Deducing the thermal structure in the tongue of Gornergletscher, Switzerland, from radar surveys and borehole measurements

Author： Eisen O. Bauder A. Lüthi M. Riesen P. Funk M.

Publisher： International Glaciological Society

ISSN： 1727-5644

Source： Annals of Glaciology, Vol.50, Iss.51, 2009-08, pp. : 63-70

Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.

Previous Menu Next

Abstract

We present the thermal distribution in the confluence area of Gorner- and Grenzgletscher, Valais, Switzerland. The area was mapped by ice-penetrating radar at 1–5 and 40 MHz. The higher-frequency data reveal a thick surface layer of low backscatter in the center of the Grenzgletscher branch. Based on datasets of borehole-temperature measurements and flow velocity, we interpret this as a thick layer of cold ice, advected from the accumulation region of Grenzgletscher. Along seven profiles the base of the low-backscatter zone can be found at a maximum depths between approximately 100 and 200 m. Laterally, the layer extends some 400 m, ∼1/3 of the width of the Grenzgletscher branch. The lower boundary of the low-backscatter zone is systematically higher than the cold–temperate transition surface found in the boreholes. This discrepancy is attributed to the direct sensitivity of radar backscatter to liquid-water inclusions, rather than to the temperature distributions as observed in boreholes. We present the current state of the cold layer and discuss its influence on other glacier characteristics.