New geophysical methods of investigating the nature and distribution of mountain permafrost with special reference to radiometry techniques

A series of geophysical surveys were undertaken within the PACE geophysical work package. Various methods were applied including refraction seismics, DC resistivity, ground penetrating radar (GPR), electromagnetic induction, radiometry and bottom temperature of snow cover (BTS). The focus of the sur veys was to determine the internal structures and distribution of mountain permafrost. This paper gives a preliminary overview of progress. The two-di mensional DC resistivity tomography combines the geoelectrical sounding and mapping and makes it possible to model internal structures. This method wa s applied at all PACE drill sites. Electromagnetic induction methods showed good results, in particular the EM-31 for determining the permafrost distr ibution and the PROTEM to assess the overall permafrost thickness. A major new development discussed here is the use of passive microwave (11.4 GHz) f or airborne remote measurement of the bottom temperature of snow cover (BTS ). Manual BTS measurements agreed very well with the BTS determined by radi ometry. To reduce ambiguity, several geophysical methods should be deployed at the same locality. As a further step, such measurements could be interp reted using joint inversions. Copyright (C) 2001 John Wiley & Sons, Ltd.