Fast Track Article

• Main Authors: Matthias Leopold, Jörg Völkel, David P. Dethier, Mark W. Williams
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2013
• Subjects: permafrost
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.298.4699; http://snobear.colorado.edu/Markw/Research/13_leopold.pdf

with 7 figures and 2 tables Abstract. Melting mountain permafrost is reported from alpine areas around the world as a direct conse-quence of rising air temperatures over the past decades. However, alpine sites that offer sufficient older data to compare with recent conditions are rare. The study site Niwot Ridge, situated at ~ 3600 m a.s.l. in the Front Range of the Rocky Mountains, Colorado, USA, offers permafrost distribution data from the early 1970s. We used four different approaches to evaluate and compare the old data with recent conditions and to discuss consequences in how the old data should be considered. (i) Air photographs and survey stakes were used to compare modern surface conditions of a solifluction lobe with those in the past. Despite high resolution of the air photographs (0.3 m), the error of position after geo-rectification was higher (� � ��1.0 1.0 m) than average displacement rates of gelifluction lobes (10 mm * a –1), rendering this approach unsuitable. Replication of a 1963 –1967 study of soil movement from 2006 – 2009 yielded average movement rates of 11.4 mm * a –1 compared to 9.4 mm * a –1 in the 1960s. (ii) Temperature profiles of a three-year survey (2007 – 2009) to depths of 7 m were compared with data from the 1970s from the same site. Modern temperature profiles document a complex an-