Introduction

In many periglacial applications ground ice detection and quantification is the major objective. Typical examples are low-altitude scree slopes, which are covered with blocky material and may contain ground ice throughout the year far below the regional limit of permafrost due to microclimatic conditions that resemble those of high-altitude periglacial areas (see Sawada et al. 2003, Delaloye et al. 2003, Delaloye and Lambiel 2005, Zacharda et al. 2007). Essential preconditions for this extraordinary microclimatic phenomenon are assumed to be a thick layer of blocks with an open void system, i.e. steep slopes with almost no fine material. Summer ice observations and cold air outflow from the blocks in the near subsurface, as well as the occurrence of cold-adapted mosses and different invertebrate groups (e.g. beetles and spiders) that normally live in high alpine or polar areas are used as indicators for the possible presence of ground ice (Gude et al. 2003, Zacharda et al. 2005). The ‘thermal semi-conductor’ effect of the coarse rocks is also widely used in construction, e.g. for the permanent cooling of railroad embankments in permafrost regions (Cheng et al. 2007).

However, whether significant ice occurrences could be permanently present within the scree slopes is still an open question. Delaloye and Lambiel (2005) describe a cold ventilated talus slope in the Swiss Alps, where sediments more or less saturated with ice were found at 7–8 m depth during construction of two cable car pylons.