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A contemporary winter ground thermal profile in the Lesotho highlands and implications for active and relict soil frost phenomena
Author(s) -
Sumner Paul
Publication year - 2003
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.1003
Subject(s) - permafrost , holocene , ground freezing , geology , frost (temperature) , glacial period , pleistocene , borehole , spring (device) , groundwater , physical geography , geomorphology , climatology , atmospheric sciences , paleontology , oceanography , geography , geotechnical engineering , mechanical engineering , engineering
A 2 m deep ground thermal prole is constructed from temperature data collected over the winter and spring of 2000 at 3220 m a.s.l. near the Thabana Ntlenyana summit (3482 m) in Lesotho, southern Africa. The zero isotherm is found to have penetrated to 0·16 m soil depth. Ground remained frozen at 0·05 m for a total of 79 days and for shorter periods at 0·02 m and 0·10 m. Diurnal freezing and thawing is restricted to the upper 0·10 m and conforms to the observed depth of active micro‐patterned ground found in the region. Holocene temperature depressions projected along the thermal prole can account for freezing down to 0·45 to 0·65 m. Deeper sorting to 1 m, evident from relict patterned ground near the logger site, corresponds to at least a 2·5 °C temperature depression and such landforms are evidently pre‐Holocene. Projections indicate a seasonal freezing depth exceeding 2 m during the Pleistocene Last Glacial Maximum although the existence of permafrost appears unlikely. Copyright © 2003 John Wiley & Sons, Ltd.