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Velocities of outlet glaciers, ice streams, and ice shelves, Antarctica, from satellite images

Metadata also available as - [Questions & Answers] - [Parseable text] - [DIF]

Metadata:

Identification_Information
Data_Quality_Information
Spatial_Data_Organization_Information
Spatial_Reference_Information
Entity_and_Attribute_Information
Distribution_Information
Metadata_Reference_Information

Identification_Information:

Citation:

Citation_Information:

Originator: B.K. Lucchitta

Originator: J.M. Barrett

Originator: J.A. Bowell

Originator: J.G. Ferrigno

Originator: K.F. Mullins

Originator: C.E. Rosanova

Originator: R.S. Williams, Jr.

Publication_Date: 1995

Title:

Velocities of outlet glaciers, ice streams, and ice shelves, Antarctica, from satellite images

Publication_Information:

Publication_Place: Flagstaff, Arizona
Publisher: U.S. Geological Survey

Other_Citation_Details:

Data contained in this data set are background information supporting the following publications. Refer to data set documentation to determine which publication should be cited for when referring to an element of this data set.
Ferrigno, J.G., Lucchitta, B.K., Mullins, K.F., Allison, A.L., Allen, R.J., and Gould, W.G., 1993, Velocity measurements and changes in position of Thwaites Glacier Ice Berg Tongue from aerial photographs, Landsat images, and NOAA AVHRR data: Annals of Glaciology, v.17, p. 239- 244.
Lucchitta, B.K., Mullins, K.F., Allison, A.L., and Ferrigno, J.G., 1993, Antarctic glacial tongue velocities from Landsat images: First results: Annals of Glaciology, v. 17, p. 356-366.
Lucchitta, B.K., Smith, C.E., Bowell, J.A., and Mullins, K.F., 1994, Velocities and mass balance of Pine Island Glacier, West Antarctica, Derived from ERS-1 SAR images: Proceedings, 2nd ERS-1 Symposium, Hamburg, Germany, 11-14 Oct. 1993, ESA SP-361, p. 147-151.
Lucchitta, B.K., Mullins, K.F., Smith, C.E., and Ferrigno, J.G., in press, Velocities of Smith Glacier Ice Tongue and Dotson Ice Shelf, Walgreen Coast, Marie Byrd Land, West Antarctica: Annals of Glaciology, v. 20.
Lucchitta, B.K., Smith, C.E., and Mullins, K.F., Velocities and mass balance of Pine Island Glacier, West Antarctica: Submitted to Annals of Glaciology.

Online_Linkage:

<http://geochange.er.usgs.gov/pub/antarctica/glacier-velocity/Core/meta/report.html>

Description:

Abstract:: This report summarizes the results of velocity measurements of outlet glaciers, ice streams, and ice shelves around the Antarctic periphery. For some regions, where suitable images were available, the same area was measured repeatedly to validate the data or register changes in velocity with time. The results given here are a compendium of published papers and work in progress. The results constitute a data base that will be added to and amended as more velocity measurements become available.
Purpose:: Changes in global climate and sea level are intricately linked to changes in the area and volume of polar ice sheets. Thus, melting of the ice sheets may severely impact the densely populated coastal regions on Earth. Melting of the West Antarctic ice sheet alone could raise sea level by approximately 5 m. In spite of their importance, the current mass balances (the net gains or losses) of the Antarctic ice sheets are not known. Because of difficult logistic problems in Antarctica, field research has focused on only a few major ice streams and outlet glaciers. Yet, to understand the ice sheet dynamics fully, we must carefully document all of the coastal changes associated with advance and retreat of ice shelves, outlet glaciers, and ice streams.
A critical parameter of ice sheets is their velocity field, which, together with ice thickness, allows the determination of discharge rates. Remote sensing, using moderate- to high- resolution satellite images, permits glacier movement to be measured on sequential images covering the same area; the velocities can be measured quickly and relatively inexpensively by tracking crevasses or other patterns that move with the ice. Especially important are velocities where the ice crosses the glaciers grounding lines (locations along the coast where the ice is no longer ground supported and begins to float).

Time_Period_of_Content:

Time_Period_Information:

Range_of_Dates/Times:

Beginning_Date: 1972
Ending_Date: 19921204

Currentness_Reference:

Range specified indicates date of earliest image used and date of latest image used.

Status:

Progress: Complete
Maintenance_and_Update_Frequency: As needed

Spatial_Domain:

Bounding_Coordinates:

West_Bounding_Coordinate: -142.0
East_Bounding_Coordinate: 130.0
North_Bounding_Coordinate: -67.0
South_Bounding_Coordinate: -76.0

Keywords:

Theme:

Theme_Keyword_Thesaurus: none
Theme_Keyword: Glacier
Theme_Keyword: Glacier tongues
Theme_Keyword: Glacier velocity

Place:

Place_Keyword_Thesaurus: None
Place_Keyword: Antarctica

Theme:

Theme_Keyword_Thesaurus: National Geologic Map Database Catalog themes, augmented
Theme_Keyword: 0400 - Glaciology

Theme:

Theme_Keyword_Thesaurus: ISO 19115 Topic Categories
Theme_Keyword: geoscientificInformation

Place:

Place_Keyword_Thesaurus: Augmented FIPS 10-4 and FIPS 6-4, version 1.0
Place_Keyword: AY = Antarctica

Access_Constraints: none

Use_Constraints: none

Point_of_Contact:

Contact_Information:

Contact_Person_Primary:

Contact_Person: Baerbel K. Lucchitta
Contact_Organization: Branch of Astrogeology

Contact_Address:

Address_Type: mailing address
Address:: Mail Stop 9580
U.S. Geological Survey
2255 N. Gemini Drive
City: Flagstaff
State_or_Province: AZ
Postal_Code: 86001-1689
Country: USA

Contact_Voice_Telephone: (520) 556-7176

Contact_Facsimile_Telephone: (520) 556-7014

Contact_Electronic_Mail_Address: blucchitta@iflag2.wr.usgs.gov

Data_Quality_Information:

Attribute_Accuracy:

Attribute_Accuracy_Report:: We use two methods to determine the glacial velocities: an interactive one in which we visually trace crevasse patterns (Lucchitta and others, 1993) and an autocorrelation program developed by Bindschadler and Scambos (1991) and Scambos and others (1992). First, we digitally co-register the images by using a minimum of three well-dispersed fixed points (such as nunataks or ice walls) to calculate a least-squares fit to a first-order polynomial equation. This insures that only a rotational/translational correction is made and no new internal error is introduced during the geometric resampling. In the interactive technique, we then match and align the crevasse patterns displaced with time, and record the starting/ ending image coordinates for each point. To obtain the distribution of average velocities over the length of the glacier tongues, we also use the distance from the location of each point on the earlier image to a base line drawn perpendicular to glacier movement and ideally lying on the grounding line; where the grounding line is complex, the base line may only approximate its position. Next, a digitized file is made, tracing the glacier ice movements and defining the glacier's baseline (or grounding line). This file is used to calculate the velocity and distance statistics by measuring the displacements along the curve that approximates the ices movement per given time interval. For each measured point, a displacement vector is plotted on the image, commonly the earlier one of the pair, to illustrate the relative velocities between glaciers and time intervals.

Logical_Consistency_Report:

Because the velocity field may also change across the glacier tongues, we divide the wider glaciers into several longitudinal paths. Next we obtain an estimate of the spread of measured points by performing a regression analysis on the data. This includes an option to cull bad data points by inputting a variable for the standard deviation. If used, the mean absolute deviation of the points about this line is calculated and any points lying outside that distance are disregarded during the statistical analysis. Calculations are made for the entire glacier as well as for each individual path. The 95% confidence interval for the regression coefficient is calculated along with the correlation coefficient.

Completeness_Report:

The files contained in this data base are the output ASCII files generated by this statistical software. Each file identifies the images used, their dates, and resolutions, the time interval between image acquisitions and the statistical variables used to make the calculations. These data are followed by a table of the distance and velocity values for each point and the statistics calculated per path. The measurement results are shown in graphs that display average velocities per given time interval versus the distance from the base line for all points in each field (not included in this data base).
In the auto-correlation method we use the same techniques for coregistration and graphic and statistical display. However, we may not divide the glaciers into segments and paths, but instead combine all velocities and show variations across the glacier by color contours (also not shown in this report).

Positional_Accuracy:

Horizontal_Positional_Accuracy:

Horizontal_Positional_Accuracy_Report:: Accuracy of point positions is limited by the digital representation of the images. The accuracy with which individual features of the ice tongues are correlated (from image to image) cannot be assessed, because it is confounded with the spatial variation of the velocity field.

Lineage:

Source_Information:

Source_Citation:

Citation_Information:

Originator: Ferrigno, J.G.

Originator: Lucchitta, B.K.

Originator: Mullins, K.F.

Originator: Allison, A.L.

Originator: Allen, R.J.

Originator: Gould, W.G.

Publication_Date: 1993

Title:

Velocity measurements and changes in position of Thwaites Glacier Ice Berg Tongue from aerial photographs, Landsat images, and NOAA AVHRR data

Series_Information:

Series_Name: Annals of Glaciology
Issue_Identification: v.17, p. 239-244

Type_of_Source_Media: paper

Source_Time_Period_of_Content:

Time_Period_Information:

Single_Date/Time:

Calendar_Date: 1993

Source_Currentness_Reference: publication date

Source_Citation_Abbreviation: Ferrigno et al., 1993

Source_Contribution: Velocity of Thwaites Glacier tongue

Source_Information:

Source_Citation:

Citation_Information:

Originator: Lucchitta, B.K.

Originator: Mullins, K.F.

Originator: Allison, A.L.

Originator: Ferrigno, J.G.

Publication_Date: 1993

Title:

Antarctic glacial tongue velocities from Landsat images: First results

Series_Information:

Series_Name: Annals of Glaciology
Issue_Identification: v. 17, p. 356-366

Type_of_Source_Media: paper

Source_Time_Period_of_Content:

Time_Period_Information:

Single_Date/Time:

Calendar_Date: 1993

Source_Currentness_Reference: publication date

Source_Citation_Abbreviation: Lucchitta et al., 1993

Source_Contribution:

Velocities of Stancomb-Wills, Berg, Thwaites, Land, Drygalski, Kaya, and Riiser-Larsen glacier tongues.

Source_Information:

Source_Citation:

Citation_Information:

Originator: Lucchitta, B.K.

Originator: Smith, C.E.

Originator: Bowell, J.A.

Originator: Mullins, K.F.

Publication_Date: 1994

Title:

Velocities and mass balance of Pine Island Glacier, West Antarctica, Derived from ERS-1 SAR images

Series_Information:

Series_Name: Ecological Society of America Special Publication
Issue_Identification: 361, p. 147-151

Other_Citation_Details:

Proceedings, 2nd ERS-1 Symposium, Hamburg, Germany, 11-14 Oct. 1993

Type_of_Source_Media: paper

Source_Time_Period_of_Content:

Time_Period_Information:

Single_Date/Time:

Calendar_Date: 1994

Source_Currentness_Reference: publication date

Source_Citation_Abbreviation: Lucchitta et al., 1994a

Source_Contribution: Velocity of Pine Island Glacier

Source_Information:

Source_Citation:

Citation_Information:

Originator: Lucchitta, B.K.

Originator: Mullins, K.F.

Originator: Smith, C.E.

Originator: Ferrigno, J.G.

Publication_Date: 1994

Title:

Velocities of Smith Glacier Ice Tongue and Dotson Ice Shelf, Walgreen Coast, Marie Byrd Land, West Antarctica

Series_Information:

Series_Name: Annals of Glaciology
Issue_Identification: v. 20, p. 101-109

Type_of_Source_Media: paper

Source_Time_Period_of_Content:

Time_Period_Information:

Single_Date/Time:

Calendar_Date: 1994

Source_Currentness_Reference: publication date

Source_Citation_Abbreviation: Lucchitta et al., 1994b

Source_Contribution: Velocity of Smith glacier ice tongue and Dotson Ice Shelf

Source_Information:

Source_Citation:

Citation_Information:

Originator: Lucchitta, B.K.

Originator: Smith, C.E.

Originator: Mullins, K.F.

Publication_Date: 1995

Title:

Velocities and mass balance of Pine Island Glacier, West Antarctica

Series_Information:

Series_Name: Annals of Glaciology
Issue_Identification: v. 21

Other_Citation_Details: in press

Type_of_Source_Media: paper

Source_Time_Period_of_Content:

Time_Period_Information:

Single_Date/Time:

Calendar_Date: 1995

Source_Currentness_Reference: publication date

Source_Citation_Abbreviation: Lucchitta et al., 1995

Source_Contribution: Velocity of Pine Island glacier

Process_Step:

Process_Description:: For Landsat images, we obtain either computer-compatible tapes (CCTs) of MSS images, or, where tapes are nonexistent, the lowest generation transparency available for band 7 (near-infrared). These transparencies are third- and fourth-generation negatives, which have lost some image detail through the duplication process. We use only photographic products for TM images because of the high cost of CCTs. For TM images acquired before 1989 we obtain fourth-generation negatives of band 4 (near- infrared), and for images acquired after 1989 we use third- generation color negatives (only color photographic products are now available from the vending company). The quality of some of these images is poor, as they are not especially processed for the high reflectivity of snow and ice. The transparencies are scanned at 50 micron to obtain a digital data set. The ground resolution of the scanned images varies, depending on the size of the original transparency. To obtain the ground resolution per pixel, the nominal Landsat image height on the ground, in km, is scaled to the actual image height of the scanned images.
We generally register Landsat 1, 2, and 3 images to Landsat 4 and 5 images, because the latter have more stable internal geometry and higher resolution than the earlier images. Several tests were made to compare the internal geometry of 3rd and 4th generations negatives with the original digital data. All of these tests, as well as several made between original and scanned images of transparencies, showed an insignificant degree of geometric error between products. These tests demonstrate that geometrical errors within the transparencies will contribute little to statistical variance between measurements. Loss of resolution and misidentification of features play a more important role in measurement error made with these images. Borgeson and others (1985) found that Landsat 5 images are accurate to about 0.4 pixels, meeting national Horizontal Map Accuracy standards for scales of 1:100,000 and smaller, and that Landsat 4 images are accurate to 0.8 pixel levels. Welch and others (1985) reported that Landsat 4 and 5 images meet accuracy standards for maps of 1:50,000 scale or smaller and are well suited to maps of 1:100,000 scale.
Process_Date: 1994
Source_Produced_Citation_Abbreviation: Ferrigno et al., 1993
Source_Produced_Citation_Abbreviation: Lucchitta et al., 1993
Source_Produced_Citation_Abbreviation: Lucchitta et al., 1994a
Source_Produced_Citation_Abbreviation: Lucchitta et al., 1994b

Process_Step:

Process_Description:: For ERS images, we obtain CCTs of the geocoded version (placed in Universal Polar Stereographic projection using the WGS 1984 ellipsoid). The pixel size is 12.5 m on the ground (resolution approximately 30m). The images are coregistered by either (1) matching fixed points such as nunataks (land masses projecting through the ice), or (2) using the furnished coordinates based on orbital parameters. We obtained the same results by both methods, increasing our confidence in the accuracy of the nominal image location, which is supposed to be less than 50 m (Roth and others, in press). For a more detailed error evaluation for Landsat images see Lucchitta and others (1993 and 1994), and for ERS-1 images see Lucchitta and others (1994 and 1995).
Process_Date: 1994
Source_Produced_Citation_Abbreviation: Lucchitta et al., 1995

Spatial_Data_Organization_Information:

Indirect_Spatial_Reference:: Point locations contained in the data files are not georeferenced although in principle they could be if the corners of the images from which they were digitized were georeferenced.

Spatial_Reference_Information:

Horizontal_Coordinate_System_Definition:

Local:

Local_Description:: We generally register Landsat 1, 2, and 3 images to Landsat 4 and 5 images, because the latter have more stable internal geometry and higher resolution than the earlier images.
We digitally co-register the images by using a minimum of three well-dispersed fixed points (such as nunataks or ice walls) to calculate a least-squares fit to a first-order polynomial equation. This insures that only a rotational/ translational correction is made and no new internal error is introduced during the geometric resampling. In the interactive technique, we then match and align the crevasse patterns displaced with time, and record the starting/ending image coordinates for each point. To obtain the distribution of average velocities over the length of the glacier tongues, we also use the distance from the location of each point on the earlier image to a base line drawn perpendicular to glacier movement and ideally lying on the grounding line; where the grounding line is complex, the base line may only approximate its position. Next, a digitized file is made, tracing the glacier ice movements and defining the glacier's baseline ( or grounding line). This file is used to calculate the velocity and distance statistics by measuring the displacements along the curve that approximates the ices movement per given time interval. For each measured point, a displacement vector is plotted on the image, commonly the earlier one of the pair, to illustrate the relative velocities between glaciers and time intervals.
Local_Georeference_Information:: Although in principle the images could be registered to the earth's surface, for this exercise georeference is not necessary, since the objective is merely to understand ice movement through time and among paths within a glacier tongue. Hence the data are not explicitly georeferenced.

Entity_and_Attribute_Information:

Overview_Description:

Entity_and_Attribute_Overview:: The velocity files are grouped within folders by name of glacier or shelf and by year of the two image pairs used in the calculations. For example: in the landsat/thwaites directory the file th7384.dst contains the velocity data for the 1973/1984 image pair covering the Thwaites glacier region. For each pair, the following information is given: (1) the displacement per given time interval for each point of a path, segment, or the entire glacier, (2) the velocities per year for the same points, (3) statistical parameters of individual paths, segments, or entire glaciers, including standard deviations, and (4) distance to grounding line for each point.
Entity_and_Attribute_Detail_Citation: Lucchitta et al., 1993

Distribution_Information:

Distributor:

Contact_Information:

Contact_Person_Primary:

Contact_Person: Peter N. Schweitzer

Contact_Address:

Address_Type: mailing address
Address:: Mail Stop 918 National Center
U.S. Geological Survey
12201 Sunrise Valley Drive
City: Reston
State_or_Province: VA
Postal_Code: 20192
Country: USA

Contact_Voice_Telephone: (703) 648-6533

Contact_Facsimile_Telephone: (703) 648-6560

Contact_Electronic_Mail_Address: pschweitzer@usgs.gov

Distribution_Liability:

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards (or with the North American Stratigraphic Code). Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Standard_Order_Process:

Digital_Form:

Digital_Transfer_Information:

Format_Name: TEXT
Format_Specification: somewhat regular but not entirely tabular information
Format_Information_Content: Glacier-velocity data

Digital_Transfer_Option:

Online_Option:

Computer_Contact_Information:

Network_Address: