Coastlines: Environmental Systems Research Institute (ESRI) shapefiles and Comma Separated Value (.csv) text files
Terminus Histories: Text (.csv) files
Mosaic Information: Text (.csv) files
Matlab Script: .m file

Data are available on the FTP site in ftp://sidads.colorado.edu/pub/DATASETS/AGDC/nsidc0522_macgregor_V01/. This directory contains four text files, listed below, and a sub-folder with the coastline data in ESRI shapefile format.

Text Files

Text files are named according to the following convention.

ase_xxxx_aaaa.csv

Where:

Shapefiles

Shapefile names follow the convention described in the mosaic table files (ase_mosaic_landsat.csv and ase_mosaic_ers.csv). Mosaic years are followed by a one- or two-character identifier, which specifies whether the mosaic was formed from scenes in the first (a) or second (b) half of the calendar year, and, if there are multiple mosaics for a given half of that calendar, the chronological order of each mosaic (e.g., 2000a1, 2000a2, 2000a3).

Where available, an outline of the detached Thwaites Glacier Tongue is also included. These files end in "_tongue", and their year labeling follows the same style as for the coastlines. If more than one detached ice tongue is outlined (e.g., late 1972, 2010-2011), then these files are sub-labeled as "...tongue1" or "...tongue2".

Matlab

The Matlab script, ase_load.m, is an example of how to load and plot the shapefile and terminus history data into Matlab.

Files range in size from 3 KB to 77 KB.

Total volume of the data set is 23 MB.

This data set spans the eastern Amundsen Sea Embayment in West Antarctica, including Thwaites Glacier, Pine Island Glacier, and Smith Glacier.

Southernmost Latitude: 76° S
Northernmost Latitude: 74° S
Westernmost Longitude: 110° W
Easternmost Longitude: 100° W

~200 m: Estimated resolution of the data set is based on the differences between satellite scenes used, and ice flow speeds. The Landsat data resolution ranges from 60 m to 15 m. For more information see MacGregor, et. al., 2012.

Shapefiles: Standard polar stereographic projection for Antarctica. The standard parallel is 71 degrees South.

Landsat Data: 158 scenes acquired between December 1972 and November 2011

ERS SAR Data: 38 scenes acquired between 1992 and 1998.

Aerial Photography: For Pine Island Glacier only, the terminus history data include positions derived from published coastlines, which themselves were derived from 1947 and 1966 aerial photography and 1963 satellite photography.

This data set contains coastline positions for the Amundsen Sea Embayment, in polar stereographic coordinates (x/y, km), and terminus position (km) for a number of glaciers in the region.

Coastline

Coastline data are provided in ESRI shapefile format, organized by year.

Terminus Histories

Terminus History data are provided in comma separated value (.csv) text file format. NaN indicates missing data.

Data are available via FTP.

Data are accessible using image processing software and Matlab.

Data were acquired from the NASA/USGS Landsat satellites, the European Remote Sensing Satellite (ERS), and aerial photography.

Coastlines were traced manually on Landsat and ERS/SAR mosaics, at a scale of 1:50,000. For more details, see MacGregor et. al. 2012.

Except where noted, terminus positions are calculated as the linearly interpolated intersection of traced coastline with fixed flowlines determined from a 1996 surface velocity map. The terminus position values are relative to the intersection of the Mosaic of Antarctica (MOA) grounding line with the flowline. The flowlines used are shown in Figure 1a of MacGregor et. al. 2012, and the terminus position data are identical to those shown in Figure 3 of that same study. Note that the flowlines used are not provided, and that the coastlines of these glaciers often jagged, with the notable exception of Pine Island Glacier. The flowline-derived terminus positions should therefore be considered only one possible representation of the terminus history, with the ice-shelf margins being the primary example of where these terminus histories break down. However, we experimented with the position of the flowlines to find those that best captured the main calving behavior of each glacier. For more details, refer to MacGregor et. al. 2012.

For Pine Island Glacier, the terminus position is also calculated using a flowband method, as shown in Fig. 4a of MacGregor et. al. 2012 and described therein.

Not-a-number (NaN) values for terminus position indicate that the flowline used for a given glacier (column) did not intersect the traced coastline for that date (row). Terminus positions for Pine Island Glacier in 1947, 1963, and 1966 were derived from published coastlines referenced in MacGregor et al. 2012, and they are not included in the accompanying set of coastline shapefiles.

MacGregor, J.A., G.A. Catania, M.S. Markowski and A.G. Andrews. 2012. Widespread Rifting and Retreat of Ice Shelf Margins in the Eastern Amundsen Sea Embayment Between 1972 and 2011, Journal of Glaciology, 58(209), 458-466, doi:10.3189/2012JoG11J262.

• Antarctic Glaciological Data Center: http://nsidc.org/agdc
• Landsat Satellite: http://landsat.gsfc.nasa.gov/about/
• ERS Satellite Overview: http://www.esa.int/esaEO/SEMGWH2VQUD_index_0_m.html