Inferring snow pack ripening and melt out from distributed ground surface temperature measurements

Abstract. The seasonal snow cover and its melting are heterogeneous both in space and time. Describing and modelling this variability are important because it affects divers phenomena such as runoff, ground temperatures or slope movements. This study investigates the derivation of melting characteristics based on spatial clusters of temperature measurements. Results are based on data from Switzerland where ground surface temperatures were measured with miniature loggers (iButtons) at 40 locations, referred to as footprints. At each footprint, ten iButtons have been distributed randomly few cm below the ground surface over an area of 10 m × 10 m. Footprints span elevations of 2100–3300 m a.s.l. and slope angles of 0–55°, as well as diverse slope expositions and types of surface cover and ground material. Based on two years of temperature data, the basal ripening date and the melt-out date are determined for each iButton, aggregated to the footprint level and further analysed. The date of melt out could be derived for nearly all iButtons, the ripening date could be extracted for only approximately half of them because it requires ground freezing below the snow pack. The variability within a footprint is often considerable and one to three weeks difference between melting or ripening of the points in one footprint is not uncommon. The correlation of mean annual ground surface temperatures, ripening date and melt-out date is moderate, making them useful intuitive complementary measured for model evaluation.

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Inferring snowpack ripening and melt-out from distributed measurements of near-surface ground temperatures

The Cryosphere ◽

10.5194/tc-6-1127-2012 ◽

2012 ◽

Vol 6 (5) ◽

pp. 1127-1139 ◽

Cited By ~ 45

Author(s):

M.-O. Schmid ◽

S. Gubler ◽

J. Fiddes ◽

S. Gruber

Keyword(s):

Ground Surface ◽

Spatial Clusters ◽

Near Surface ◽

Ground Temperatures ◽

M 10 ◽

Surface Temperatures ◽

Ground Freezing ◽

Melting Characteristics ◽

Seasonal Snow Cover ◽

Ground Material

Abstract. Seasonal snow cover and its melt regime are heterogeneous both in time and space. Describing and modelling this variability is important because it affects diverse phenomena such as runoff, ground temperatures or slope movements. This study presents the derivation of melting characteristics based on spatial clusters of ground surface temperature (GST) measurements. Results are based on data from Switzerland where ground surface temperatures were measured with miniature loggers (iButtons) at 40 locations referred to as footprints. At each footprint, up to ten iButtons have been distributed randomly over an area of 10 m × 10 m, placed a few cm below the ground surface. Footprints span elevations of 2100–3300 m a.s.l. and slope angles of 0–55°, as well as diverse slope expositions and types of surface cover and ground material. Based on two years of temperature data, the basal ripening date and the melt-out date are determined for each iButton, aggregated to the footprint level and further analysed. The melt-out date could be derived for nearly all iButtons; the ripening date could be extracted for only approximately half of them because its detection based on GST requires ground freezing below the snowpack. The variability within a footprint is often considerable and one to three weeks difference between melting or ripening of the points in one footprint is not uncommon. The correlation of mean annual ground surface temperatures, ripening date and melt-out date is moderate, suggesting that these metrics are useful for model evaluation.

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Assessing Arctic Ground Surface Temperatures from Borehole Temperatures and Paleoclimatic Model Simulations

10.5194/egusphere-egu21-9222 ◽

2021 ◽

Author(s):

Hugo Beltrami ◽

Fracisco José Cuesta-Valero ◽

Almudena García-García ◽

Stephan Gruber ◽

Fernando Jaume-Santero

Keyword(s):

Surface Temperature ◽

Ground Surface ◽

Phase Iii ◽

The Arctic ◽

Depth Range ◽

Model Simulations ◽

Ground Temperatures ◽

Surface Temperatures ◽

Intercomparison Project ◽

Borehole Temperature

The surface temperature response to changes in our planet&#8217;s external forcing is larger at higher latitudes, a phenomenon known as polar amplification. The Arctic amplification has been particularly intense during the last century, with arctic-wide paleoclimatic reconstructions and state-of-the-art model simulations revealing a twofold arctic warming in comparison with the average global temperature increase. As a consequence, Arctic ground temperatures respond with rapid warming, but this response varies with snow cover and permafrost processes. Thus, changes in arctic ground temperatures are difficult to reconstruct from data, and to simulate in climate models.Here, we reconstruct the ground surface temperature histories of 120 borehole temperature profiles above 60&#186;N for the last 400 years. Past surface temperature evolution from each profile was estimated using a Perturbed Parameter Inversion approach based on a singular value decomposition method. Long-term surface temperature climatologies (circa 1300 and 1700 CE) and quasi-steady state heat flow are also estimated from linear regression through the depth range 200 to 300 m of each borehole temperature profile. The retrieved temperatures are assessed against simulated ground surface temperatures from five Past Millennium and five Historical experiments from the Paleoclimate Modelling Intercomparison Project Phase III (PMIP3), and the fifth phase of the Coupled Model Intercomparison Project (CMIP5) archives, respectively.Preliminary results from borehole estimates and PMIP3/CMIP5 simulations reveal that changes in recent Arctic ground temperatures vary spatially and are related to each site&#8217;s earlier thermal state of the surface. The magnitudes of ground warming from data and simulations differ with large discrepancies among models. As a consequence, a better understanding of freezing processes at and below the air-ground interface is necessary to interpret subsurface temperature records and global climate model simulations in the Arctic.

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Relations between air and surface temperature in discontinuous permafrost terrain near Mayo, Yukon Territory

Canadian Journal of Earth Sciences ◽

10.1139/e04-082 ◽

2004 ◽

Vol 41 (12) ◽

pp. 1437-1451 ◽

Cited By ~ 43

Author(s):

K C Karunaratne ◽

C R Burn

Keyword(s):

Surface Temperature ◽

Ground Surface ◽

Absolute Temperature ◽

Yukon Territory ◽

Near Surface ◽

Ground Temperatures ◽

Surface Temperatures ◽

Air Temperatures ◽

Discontinuous Permafrost ◽

Data Loggers

The association of site characteristics with the n-factor, a ratio of air to ground surface temperature, was investigated at five sites in the boreal forest near Mayo, Yukon Territory. Permafrost was in equilibrium with surface conditions at three sites, was degrading at another, and was absent from the fifth. Air and near-surface ground temperatures were recorded by data loggers between September 2000 and April 2002, and mean daily temperatures were accumulated to calculate n-factors for the freezing (nf) and thawing (nt) seasons. Air temperature did not vary between the sites, so inter-site differences in nf and nt were because of variations in surface temperature. Variations in nf between the sites over the two winters were primarily because of differences in snow depth, but at sites with similar snow cover, the surface temperatures were relatively high when the site was underlain by unfrozen ground. During summer, daily mean surface temperatures were initially less than air temperatures. However, once the thawing front had penetrated below the depth of diurnal temperature fluctuation, the air and ground surface temperatures converged. Since the rate of thaw penetration is governed by soil thermal diffusivity, nt varies directly with this property. These results indicate that subsurface conditions, particularly absolute temperature and ground thermal properties, exert considerable influence on n-factors, and, at the Mayo sites, the influence is greater than that of the vegetation.

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Small-scale variation of snow in a regional permafrost model

The Cryosphere ◽

10.5194/tc-10-1201-2016 ◽

2016 ◽

Vol 10 (3) ◽

pp. 1201-1215 ◽

Cited By ~ 28

Author(s):

Kjersti Gisnås ◽

Sebastian Westermann ◽

Thomas Vikhamar Schuler ◽

Kjetil Melvold ◽

Bernd Etzelmüller

Keyword(s):

Snow Cover ◽

Ground Surface ◽

Grid Cell ◽

Ground Temperature ◽

Fine Tuning ◽

Small Scale ◽

Near Surface ◽

Ground Temperatures ◽

Surface Temperatures ◽

Scale Variation

Abstract. The strong winds prevalent in high altitude and arctic environments heavily redistribute the snow cover, causing a small-scale pattern of highly variable snow depths. This has profound implications for the ground thermal regime, resulting in highly variable near-surface ground temperatures on the metre scale. Due to asymmetric snow distributions combined with the nonlinear insulating effect of snow, the spatial average ground temperature in a 1 km2 area cannot be determined based on the average snow cover for that area. Land surface or permafrost models employing a coarsely classified average snow depth will therefore not yield a realistic representation of ground temperatures. In this study we employ statistically derived snow distributions within 1 km2 grid cells as input to a regional permafrost model in order to represent sub-grid variability of ground temperatures. This improves the representation of both the average and the total range of ground temperatures. The model reproduces observed sub-grid ground temperature variations of up to 6 °C, and 98 % of borehole observations match the modelled temperature range. The mean modelled temperature of the grid cell reproduces the observations with an accuracy of 1.5 °C or better. The observed sub-grid variations in ground surface temperatures from two field sites are very well reproduced, with estimated fractions of sub-zero mean annual ground surface temperatures within &pm;10 %. We also find that snow distributions within areas of 1 km2 in Norwegian mountain environments are closer to a gamma than to a lognormal theoretical distribution. The modelled permafrost distribution seems to be more sensitive to the choice of distribution function than to the fine-tuning of the coefficient of variation. When incorporating the small-scale variation of snow, the modelled total permafrost area of mainland Norway is nearly twice as large compared to the area obtained with grid-cell average snow depths without a sub-grid approach.

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ON SHALLOW‐HOLE TEMPERATURE MEASUREMENTS—A TEST STUDY IN THE SALTON SEA GEOTHERMAL FIELD

Geophysics ◽

10.1190/1.1440728 ◽

1977 ◽

Vol 42 (3) ◽

pp. 572-583 ◽

Cited By ~ 10

Author(s):

Tien‐Chang Lee

Keyword(s):

Numerical Methods ◽

Ground Surface ◽

Nonlinear Least Squares ◽

Geothermal Gradient ◽

Geothermal Field ◽

The Other ◽

Temperature Measurements ◽

Salton Sea ◽

Depth Interval ◽

Average Value

Shallow‐hole (<13 m) temperature measurements made at various depths and/or times may yield reliable values of geothermal gradient and thermal diffusivity if the groundwater table is shallow (a few meters) such that the effect of time‐dependent moisture content and physical properties is negligible. Two numerical methods based on nonlinear least‐squares curve fitting are derived to remove the effect of annual temperature wave at the ground surface. One method can provide information on the gradient and diffusivity as a function of depth while the other gives average value over the depth interval measured. Experiments were carried in six test holes cased with 2 cm OD PVC pipes in the Salton Sea geothermal field. A set of 5 to 7 thermistors was permanently buried inside the individual pipes with dry sand. Consistent gradient determinations have been obtained with both numerical methods from six monthly observations. By linearly extrapolating the depths to the 100°C and 200°C isotherms from the calculated gradients and mean ground temperatures, we have found good agreement with the nearby deep‐well data for four holes. Discrepancy is found for two holes, one of which is located near the field of [Formula: see text] mud volcanoes and the other near the volcanic Red Hill, reflecting complicated local hydrologic conditions.

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Late Weichselian thermal state at the base of the Scandinavian Ice Sheet

10.5194/cp-2019-49 ◽

2019 ◽

Cited By ~ 1

Author(s):

Dmitry Y. Demezhko ◽

Anastasia A. Gornostaeva ◽

Alexander N. Antipin

Keyword(s):

Thermal State ◽

Ice Sheet ◽

Ground Surface ◽

Substantial Part ◽

Temperature Pattern ◽

Glacial Cycle ◽

Surface Temperatures ◽

Scandinavian Ice Sheet ◽

Late Weichselian ◽

The Last Glacial

Abstract. Geothermal estimates of the ground surface temperatures for the last glacial cycle in Northern Europe has been analyzed. During the Middle and Late Weichselian (55–12 kyr BP) a substantial part of this area was covered by the Scandinavian Ice Sheet. The analysis of geothermal data has allowed reconstructing limits of the ice sheet extension and its basal thermal state in the Late Weichselian. Ground surface temperatures outside the ice sheet were extremely low (from −8 to −18 °C). Within the ice sheet, there were both thawed and frozen zones. The revealed temperature pattern is generally consistent with the modern one for the ground surface temperatures in Greenland that makes it possible to consider these ice sheets as analogues. The anomalous climatically induced surface heat flux and orbital insolation of the Earth varied consistently outside the glaciation and independently within the limits of the ice sheet.

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Ground thermal and geomechanical conditions in a permafrost-affected high-latitude rockslide site (Polvartinden, Northern Norway)

10.5194/tc-2016-223 ◽

2016 ◽

Author(s):

Regula Frauenfelder ◽

Ketil Isaksen ◽

Jeannette Nötzli ◽

Matthew J. Lato

Keyword(s):

Temperature Regime ◽

Laser Scanning ◽

Ground Surface ◽

Failure Zone ◽

Climate Data ◽

Conduction Model ◽

Near Surface ◽

Northern Norway ◽

Surface Temperatures

Abstract. In June 2008, a rockslide detached in the northeast facing slope of Polvartinden, a high-alpine mountain in Signaldalen, Northern Norway. Here, we report on the observed and modelled past and present near-surface temperature regime close to the failure zone, as well as on a subsequent simulation of the subsurface temperature regime, and on initial geomechanical mapping based on laser scanning. The volume of the rockslide was estimated to be approximately 500 000 m3. The depth to the actual failure surface was found to range from 40 m at the back of the failure zone to 0 m at its toe. Visible in-situ ice was observed in the failure zone just after the rockslide. Between September 2009 and August 2013 ground surface temperatures were measured with miniature temperature data loggers at fourteen different localities close to the original failure zone along the northern ridge of Polvartinden, and in the valley floor. The results from these measurements and from a basic three-dimensional heat conduction model suggest that the lower altitudinal limit of permafrost at present is at 600–650 m a.s.l., which corresponds to the upper limit of the failure zone. A coupling of our in-situ data with regional climate data since 1958 suggests a general gradual warming and that a period with highest mean near surface temperatures on record ended four months before the Signaldalen rockslide detached. A comparison with a transient permafrost model run at 10 m depth, representative for areas where snow accumulates, strengthen this findings, which are also in congruence with measurements in nearby permafrost boreholes. It is likely that permafrost in and near the failure zone is presently subject to degradation. This degradation, in combination with the extreme warm year antecedent to the rock failure, is seen to have played an important role in the detaching of the Signaldalen rockslide.

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Ground thermal contrasts and variability at an alpine pyramidal peak in central Austria (Innerer Knorrkogel, Venediger Mountains)

10.5194/egusphere-egu21-12588 ◽

2021 ◽

Author(s):

Andreas Kellerer-Pirklbauer ◽

Gerhard Karl Lieb

Keyword(s):

Snow Cover ◽

Thermal Regime ◽

Ground Surface ◽

Temperature Monitoring ◽

Ground Temperature ◽

Freeze Thaw ◽

Ground Temperatures ◽

Frost Weathering ◽

Second Year ◽

Ridge Flank

Ground temperatures in alpine environments are severely influenced by slope orientation (aspect), slope inclination, local topoclimatic conditions, and thermal properties of the rock material. Small differences in one of these factors may substantially impact the ground thermal regime, weathering by freeze-thaw action or the occurrence of permafrost. To improve the understanding of differences, variations, and ranges of ground temperatures at single mountain summits, we studied the ground thermal conditions at a triangle-shaped (plan view), moderately steep pyramidal peak over a two-year period (2018-2020).We installed 18 monitoring sites with 23 sensors near the summit of Innerer Knorrkogel (2882m asl), in summer 2018 with one- and multi-channel datalogger (Geoprecision). All three mountain ridges (east-, northwest-, and southwest-facing) and flanks (northeast-, west-, and south-facing) were instrumented with one-channel dataloggers at two different elevations (2840 and 2860m asl) at each ridge/flank to monitor ground surface temperatures. Three bedrock temperature monitoring sites with shallow boreholes (40cm) equipped with three sensors per site at each of the three mountain flanks (2870m asl) were established. Additionally, two ground surface temperature monitoring sites were installed at the summit.Results show remarkable differences in mean annual ground temperatures (MAGT) between the 23 different sensors and the two years despite the small spatial extent (0.023 km&#178;) and elevation differences (46m). Intersite variability at the entire mountain pyramid was 3.74&#176;C in 2018/19 (mean MAGT: -0.40&#176;C; minimum: -1.78&#176;C; maximum: 1.96&#176;C;) and 3.27&#176;C in 2019/20 (mean MAGT: 0.08&#176;C; minimum: -1.54&#176;C; maximum: 1,73&#176;C;). Minimum was in both years at the northeast-facing flank, maximum at the south-facing flank. In all but three sites, the second monitoring year was warmer than the first one (mean +0.48&#176;C) related to atmospheric differences and site-specific snow conditions. The comparison of the MAGT-values of the two years (MAGT-2018/19 minus MAGT-2019/20) revealed large thermal inhomogeneities in the mountain summit ranging from +0.65&#176; (2018/19 warmer than 2019/20) to -1.76&#176;C (2018/19 colder than 2019/20) at identical sensors. Temperature ranges at the three different aspects but at equal elevations were 1.7-2.2&#176;C at ridges and 1.8-3.7&#176;C at flanks for single years. The higher temperature range for flank-sites is related to seasonal snow cover effects combined with higher radiation at sun-exposed sites. Although the ground temperature was substantially higher in the second year, the snow cover difference between the two years was variable. Some sites experienced longer snow cover periods in the second year 2019/20 (up to +85 days) whereas at other sites the opposite was observed (up to -85 days). Other frost weathering-related indicators (diurnal freeze-thaw cycles, frost-cracking window) show also large intersite and interannual differences.Our study shows that the thermal regime at a triangle-shaped moderately steep pyramidal peak is very heterogeneous between different aspects and landforms (ridge/flank/summit) and between two monitoring years confirming earlier monitoring and modelling results. Due to high intersite and interannual variabilities, temperature-related processes such as frost-weathering can vary largely between neighbouring sites. Our study highlights the need for systematic and long-term ground temperature monitoring in alpine terrain to improve the understanding of small- to medium-scale temperature variabilities.

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Influences of avalanche-defence snow-supporting structures on ground temperature in Alpine permafrost terrain

Annals of Glaciology ◽

10.3189/172756400781820336 ◽

2000 ◽

Vol 31 ◽

pp. 422-426 ◽

Cited By ~ 14

Author(s):

Marcia Phillips ◽

Perry Bartelt ◽

Marc Christen

Keyword(s):

Thermal Characteristics ◽

Temperature Measurements ◽

Finite Element Program ◽

Ground Temperatures ◽

Dimensional Finite Element ◽

Element Program ◽

Temporal And Spatial ◽

Supporting Structures ◽

Borehole Core

AbstractTo investigate the effects of steel snow-supporting structures on the thermal regime of the ground in typical Alpine permafrost avalanche terrain, ground temperatures were monitored and simulated on an avalanche slope equipped with experimental snow-supporting structures. Temperature measurements were effected in lm boreholes above and below a row of snow nets and in two 18 m boreholes located between the structures and in a reference location. The presence of the structures can induce modifications of the temporal and spatial snow-cover distribution, leading to differences in active-layer temperatures just below and above the structures: snow accumulates above the supporting surface of the structures, and frequently there is less snow below. The long-term thermal effect of these variations near a snow net was simulated using a two-dimensional finite-element program based on heat conduction. The material and thermal characteristics of the ground simulated are obtained from temperature measurements and from borehole-core information.

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Holocene paleoenvironmental reconstruction from deep ground temperatures: a comparison with paleoclimate derived from the δ18O record in an ice core from the agassiz Ice Cap, Canadian Arctic Archipelago

Journal of Glaciology ◽

10.1017/s002214300000722x ◽

1991 ◽

Vol 37 (126) ◽

pp. 209-219 ◽

Cited By ~ 9

Author(s):

Alan E. Taylor

Keyword(s):

Surface Temperature ◽

Snow Cover ◽

Ice Core ◽

Canadian Arctic ◽

Ground Surface ◽

Temperature Profiles ◽

Canadian Arctic Archipelago ◽

Ground Surface Temperature ◽

Ice Cap ◽

Surface Temperatures

Abstract Changes in ground-surface temperature for the past few hundred years have been derived from deep temperature profiles at three wells in the northeastern Canadian Arctic Archipelago, and compared with the climatic history derived from the oxygen-isotope ratio 18O/16O measured in an ice core from the Agassiz Ice Cap, about 180-260 km to the east. Analysis of the ground-temperature profiles suggests that surface temperatures in the area decreased after the Little Climatic Optimum about 1000 years ago until the Little Ice Age (LIA). About 100 years ago, ground-surface temperatures appear to have increased by 2-5K to reach today’s values, while air temperatures increased by 2-3K, according to the isotope record. Part of the larger ground-surface temperature change may be due to other paleoenvironmental effects, such as an increase in snow cover coincident with the end of the LIA. The δ18O climatic record was successful in predicting the general features of the ground-temperature profiles observed at two of the sites, but not the third. There is contemporary evidence that surface temperatures at the latter site may be substantially modified by other environmental factors such as snow cover.

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