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Temperature regime of a small sandstone tor, latitude 80 °N, Ellesmere Island, Nunavut, Canada
Author(s) -
Lewkowicz Antoni G.
Publication year - 2001
Publication title -
permafrost and periglacial processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.867
H-Index - 76
eISSN - 1099-1530
pISSN - 1045-6740
DOI - 10.1002/ppp.396
Subject(s) - geology , lapse rate , elevation (ballistics) , crest , ridge , snowpack , altitude (triangle) , weathering , atmospheric sciences , permafrost , snow , geomorphology , oceanography , paleontology , mathematics , physics , geometry , quantum mechanics
Near‐surface rock temperatures were recorded hourly for more than one year around a sandstone tor located on a ridge‐crest at an elevation of 270 m asl. There were significant differences between air and rock temperatures except during the polar night. The SSE‐ and WSW‐facing sides experienced large amplitude diurnal temperature cycles in the late‐winter and spring, and these crossed through 0 °C from mid‐April to May, well before air temperatures rose above freezing. Rock temperatures at a depth of 15 mm on the SSE‐face exceeded air temperature by up to 31 °C. During most of the summer, rock faces and air temperatures remained above 0 °C. Diurnal temperature cycles were smaller in amplitude in the autumn and few cycles through 0 °C were measured because of persistent cloud cover and the absence of a radiation‐reflecting snowpack. Modelling using a constant environmental lapse rate shows that although the timing and number of temperature cycles through 0 °C are influenced by altitude, the importance of rock‐face orientation on the relative numbers of cycles is independent of tor elevation. The average rate of micro‐weathering measured on several tors over four years was 0.012 mm a −1 . No loss of larger clasts was observed at the monitored tor over 11 years suggesting that the combined rate of all types of weathering is low. Copyright © 2001 John Wiley & Sons, Ltd.