Citation:

tc-12-2461-2018

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Coverage:

Median Latitude: -75.391665 * Median Longitude: -136.266670 * South-bound Latitude: -77.500000 * West-bound Longitude: -158.416670 * North-bound Latitude: -73.283330 * East-bound Longitude: -114.116670

Event(s):

MarieByrdLand * Latitude Start: -77.500000 * Longitude Start: -158.416670 * Latitude End: -73.283330 * Longitude End: -114.116670 * Location: Antarctic * Method/Device: Multiple investigations (MULT)

Comment:

1. This dataset contains shapefiles of the grounding lines (hereafter GLs) and ice frontal positions derived by Christie et al. (2018) for the Marie Byrd Land Sector of West Antarctica, 2003-2015.

2. Grounding lines were derived from a combination of Landsat 7 Enhanced Thematic Mapper, Landsat 8 Operational Land Imager and Terra-ASTER Level 1 Terrain Corrected optical satellite imagery (see Christie et al., 2018; their Figure S1), and represent the inflexion point of the ice-sheet-shelf grounding zone, otherwise known as 'Point Ib' (following the notation of Fricker et al., 2009, doi:10.1017/S095410200999023X). Acting as a reliable proxy for the true GL, G, which cannot be detected directly from satellite imagery, Point Ib typically resides ~1-2 km downstream of the G throughout most of the Marie Byrd Land Sector. For more information on GL detection techniques and the anatomy of the grounding zone, users are referred to Fricker et al. (2009, doi:10.1017/S095410200999023X), Brunt et al. (2010, doi:10.3189/172756410791392790), Bindschadler et al. (2011, doi:10.5194/tcd-5-183-2011), Rignot et al. (2011, doi:10.1029/2011GL047109) and Christie et al. (2016, doi:10.1002/2016GL068972).

3. Grounding lines exist for years 2003, 2008, 2010 and 2015, and were derived from optical images acquired during austral summertime (January, February, March) where cloud cover totalled <40%. For years 2003 and 2008, additional Landsat scenes acquired in December 2002/2007 were utilised where 2003 and 2008 Landsat and ASTER spatial coverage was restricted by excessive summertime cloud cover. The final Ib products derived from this workflow were smoothed using a polynomial approximation with exponential kernel (PAEK) algorithm with a 500 m tolerance (cf. Moholdt et al., 2013, hdl:10013/epic.42133.d004), and reflect the mean summertime GL position for each year as resolved from all available Landsat or ASTER imagery. For positional uncertainty considerations and other methodological information, users are referred to Christie et al. (2018). A database of all Landsat and ASTER imagery used can be found in Christie et al. (2018, their Dataset S1). All Landsat and ASTER data are available from NASA/USGS via https://earthexplorer.usgs.gov/.

4. Frontal positions were derived using a similar workflow, and represent the mean austral summertime position for each year surveyed. As for grounding line data, frontal position products were smoothed using PAEK, with an assigned tolerance of 100 m to preserve the complex configuration of the ice front near e.g. lateral shear margins or dense crevasse fields.

5. The datasets are contained in a single zip archive file and are provided in standard ESRI shapefile format. The data are defined in the Antarctic Polar Stereographic Projection (EPSG:3031) with a standard parallel of -71° S.

6. Each dataset contains polyline data with the following attributes:

GROUNDING LINE - ATTRIBUTE DESCRIPTION:

. PLATFORM: Satellite used.

. SENSOR: Satellite sensor imagery used to constrain Point Ib.

. DESCRIP: Grounding zone classification (grounded land ice, grounded isolated island or ice rise, pinning point or connecting island)

. AUTH_ID: Author(s): FDWC, F.D.W. Christie; RRB, R.R. Bisset.

ICE FRONT - ATTRIBUTE DESCRIPTION:

. PLATFORM: Satellite used.

. SENSOR: Satellite sensor imagery used to constrain ice frontal position.

. DESCRIP: Ice front classification and geographical information (ice shelf front, ice tongue; geographical information from Swithinbank et al. (2003a; 2003b))

. AUTH_ID: Author(s): FDWC, F.D.W. Christie.

References:

Bindschadler, R., et al.: Getting around Antarctica: New high-resolution mappings of the grounded and freely-floating boundaries of the Antarctic ice-sheet created for the International Polar Year, Cryosphere, 5, 569-588, doi:10.5194/tcd-5-183-2011, 2011.

Brunt, K., Fricker, H. A., Padman, L., Scambos, T., and O'Neel, S.: Mapping the grounding zone of the Ross Ice Shelf, Antarctica, using ICESat laser altimetry, Ann. Glaciol., 51, 71-79, doi:10.3189/172756410791392790, 2010.

Christie, F. D. W., Bingham, R. G., Gourmelen, N., Tett, S. F. B., and Muto, A.: Four-decade record of pervasive grounding line retreat along the Bellingshausen margin of West Antarctica, Geophys. Res. Lett., 43, 5741-5749, doi:10.1002/2016GL068972, 2016.

Christie, F.D.W., Bingham, R.G., Gourmelen, N., Steig, E.J., Bisset, R.R., Pritchard, H.D., Snow, K., and Tett, S.F.B.: Marie Byrd Land glacier change driven by spatial and inter-decadal climate-ocean variability, Cryosphere (in review).

Fricker, H. A., Coleman, R., Padman, L., Scambos, T. A., Bohlander, J., and Brunt, K. M.: Mapping the grounding zone of the Amery Ice Shelf, East Antarctica using DInSAR, MODIS and ICESat, Antarct. Sci., 21(5), 515-532, doi:10.1017/S095410200999023X, 2009.

Moholdt, G., Fricker, H., Padman, L., Paolo, F.S.: Synthesized grounding line and ice shelf mask for Antarctica. Scripps Institution of Oceanography, UCSD, 25 pp., hdl:10013/epic.42133.d004, 2009.

Rignot, E., Mouginot, J., and Scheuchl, B.: Antarctic grounding line mapping from differential satellite radar interferometry, Geophys. Res. Lett., 38, L10504, doi:10.1029/2011GL047109, 2011.

Swithinbank, C., Williams, R.S., Jr., Ferrigno, J.G., Foley, K.M., and Rosanova, C.E.: Coastal-change and glaciological map of the Bakutis Coast area, Antarctica: 1972-2002: U.S. Geological Survey Geologic Investigations Series Map, I-2600-F; scale: 1:1,000,000, with accompanying pamphlet (10 p.), 2003a.

Swithinbank, C., Williams, R.S., Jr., Ferrigno, J.G., Foley, K.M., Hallam, C.A., and Rosanova, C.E.: Coastal-change and glaciological map of the Saunders Coast area, Antarctica: 1972-1997: U.S. Geological Survey Geologic Investigations Series Map, I-2600-G; scale: 1:1,000,000, with accompanying pamphlet (9 p.), 2003b.

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