Ninth International Conference on Permafrost ... - IARC Research

A Provisional Permafrost Map of the Transantarctic MountainsJ.G. BockheimDepartment of Soil Science, University of Wisconsin, 1525 Observatory Drive, Madison, WI 53706-1299, USAM. McLeodLandcare Research, Private Bag 3127, Hamilton, New ZealandM.R. BalksDepartment of Earth and Ocean Sciences, University of Waikato, Private Bag 3105, Hamilton, New ZealandIntroductionThe Transantarctic Mountains (TAM) extend 3,500 kmacross the Antarctic continent from 69°S in northern VictoriaLand to 87°30′S in the upper Scott Glacier region. TheTAM form a natural barrier between ice in East and WestAntarctica and record the history of Cenozoic glaciations ofAntarctica (Lyons & Elliot 2006). The TAM have an ice-freearea of 20,910 km 2 , which constitutes 42% of the total icefreearea (49,500 km 2 ) of Antarctica.Bockheim (1995) prepared the first permafrost map ofAntarctica. He showed that permafrost was limited to icefreeareas and that all of East Antarctica and most of WestAntarctica contain continuous permafrost. More recently,Bockheim and others (2007) prepared a provisionalpermafrost map of the McMurdo Dry Valleys portion of theTAM (6,700 km 2 ), reporting that buried ice, ice-cementedpermafrost, and dry-frozen permafrost comprised 2, 55,and 43% of the area, respectively. A task force under theauspices of the IPA and Scientific Committee on AntarcticResearch (SCAR), identified as the Antarctic Permafrost andSoils (ANTPAS) Group (http://erth.waikato.ac.nz/antpas/),is preparing a series of permafrost and ground-ice mapsof Antarctica. The text that will accompany these maps isincluded in this volume (Bockheim et al. 2008). The posteraccompanying the present abstract displays permafrostdistribution in the TAM on three maps at scales of 1:1million.MethodsTo prepare a permafrost map of the TAM, we used 62scanned and geo-rectified 1:250K topographic maps preparedby the US Geological Survey (http://usarc.usgs.gov/drg_dload.shtml). We joined these seamless maps in ArcGIS 9.2and used the composite map as a base map. To display theentire TAM, we divided the mountains into three regions:northern Victoria Land (69°30′–75°S), central Victoria Land(75–80°30′S), and southern Victoria Land (80°30′–86°30′S).Each map could be displayed as a standard A0 wall size (841x 1188 mm) at a scale of 1:1 million.Expert permafrost scientists working in Antarcticaprepared a legend that includes the following map units:(i) buried or ground ice within the upper 100 cm, (ii) icecementedpermafrost with a surface within 70 cm, (iii) icecementedpermafrost with a surface below 70 cm (excludingdry-frozen permafrost), and (iv) dry-frozen permafrostwith an ice-cemented surface below 70 cm. To determinethe distribution of these permafrost forms throughout theTAM, we used published data and data archived by theNational Snow & Ice Data Center (http://nsidc.org/cgi-bin/get_metadata.Pl?id-ggd221) and New Zealand LandcareResearch (http://www.landcareresearch.co.nz). In northernVictoria Land, we used data from Denton and others (1986)and Guglielmin and French (2004). In central Victoria Land,we used data collected by Bockheim and others (1989,2007). For southern Victoria Land, data were used fromClaridge and Campbell (1968) and Bockheim and others(1990). For unmapped areas we extrapolated the databaseusing the following criteria: ice-cored drift was identifiedfrom a stippled pattern on topographic maps; ice-cementedpermafrost was identified from patterned ground on remotelysensed images and proximity to streams, lakes, and ponds;and dry-frozen permafrost comprised the remaining areas,particularly in interior mountains and broad central valleys.Polygons were drawn on the base maps, numbered, andidentified in the accompanying attribute table by permafrostform. The maps were prepared using an agreed upon colourscheme for continuous permafrost that included: dark brown= buried or ground ice; dark green = ice-cemented permafrost70 cm(excluding dry-frozen permafrost); dark red = dry-frozenpermafrost with an ice-cemented surface below 70 cm. Theareal distribution of permafrost by form was determinedusing a GIS.ResultsBuried ice comprised 12% of the total permafrost in theTAM and was most abundant in northern Victoria Land. Icecementedpermafrost, with the surface at