207000000000000e+1
6.429674300000000e+5	6.337508700000000e+6	6.400800000000000e+2	5.784238900000000e+2	-6.166000000000000e+1

File Size

File sizes range from 1 KB to 5.2 MB

Spatial Coverage

East Fork Toklat, Gulkana Glacier, MIddle Toklat, Muldrow, Ruth, and Scott Peal Toklat Glaciers are in central Alaska, in the Alaska Range.

Kennicott and Nabesna Glaciers are in southcentral Alaska, in the Wrangell Mountains.

Bear Lake, Bering Glacier-Bagley Icefield, Columbia, Harvard, Knik, Tazlina, Valdez, Wolverine, Worthington, Wortmanns, and Yale Glaciers are in southcentral Alaska, in the Chugach Mountains.

Double, Shamrock, Tanaina, Tuxedni, and Turquoise Glaciers are in southcentral Alaska, in the Chigmit Mountains.

Aialik, Bear, Chernof, Dinglestadt, Exit, Holgate, Kachemak, Little Dinglestadt, McCarty, Northeastern, Northwestern, Skilak, and Tustumena Glaciers are in southcentral Alaska, in the Kenai Mountains, and comprise the Harding Icefield.

Hubbard Glacier is in the St. Elias Mountains, in southeast Alaska.

Muir Glacier is in southeast Alaska, in the Takhinsha Mountains.

Baird, LeConte, Lemon Creek, Llewellyn, Mendenhall, North Dawes, and Triumph Glaciers are in southeast Alaska, in the Coast Mountains.

 

GLACIER (Abbrev.) LATITUDE (N) LONGITUDE (W) WGI GLACIER NUMBER*
AIALIK (Aia) 59.96700 149.81700 US2N31850000
BAIRD (Bai) 57.23330 132.37500 US2P00101800
BEAR (Bea) 60.05000 149.66700 US2N32050000
BEAR LAKE (Blk) 60.18000 149.25000 US2P00200402
BERING BAGLEY (BerBag) 60.50000 142.50000 US2N00700001
CHERNOF (Che) 59.85800 150.41700 US2N28020000
COLUMBIA (Col) 61.30000 146.88330 US2T00200627
DINGLESTADT (Din) 59.75000 150.50000 US2N28080000
DOUBLE (Dou) 60.66700 152.66700 US2N10499990
EXIT (Exi) 60.16700 149.70000 US2N32630000
GULKANA (Gul) 63.27000 145.42000 US2O01200001
HARVARD (Har) 61.40000 147.38000 US2T00200628
HOLGATE (Hol) 59.86700 149.91700 US2N31680000
HUBBARD (Hub) 60.50000 139.50000 US2T00300001
KACHEMAK (Kac) 59.70000 150.55000 US2N28110000
KENNICOTT (Ken) 61.60000 143.05000 US2N00400604
KNIK (Kni) 61.35000 148.13000 US2N00600001
LECONTE (Lec) 57.00000 132.33333 US2T00101803
LEMON CREEK (Lem) 58.37000 134.35000 US2P00201804
LITTLE DINGLESTADT (Ldg) 59.66700 150.35800 US2N30140000
LLEWELLYN (Llew) 59.00000 134.17000 CD2O010DA001
MCCARTY (Mcc) 59.21700 150.78300 US2N30350000
MENDENHALL (Men) 58.50000 134.53000 US2T00101805
MUIR 1948 (Mui) 59.15000 136.40000 US2N75000010
MUIR 1972 (Mui) 59.15000 136.40000 US2N75000010
MUIR 2000 (Mui) 59.15000 136.40000 US2N75000010
MULDROW (Mul) 63.25000 150.50000 US2O47900010
NABESNA (Nab) 61.92000 143.08000 US2O01200002
NORTH DAWES (NDw) 57.63000 133.00000 US2N84200500
NORTHEASTERN (Nea) 59.80000 149.96700 US2N31350000
NORTHWESTERN (Nwn) 59.88300 150.05000 US2N31250000
RUTH (Rut) 62.98000 150.73000 US2N18503000
SHAMROCK (Sha) 61.05000 152.83300 US2N11800010
SKILAK (Ski) 60.16700 150.01700 US2N26450000
TANAINA (Tan) 60.91700 152.83300 US2N10605000
TAZLINA (Taz) 61.50000 146.58330 US2N00400602
TOKLAT 1-East Fork (TEF) 63.42000 149.67000 US2O46000100
TOKLAT 2-Middle (TkM) 63.38000 149.91000 US2O46200100
TOKLAT 3-Scott Peak (TSP) 63.38000 150.12000 US2O46300100
TRIUMPH (Tri) 57.44000 132.28000 CD2N001EA555
TURQUOISE (Tur) 60.78300 153.66700 US2O16100010
TUSTUMENA (Tus) 59.95000 150.25000 US2N27250000
TUXEDNI (Tux) 60.12000 153.12000 US2N09100010
VALDEZ (Val) 61.29000 146.20000 US2N00500501
WOLVERINE (Wol) 60.41670 148.90000 US2P00200411
WORTHINGTON (Wor) 61.16667 145.79170 US2N00400603
WORTMANNS (Wrt) 60.95000 145.70000 US2N00500502
YALE (Yal) 61.32000 147.38000 US2T00200629

*World Glacier Inventory Number

Spatial Coverage Map

Location map of glaciers

Projection

Universal Transverse Mercator (UTM) projection.

Temporal Coverage

Glaciers were profiled in May 1994; May and June 1995; June 1996; May, June, and August, 2000; and May and June, 2001.

Error Sources

Accuracy of the elevation data is typically 0.3 m or better. Error sources include GPS-determined elevation of the aircraft, and pitch and roll of the aircraft. Accuracy of the profile and elevation change data is approximately 5 m, due to map and digitization errors. Please refer to the following for additional quality and accuracy information:

Echelmeyer, K.A., W.D. Harrison, C.F. Larsen, J. Sapiano, J.E. Mitchell, J. DeMallie, B. Rabus, G. Adalgeirsdottir, and L. Sombardier. 1996. Airborne Surface Profiling of Glaciers: a Case-Study in Alaska. J. Glaciol., 42, 142:538-546.

Supporting Online Material for Arendt, A.A., K.A. Echelmeyer, W.D. Harrison, C.S. Lingle, and V.B. Valentine. 2002. Rapid Wastage of Alaska Glaciers and Their Contribution to Rising Sea Level. Science, 297:382-386.

3. Data Access

Data are available via ftp.

Data Acquisition Methods

This study used a laser altimeter for measuring the distance from a small aircraft to the glacier surface, a gyro and compass for determining the pointing direction of the laser beam, and continuous kinematic Global Positioning System (GPS) equipment for determining the exact position of the aircraft during the flight over a glacier. Carrier phase measurements were made once per second with two GPS receivers. The laser altimeter (ranger) operated at 905 nm, and sampled at 25 Hz, which corresponds to a measurement interval of about 1.2 m along the surface at a typical aircraft speed of 30m/s. The laser beam footprint diameter was 0.18 m at a distance of 100 m. Reflections were obtained at a maximum distance of 500 m from snow and approximately 200 m from ice, rock, and vegetation. The orientation of the beam was measured by a vertical-axis gyro and a magnetic compass, each sampled at 25 Hz.

The data were stored by an onboard computer and by the GPS receivers, and later processed to give an elevation profile along a specific track on the surface of the glacier. The measured glacier surface elevations were compared to map elevations at the same coordinates to obtain elevation changes over the period of time between the map photo date and the laser profiling date. The glacier profiles were compared to contours on 15-min US Geological Survey (USGS) and Canadian Department of Energy, Mines, and Resources topographic maps made from aerial photographs acquired in the 1950s to early 1970s (depending on location). The investigators digitized contour lines on topographic maps using a Numonics digitizing board and Sigma Scan software. A cubic spline was fit to the contour points to increase the data density. Where a laser altimetry profile crossed a contour line, the nearest profile point to any of the contour points (original or interpolated) was taken as the crossing point (these points were within a few meters horizontally of each other). The measured glacier surface elevation from the profile was compared to the elevation of the contour line from the map. The profile elevation, in height above the ellipsoid, was corrected to the map datum (NGVD29) by subtracting the height of the geoid at the crossing point coordinates (source: NGS Alaska Geoid93 Model or NGS Alaska Geoid99 Model).

4. References and Related Publications

Echelmeyer, K.A., W.D. Harrison, C.F. Larsen, J. Sapiano, J.E. Mitchell, J. DeMallie, B. Rabus, G. Adalgeirsdottir, and L. Sombardier. 1996. Airborne Surface Profiling of Glaciers: a Case-Study in Alaska. J. Glaciol., 42, 142:538-546.

Sapiano, J.J., W.D. Harrison, and K.A. Echelmeyer. 1998. Elevation, Volume and Terminus Changes of Nine Glaciers in North America. J. Glaciol., 44, 146:119-135.

Arendt, A.A., K.A. Echelmeyer, W.D. Harrison, C.S. Lingle, and V.B. Valentine. 2002. Rapid Wastage of Alaska Glaciers and Their Contribution to Rising Sea Level. Science, 297:382-386.

5. Document Information

Document Creation Date

September 18, 2002

Document Revision Date

April 21, 2004

Document URL

http://nsidc.org/data/g01378.html