Challenges and solutions for long-term permafrost borehole temperature monitoring and data interpretation

Abstract

Abstract. Long-term borehole temperature monitoring in mountain permafrost environments is challenging under the hostile conditions reigning in alpine environments. On the basis of data measured in the SLF borehole network we show three situations where ground temperature data should be interpreted with caution. (i) Thermistors have the tendency to drift, particularly if exposed to moisture or mechanical strain. This induces apparent warming or cooling, which can be difficult to differentiate from real ground temperature changes. Recalibration of thermistor chains is impossible if they cannot be extracted as a result of borehole deformation in creeping permafrost terrain. A solution using zero-curtain-based detection of drift and correction of data is presented. This method is however limited to the active layer, due to the lack of a reference temperature at greater depth. (ii) In contrast to drift-induced apparent warming, actual warming may be induced by natural processes or by the effects of construction activity. (iii) Control data from neighbouring boreholes are sometimes used to fill data gaps and discern drift -however these data may only underline the strong spatial variability of ground temperatures rather than provide measurement redundancy. A selection of recently observed problems regarding borehole monitoring in a hostile measurement environment are discussed, and advantages and possible drawbacks of various solutions including measurement redundancy or alternate instrumentation are presented.

Thermomechanical Stresses Drive Damage of Alpine Valley Rock Walls During Repeat Glacial Cycles

“…Meanwhile, we assume isotropic thermal properties, even though foliation and geological structure may result in anisotropic behavior. However, despite these simplifications and assumptions, our modeled temperature field matches local observations in a borehole (Luethi & Phillips, ), and the predicted amplitudes of seasonal surface displacements fit comfortably within the range of past field measurements (Bakun‐Mazor et al, ; Gischig et al, ).…”

“…Gischig et al, 2011b;Moore et al, 2011). The modeled depth of the thermally active layer matches long-term temperature measurements from a nearby 10-m deep borehole at Eggishorn (Luethi & Phillips, 2016). Our thermal properties and model boundary conditions yield a geothermal gradient of Journal of Geophysical Research: Earth Surface ~21°C km À1 (see Figure 5), similar to a reported geothermal gradient of 23°C km À1 in the Aar massif by Rybach & Pfister (1994).…”

Water Quality Monitoring Using Wireless Sensor Networks

“…According to Holmberg et al [1997], drift is a temporal shift of sensor response under constant physical and chemical conditions. These conditions are typically induced by water damage to the sensors or water fluxes within the ground, which could affect the interpretation of data to be seen as measurement errors [Luethi and Phillips 2016]. Luethi and Phillips [2016] discussed the challenges and solutions for long-term permafrost borehole temperature monitoring and data interpretation.…”

“…These conditions are typically induced by water damage to the sensors or water fluxes within the ground, which could affect the interpretation of data to be seen as measurement errors [Luethi and Phillips 2016]. Luethi and Phillips [2016] discussed the challenges and solutions for long-term permafrost borehole temperature monitoring and data interpretation. Utilizing WSN for WQM requires sensors to detect certain parameters in real time, which comes with technology-related limitations known as sensor drift.…”

A decade of detailed observations (2008–2018) in steep bedrock permafrost at the Matterhorn Hörnligrat (Zermatt, CH)

“…To the best of our knowledge, in the entire European Alps only the Aiguille du Midi site (Chamonix, France, 3842 m a.s.l.) (Ravanel and Deline, 2011;Magnin et al, 2015), the permafrost borehole on the Jungfraujoch (Grindelwald, Switzerland, 3700 m a.s.l.) (Wegmann, 1997(Wegmann, , 1998Noetzli et al, 2019), the geothermal profiles on Stockhorn (Gruber et al, 2004c) and two simple ground surface temperature sensors located on the summit of the Matterhorn (4478 m a.s.l.)…”