No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Long-term soil temperature dynamics in the Sierra Nevada, Spain
Abstract
Soil temperatures play a key role on the dynamics of geomorphological processes in periglacial environments. However, little is known about soil thermal dynamics in periglacial environments of semiarid mid-latitude mountains, where seasonal frost is dominant. From September 2006 to August 2012 we have monitored soil temperatures at different depths (2, 10, 20, 50 and 100 cm) in a solifluction landform located at 3005 m.a.s.l. in the summit area of the Sierra Nevada (South Spain). Mean annual temperatures in the first meter of the soil ranged from 3.6 to 3.9 °C while the mean annual air tem-perature at the nearby Veleta peak was 0.08 °C. Therefore, these data point out the inexistence of widespread permafrost conditions today in this massif. Seasonal frost controls the geomorphodynamics even in the highest lands. Climate conditions have shown a large interannual variability, as it is characteristic in a high mountainous Mediterranean environment. These variations are reflected in the patterns of soil thermal dynamics. The depth and duration of the frozen layer are strongly conditioned by the thickness of the snow cover. The date of the first significant snowfalls conditioned the beginning and rhythm of freezing of the soil. Wet years resulted in a thick snow cover which insulated the ground from external climate oscillations and favored a shallow frost layer (. On the other hand, years with low precipitations promoted deeper freezing of the soil down to 60–70 cm extending until late May or early June. When snow melted a high increase of temperatures of 10–12 °C in few weeks was recorded at all depths. At this time of the year, periglacial activity is enhanced due to higher water availability and the ex-istence of freeze–thaw cycles. These were recorded mostly in spring and autumn in the first 50 cm depth of the soil, ranging from 9.8 days (at 2 cm) to 3.7 days (at 50 cm). However, the inactivity of solifluction landforms suggests that the combination of present-day soil temperatures together with moisture conditions is not favorable to promote solifluction activity in the periglacial belt of the Sierra Nevada. Future climate scenarios point to a temperature increase and precipitation decrease in the area, which would entail deeper but shorter frozen soil layers. These conditions would not be favorable for active periglacial slope processes in the Sierra Nevada.
... Consequently, the distribution of periglacial phenomena in the Iberian Peninsula is a result of both present and past climate conditions. The periglacial belt expanded more or less according to the intensity of the cold during Quaternary glaciations, and receded to higher elevation areas during interglacials, such as has been the case during the Holocene (Oliva et al., 2014b). During the coldest phases, periglacial features also developed in central Spain at elevations of only 700 m (Serrano et al., 2010), as well as near the shoreline along the Atlantic coast (P erez-Alberti et al., 1998a;Vieira and Cordeiro, 1998). ...
... Solifluction landforms are widespread in the glacial valleys of Sierra Nevada, showing a wide variety of typologies . The monitoring of these periglacial slope features revealed their inactivity or weak activity today in the massif, with displacement rates in all cases <1 cm/year (Oliva, 2009;Oliva et al., 2008Oliva et al., , 2009Oliva et al., , 2014b. This suggests their formation under more favourable past climate regimes. ...
... According to climate projections, the warming trend recorded in the Iberian Peninsula over the last several decades will continue and intensify in the near future (IPCC, 2013). This climate pattern will doubtlessly have significant consequences for environmental dynamics in the present-day periglacial belt in the Iberian Mountains through complex feed-back processes, driven largely by changes in snow depth and spatial variability associated with variations in surface runoff (L opez- Moreno et al., 2013Moreno et al., , 2014a, in the duration and recurrence of warm events (L opez- Moreno et al., 2014b), upslope vegetation shifts (Pauli et al., 2012) and/or changes in soil thermal regimes (Oliva et al., 2014b). Consequently, during the coming decades it is expected that periglacial activity in Iberian mountains will become weaker and more restricted to increasingly higher elevations. ...
This article focuses on the characterization of auriferous deposits, identification of hitherto unknown Roman mining infrastructure remains, and the early attempts of exploitation carried out in north-west Iberia. The research has combined airborne laser scanning (LiDAR) and field prospection to explore the geomorphological signature and landscape transformation resulting from Roman mining works in two unknown sectors of the western Duero Meseta. The integration of geological and remote sensing information contributed to extend the Roman's mining domains, traditionally focused on the river headwaters of the north-west. The article explores the complex hydraulic system developed in the Jamuz and lower sector of the Eria river valleys, as well as the evidence of open-cast mining and their relationship with the Roman army. The results suggest that the highly dispersed and reduced dimensions of the mining sites correspond to a selected method of gold prospection, employed for the identification of viable exploitation sectors. Thus, the initiation of the mining works could have started in the Jamuz valley and developed systematically in this area, to subsequently spread towards the upstream sectors and nearby valleys. This research contributes to gain new insights into the extension and complexity of the mining infrastructure, indicating the importance of the gold-bearing raña deposits within the framework of Roman gold mining in north-west Spain.
... Poglioti et al (2015) suggested that snow likely plays a major role only on the inter-annual variability of active layer thickness (ALT) in the Cime Bianche, Alps. Numerous studies have shown that snow cover is a driving factor of permafrost presence and the thermal regime of seasonal frost ground (bedrock) or the active layer in mid-latitude high mountain regions, (e.g., Alps, Sierra Nevada (Spain), Qinghai-Tibet Plateau, etc.) (Luetschg et al. 2004;Gadek et al. 2010;Jin et al. 2008;Chang et al. 2014;Magnin et al. 2015Magnin et al. , 2017Oliva et al. 2014Oliva et al. , 2016, Arctic or sub-Arctic (Zhang et al. 1997;Zhang 2005;Lafrenière et al. 2013;Davesne et al. 2017), and Antarctic (Vieira et al. 2010;Oliva et al. 2017;Ferreira et al. 2017). ...
... The influence of the snow cover on the active layers or ground mainly depends on the thickness and spatial-temporal characteristics of snow cover, including the timing and the duration of snow cover (Goodrich 1982;Zhang 2005;Luetschg et al. 2008;Magnin et al. 2015Magnin et al. , 2017Oliva et al. 2014Oliva et al. , 2017. The heterogeneity of snow cover thickness is the main factor controlling the spatial variability of GST and ALT at a small distance of tens to hundreds of meters (Poglioti et al. 2015;Davesne et al. 2017). ...
... And the thin, discontinuous snow cover in mid-autumn, 2014 weaken the effects of air temperature and solar radiation, having a positive effect on the cooling process of active layer ( Figure 5, Table 3), which is in accordance with the results in previous studies (Keller and Tamás 2003;Pogliotti 2010;Magnin et al. 2017). Other studies have demonstrated that the onset time of longterm snow cover in the winter affect the cooling or freezing process of the ground and active layer in thick snow cover areas due to thermal insulation (Zhang 2005;Luetschg et al. 2008;Magnin et al. 2017;Oliva et al. 2014Oliva et al. , 2017. Our heat flux data shows in the case of lower T a , the lost heat from the ground (G 5cm = -10.75 ...
Snow cover is characterized by the high albedo, low thermal conductivity, and notable heat transition during phase changes. Thus, snow cover significantly affects the ground thermal regime. A comparison of the snow cover in high latitudes or high-altitude snowy mountain regions indicates that the eastern Tianshan Mountains (China) show a characteristically thin snow cover (snow depth below 15 cm) with remarkable temporal variability. Based on snow depth, heat flux, and ground temperature from 2014 to 2015 in the Urumqi River source, the spatialtemporal characteristics of snow cover and snow cover influences on the thermal conditions of active layer in the permafrost area were analyzed. During the autumn (Sept. - Oct.), thin and discontinuous snow cover can noticeably accelerate the exothermic process of the ground, producing a cooling effect on the shallow soil. During the winter (Nov. - Mar.), it is inferred that the effective thermal insulation starts with snow depth exceeding 10 cm during early winter. However, the snow depth in this area is generally below 15 cm, and the resulting snow-induced thermal insulation during the winter is very limited. Due to common heavy snowfalls in the spring (Apr. to May), the monthly mean snow thickness in April reached to 15 cm and remained until mid-May. Snow cover during the spring significantly retarded the ground warming. Broadly, snow cover in the study area exerts a cooling effect on the active layer and plays a positive role in the development and preservation of permafrost.
... Consequently, the distribution of periglacial phenomena in the Iberian Peninsula is a result of both present and past climate conditions. The periglacial belt expanded more or less according to the intensity of the cold during Quaternary glaciations, and receded to higher elevation areas during interglacials, such as has been the case during the Holocene (Oliva et al., 2014b). During the coldest phases, periglacial features also developed in central Spain at elevations of only 700 m (Serrano et al., 2010), as well as near the shoreline along the Atlantic coast (P erez-Alberti et al., 1998a;Vieira and Cordeiro, 1998). ...
... Solifluction landforms are widespread in the glacial valleys of Sierra Nevada, showing a wide variety of typologies . The monitoring of these periglacial slope features revealed their inactivity or weak activity today in the massif, with displacement rates in all cases <1 cm/year (Oliva, 2009;Oliva et al., 2008Oliva et al., , 2009Oliva et al., , 2014b. This suggests their formation under more favourable past climate regimes. ...
... According to climate projections, the warming trend recorded in the Iberian Peninsula over the last several decades will continue and intensify in the near future (IPCC, 2013). This climate pattern will doubtlessly have significant consequences for environmental dynamics in the present-day periglacial belt in the Iberian Mountains through complex feed-back processes, driven largely by changes in snow depth and spatial variability associated with variations in surface runoff (L opez- Moreno et al., 2013Moreno et al., , 2014a, in the duration and recurrence of warm events (L opez- Moreno et al., 2014b), upslope vegetation shifts (Pauli et al., 2012) and/or changes in soil thermal regimes (Oliva et al., 2014b). Consequently, during the coming decades it is expected that periglacial activity in Iberian mountains will become weaker and more restricted to increasingly higher elevations. ...
... However, the frozen ground is undergoing a process of degradation as a result of the temperature increase recorded in the south of the Iberian Peninsula during the last few decades (Bladé and Castro-Díez, 2010). Permanently negative soil temperatures have not been found in other areas of Sierra Nevada, such as in the southern cirque of Rio Seco, at 3005 m (Oliva et al., 2014c), or in the summit plateau of the Cerro de los Machos, at 3327 m (Salvador-Franch et al., 2012), where the average annual temperatures in the first decimetres of the soil ranged between 1.7 °C and 3.9 °C. Subsurface temperatures exercise decisive control over the prevailing geomorphological processes in periglacial mountain environments, particularly in permafrost areas (Haeberli et al., 2010). ...
... The minimum temperature inside the bedrock is reached at the shallowest sensors throughout the cold season, always depending on the prevailing temperature conditions and the snow cover formed during the autumn–winter. The snow cover thickness in the summit area of Sierra Nevada shows a strong annual and interannual variability, as well as its duration, which may last between 6 to 9 months (Oliva et al., 2014c).Table 1 Operating timing of the loggers installed at different depths inside the borehole during the control period. ...
... The results presented in this study complement previous works about soil temperatures in other landforms of the high lands of Sierra Nevada (Gómez-Ortiz et al., 1999; Salvador-Franch et al., 2011, 2012 Oliva et al., 2014b Oliva et al., , 2014c). The temperatures of the Veleta bedrock down to 60 m depth showed values away from the freezing point (Fig. 6 ), demonstrating the absence of permafrost. ...
... From a hydrological point of view, snowmelt controls the mountain runoff rate during the spring (Barnett et al., 2005;Adam et al., 2009;Stahl et al., 2010), river flow magnitude and timing (Morán-Tejeda et al., 2014;Sanmiguel-Vallelado et al., 2017), water infiltra-tion and groundwater storage (Gribovszki et al., 2010;Evans et al., 2018), and transpiration rate (Cooper et al., 2020). The presence and duration of snowpack affect terrestrial ecosystem dynamics because the snow ablation date affects photosynthesis (Woelber et al., 2018), forest productivity (Barnard et al., 2018), freezing and thawing of the soil (Luetschg et al., 2008;Oliva et al., 2014), and thickness of the active layer in permafrost environments (Hrbáček et al., 2016;Magnin et al., 2017). Snowpack also has remarkable economic impacts. ...
... These expected decreases in snow will likely have important impacts on the ecosystem. During spring, a snow cover cools the soil (Luetschg et al., 2008), delays the initiation of freezing (Oliva et al., 2014), functions as a thick active layer (Hrbáček et al., 2016), and protects alpine rocks from exposure to solar radiation and high air temperatures (Magnin et al., 2017). Due to warming temperatures, the remaining glaciers in the Pyrenees are shrinking and are expected to disappear before the 2050s (Vidaller et al., 2021). ...
The Mediterranean Basin has experienced one of the highest warming rates on earth during the last few decades, and climate projections predict water scarcity in the future. Mid-latitude Mediterranean mountain areas, such as the Pyrenees, play a key role in the hydrological resources for the highly populated lowland areas. However, there are still large uncertainties about the impact of climate change on snowpack in the high mountain ranges of this region. Here, we perform a snow sensitivity to temperature and precipitation change analysis of the Pyrenean snowpack (1980–2019 period) using five key snow–climatological indicators. We analyzed snow sensitivity to temperature and precipitation during four different compound weather conditions (cold–dry (CD), cold–wet (CW), warm–dry (WD), and warm–wet (WW)) at low elevations (1500 m), mid elevations (1800 m), and high elevations (2400 m) in the Pyrenees. In particular, we forced a physically based energy and mass balance snow model (FSM2), with validation by ground-truth data, and applied this model to the entire range, with forcing of perturbed reanalysis climate data for the period 1980 to 2019 as the baseline. The FSM2 model results successfully reproduced the observed snow depth (HS) values (R2>0.8), with relative root mean square error and mean absolute error values less than 10 % of the observed HS values. Overall, the snow sensitivity to temperature and precipitation change decreased with elevation and increased towards the eastern Pyrenees. When the temperature increased progressively at 1 ∘C intervals, the largest seasonal HS decreases from the baseline were at +1 ∘C. A 10 % increase in precipitation counterbalanced the temperature increases (≤1 ∘C) at high elevations during the coldest months because temperature was far from the isothermal 0 ∘C conditions. The maximal seasonal HS and peak HS max reductions were during WW seasons, and the minimal reductions were during CD seasons. During WW (CD) seasons, the seasonal HS decline per degree Celsius was 37 % (28 %) at low elevations, 34 % (30 %) at mid elevations, and 27 % (22 %) at high elevations. Further, the peak HS date was on average anticipated for 2, 3, and 8 d at low, mid, and high elevation, respectively. Results suggest snow sensitivity to temperature and precipitation change will be similar at other mid-latitude mountain areas, where snowpack reductions will have major consequences for the nearby ecological and socioeconomic systems.
... This geomorphological setting is similar to that observed in the Ground temperatures at 10 cm show lower temperatures than in other high mountain areas in Iberia. Between 2006 and 2012 MAGT in a solifluction lobe (3005 m) ranged from 2.3 and 4.8°C with an average of 3.7°C (Oliva et al., 2014b), whereas a MAGT in a sorted stone circle at 3297 m oscillated between 1.2 and 2.5 with an average of 1.8°C (Salvador-Franch et al., 2011). In the Eastern Pyrenees, MAGTs at the same depth between 2007 and 2013 were 2.4, 5.9 and 6.3°C at 2730, 2230 and 2160 m (Salvador-Franch et al., 2015). ...
... This high interannual variability largely controlled by the presence or absence of snow cover has been also observed in other Iberian areas. In the Guadarrama massif, at 2212 m, the number of freeze-thaw days ranged between 2 and 41 between 2002 and 2007 at 10 cm depth (Andrés and Palacios, 2010), while in Sierra Nevada it fluctuated annually between 0 and 10 at the same depth at 3005 m (Oliva et al., 2014b). ...
The present study focuses on the analysis of the ground and near-rock surface air thermal conditions at the Forcadona glacial cirque (2227 m a.s.l.) located in the Western Massif of the Picos de Europa, Spain. Temperatures have been monitored in three distinct geomorphological and topographical sites in the Forcadona area over the period 2006–11. The Forcadona buried ice patch is the remnant of a Little Ice Age glacier located in the bottom of a glacial cirque. Its location in a deep cirque determines abundant snow accumulation, with snow cover between 8 and 12 months. The presence of snow favours stable soil temperatures and geomorphic stability. Similarly to other Cantabrian Mountains, the annual thermal regime of the soil is defined by two seasonal periods (continuous thaw with daily oscillations and isothermal regime), as well as two short transition periods. However, the results showed evidence of a significantly different annual thermal regime at the ground and near-rock surface air. Relatively stable soil thermal regimes were observed at the moraine and talus sites, while a more dynamic pattern was recorded at the rock wall site. Here, a higher interannual variability in the number of freeze–thaw days was also detected, which showed evidence of the important role of the snow cover as a ground surface insulator in the area. Seasonal frost conditions are widespread today in the high lands of the massif. No permafrost regime was detected in the area, though mean temperatures measured at 0.5 m depth at the Forcadona buried ice patch during 2006–07 (0.1 °C) suggest that permanent negative values may be reached at deeper layers.
... Snow cover has been widely found to have a strong influence on the thermal regime of the ground (e.g., Oliva et al., 2014;T. Zhang, 2005;W. ...
Understanding volcanic eruption triggers is critical toward anticipating future activity. While internal magma dynamics typically receive more attention, the influence of external processes remains less understood. In this context, we explore the relationship between seasonal snow cycles and eruptive activity at Ruapehu, New Zealand. This is motivated by apparent seasonality in the eruptive record, where a higher than expected proportion of eruptions (post‐1960) occur in spring (including the two previous eruptions of 2006 and 2007). Employing recent advancements in passive seismic interferometry, we compute sub‐surface seismic velocity changes between 2005 and 2009 using the cross‐wavelet transform approach. Stations on the volcano record a higher velocity in winter, closely correlated with the presence of snow. Inverting for depth suggests these changes occur within the upper 300 m. Notably, we observe that the timing of the previous two eruptions coincides with a period associated with an earlier velocity decrease at approximately 200–300 m depth relative to the surface. Reduced water infiltration (as precipitation falls as snow) is considered a likely control of seasonal velocities, while modeling also points to a contribution from snow‐loading. We hypothesize that this latter process may play a role toward explaining seasonality in the eruptive record. Our findings shed light on the complex interactions between volcanoes and external environmental processes, highlighting the need for more focused research in this area. Pursuing this line of inquiry has significant implications toward improved risk and hazard assessments at not just Ruapehu, but also other volcanoes globally that experience seasonal snow cover.
... Changes in precipitation and temperature, and the decrease in snow cover, together with an increase in vegetation density in headwater zones, have led to a marked reduction in water availability in these regions (L opez- Moreno et al., 2008aMoreno et al., , 2020. This situation is related to the rapid decline of the glaciers in the Pyrenees (Bartolomé et al., 2024;Kamp et al., 2023;Moreno et al., 2021) and to the absence of widespread permafrost conditions in the Sierra Nevada today (Oliva et al., 2014). ...
This study describes temperature and precipitation trends in the two National Parks located in the two highest mountain ranges on the Iberian Peninsula: the Sierra Nevada (Sierra Nevada National Park, SN) and the Pyrenees (Aigüestortes i Sant Maurici National Park, ASM). Special focus is placed on analysing disparities between the lowlands and the highlands, as well as the agreement between observational data and grid data (IBERIA01 and E‐OBS). For this purpose, a quality‐controlled and homogeneity‐adjusted database of the daily maximum temperature, minimum temperature and precipitation (SMADS database) has been generated. Regional trends in mean temperature indicate that warming in ASM (0.17°C·decade⁻¹) was greater than in the Sierra Nevada (SN) (0.13°C·decade⁻¹) in the longest joint period, 1930–2020. For annual precipitation, the trends over the past nine decades were negative, although not significantly. Only the summer in SN showed a significant negative trend, which has intensified in recent decades to −13.4%·decade⁻¹ for 1975–2020. A parallel evolution was observed in the annual mean temperature of the highlands (>1500 m) and lowlands (<1500 m) of ASM, with a common trend of 0.17°C·decade⁻¹, while in SN negative elevation‐dependent warming was detected. Differences between lowlands and highlands were also noted in precipitation trends in both mountain ranges: a positive trend in precipitation was found in the lowlands while in the highlands practically null trends (ASM) or decreasing precipitation trends (SN) were detected. The comparison of the Spanish Mountain Adjusted Daily Series (SMADS) results with the IBERIA01 and E‐OBS grid series yielded differences no greater than ±0.2°C·decade⁻¹. No notable differences were detected between the regional trends calculated with observational series or with grid series. These results worsened when the differences in the trends detected in the individual observed temperature series were compared against the corresponding grid series.
... Snowpack is an excellent thermal insulator due to its low thermal properties [29][30][31] and can insulate the soil from meteorological conditions such as cold weather [32,33]. Hence, the snowpack controls the duration and depth of the frozen layers within a soil [34], but this phenomenon is also controlled by other factors such as soil properties, precipitation patterns, and temperature. ...
The freeze–thaw process controls several hydrologic processes, including infiltration, runoff, and soil erosion. Simulating this process is important, particularly in cold and mountainous regions. The Soil and Cold Regions Model (SCRM) was used to simulate, study, and understand the behavior of twelve homogenous soils subject to a freeze–thaw process, based on meteorological data at a snow-dominated forest site in Laramie, WY, USA, from 2010 and 2012. The relationships of soil pore size, soil particle contact, and meteorological data were varied. Our analysis of the model compared simulations using metrics such as soil frost depth, days with ice, and maximum ice content. The model showed that the freeze–thaw process was strongest in the period with a shallow snowpack, with particle packing within the soil profile being an important factor in this process; that soil texture and water content control soil thermal properties; and that water movement towards the freezing front was especially important in fine-textured soils, where water and ice were concentrated in the upper layers. Based on these results, future research that combines a broader set of soil conditions with an extended set of field meteorology and real soil data could elucidate the influence of soil texture on the thermal properties related to soil frost.
... This effect is quantified at ca. 4 C on near-surface temperature during spring at Swiss Alps (Scherrer et al., 2012). In Iberian mountain ranges, years with less snow condition colder ground temperatures than snow-rich years, when the snow isolates the ground from atmospheric oscillations; this has major implications for terrestrial ecosystems in high altitude regions (Oliva et al., 2014;G omez-Ortiz et al., 2019). ...
In a warmer climate, significant variations in the snow regime are expected. Thus, it is crucial to better understand present‐day snow cover regime, its duration and thickness, in order to anticipate future changes. This work presents the first characterization of snow patterns in the Catalan Pyrenees based on 11 snow stations located in high elevation areas (>2,000 m). Here, we examine spatio‐temporal evolution of the daily snow depth and new snow height (HN) since the earliest 2000s to 2020. In addition, we analyse the different synoptic patterns that cause HN events in the study area as well as the low frequency climate modes on the different stages of the snow season. Our results show evidence that the measured snow amount differs considerably between the western and the eastern Catalan Pyrenees independently of the considered elevation. While the eastern part has an average seasonal cumulative HN of 278 cm, the western sector gets almost twice (433 cm). Nonetheless, the onset of the snow melting does not show substantial differences, being primarily ruled by the elevation in both areas. The longest snow records (Núria, 1971 m) point to an increase of HN from 1985 to 2020, a trend which is also observed in most stations from 2000 to 2020. Nevertheless, some stations of the N western fringe record negative trends associated with the low frequency variability of the Western Mediterranean Oscillation (WeMO). Results also indicate that the NW Atlantic low‐pressure systems are the circulation weather types that provide more abundant HN in the majority of snow stations. The Atlantic advections are more frequent in autumn and winter, while the Mediterranean advections provide more intense and recurrent HN in spring. The atmospheric circulation is basically ruled by the East Atlantic/West Russia and the WeMO teleconnection patterns.
... Snow cover and freeze-thaw cycling affect soil aggregate stability. Snow cover serves as an insulator against freezing air temperatures, reducing the frequency and intensity of the freeze-thaw cycles (Oliva et al., 2014). Therefore, insulation from snow and straw cover increased the MWD (Boswell et al., 2020). ...
Soil degradation in vineyards is a global problem, indicating the need for the adoption of sustainable practices. Studies on the seasonal and long-term management impacts on soil properties and hydrological responses in vineyards are needed. Rainfall simulation experiments (60 mm h − 1 for 30 min) and soil sampling were conducted on Cambisols in eastern Croatia during the dry and wet seasons in long-term grass-covered and tilled vineyards. The results show that bulk density (BD), soil organic matter (SOM), available phosphorous (P 2 O 5), soil water content (SWC), mean weight diameter (MWD), and water-stable aggregates (WSA) were significantly higher in grass-covered plots than in tilled plots. WSA was significantly lower in the wet period, whereas the opposite trend was observed for SWC and MWD. The time to ponding (PT) and time to runoff (RT) were high (p < 0.05) in the tilled plot in the dry season and low in the wet season. The sediment concentration (SC), soil loss (SL), carbon loss (C loss), and P 2 O 5 loss were significantly higher in the tilled plot than in the grass-covered plot. Runoff, SC, SL, C loss, and P 2 O 5 loss were significantly lower in the dry period. Although the grass-covered plots exhibited high compaction, the stable structure reduced SL by 91% and 94% in the dry and wet seasons, respectively. The tilled plots increased disaggregation and the availability of sediments for transport, enhancing C loss (4.5 times higher) and P 2 O 5 loss (6.4 times higher) compared with the values in the grass-covered plots. Tillage as an unsustainable practice was more pronounced in the wet season with 16.4, 10.1, and 11.1 times higher sediment, P 2 O 5, and C losses, respectively, than those in the grass-covered plots. More sustainable practices are needed to decrease soil degradation and reverse these processes.
... Due to the high albedo and excellent insulating heat property, snow cover has an dual-influence of warming or cooling the underlying soil depending on the thickness of snow (French, 2007;Zhang, 2005), and these influences vary with the snow density, depth, and the timing and duration of snow cover (Ling and Zhang, 2003;Luetschg et al., 2008;Oliva et al., 2014). Here, taking thick eternal snow cover as an example, the thick snow cover mainly played a role in the heat insulation, which resulted in the difficulty of heat transfer from the atmosphere into soil during the warm season and from soil into the atmosphere in the cold season (Kudriavtsev, 1992;Zhang, 2005). ...
The hydrothermal process within the aeolian sand layer on the Qinghai-Tibetan Plateau (QTP) plays a key role in understanding the interaction between desertification and underlying frozen soil. However, little is known about the hydrothermal dynamics of aeolian sand and underling soil layer in the frozen soil zone on the QTP. In this study, a sparse vegetation cover site and three aeolian sand cover sites with different sand thicknesses were established to study the hydrothermal dynamics within aeolian sand layer. The results show that the thickness of aeolian sand is critical in the soil hydrothermal process under sand cover. The increase in thickness of the aeolian sand layer resulted in an advance in the onset of the freezing and thawing of soil, and accelerated movement of the freezing and thawing front. In addition, the increase in sand thickness caused an increase in soil temperature during the thawing stage and the warming period of the thawed stage, whereas a decrease occurred during the cooling period of the thawed stage, the freezing stage and the frozen stage, which ultimately caused the enlargement of the annual range of ground temperature. Furthermore, in the study area, the actual evapotranspiration of sand-covered surface was larger than that of the naked surface. The water content also decreased with increasing sand thickness in different stages, which separately decreased the heat budget in both the warm and cold season because of the smaller thermal conductivity of aeolian sand with a lower water content. This study states that through the special hydrothermal process, have an adverse impact on the occurrence and formation of the frozen soil in the QTP.
... For three out of the seven proverbs in which there is no agreement (Phy2, Phy5, and Bio3), the comparison had to be done with scientific literature from outside Spain due to lack of more local reports, which weakens the term of the comparison. Similarly, at least for one of the proverbs (i.e., Phy9 referring to soil humidity), the mismatch could be explained by the use of different scales of observation as the reference used (i.e., Oliva et al. 2014) studied soil temperature at higher altitudes (e.g., above 3000 m.a.s.l) than the villages surveyed. ...
Local communities’ dependence on the environment for their livelihood has guided the development of indicators of local weather and climate variability. These indicators are encoded in different forms of oral knowledge. We explore whether people recognize and perceive as accurate one type of such forms of oral knowledge, climate-related proverbs. We conducted research in the Alta Alpujarra Occidental, Sierra Nevada, Spain. We collected locally recognized proverbs and classified them according to whether they referred to the climatic, the physical, or the biological system. We then conducted questionnaires (n = 97) to assess informant’s ability to recognize a selection of 30 locally relevant proverbs and their perception of the accuracy of the proverb. Climate-related proverbs are abundant and relatively well recognized even though informants consider that many proverbs are not accurate nowadays. Although proverbs’ perceived accuracy varied across informant’s age, level of schooling, and area of residence, overall proverb’s lack of reported accuracy goes in line with climate change trends documented by scientists working in the area. While our findings are limited to a handful of proverbs, they suggest that the identification of mismatches and discrepancies between people’s reports of proverb (lack of) accuracy and scientific assessments could be used to guide future research on climate change impacts.
... Previous investigations in other areas have shown that Tss{an} varies only slightly, at most, with depth in the soil profile (West, 1952;Baxter, 1997;Rajver et al., 2006;Garcia-Suarez and Butler, 2006;Oliva et al., 2014), except where there is seasonal soil freezing or permafrost, where Tss{an} may decrease with depth (Goodrich, 1982;Wundram et al., 2010). That is, for non-freezing soils Tss{an}~Tgs{an} and Eq. ...
Shallow soil temperature (Tss) was monitored at many clusters of sites in valley bottom areas, bordering mountain slopes, and subalpine upland areas within the Tahoe Basin of the Sierra Nevada, USA. Objectives of this survey were to: (i) accurately log Tss for an entire year across the panoply of ground surface environments that cover the southern Tahoe Basin area, and (ii) identify the primary factors responsible for inter-site variations in seasonal and annual mean Tss. The Tss data for snow-free and annual mean periods exhibit wider inter-site ranges than published observations for other regions, attributable to the great diversity of ground surface environments sampled. Two energy balance based models of ground surface temperature are introduced, each applicable to a wide variety of surface environments and formulated with regional calibration coefficients that can incorporate effects of seasonal snow-cover on annual mean Tss. The models closely fit summer monthly and annual mean Tss data from most sites, and confirm that the large inter-site range of shading (by vegetation and terrain) is responsible for most of the large inter-site range of observed Tss. Additionally, data and model results strongly suggest spatially heterogeneous soil warming rates in response to regional climate warming, and support the value of resolving spatial variations in Tss for groundwater flow tracing techniques.
... We update data and provide the most extensive and complete review of the thermal regime of a southern massif in Europe, complementing previous works. [18][19][20][21]27,[29][30][31][32][33][34][35] ...
Outside the Alps, the Sierra Nevada is probably the best studied European massif with respect to its past and current environmental dynamics. A multi‐approach research program started in the early 2000s focused on the monitoring of frozen ground conditions in this National Park. Here, we present data on the thermal state and distribution of permafrost and seasonal frozen ground in different sites across the highest areas of the massif. New results confirm the absence of widespread permafrost conditions, with seasonal frost prevailing above 2500 m. Small permafrost patches have been only detected in glaciated areas of the Veleta and Mulhacén cirques during the Little Ice Age at elevations of 3000–3100 m. The remnants of those glaciers are still preserved under the thick debris layer covering the cirque floors. Geomatic and geophysical surveying of a rock glacier existing in the Veleta cirque, together with the monitoring of soil temperature at different depths, have revealed permanently frozen conditions undergoing a process of degradation. In the rest of the massif, a seasonal frost regime prevails, even at the highest plateaus at 3300–3400 m, where annual soil temperatures average 2.5°C. The monitoring of soil temperatures in other different periglacial features has also revealed positive average values ranging between 2°C (inactive sorted‐circles) and 3–4°C (inactive and weakly active solifluction lobes). Consequently, we conclude that the present‐day climatic regime does not allow the existence of permafrost in the Sierra Nevada, and environmental dynamics is controlled by the intensity and duration of seasonal frost in the ground.
... The Sierra Nevada is located in its SE corner next to the Mediterranean Sea (37º 03′ N/3º 22′ W) and forms part of the Betic Range ( Fig. 1 Currently, there are no glaciers in Sierra Nevada and periglacial dynamics prevail between 2600 m and the summits above 3400 m; small permanent snow fields only exist in northern glacial cirques at the foot of the highest peaks . Mean annual air temperatures at 2500 m average 4.4 °C with an annual precipitation of 710 mm, in the form of snow between October and May (1965-1992, Oliva et al. 2014b. At the summit plateaus at 3300-3400 m, the mean annual ground temperature is ~ 0 °C (Oliva et al. 2016a), with negative values in LIA-glaciated environments such as in the Veleta cirque (Gómez-Ortiz et al. 2014). ...
Pleistocene glaciers shaped the highest lands of the National Park of Sierra Nevada, South Spain. Alpine glaciers filled the western valleys of the massif with hundreds of meters of ice. Surface exposure dating shows evidence of glacial expansion during the Younger Dryas and the subsequent disappearance of glaciers of the massif during the Early Holocene. Since then, glacial records and lake sediments reveal that the massif has been ice-free for the most part of the Holocene, with the development of small glaciers during the coldest phases inside the highest northern cirques. This occurred at 2.8–2.7, 1.4–1.2 cal. ka BP and during the Little Ice Age (1300–1850 CE), when documentary sources confirm also the existence of some glaciers at the foot of the highest summits. This historical period was probably the coldest and wettest phase of the Holocene in the massif and recorded the largest glaciers of the current interglacial. Those glaciers finally melted away during the mid-20th century.
... Nevertheless, most contributions to date on the Central Cantabrian Mountains have focused on the search for active processes Frochoso, 1994, 1998;Serrano and González-Trueba, 2004b;González-Trueba, 2007a;Santos-González et al., 2009;González-Trueba and Serrano, 2010b;Santos-González, 2011;Pellitero, 2013;Pisabarro et al., 2015Pisabarro et al., , 2017 and conclude that snow cover is the driver of freeze-thaw cycles (F/Tc) and seasonal frozen grounds (SFG). In this sense, the study of the ground thermal regime (GTR) facilitates the understanding of the capacity of the climate to trigger active periglacial processes and shows it to be a good indicator of snow cover characteristics (Zhang, 2005;French, 2007;Ballantyne, 2018), particularly in the Mediterranean mountains (Vieira et al., 2003;Andrés and Palacios, 2010;Oliva et al., 2014Oliva et al., , 2016 where the snow cover is highly variable in time because of the climatic characteristics of this region. ...
Snowfalls are important meteorological events affecting the physical environment of the Cantabrian Mountains. This work analyzes the effects of snow on several elements such as relief, landforms, ground climate and snowmelt waters. The ground thermal regime and associated parameters were studied using temperature data loggers and satellite images and were described in combination with observed geomorphological processes and landforms. A geomorphological map was drawn up and trends in climate patterns and runoff were calculated. Ground temperature monitoring in warm years is not optimal, though allow to know the limit conditions for developing cold processes. Results show that geomorphological processes are not significant and that solifluction deriving from snowmelt, is the only active process in years without freeze or with thick snow cover. Snowfall evolution in recent decades in correlation with flow water and climate features provide the certainty that snow distribution also affects efficacy in runoff generation and moves the flow peak in rivers due to early snowmelt.
... The first snow accumulation in the fall has a cooling effect on the ground due to the high surface albedo of the fresh snow when the solar radiation is still relatively high. In the spring, the melting snow maintains soil temperature near 0 °C until the ground is completely snow free, at which point the high solar radiation drives a sharp increase in soil temperature (Zhang, 2005;Oliva et al., 2014). The topographically defined snowpack distribution produces a spatial gradient in soil properties (Freppaz et al., 2012). ...
In alpine tundra the influence of snow-cover duration (SCD) and pedoclimatic conditions on soil nutrient forms during the growing season has received little attention. The hypothesis that SCD influences the soil temperature, which in turn can affect the annual changes in topsoil nitrogen (N) and carbon (C) forms, was tested for five growing seasons at three study sites in the alpine tundra of the NW Italian Alps. Among the pedoclimatic conditions studied (soil temperature, soil moisture, and number of freeze/thaw cycles), the mean soil temperature of the growing season was inversely correlated with the SCD (p < 0.01), which ranged from 216 to 272 days. Independently from the soil characteristics (e.g., degree of evolution), the microbial carbon (Cmicr) of the growing season was inversely correlated with the SCD and the mean soil temperature of the snow-covered season, suggesting the consumption of soil resources made by the Cmicr under the snowpack. During the growing season ammonium (N-NH4+), dissolved organic carbon (DOC), and Cmicr were positively correlated with soil temperature and moisture. Path analysis shows that the interannual variability of topsoil N and C forms was significantly controlled by the pedoclimatic conditions recorded in both the snow-covered and the subsequent growing seasons, which in turn were influenced by SCD. Therefore, SCD played a fundamental role in terms of pedoclimatic conditions during the growing season, contributing to explaining the interannual variability of soil N and C forms, and may be a key factor for predicting the nutrient cycling in alpine tundra in the context of a changing climate.
... Most of the study sites of these networks are located in polar and subpolar environments; a wide range of data derived from these initiatives are accessible online (http://gtnp.arcticportal.org/). During the last few years, there has also been an increase of studies on active layer and seasonal frost dynamics in mountain environments, mainly in the major ranges of the world (e.g., Harris et al., 2003;Magnin et al., 2015;Oliva et al., 2014;Pogliotti et al., 2015). As some of these regions are densely populated, new approaches on permafrost and seasonal frost studies are essential to achieve a better understanding of terrestrial ecosystem dynamics in these areas as well as to help mitigate natural hazards associated with ground thermal conditions (Kääb et al., 2005;Fischer et al., 2012). ...
... An exponential increase in studies related to permafrost state has also been observed in mountain environments, especially from highly populated regions (e.g., European Alps) with a major focus on geomorphological hazards (Kääb et al., 2005; Harris et al., 2009 ). In contrast, there is a significant lack of information on soil thermal dynamics in seasonal frost environments, with only a few studies focusing on midlatitude mountain ranges (e.g., Oliva et al., 2014b). Soil thermal regime has major implications for terrestrial ecosystems in cold-climate environments since it comprises the physical, hydrological, geomorphological and biological processes affecting the soils. ...
The Iberian Peninsula is amongst the most elevated regions of Europe and it includes a wide range of glacial landforms and deposits distributed across its main mountain ranges. Today, periglacial processes are only active in the highest mountains, but during Pleistocene cold phases they were widespread across Iberia. A variety of periglacial phenomena developed above the glaciated domain during the Last Glacial Cycle as well as below glacial fronts, even at mid and low-altitude environments in central and NW Iberia, as revealed by geomorphic evidence. Most relict permafrost-related features formed immediately after glacial retreat under paraglacial conditions (e.g. rock glaciers). Periglacial processes have been confined to high altitudes since the onset of the Holocene, and at present are active only above 2000–2200 m in northern Iberian ranges and above 2500 m in the southern Sierra Nevada.
Europe includes a vast surface extent from subtropical to polar latitudes. The rough relief of the continent with several peninsulas, islands, capes, bays and several mountain ranges exceeding 2,500–3,000 m conditions a broad diversity of climate regimes, which has determined the distribution of past and present periglacial dynamics. Quaternary climate variability has favoured an alternation of glacial and periglacial processes in present-day cold-climate areas of the continent, such as mountain regions and high latitudes. In these areas, we found a wide variety of glacial and periglacial features. Regions that were covered by the ice during Pleistocene glacial cycles have subsequently been shaped by periglacial processes which, in some cases, still prevail nowadays. By contrast, periglacial landforms are relict in areas that were affected by periglacial processes during past glacial cycles. Indeed, some of these inherited landforms showed evidence of the past occurrence of permafrost, which is currently limited to the highest mountain areas at ca. 2,500–3,000 m in southern-central Europe decreasing to ca. 800–1,000 m in Iceland and northern Scandinavia. At lower elevations, environmental dynamics in the current periglacial belt in mountain regions are controlled by seasonal frost.
The Mediterranean basin has experienced one of the highest warming rates on Earth over the last decades and climate projections anticipate water-scarcity future scenarios. Mid-latitude Mediterranean mountain areas such as the Pyrenees play a key role in the hydrological resources for intensely populated lowland areas. However, there are still large uncertainties about the impact of climate change on the snowpack in high mountain ranges of the Mediterranean region. Here, we provide a climate sensitivity analysis of the Pyrenean snowpack through five key snow climate indicators. Snow sensitivity is analyzed during compound temperature and precipitation extreme seasons, namely Cold-Dry (CD), Cold-Wet (CW), Warm-Dry (WD) and Warm-Wet (WW) seasons, for low (1500 m), mid (1800 m) and high (2400 m) elevation sectors of the Pyrenees. To this end, a physically-based energy and mass balance snow model (FSM2) is validated by ground-truth data, and subsequently applied to the entire range, forcing perturbed reanalysis climate data for the 1980–2019 baseline scenario. The results have shown that FSM2 successfully reproduces the observed snow depth (HS) values, reaching R2 > 0.8, and relative RMSE and MAE lower than 10 % of the observed HS. Overall, climate sensitivity decreases with elevation and increases towards the eastern Pyrenees. When temperature is progressively warmed at 1 ºC intervals, the largest seasonal HS decreases from baseline climate are found at +1 ºC, reaching values of -47 %, -48 % and -25 % for low, mid and high elevations, respectively. Only an upward trend of precipitation (+10 %) could counterbalance temperature increases (<= 1 ºC) at high elevations during the coldest months of the season, since temperature is far from the isothermal 0 ºC conditions. The maximum (minimum) seasonal HS and peak HS max reductions are observed on WW (CD) seasons. During the latter seasons, the seasonal HS is expected to be reduced by -37 % (- 28 %), -34 % (- 30 %), -27 % (-22 %) per ºC, at low, mid and high elevation areas, respectively. For snow ablation climate indicators, the largest decreases are observed during WD seasons, when the peak HS date is anticipated 10 days and snow duration (ablation) decreases (increases) 12 % per ºC. The results suggest similar climate sensitivities in mid-latitude mountain areas; where significant snowpack reductions are anticipated, with relevant consequences in the ecological and socioeconomic systems.
The Sierra NevadaSierra Nevada was the southernmost massif in Europe hosting glaciersGlaciers during the QuaternaryQuaternary. The remains of those ice masses disappeared in the middle of the twentieth century. The Pleistocene glaciersGlaciers in the Sierra NevadaSierra Nevada remained confined to the high mountains, occupying the headwaters of ravines, with maximum lengths of 6–9 km. During the last decade, Cosmic-Ray Exposure (CRE) dating has complemented previously known geomorphological evidence, shedding new light on the chronology of various phases of glacial expansion and retreat. A moraine development phase occurred prior to the Last Glacial CycleLast Glacial Cycle, around 130 ka, although most depositional and erosive records of glacial origin have been dated to the Last Glacial CycleLast Glacial Cycle. This phase recorded two maximum advance pulses, the first around 30 ka and another of very similar extent at 20–19 ka. Later, the glaciersGlaciers retreated significantly until they advanced again during the Oldest Dryas (17–16 ka). Then, after the almost total disappearance of the ice masses in the Sierra NevadaSierra Nevada during the Bølling–Allerød (15–14 ka), small glaciersGlaciers were formed during the Younger Dryas (12–11 ka). These glaciersGlaciers disappeared at the beginning of the HoloceneHolocene (10–9 ka), generating rock glaciersGlaciers in the recently deglaciated cirques. At the end of the HoloceneHolocene, including the Little Ice AgeLittle Ice Age (LIA, 1300–1850 AD), very small glaciersGlaciers were formed in the shelter of the northern walls of the highest peaks (Mulhacén and Veleta). They disappeared at the end of the LIA, giving rise to incipient rock glaciersGlaciers.
The Sierra Nevada constitutes one of the massifs in Europe where periglacial processes have been more extensively and thoroughly examined. Periglacial phenomena in the massif are distributed from the mountaintops at 3300–3400 m a.s.l. down to elevations of 1100–1200 m. Active periglacial dynamics prevail today above 2500 m with a variety of landforms mostly related to frost shattering, cryoturbation and solifluction processes, among others. Besides, inherited periglacial landforms formed during Quaternary glacial phases are also found in the summit plateaus (i.e. patterned ground features) and valley heads (i.e. inactive rock glaciers). Since the early 2000s, a multi-approach research program has been carried out in the Sierra Nevada to monitor present-day periglacial dynamics and frozen ground conditions in the high lands of this massif. Results show evidence of the key role of seasonal frost driving environmental dynamics above 2500 m. Permafrost is spatially limited, and only confined to the areas that were glaciated during the Little Ice Age (LIA), namely in the Veleta and Mulhacén cirques above 3000–3100 m. Buried ice derived from LIA glaciers and isolated permafrost patches developed subsequently are still preserved under the thick debris mantle distributed across the cirque floors as revealed by the monitoring of soil temperature at different depths in the Veleta cirque. Here, geomatic and geophysical surveys of an incipient rock glacier indicate that permafrost conditions are undergoing a process of degradation. Seasonally frozen ground prevails in the rest of the Sierra Nevada, even at the summit surfaces at 3300–3400 m where mean annual soil temperatures are in the order of ~2.5 °C. In other periglacial landforms, positive temperatures were also recorded, ranging between 2 °C (inactive sorted-circles) and 3–4 °C (inactive and weakly active solifluction lobes).KeywordsSierra NevadaPeriglacial processesPermafrostSeasonal frost
Active layer is a key component for permafrost environment studies as many subsurface biological, biogeochemical, ecological, and pedogenic activities prevail in this layer. This study focuses on active layer temperature monitoring in an area with sporadic permafrost at two adjacent sites along China-Russia Crude Oil Pipeline (CRCOP), North-East China. Site T1 is located in disturbed ground on the right-of-way (on-ROW) 2 m away from the center of the oil pipeline. T2 is located in a natural and undisturbed site, around 16.6 m off-ROW. Our objective was to study seasonal variability of the active layer depth and thermal regime from October 2017 to September 2018. The monitoring sites consist of soil temperature probes arranged in a vertical array at different depths at both sites. The following parameters were computed: number of isothermal days (ID), freezing days (FD), thawing days (TD), freezing degree days (FDD), thawing degree days (TDD), number of freeze-thaw days (FTD). The mean air temperature in the monitoring period reached - 3.2°C. The temperature profile indicates that the maximum active layer thickness observed during the study period was 10 m at T1 and 2 m at T2. The majority of the soil temperatures were above or close to 0°C, resulting in great values of TDD, especially in the first 4 m depth. TDD for T1 were predominant and ranged between 600–1160°C·days (0–4 m depth) reflecting the influence of oil temperature from the pipeline. In T2 borehole FDD were predominant for all the soil layer depths resulting in less permafrost degradation. This comparison emphasizes the significant influence of vegetation removal and the dispersed heat from the pipeline on the active layer thickness.
Three Iberian mountain ranges encompassed glaciers during the Little Ice Age (LIA): the Pyrenees, Cantabrian mountains and Sierra Nevada. The gradual warming trend initiated during the second half of the 19th century promoted the progressive shrinking of these glaciers, which completely melted during the first half of the 20th century in the Cantabrian mountains and Sierra Nevada and reduced by 80% of their LIA extent in the Pyrenees. In these formerly glaciated environments, the transition between glacial and periglacial conditions results in an accelerated paraglacial readjustment, with very active geomorphic processes. Cirque walls generate a large amount of sediments through rock‐falls and slides. LIA moraines, devoid of vegetation and composed of highly unstable sediments, are being intensely mobilized by slope processes. Inside the moraines, the shrinking of LIA glaciers favoured the development of buried ice patches, with permafrost‐related landforms, small periglacial features generated by solifluction and cryoturbation processes and remarkable hydrological changes. Present‐day morphodynamics is mostly related to seasonal frost, though patches of permafrost have formed in contact with the buried ice, undergoing a process of degradation since it is not balanced with present‐day climate. This is reflected in the occurrence of multiple collapses and subsidence of the debris cover where the frozen bodies sit. Next to the small glaciated environments in the highest Pyrenean massifs, there is a permafrost belt undergoing also rapid geomorphic changes. Based on the observed processes, we discuss spatio‐temporal patterns of paraglacial readjustment in Iberian mountains and compare it with other mid‐latitude mountain environments.
Standing corn residue has been proven to reduce wind erosion in Northeast China, but how standing corn residue affects soils during winter remained unclear. Our objective was to compare soil frost depth associated with two zero-tillage methods [i.e., chopping corn stalks into small sections then spread them on soil (hereafter referred to as ‘CCR’) and standing corn residue (hereafter referred to as ‘SCR’)]. Frost tubes were used to determine soil frost depth, and soil heat flux plates were used to measure soil heat flux 8-cm beneath the soil surface. Compared with CCR treatment, SCR reduced maximum soil frost depth significantly (p < 0.05) due to thicker snow cover, which insulated the soil surface from cold winter air. And the thicker snow cover hastened the frozen soil completely thawed approximate 20 days, which has implications for early sowing. Early sowing meant that corn could have longer growing time, which could help long-growing-time corn varieties become maturity before killing frost in cold areas, longer growing time could also result in fully filled grain, and increase economic profit for farmers.
This article was submitted without an abstract, please refer to the full-text PDF file.
The heterogeneity of the Norwegian mountain landscape under investigation led to a multi-scale approach. We combined micro-spatial differentiations within small catchments (micro-scale), altitudinal changes of an oceanic and a continental mountain system (meso-scale), and oceanic-continental alteration between these two mountain regions (macro-scale). We analysed differences between micro-climatic site conditions at the spatial scales given above. It was assumed that different superior meteorological phenomena along altitudinal and regional gradients find their expression in local temperature conditions. It turned out that micro-topographic site conditions were superiorly determining thermal changes along altitudinal and oceanic-continental broad-scale gradients. The adiabatic lapse rate did not show high correlations with local temperature gradients. Regional climatic differences between the oceanic western and the continental eastern mountains were significant by means of local and altitudinal temperature gradients. We used isopleth-diagrams of temperature differences and corresponding histograms between each, site-site, low alpine-middle alpine, and oceanic mountain-continental mountain couples to quantify these over-laying phenomena. As a result we quantified the significance of complex differences of temperature gradients across topography, altitude and region in order to enable micro-climate extrapolation and modelling in high mountain landscapes.
La presente tesis doctoral se integra en los trabajos que el Grupo de Investigación «Paisaje y paleoambientes en la montaña mediterránea», dirigido por el Dr. Antonio Gómez Ortiz, lleva realizado en Sierra Nevada desde finales de los años 80. En áreas protegidas, como es el caso del Parque Nacional de Sierra Nevada, la investigación cumple y debe cumplir un papel clave en la transferencia de conocimiento entre la comunidad científica y la sociedad. Sólo transmitiendo la singularidad de su geodiversidad a la sociedad se podrá valorar en su justa medida las riquezas naturales que sus relieves contienen. En esta línea, la investigación geomorfológica en la Sierra se ha centrado mayormente en el estudio del glaciarismo, con especial incidencia en el Último Máximo Glacial (UMG), por su importancia en el modelado del macizo, y en la Pequeña Edad del Hielo (PEH), por su proximidad temporal. Paralelamente, durante las dos últimas décadas los investigadores han profundizado en el estudio y monitorización de los procesos fríos actuales y su respuesta al incremento térmico registrado durante este intervalo de tiempo. Esta tesis doctoral complementa este conocimiento previo y rellena un vacío cronológico relativo a la evolución cuaternaria del paisaje de cumbres de Sierra Nevada: el Holoceno.
La tesis sintetiza una reconstrucción paleoecológica para los últimos milenios a partir del estudio de dos registros sedimentarios ubicados en el cinturón periglaciar actual: los lóbulos de solifluxión y los sedimentos de las lagunas de alta montaña ofrecen información de las transformaciones ambientales acontecidas en el área cimera durante el pasado. Estos cambios son indicativos de las distintas pulsaciones climáticas holocenas en un ámbito que, por su altura y extensión, se mantuvo fuera del alcance de la actividad antrópica hasta las últimas centurias. Por lo tanto, el área de cumbres de este macizo semiárido es un ámbito especialmente indicado para el estudio de los procesos geomorfológicos y, en extensión, de la variabilidad climática natural acontecida en el sur peninsular durante los últimos 7 ka BP.
Landscape dynamics in the periglacial belt of a high mountain Mediterranean environment is a process of rapid evolution but complex reconstruction. Following this purpose, in this paper we discuss data from two sources concerning the past evolution of the present-day periglacial environment in the Sierra Nevada (southern Iberian Peninsula): mountain lake sediments and documentary sources. La Mosca lake sedimentary record provides information about the palaeocological evolution in the Mulhacén cirque over the last three millennia, while documentary sources enable us to reconstruct the landscape evolution in the high lands of this massif over the last eight centuries. During the late Holocene cold and wet phases have favoured the activity of geomorphic processes, with ephemeral development of glaciers in the highest northern cirques, abundance of late-lying snow patches and a decrease of the vegetation cover in the highest catchments. By contrast, warm periods have been more conducive to geomorphic stability, with an extension of the vegetation grass cover, but without glaciers and with a lower density of snow patches in summer. The comparison of the palaeocological evolution and associated palaeoclimatic conditions in the Sierra Nevada with other regional proxies shows evidence of the moderate sensitivity of the geomorphological processes occurring in the massif during the late Holocene with respect to the climate variability prevailing in the Iberian Peninsula and neighbouring areas. According to lake sedimentary records, the ‘Little Ice Age’ has been the coldest period during the late Holocene. Historical sources suggest a temperature increase of 0.93°C since the middle of the 19th century.
This article discusses the methodology and techniques used in observations of permafrost, which is confined to a small enclave in south-east Spain (Corral del Veleta, Sierra Nevada, 3398 m altitude, 37°03′ N, and 3°22′ W). Several geophysical, geothermal and geomorphologic prospecting techniques were used to locate the permafrost at Corral del Veleta, an area highly sensitive to slight climatic variations, and to study its evolution under marginal conditions. The results from the application of this methodology confirm the location of Europe's southernmost permafrost remnant. Copyright © 2001 John Wiley & Sons, Ltd.
Le présent article discute la méthodologie et les techniques utilisées pour observer le pergélisol qui se trouve dans un petit territoire du sud-est de I'Espagne (Corral del Veleta, Sierra Nevada, 3.398 m d'altitude, 37° 03′ N, 3°22′ W). Différentes techniques de prospection géophysiques, géothermiques et géomorphologiques ont été utilisées pour localiser le pergélisol dans le site de Corral del Veleta, un endroit hautement sensible aux variations climatiques et favorables à l'étude de son évolution sous des conditions marginales. Les résultats de l'application de cette méthodologie confirment qu'il s'agit du lambeau le plus méridional de pergélisol européen. Copyright
The results of the International Permafrost Association's International Polar Year Thermal State of Permafrost (TSP) project are presented based on field measurements from Russia during the IPY years (2007–09) and collected historical data. Most ground temperatures measured in existing and new boreholes show a substantial warming during the last 20 to 30 years. The magnitude of the warming varied with location, but was typically from 0.5°C to 2°C at the depth of zero annual amplitude. Thawing of Little Ice Age permafrost is ongoing at many locations. There are some indications that the late Holocene permafrost has begun to thaw at some undisturbed locations in northeastern Europe and northwest Siberia. Thawing of permafrost is most noticeable within the discontinuous permafrost domain. However, permafrost in Russia is also starting to thaw at some limited locations in the continuous permafrost zone. As a result, a northward displacement of the boundary between continuous and discontinuous permafrost zones was observed. This data set will serve as a baseline against which to measure changes of near-surface permafrost temperatures and permafrost boundaries, to validate climate model scenarios, and for temperature reanalysis. Copyright © 2010 John Wiley & Sons, Ltd.
We present a review of the changing state of European permafrost within a spatial zone that includes the continuous high latitude arctic permafrost of Svalbard and the discontinuous high altitude mountain permafrost of Iceland, Fennoscandia and the Alps. The paper focuses on methodological developments and data collection over the last decade or so, including research associated with the continent-scale network of instrumented permafrost boreholes established between 1998 and 2001 under the European Union PACE project. Data indicate recent warming trends, with greatest warming at higher latitudes. Equally important are the impacts of shorter-term extreme climatic events, most immediately reflected in changes in active layer thickness. A large number of complex variables, including altitude, topography, insolation and snow distribution, determine permafrost temperatures. The development of regionally calibrated empiricalstatistical
models, and physically based process-oriented models, is described, and it is shown that, though more complex and data dependent, process-oriented approaches are better suited to estimating transient effects of climate change in complex mountain topography. Mapping and characterisation of permafrost depth and distribution requires integrated multiple geophysical approaches and recent advances are discussed. We report on recent research into ground ice formation, including ice segregation within bedrock and vein ice formation within ice wedge systems. The potential impacts of climate change on rock weathering, permafrost creep, landslides, rock falls, debris flows and slow mass movements are also discussed. Recent engineering responses to the potentially damaging effects of climate warming are outlined, and risk assessment strategies to minimise geological hazards are described. We conclude that forecasting changes in hazard occurrence, magnitude and frequency is likely to depend on process-based modelling, demanding improved understanding of geomorphological process-response systems and their impacts on
human activity.
This paper contributes to the study of permafrost in the Pyrenees by reporting geoelectrical investigations and thermal measurement on the Little Ice Age (LIA) forefields of two glaciers. The aim was to assess the internal composition of sedimentary bodies (debris rock glaciers and moraine deposits) located in this proglacial environment. Ground ice was prospected using two DC resistivity techniques: vertical electrical soundings and resistivity mapping at a fixed pseudo-depth. Extreme specific resistivities ranging between 1 and 25 MΩ m were detected under a thin (1–2 m) unfrozen layer, indicating the presence of a massive ice layer, certainly buried glacier ice. This ice of glacial origin probably covers former permafrost bodies, i.e. a much thicker layer of perennially frozen sediments. Low subsurface temperatures measured on the deposits indicate that buried glacier ice could have been preserved on top of permafrost since the end of the LIA or earlier Holocene glacier advances. This stratigraphy demonstrates that glaciers and pre-existing perennially frozen sediments (permafrost) were in contact during the LIA. Copyright © 2004 John Wiley & Sons, Ltd.
Mountains make up a significant proportion of the global land mass and of the global permafrost area. Besides mid-latitude
mountain ranges, large proportions of Arctic and Antarctic permafrost are subject to processes and exhibit phenomena that
are typical for mountain permafrost. Natural hazards related to the degradation of permafrost in densely populated mountains
as well as the role of permafrost in landscape evolution make it a fascinating and important research field. This chapter
provides an overview of the most important facts, concepts, and terms related to mountain permafrost and provides key starting
points for further reading.
The permafrost regions currently occupy about one quarter of the Earth's land area.Climate-change scenarios indicate that global warming will be amplified in the polarregions, and could lead to a large reduction in the geographic extent of permafrost.Development of natural resources, transportation networks, and human infrastructurein the high northern latitudes has been extensive during the second half of the twentiethcentury. In areas underlain by ice-rich permafrost, infrastructure could be damagedseverely by thaw-induced settlement of the ground surface accompanying climatechange. Permafrost near the current southern margin of its extent is degrading, andthis process may involve a northward shift in the southern boundary of permafrostby hundreds of kilometers throughout much of northern North America and Eurasia.A long-term increase in summer temperatures in the high northern latitudes couldalso result in significant increases in the thickness of the seasonally thawed layerabove permafrost, with negative impacts on human infrastructure located on ice-richterrain. Experiments involving general circulation model scenarios of global climatechange, a mathematical solution for the thickness of the active layer, and digitalrepresentations of permafrost distribution and ice content indicates potential forsevere disruption of human infrastructure in the permafrost regions in response toanthropogenic climate change. A series of hazard zonation maps depicts generalizedpatterns of susceptibility to thaw subsidence. Areas of greatest hazard potential includecoastlines on the Arctic Ocean and parts of Alaska, Canada, and Siberia in whichsubstantial development has occurred in recent decades.
The geomophic action of the seasonal snow cover on the northeastern slope of Pico Cuina (Sierra de Ancares, Leon province), is described. Mass movement of the snow is responsible for the quarrying of bedrock and the transport of loose clasts to the lower margins of the slope. Such geomorphic activity gives rise to a set of characteristic geoforms such as smoothed surfaces, striae, grooves, crescentic fractures, micro-ridges and protalus ramparts. Mass displacement of the snow cover comprises both fast (full-depth avalanches) and slow (snowslide) movements.
The Picos de Europa massif is the maximun exponent of the Atlantic High Mountain of SW Europe. The present day climate derive initially from its volume and altitude, with peaks of around 2.700 m, and from its geographical location. Its proximity to the Cantabrian Sea, only 20 km away, defines it as an oceanic high mountain massif with wet winters (2.500-3.000 mm/year). Its climate is characterised by warmer temperatures than other Iberian high mountain areas (Pyrenees and Sierra Nevada), and the distribution of snow in time and space, highly abundant, but unstable (wet snow), is a fundamental geoecological factor in the massif. In this work we have analysed the distribution and dynamic of the snow covering depends on factors such as altitude, topography, orientation, exposure and wind redistribution processes. At 1500 m the duration of the snow cover is 6/7 months, whereas at over 2000 m, a duration of around 8 months is estimated, though this is highly variable depending on several factors. The dominant process on the high mountain of Picos de Europa is the nivation, related to karst, solifluction and gelifraction. The duration and distribution of the snow cover dictates the seasonal variations of the meteorization (thermal regulation of the freeze/thaw cycles on the ground), the availability of water on the slopes and the sediment transport. The nivation also is an effective morphological agent.
Current processes of gelifluction and fluvial sediment transfer have been monitored by our research groups for several years in the periglacial altitudinal belt of the southern Hohe Tauern mountain range, central Alps, Austria. These studies furnish information on boundary conditions and forcing factors of the morphodynamic system under observation, and allow the interpretation of its spatio-temporal patterns and oscillations. As one of the main results, a close connection between cryogenic processes and the destruction of vegetation cover, the intensity of gelifluction and also the amount of sediment transfer in the headwater channels can be demonstrated. Through a combination of these results with data on Holocene slope, soil and channel dynamics, projections into the past are made possible and allow, by comparison with the vegetational and glacial history of the area, palaeoclimatic and palaeoecologic reconstructions on a Holocene scale. -from Authors
This paper presents the results of a numerical study of the effects of snow cover on long-term, periodic, steady-state equilibrium ground temperatures. It is shown that mean annual ground temperatures decrease with depth when the soil thermal conductivity is greater in the frozen than in the unfrozen phase. For permafrost conditions the increase in mean annual ground temperatures due to seasonal snow cover is augmented significantly when soil latent heat is present. In seasonal frost cases the calculated depth of frost penetration is extremely sensitive to details of the snow cover buildup. In permafrost cases calculated mean annual temperatures are extremely sensitive to the assumptions made in treating the snow cover. In either case, because it is difficult to model snow cover accurately, the reliability of ground thermal regime computations is adversely affected. Keywords: ground thermal regime, ground temperatures, soil temperatures, numerical model, finite difference, snow cover.
A continuous record is presented of active layer processes at Endalen, Svalbard, over the period 2005–08. The monitored slope has a gradient of around 7° and in 2005, active layer depth was 94 cm, but this increased by around 14 cm over the next three years. The presence of an ice-rich transient layer proved highly significant in determining the timing and profiles of solifluction movement. Frost heaving was 4.2 cm in 2005–06, 6.6 cm in 2006–07 and 3.2 cm in 2007–08, but thaw settlement exceeded frost heave in each year, giving a net total ground surface lowering of 6.2 cm. In winter, segregation ice was concentrated within the upper and lower active layer, leaving the central parts ice-poor. During the summers of 2006 and 2008, thawing of the transient layer was associated with artesian pore pressures at 90 cm depth and basal soil shearing, but in 2007, when the thaw front failed to reach the ice rich basal zone, pore pressures during thaw were sub-hydrostatic and no basal shearing was observed. Solifluction shear strain during thaw settlement resulted in downslope surface displacements of 2.3 cm in 2005–06, 1.2 cm in 2006–07 and 1 cm in 2007–08. Copyright © 2011 John Wiley & Sons, Ltd.
The Posets massif is located in the Central Pyrenees and reaches a height of 3363 m a.s.l. at the Posets peak, the second highest massif in the Pyrenees. Geomorphological maps of scales 1:25000 and 1:10000, BTS (bottom temperature of winter snow), ground measurements and snow poles were used to observe the more representative periglacial active landform association, ground thermal regime, the winter snow cover evolution and basal temperatures of snow. The main active periglacial landforms and processes related to the ground thermal regime and snow cover were studied. Mountain permafrost up to 2700 m a.s.l. on northexposed slopes and up to 2900 m a.s.l. on south-exposed slopes were detected. Three permafrost belts were differentiated: sporadic permafrost between 2700 and 2800 m a.s.l. and between 2850 and 3000 m a.s.l., discontinuous permafrost between 2800 and 2950 and between 2950 and 3050, and continuous permafrost up to 2900 m a.s.l. and up to 3050 m a.s.l. on northern and southern slopes, respectively.
Cosmogenic 36Cl surface exposure dating was carried out on 19 samples from glacially polished bedrock, rock glaciers and moraines of four glaciated valleys with different orientations in the Sierra Nevada (Spain) around Pico del Veleta (37° 3′N 3° 21′W, 3398 m asl). Remains of moraines older than the global Last Glacial Maximum exist, but their poor preservation makes them an unreliable subject for surface exposure dating. Results show that the last local glacial maximum advance took place earlier than the global Last Glacial Maximum, but within the MIS 2, although additional dating is needed to confirm this. Exposure ages from bedrock steps show a general glacier retreat in progress by 15–14 ka. Shortly afterwards an extensive system of rock glaciers formed at the base of the valley headwalls, with the most recent rock glacier lasting until 7 ka ago. From their location, morphology and analysis of other proxies, we interpret their origin as related to the deglaciation process and marked instability of cirque headwalls, rather than to extreme periglacial conditions. A recent similar occurrence was the transformation of the Little Ice Age glacier on the north face of the Pico del Veleta into a rock glacier under temperate high mountain climatic conditions.
Landscape dynamics in the periglacial belt of a high mountain Mediterranean environment is a process of rapid evolution but complex reconstruction. Following this purpose, in this paper we discuss data from two sources concerning the past evolution of the present-day periglacial environment in the Sierra Nevada (southern Iberian Peninsula): mountain lake sediments and documentary sources. La Mosca lake sedimentary record provides information about the palaeocological evolution in the Mulhacén cirque over the last three millennia, while documentary sources enable us to reconstruct the landscape evolution in the high lands of this massif over the last eight centuries. During the late Holocene cold and wet phases have favoured the activity of geomorphic processes, with ephemeral development of glaciers in the highest northern cirques, abundance of late-lying snow patches and a decrease of the vegetation cover in the highest catchments. By contrast, warm periods have been more conducive to geomorphic stability, with an extension of the vegetation grass cover, but without glaciers and with a lower density of snow patches in summer. The comparison of the palaeocological evolution and associated palaeoclimatic conditions in the Sierra Nevada with other regional proxies shows evidence of the moderate sensitivity of the geomorphological processes occurring in the massif during the late Holocene with respect to the climate variability prevailing in the Iberian Peninsula and neighbouring areas. According to lake sedimentary records, the ‘Little Ice Age’ has been the coldest period during the late Holocene. Historical sources suggest a temperature increase of 0.93°C since the middle of the 19th century.
The presence of seasonal snow cover during the cold season of the annual air temperature cycle has significant influence on the ground thermal regime in cold regions. Snow has high albedo and emissivity that cool the snow surface, high absorptivity that tends to warm the snow surface, low thermal conductivity so that a snow layer acts as an insulator, and high latent heat due to snowmelt that is a heat sink. The overall impact of snow cover on the ground thermal regime depends on the timing, duration, accumulation, and melting processes of seasonal snow cover; density, structure, and thickness of seasonal snow cover; and interactions of snow cover with micrometeorological conditions, local microrelief, vegetation, and the geographical locations. Over different timescales either the cooling or warming impact of seasonal snow cover may dominate. In the continuous permafrost regions, impact of seasonal snow cover can result in an increase of the mean annual ground and permafrost surface temperature by several degrees, whereas in discontinuous and sporadic permafrost regions the absence of seasonal snow cover may be a key factor for permafrost development. In seasonally frozen ground regions, snow cover can substantially reduce the seasonal freezing depth. However, the influence of seasonal snow cover on seasonally frozen ground has received relatively little attention, and further study is needed. Ground surface temperatures, reconstructed from deep borehole temperature gradients, have increased by up to 4°C in the past centuries and have been widely used as evidence of paleoclimate change. However, changes in air temperature alone cannot account for the changes in ground temperatures. Changes in seasonal snow conditions might have significantly contributed to the ground surface temperature increase. The influence of seasonal snow cover on soil temperature, soil freezing and thawing processes, and permafrost has considerable impact on carbon exchange between the atmosphere and the ground and on the hydrological cycle in cold regions/cold seasons.
The Argualas rock glacier is located on the southern side of the Central Pyrenees (Argualas massif). Vertical electric sounding, debris surface analysis and a topographic survey were performed on this rock glacier between 1991 and 2000. High precision measurement records were obtained using a total station. Horizontal and vertical movements of the rock glacier were measured by means of sixteen steel rods. Horizontal and vertical angles and distances to each rod were measured from three stations on a bedrock ridge. Total and annual average displacements were derived from the emergence value and the horizontal displacement of each rod. Then the horizontal and vertical displacement rates in different sectors of the rock glacier were compared. The inferred surface deformation was characterized by both extensional and compressive flows as well as thinning of the frozen body. The displacement rates showed temporal variations related to atmospheric thermal changes, pointing to a high sensibility of the rock glacier.
Variations in ground thermal regime were studied over a small area in the east-central part of the Mackenzie Delta, Northwest Territories, about 50 km northwest of Inuvik. Vegetation shows a successional sequence related to river migration and there is a complex interaction between vegetation, topography, and microclimate.Measurements from five sites show that significant differences in thermal regime exist beneath various types of vegetation. There is a general decrease in mean annual ground temperatures with increasing vegetation. The mean annual air temperature in this area is −9 °to −10 °C, but microclimatic factors lead to mean surface temperatures of between 0 °C and −4.2 °C.In summer, variations in net radiation account for the differences in ground thermal regime at the three sites on the slip-off slope. At the other two sites a surface layer of moss and peat leads to small values in ground heat flux and is instrumental in maintaining lower temperatures there. Removal of 10 cm of organic material at one site led to an increase of 3 °C in the mean daily 10 cm temperature.In winter, on the slip-off slope, variations in snow accumulation lead to ground temperature variations greater than those due to vegetation per se. Spatial variation of about 20 °C in ground surface temperature was measured in March 1970; during July and August 1970 the maximum spatial variation observed was only 10 °C. Differences of up to 6 °C in 1 m temperatures were measured over a distance of only 12 m. Snow cover is a permafrost-controlling factor in this area; where accumulations are greatest a talik has formed due to the insulating effect of deep snow.
The seasonal changes in soil temperature at 5 cm below the surface were moni- tored on an upper windy ridge (2675 m a.s.l.) and lower leeward slope (2640 m a.s.l.) in Pinus pumila scrub on Mt. Shogigashira in central Japan, from October 2001 to September 2002. The scrub heights were ca. 20 cm and 100 cm on the upper windy ridge and lower lee- ward slope, respectively. The soil temperature on the upper windy ridge decreased from the autumn to mid-February and increased thenceforth. The soil temperature was sometimes lower than -10˚C in winter. In contrast, the soil temperature on the lower leeward slope was relatively stable at about -1˚C during the winter. It appears that accumulation of snow pre- vented cooling of the soil surface. In the snow-free period, the daily maximum soil-tempera- ture was higher on the upper windy ridge than on the lower leeward slope. This difference was evident in May after the snowmelt, and decreased gradually toward the autumn. The solar radiation was highest at around the summer solstice. Much solar radiation penetrated to the soil surface on the upper windy ridge because of its poorly developed canopy, which increased the soil temperature. Thus, this study shows that seasonal changes in soil tempera- ture are different between the upper windy ridge and lower leeward slope due to snow accu- mulation, canopy development and seasonal changes in solar radiation.
Sierra Nevada is a protected mountain in the Iberian Peninsula classified as a Biosphere Reserve (1986), Natural Park (1989) and National Park (1999). All these environmental protection programmers are a consequence of its unique landscape in the context of the mid-latitude semiarid mountains, with enclaves of exceptional scientific and cultural value. Thanks to its high altitude, Sierra Nevada held the southernmost Quaternary glaciers in Europe, as well as it happened during the Little Ice Age. In turn, Sierra Nevada is also singular thanks to its vast cultural heritage, since very early societies settled on its
slopes and valleys and accommodate their lifestyles and economy to the characteristics of this mountain environment. Currently, Sierra Nevada has become an important tourist centre and receives a large amount of visitors. This process of change has conditioned the implementation of a different economic model: it brings benefits to the populations but it involves changes in the landscape as well, sometimes questionable. From this perspective, a critical revision of the legislation is required balancing the sustainable
economic development of the population and the preservation and safeguarding of the heritage values of the landscape. With this goal, we suggest creating and implementing the Sites of Geomorphological Interest.
Air and shallow ground temperatures from two monitoring sites at the Serra da Estrela (Portugal) are analysed. The Cântaro Gordo site is located at 1875 m ASL and the Fraga das Penas at 1640 m ASL. The climate of the study area is Mediterranean and very irregular, both on a yearly and monthly basis. This is particularly significant during winter, when differences in snow cover have direct influence on the ground thermal regimes and therefore on geocryological processes. To assess the significance of the ground thermal regimes for the geomorphological dynamics, bi-hourly records of temperature are studied at a daily basis. Eight types of daily regime were identified: isothermal unfrozen, non-isothermal unfrozen, surficial freeze – thaw, surficial freeze – thaw and subsurficial frost, surficial and subsurficial freeze – thaw, subsurficial frost, surficial and subsurficial frost and surficial frost but no daily rhythm. The occurrence of these regimes is analysed and their geomorphological significance is presented. Based on the altitudinal differences of the two monitoring sites, on the occurrence of the different regimes and on field observations, a conceptual model for the altitudinal and seasonal zoning of the daily thermal regimes of the ground is presented. This model was prepared for the Serra da Estrela, but it can be used in other Mediterranean or tropical areas if altitude and seasonal precipitation differences are taken in explanation. D 2002 Elsevier Science B.V. All rights reserved.
This paper examines a statistical relationship between air temperature, snow cover and its basal temperature in the zone of sporadic permafrost occurrence in the Tatra Mountains of Poland and Slovakia. A two-year record was analysed containing daily values of air temperature and snow cover depth at a reference station, and also winter ground surface temperature at 5 sites located in different topographic conditions. Correlation coefficients between the daily basal temperature of snow cover and mean air temperature or/and snow depth from previous days were calculated. The results show that inter-seasonal changes of winter ground surface temperature may be related both to changes in snow depth and air temperature in winter, and to air temperature changes in snow-free period. We infer that snow cover is an important but not necessarily a critical factor determining sporadic permafrost occurrence in the Tatra Mountains.
Numerous solifluction landforms in two valleys of the western part of the Sierra Nevada range in the southern Iberian Peninsula were classified according to morphology and used to reconstruct solifluction activity for the Late Holocene. Lobes are almost inactive under the current semiarid climate and water availability appears to be the crucial control on activity within the high-elevation study areas. The presence of numerous inactive solifluction lobes suggests that past climate conditions must have been more favourable for lobe development. Chronostratigraphic profiles of several lobes indicate that colder and/or wetter periods (e.g. the Little Ice Age) tend to promote slope movements, with sparser vegetation cover and higher solifluction rates whereas a denser vegetation cover spreads across valley floors and soils develop during warmer periods (e.g. the Medieval Warm Period). Copyright © 2009 John Wiley & Sons, Ltd.
Climate variability during the Mid-Late Holocene has influenced the activity of geomorphic processes in the current periglacial belt of the Sierra Nevada. We studied two types of sedimentary records that reveal a synchronous timing for slope instability in this high semi-arid massif: solifluction landforms and mountain lake sediments. Lithological and sedimentological properties of both records have recorded numerous cycles of different magnitude of slope processes in the massif. Solifluction deposits record seven phases of solifluction activity and soil development during the last 7 ka bp and lake sediments show evidence of eight periods with increased geomorphic activity in the catchments over the last 6 ka bp. Although present-day climate conditions do not promote active solifluction processes in the Sierra Nevada, colder and wetter periods during the Holocene triggered solifluction and transported coarse-grained sediments into the lakes. By contrast, warm phases favoured soil formation and spread an incipient vegetation cover over the headwaters of the highest valleys, diminishing the grain size of the particles reaching the lakes. Lake sediments record an aridification trend in the massif intensifying since 4·2 ka bp that has conditioned solifluction activity to shift gradually to higher elevations. During major cooler phases such as the Little Ice Age active solifluction was recorded back down to 2500 m altitude. Copyright © 2010 John Wiley & Sons, Ltd.
A large number of radiocarbon dates from charcoal layers buried beneath stacked solifluction lobes at Pippokangas, in the northern boreal zone of Finnish Lapland, are used to reconstruct a Holocene history of solifluction. Although the site is surrounded by Scots pine forest, the solifluction lobes occur on the lower slopes of a kettle hole, the microclimate of which prevents the growth of trees. Samples from the upslope end of charcoal layers have enabled the recognition of four synchronous phases of solifluction lobe initiation: 7400–6700, 4200–3400, 2600–2100 and 1500–500 cal. yr BP. Rates of lobe advance are shown to be lobe-dependent and age-dependent: initially, average rates were commonly 0.14–0.19 cm yr−1, later falling to 0.02–0.07 cm yr−1 or less as the lobes approached the bottom of the slope. The absence of charcoal prior to 8000 cal. yr BP, together with single IRSL and TL dates, indicate a relatively stable early Holocene landscape. The onset of solifluction around 7400 cal. yr BP. appears to have followed the immigration of pine around the site, which increased the frequency of forest fires. Phases of solifluction activity seem to have been triggered by millennial-scale variations in effective moisture (the climatic hypothesis), rather than episodic burning of the surface vegetation cover (the geoecological hypothesis), although climate may also have affected fire frequency and severity. Copyright © 2005 John Wiley & Sons, Ltd.
Two sets of small-scale centrifuge experiments were undertaken to simulate solifluction processes associated with one-sided freezing (with no permafrost) and two-sided freezing (with permafrost) within an active layer 0.8–0.9 m thick at the prototype scale. Models were frozen on the laboratory floor under normal acceleration due to gravity and thawed in the centrifuge under an acceleration of 10 gravities. In the one-sided freezing experiment, ice segregation was concentrated near the surface, whereas in the two-sided model it also caused an ice-rich transition zone to form near the base of the active layer. After repeated freeze-thaw cycles the one-sided experiment revealed concave downslope profiles of movement with shear strain decreasing with depth, whereas in the two-sided experiment, convex downslope profiles indicated the greatest shear strain in the basal part of the active layer. Although smaller surface velocities were measured in the two-sided experiment, higher volumetric velocities developed. The centrifuge experiments showed displacement rates similar to field measurements and analogous to full-scale laboratory experiments. Copyright © 2008 John Wiley & Sons, Ltd.
Changes in the ground thermal regime in high-latitude cold regions have important consequences for surface and subsurface hydrology, the surface energy and moisture balance, carbon exchange, as well as ecosystem diversity and productivity. However, assessing these changes, particularly in light of significant atmospheric and terrestrial changes in recent decades, remains a challenge owing to data sparseness and discontinuous observations. The annual freezing and thawing index can be useful in evaluating permafrost and seasonally frozen ground distribution, has important engineering applications, and is a useful indicator of high-latitude climate change. The freezing/thawing index is generally defined based on daily observations, which are not readily available for many high-latitude locations. We thus employ monthly air temperatures, and provide an assessment of the validity of this approach. On the basis of a comprehensive relative error (RE) evaluation we find that our methodology introduces errors of less than 5% for most high-latitude land areas, and works well in many midlatitude regions as well. We evaluate a suite of gridded monthly temperature datasets and select the University of East Anglia's Climatic Research Unit (CRU) temperature product, available for 1901–2002. We are thus able to provide a continuous long-term 25 km × 25 km gridded Northern Hemisphere freezing/thawing index. Long-term climatologies of the freezing/thawing index delineate the cold regions of the Northern Hemisphere, as well as areas of seasonally frozen ground and permafrost. Objective trend analysis indicates that in recent decades, no significant changes have occurred in Russian permafrost regions; however, seasonally frozen ground areas are experiencing significant warming trends. Over North America, Canadian and Alaskan permafrost regions are experiencing a decrease in freezing index during the cold season, while coastal areas and eastern Canada are seeing significant increase in warm season thawing index. Copyright © 2006 Royal Meteorological Society.
This paper provides a snapshot of the permafrost thermal state in the Nordic area obtained during the International Polar Year (IPY) 2007–2009. Several intensive research campaigns were undertaken within a variety of projects in the Nordic countries to obtain this snapshot. We demonstrate for Scandinavia that both lowland permafrost in palsas and peat plateaus, and large areas of permafrost in the mountains are at temperatures close to 0°C, which makes them sensitive to climatic changes. In Svalbard and northeast Greenland, and also in the highest parts of the mountains in the rest of the Nordic area, the permafrost is somewhat colder, but still only a few degrees below the freezing point. The observations presented from the network of boreholes, more than half of which were established during the IPY, provide an important baseline to assess how future predicted climatic changes may affect the permafrost thermal state in the Nordic area. Time series of active-layer thickness and permafrost temperature conditions in the Nordic area, which are generally only 10 years in length, show generally increasing active-layer depths and rising permafrost temperatures. Copyright © 2010 John Wiley & Sons, Ltd.
This paper presents multi-year measurements of solifluction, frost heave and the concurrent thermal and hydrological regimes at two solifluction lobes with seasonal frost in the eastern Alps, Austria. The monitoring system included a new solifluction meter and time-domain-reflectometry (TDR) probes to measure the unfrozen water content of the soil. Three phases of ground thermal and hydrological conditions were identified, each with distinct consequences for soil movements. Rapid frost heave occurred during initial ground freezing in early winter. Freezing intensity and maximum frost penetration are strongly influenced by snow drifting in that period. Another period of marked heaving during spring snowmelt is attributed to meltwater infiltration into the frozen ground. Solifluction commenced at high water contents with the beginning of thaw settlement and was enhanced by daily fluctuations of snowmelt and lateral influx of meltwater. Slow movements continued, or even started, after complete thawing of the ground as long as lateral runoff from snow patches upslope elevated soil water contents. Copyright © 2003 John Wiley & Sons, Ltd.
A turf-banked solifluction lobe was instrumented for the continuous recording of surface and internal movement, thaw settlement, soil volumetric moisture content and thermal conditions during the spring and summer of 2002. Strain probe measurements showed that gelifluction occurred as a series of discrete and abrupt displacements near the thaw plane, followed by retrograde movement. Most gelifluction events took place when thaw rates were high and the soil was saturated almost to the surface, but rain was also capable of inducing gelifluction at depth. The rapid and localized character of the observed displacements suggests that gelifluction results from micro-shearing of the soil, possibly along the interface of thawing ice lenses. Copyright © 2005 John Wiley & Sons, Ltd.
The Mediterranean Region has many morphologic, geographical, historical, and societal characteristics, which make its climate scientifically interesting. The concept of Mediterranean climate is characterized by mild wet winters and warm to hot, dry summers and occur on the west side of continents between about 30° and 40° latitude. However, the presence of a relatively large mass of water is unique to the actual Mediterranean region. The Mediterranean Sea is a marginal and semi-enclosed sea; it is located on the western side of a large continental area and is surrounded by Europe to the North, Africa to the South, and Asia to the East. The chapter discusses that the climate of the Mediterranean region is to a large extent forced by planetary scale patterns. The time and space behavior of the regional features associated with such large-scale forcing is complex. Orography and land–sea distribution play an important role establishing the climate at basin scale and its teleconnections with global patterns. Different levels of services of readiness to emergencies, technological, and economic resources are likely to result in very different adaptation capabilities to environmental changes and new problems. The different economic situations and demographic trends are likely to produce contrasts and conflicts in a condition of limited available resources and environmental stress.
Field data on the rates of solifluction and associated parameters are compiled from the literature, in an attempt to evaluate factors controlling the spatial variability in solifluction processes and landforms, with special attention on the climate–solifluction relationship. The analyzed data originate from 46 sites over a wide range of periglacial environments, from Antarctic nunataks to tropical high mountains. Solifluction, broadly defined as slow mass wasting resulting from freeze–thaw action in fine-textured soils, involves several components: needle ice creep and diurnal frost creep originating from diurnal freeze–thaw action; annual frost creep, gelifluction and plug-like flow originating from annual freeze–thaw action; and retrograde movement caused by soil cohesion. The depth and thickness of ice lenses and freeze–thaw frequency are the major controls on the spatial variation in solifluction processes. Near the warm margin of the solifluction-affected environment, diurnal freeze–thaw action induces shallow but relatively rapid movement of a superficial layer 5–10 cm thick on average, often creating the thin stone-banked lobes typically seen on tropical high mountains. In addition to diurnal movement, annual frost creep and gelifluction may occur on slopes with soil climates of seasonal frost to warm permafrost, dislocating a soil layer shallower than 60 cm at a rate of centimeters per year and eventually producing medium-size solifluction lobes. In High-Arctic cold permafrost regions, two-sided freezing can induce plug-like flow of a soil mass 60 cm or thicker. The correlation between process and landform suggests that the riser height of lobes is indicative of the maximum depth of movement and prevailing freeze–thaw type. Climate change may result in new different ground freezing conditions, thereby influencing the surface velocity and maximum depth of soil movement. Soil moisture and topography also control solifluction. High moisture availability in the seasonal freezing period enhances diurnal freeze–thaw action and subsequent seasonal frost heaving. The latter contributes to raising the moisture content of the thawed layer and promotes gelifluction during the thawing period. The slope angle defines the upper limit of the surface velocity of solifluction. A diagram correlating the potential frost creep with the actual surface velocity permits an inter-site comparison of the relative magnitude of solifluction components. Physically based modelling of periglacial slope evolution requires synthetic and more detailed field monitoring and laboratory simulations of solifluction processes.
One of the distinguished efforts of A.L. Washburn was to reconstruct mean annual air temperature using periglacial features as climate indicators. This paper reviews existing periglacial indicators and proposes a strategy to improve their thermal resolution based on recent periglacial process studies, with a focus on solifluction and thermal contraction cracking and associated landforms/structures. Landforms resulting from solifluction reflect both the depth subjected to freeze–thaw and the thickness of frost-susceptible soils. The thickness of a solifluction structure can be used to infer the dominant freeze–thaw regime and minimum seasonal frost depth. Ice-wedge pseudomorphs have limited potential as a climate indicator because (1) they mainly reflect extreme winter temperatures, (2) their thermal thresholds depend on the host material, and (3) they need to be distinguished from frost wedges of other origin produced under different thermal and/or material conditions. Monitoring studies of currently active ice wedges suggest that ice-wedge cracking requires a combination of low temperature and large temperature gradients in the frozen active layer. Further field monitoring of periglacial processes and their controlling factors under various climate conditions and in various materials are needed, however, to improve the resolution of periglacial paleoclimate indicators.
Snow cover distribution strongly affects soil temperatures and, thus, plays a decisive role in determining permafrost distribution patterns. Redistribution of snow by avalanches and snow drift significantly affects the snow-melt pattern and soil temperatures in steep avalanche slopes of high mountain areas. At Flüela Pass, 2380 m a.s.l., eastern Swiss Alps, the presence and origin of permafrost that occurs at the base of an avalanche-affected slope below the regional lower limit of discontinuous permafrost was studied by field investigations and numerical simulations. Local permafrost distribution has been determined in former studies by applying geophysical methods and this was confirmed with two boreholes drilled at the slope base and in the avalanche starting zone. Temperature measurements confirm the presence of a 10 m thick permafrost body with temperatures close to the freezing point at the slope base. Numerical simulations of different snow-cover scenarios for 2002/03 demonstrate the particular effect on soil temperatures of high snow drift accompanying intense snow falls in early winter, controlling the duration of constant zero temperatures at the base of the snow pack at the beginning of the snow period. Copyright © 2004 John Wiley & Sons, Ltd.
Solifluction lobes and rock glaciers show similar geometry with a wide range of sizes. Morphometric analysis classifies these lobate landforms in the eastern Swiss Alps into five subgroups. A bouldery rock glacier has an active layer composed of matrix-free boulders, whereas a pebbly rock glacier consists of matrix-supported debris derived from less resistant rocks. Both move by permafrost creep at 5–30 m depth, but the former tends to have a longer tread. A high solifluction lobe, having a riser 0.2–3 m high, originates mainly from annual gelifluction operating within the top 0.5 m of sediment, and its variation, a mudflow-affected high solifluction lobe, occurs where prolonged snowmelt triggers a rapid flow of the thawed surficial layer. A low solifluction lobe has a riser up to 0.2 m high and occurs where thin fine-grained debris responds mainly to diurnal frost creep. These lobes show, on the whole, positive relations between the tread length (L), width (W ) and the riser height (H ). However, a regression analysis separates the rock glaciers from the solifluction lobes by a distinct gap at W (or L)=30 m and H=3 m and provides different regression lines for the two populations. The morphometry primarily determined by the transport process is H, which approximates or slightly exceeds the maximum depth of movement. The depth of movement also affects the horizontal extent of a moving mass, which defines W. A lobe appears where horizontal homogeneity exceeds 3H, and advances with time until reaching a maximum L controlled by climatic or dynamic conditions. Lobe morphometry can be used as an environmental indicator. Copyright © 2005 John Wiley & Sons, Ltd.
Results obtained during the International Polar Year (IPY) on the thermal state of permafrost and the active layer in the Antarctic are presented, forming part of ANTPAS (‘Antarctic Permafrost and Soils’), which was one of the key projects developed by the International Permafrost Association and the Scientific Committee for Antarctic Research for the IPY. The number of boreholes for permafrost and active-layer monitoring was increased from 21 to 73 during the IPY, while CALM-S sites to monitor the active layer were increased from 18 to 28. Permafrost temperatures during the IPY were slightly below 0°C in the South Shetlands near sea-level, showing that this area is near the climatic boundary of permafrost and has the highest sensitivity to climate change in the region. Permafrost temperatures were much lower in continental Antarctica: from the coast to the interior and with increasing elevation they ranged between −13.3°C and −18.6°C in Northern Victoria Land, from −17.4°C to −22.5°C in the McMurdo Dry Valleys, and down to −23.6°C at high elevation on Mount Fleming (Ross Island). Other monitored regions in continental Antarctica also showed cold permafrost: Queen Maud Land exhibited values down to −17.8°C on nunataks, while in Novolazarevskaya (Schirmacher Oasis) at 80 m a.s.l. the permafrost temperature was −8.3°C. The coastal stations of Molodeznaya at Enderby Land showed permafrost temperatures of −9.8°C, Larsemann Hills – Progress Station in the Vestfold Hills region – recorded −8.5°C, and Russkaya in Marie Byrd Land, −10.4°C. This snapshot obtained during the IPY shows that the range of ground temperatures in the Antarctic is greater than in the Arctic. Copyright © 2010 John Wiley & Sons, Ltd.
The permafrost monitoring network in the polar regions of the Northern Hemisphere was enhanced during the International Polar Year (IPY), and new information on permafrost thermal state was collected for regions where there was little available. This augmented monitoring network is an important legacy of the IPY, as is the updated baseline of current permafrost conditions against which future changes may be measured. Within the Northern Hemisphere polar region, ground temperatures are currently being measured in about 575 boreholes in North America, the Nordic region and Russia. These show that in the discontinuous permafrost zone, permafrost temperatures fall within a narrow range, with the mean annual ground temperature (MAGT) at most sites being higher than −2°C. A greater range in MAGT is present within the continuous permafrost zone, from above −1°C at some locations to as low as −15°C. The latest results indicate that the permafrost warming which started two to three decades ago has generally continued into the IPY period. Warming rates are much smaller for permafrost already at temperatures close to 0°C compared with colder permafrost, especially for ice-rich permafrost where latent heat effects dominate the ground thermal regime. Colder permafrost sites are warming more rapidly. This improved knowledge about the permafrost thermal state and its dynamics is important for multidisciplinary polar research, but also for many of the 4 million people living in the Arctic. In particular, this knowledge is required for designing effective adaptation strategies for the local communities under warmer climatic conditions. Copyright © 2010 John Wiley & Sons, Ltd.