Freeze-thaw cycles and associated geomorphology in a post-glacial environment:current glacial,paraglacial,periglacial and proglacial scenarios at Pico de Orizaba volcano,Mexico

The glacial history of Pico de Orizaba indicates that during the Last Glacial Maximum,its icecap covered up to~3000 m asl;due to the air temperature increasing,its main glacier has retreated to 5050 m asl.The retraction of the glacier has left behind an intense climatic instability that causes a high frequency of freeze-thaw cycles of great intensity;the resulting geomorphological processes are represented by the fragmentation of the bedrock that occupies the upper parts of the mountain.There is a notable lack of studies regarding the fragmentation and erosion occurring in tropical high mountains,and the associated geomorphological risks;for this reason,as a first stage of future continuous research,this study analyzes the freezing and thawing cycles that occur above 4000 m asl,through continuous monitoring of surface ground temperature.The results allow us to identify and characterize four zones:glacial,paraglacial,periglacial and proglacial.It was found that the paraglacial zone presents an intense drop of temperature,of up to~9℃ in only sixty minutes.The rock fatigue and intense freeze-thaw cycles that occur in this area are responsible for the high rate of rock disintegration and represent the main factor of the constant slope dynamics that occur at the site.This activity decreases,both in frequency and intensity,according to the distance to the glacier,which is where the temperature presents a certain degree of stability,until reaching the proglacial zone,where cycles are almost non-existent,and therefore there is no gelifraction activity.The geomorphological processes have resulted in significant alterations to the mountain slopes,which can have severe consequences in terms of risk and water.

Evaluation of periglacial landforms and formation of soil properties on the Mount Honaz,SW Türkiye

The main aim of this study is to explain periglacial processes on the summits of Mount Honaz(2571 m a.s.l.),define periglacial landforms,and determine the relationships between morphometric features and topographic factors.Mud circles,stony earth circles,non sorted steps,and non sorted stripes were identified on the summits of Mount Honaz.Pearson's correlation coefficient(r)and linear regression analyses were performed by taking metric measurements from 125 periglacial landforms to describe their morphometric features(length,width,height)of periglacial landforms and explain the relationships between them and topographic factors(elevation,slope).To explain the relationships between periglacial landforms and soil properties,soil samples from 11 periglacial landforms were taken and analysed.Periglacial landforms,which continue to develop on the summits of Mount Honaz today,have been evaluated with present climate data.Analysis of soil samples indicates a notable impact of parent material on the genesis of periglacial landforms.The high ratio of organic matter in mud circle and non sorted step landforms and the high lime ratio in stony earth circle landforms prove a strong relationship between the formation mechanisms of landforms and the soil properties.Furthermore,it is consistent with the findings obtained from the analysis that severe periglacial processes and washing and scavenging events are experienced more on the northern slopes.

Glacial reconstruction and periglacial dynamics at the end of Late Pleistocene on the surface of Cofre de Perote volcano,México:a climatological retrospective

Despite being within the intertropical region of the planet,the Mexican territory still has glacier-covered mountains.In recent decades,important advances have been made in studies on glaciology and periglacial environment in Mexico both for current and past conditions.However,in spite of Cofre de Perote volcano(4200 m a.s.l.)being a strategically located mountain,it has not yet been studied in regards to the glacial and periglacial processes;in fact,those dynamics have modified the mountain massifs in the past.To complement the series of studies on glacial history in the high mountain environment of México,this study reconstructs the glacial cover and the periglacial environment of the volcano surface during the final stage of the Late Pleistocene based on climatic retrospective and through the identification of geomorphological features.The findings indicate the existence of a large glacier(ice cap)that covered the northern,western,and southern slopes of the mountain;while in the eastern sector there were two small glaciers,one being of cirque type,and the other of valley type.The current temperature conditions prevent the occurrence of permanent ice bodies;at the same time,it was found that the periglacial blockfields of the slopes is a legacy of the climatic conditions that prevailed at the end of Late Pleistocene.

Frozen ground and periglacial processes relationship in temperate high mountains: a case study at Monte Perdido-Tucarroya area(The Pyrenees, Spain)

Seasonally frozen ground,mountain permafrost and cryogenic geomorphological processes are important components of the Pyrenean high mountains.This work presents the results of a study on the distribution of frozen ground in a marginal and paraglacial environment of temperate mountains.An inventory was made of landforms and indicators of frozen ground,and frozen ground was mapped accordingly.During 2014 and 2016 ground temperatures and thermal regimes were monitored,basal temperatures of snow-cover(BTS)were measured and a thermal map was drawn.Differential thermal behaviours were detected among different elevations and slope orientations.Periglacial processes are the most widespread,in which frost weathering and nivation,together with gelifluction and cryoturbation,are the most efficient processes;the latter two are generally linked to the presence of frozen ground.The fall in air and ground temperatures with altitude,slope orientations,and snowpack thickness and evolution determine ground thermal regimes.In the study area,three types of thermal regimes were established:climate-controlled,snowcover-controlled,and frozen ground-controlled.Seasonally frozen ground occurs across a broad range of elevation between 2650 and 3075 m asl,whereas possible permafrost only occurs above 2750 m asl.

CHARACTERISTICS OF PERIGLACIAL GEOMORPHOLOGY IN THE SOURCE AREA OF THE HUANGHE RIVER

There widely occur stretches of permafrost at more than 3,800-4,200 meters above sea level in the source area of the Huanghe (Yellow) River. The periglacial geomorphology develops quite well, including frozen disintegration geomorphology, freezing and thawing geomorphology in cold environments, periglacial dune, buried ices and fossil periglacial phenomena. In light of the relation between stratigraphy and periglacial phenomena, three periglacial periods can be divided, which are the Middle Pleistocene periglacial period, the Late Pleistocene periglacial period and modern periglacial period.

DISTRIBUTION OF PERIGLACIAL GEOMORPHOLOGY AND THE RELATIONSHIP BETWEEN PERIGLACIAL GEOMORPHOLOGY AND GLACIATED HISTORY ON FILDES PENINSULA, KING GEORGE ISLAND,ANTARCTICA

As for the formation of the submerged trough of Maxwell Bay and the external agent geomorphic-phenomena of Fildes Peninsula, we can use glaciated theory to explain them. Moreover, based on a large number of field investigation by foreign colleagues and the authors, we can consider that the last glaciated ice-stream which had a great effect on current periglacio-landform distribution, mainly flowed along the direction from northwest to southeast. The periglacio-geomorphic distribution of the peninsula has a deep brand of glaciated history. Three kinds of different profile assemblage features show that the periglacial landform have an internal relationship in genesis. They also show a difference between stoss and leeward slopes by glaciated effect.

Which adjustment methods are suitable for the wind-induced errors of Geonor T-200BM3 precipitation weighing gauges in a periglacial site?

Single Alter shielded T-200BM3 weighing precipitation gauges are widely used in the measurement of all precipitation types(rainfall,snow and mixed precipitation)in unattended boreal or alpine regions,but their original datasets must be adjusted for undercatch errors caused by wind in snowy,windy and harsh environments.Therefore,previous researchers have developed many adjustment methods for all precipitation types on different time scales.However,which adjustment method is suitable for T-200BM3 weighing gauge wind-induced error adjustment in harsh alpine regions is unclear.Therefore,precipitation measurement intercomparison experiments were conducted in the Qilian Mountains from July 2018 to July 2021,and eight adjustment methods;were evaluated for wind-induced errors for daily,individual precipitation event,hourly,and half-hourly time scales.Z2004 outperformed the other adjustment methods in regard to the daily measurements of snow and mixed precipitation.Regarding individual snowfall events,M2007 reduced the absolute value of RMSE(bias)from 1.44 to 1.32 mm(0.77-0.24 mm)and could be recommended for snowfall event adjustment.K2017-1 attained a better performance than K2017-2 in regard to half-hourly snowfall and mixed sample adjustment and was more suitable for half-hourly snowfall sample adjustment.K2017-1 reduced the absolute value of bias from 0.07 to 0.00 mm for snowfall.Finally,Z2004,M2007,and K2017-1 yielded better adjustment results for the daily accumulation precipitation amount(>2 mm d−1),individual snowfall events(>2 mm per event),and half-hourly accumulation snowfall or mixed samples(>1 mm 30 min−1),respectively.However,further intercomparison in different climate regions is needed for trace precipitation samples.

Endophytic bacteria in the periglacial plant Potentilla fruticosa var.albicans are influenced by habitat type

Background Microbial communities in different plant compartments are relatively independent entities.However,the influence of environmental factors on the microbial community in different compartments of periglacial plants remains unclear.In this study,we quantified the bacterial communities in the rhizosphere soil,as well as root and leaf endosphere compartments of a periglacial plant,Potentilla fruticosa var.albicans,using high-throughput DNA sequencing.Moreover,we evaluated the impacts of habitat types(glacier terminus zone,moraine ridge,and alpine meadow)on the bacterial community in different plant compartments of Potentilla fruticosa var.albicans.Results Our results showed that habitat type had a significant effect on the alpha diversity(Chao1 richness)of endophytic bacteria,but not on the rhizospheric bacteria.The community composition of rhizospheric and endophytic bacteria was significantly different across the three habitats,and habitat type had a greater effect on the endophytic bacteria than on rhizospheric bacteria.The contribution of rhizosphere soil to the root and leaf endophytes decreased with the transformation of habitats from glacier terminus zone to alpine meadow.In contrast,host selection pressure sequentially increased from the glacier terminus zone to the moraine ridge to the alpine meadow.Furthermore,we found that the bacterial co-occurrence network in the alpine meadow was more modular but had lower complexity and connectedness than that in the glacier terminus zone.The bacterial community was governed primarily by stochastic processes regardless of habitat type.Conclusion This study reveals that the diversity and composition of endophytic bacteria associated with Potentilla fruticosa var.albicans are more affected by habitat types than that of rhizospheric bacteria.Our study also demonstrates that the assembly patterns and co-occurrence patterns of bacterial communities associated with Potentilla fruticosa var.albicans vary by habitat type.These results advance the current understanding of community assembly and ecological interactions of microbial communities associated with periglacial plants.

Plant functional traits and microbes vary with position on striped periglacial patterned ground at Glacier National Park, Montana

The retreating snowfields and glaciers of Glacier National Park, Montana, USA, present alpine plants with changes in habitat and hydrology. The adjacent and relic periglacial patterned ground consists of solifluction terraces of green, vegetation-rich stripes alternating with sparsely vegetated brown stripes. We established georeferenced transects on striped periglacial patterned ground for long-term monitoring and data collection on species distribution and plant functional traits at Siyeh Pass and at Piegan Pass at Glacier National Park. We documented species distribution and calculated the relative percent cover(RPC) of qualitative functional traits and used 16 S rRNA from soil samples to characterize microbial distribution on green and brown stripes. Plant species distribution varied significantly and there were key differences in microbial distribution between the green and brown stripes. The rare arctic-alpine plants Draba macounii, Papaver pygmaeum, and Sagina nivalis were restricted to brown stripes, where the RPC of xeromorphic taprooted species was significantly higher at the leading edge of the Siyeh Pass snowfield. Brown stripes had a higher percentage of the thermophilic bacteria Thermacetogenium and Thermoflavimicrobium. Green stripes were co-dominated by the adventitiously-rooted dwarf shrubs Salix arctica and the possibly N-fixing Dryas octopetala. Green stripes were inhabited by Krummholz and seedlings of Abies lasiocarpa and Pinus albicaulus. Prosthecobacter, a hydrophilic bacterial genus, was more abundant on the green stripes, which had 6,524 bacterial sequences in comparison to the 1,183 sequences from the brown stripes. While further research can determine which functional traits are critical for these plants, knowledge of the current distribution of plant species and their functional traits can be used in predictive models of the responses of alpine plants to disappearing snowfields and glaciers. This research is important in conservation of rare arctic-alpine species on periglacial patterned ground.

Strongly seasonal Proterozoic glacial climate in low palaeolatitudes:Radically different climate system on the pre-Ediacaran Earth

Proterozoic （pre-Ediacaran） glaciations occurred under strongly seasonal climates near sea level in low palaeolatitudes. Metre-scale primary sand wedges in Cryogenian periglacial deposits are identical to those actively forming, through the infilling of seasonal （winter） thermal contraction-cracks in perma- frost by windblown sand, in present-day polar regions with a mean monthly air temperature range of 40 ~C and mean annual air temperatures of -20 ~C or lower. Varve-like rhythmites with dropstones in Proterozoic glacial successions are consistent with an active seasonal freeze-thaw cycle. The seasonal （annual） oscillation of sea level recorded by tidal rhythmites in Cryogenian glacial successions indicates a significant seasonal cycle and extensive open seas. Palaeomagnetic data determined directly for Prote- rozoic glacial deposits and closely associated rocks indicate low palaeolatitudes： Cryogenian deposits in South Australia accumulated at 〈10% most other Cryogenian deposits at 〈20~ and Palaeoproterozoic deposits at 〈15~ palaeolatitude. Palaeomagnetic data imply that the Proterozoic geomagnetic field approximated a geocentric axial dipole, hence palaeolatitudes represent geographic latitudes. The Cry- ogenian glacial environment included glacier-flee, continental permafrost regions with ground frozen on a kyr time-scale, aeolian sand-sheets, extensive and long-lived open seas, and an active hydrological cycle. This palaeoenvironment confiicts with the ＇snowball Earth＇ and ＇slushball Earth＇ hypotheses, which cannot accommodate large seasonal changes of temperature near the equator. Consequently, their proponents have attempted to refute the evidence for strong seasonality by introducing Popperian ＇auxiliary assumptions＇. However, non-actualistic arguments that the Cryogenian sand wedges indicate diurnal or weakly seasonal temperature changes are based on misunderstandings of periglacial pro- cesses. Modelling of a strongly seasonal climate for a frozen-over Earth is invalidated by the evidence for persistent open seas and glacier-free continental regions during Cryogenian glaciations, and gives a mean monthly air temperature range of only 〈10 ~C for 〈10~ latitude. By contrast, a strongly seasonal climate in low palaeolatitudes, based on the actualistic interpretation of cryogenic sand wedges and other structures, is consistent with a high obliquity of the ecliptic （〉54°） during Proterozoic low-latitude glaciations, whereby the equator would be cooler than the poles, on average, and global seasonality would be greatly amplified.

An integrated approach to investigate climate-driven rockfall occurrence in high alpine slopes: the Bessanese glacial basin, Western Italian Alps

Rockfalls are one of the most common instability processes in high mountains.They represent a relevant issue,both for the risks they represent for(infra)structures and frequentation,and for their potential role as terrestrial indicators of climate change.This study aims to contribute to the growing topic of the relationship between climate change and slope instability at the basin scale.The selected study area is the Bessanese glacial basin(Western Italian Alps)which,since 2016,has been specifically equipped,monitored and investigated for this purpose.In order to provide a broader context for the interpretation of the recent rockfall events and associated climate conditions,a cross-temporal and integrated approach has been adopted.For this purpose,geomorphological investigations(last 100 years),local climate(last 30 years)and near-surface rock/air temperatures analyses,have been carried out.First research outcomes show that rockfalls occurred in two different geomorphological positions:on rock slopes in permafrost condition,facing from NW to NE and/or along the glacier margins,on rock slopes uncovered by the ice in the last decades.Seasonal thaw of the active layer and/or glacier debutressing can be deemed responsible for slope failure preparation.With regard to timing,almost all dated rock falls occurred in summer.For the July events,initiation may have been caused by a combination of rapid snow melt and enhanced seasonal thaw of the active layer due to anomalous high temperatures,and rainfall.August events are,instead,associated with a significant positive temperature anomaly on the quarterly scale,and they can be ascribed to the rapid and/or in depth thaw of the permafrost active layer.According to our findings,we can expect that in the Bessanese glacierized basin,as in similar high mountain areas,climate change will cause an increase of slope instability in the future.To fasten knowledge deepening,we highlight the need for a growth of a network of high elevation experimental sites at the basin scale,and the definition of shared methodological and measurement standards,that would allow a more rapid and effective comparison of data.

Evolution and changes of permafrost on the Qinghai-Tibet Plateau during the Late Quaternary

Due to the uplift of Qinghai-Tibet Plateau （QTP）, the cryosphere gradually developed on the higher mountain summits after the Neocene, becoming widespread during the Late Quaternary. During this time, permafrost on the QTP experienced repeated expansion and degradation. Based on the remains and cross-correlation with other proxy records such as those from glacial landforms, ice-core and paleogeography, the evolution and changes of permafrost and environmental changes on the QTP during the past 150,000 years were deduced and are presented in this paper.At least four obvious cycles of the extensive and intensive development, expansion and decay of permafrost occurred during the periods of 150-130, 80-50, 30-14 and after 10.8 ka B.P.. Ehiring the Holocene, fluctuating climatic environ-ments affected the permafrost on the QTP, and the peripheral mountains experienced six periods of discernible permafrost changes： （1） Stable development of permafrost in the early Holocene （10.8 to 8.5-7.0 ka B.P.）; （2） Intensive permafrost degradation during the Holocene Megathermal Period （HMP, from 8.5-7.0 to 4.0-3.0 ka B.P.）; （3） Permafrost expansion during the early Neoglacial period （ca. 4,000-3,000 to 1,000 a B.P.）; （4） Relative degradation during the Medieval Warm Period （MWP,from 1,000 to 500 a B.R）; （5） Expansion of permafrost during the Little Ice Age （LIA,from 500 to 10.a B.P.）; （6） Observed and predicted degradation of permafrost during the 20th and 21st century. Each period differed greatly in paleoclimate, paleoenvironment, and permafrost distribution, thickness, areal extent, and ground temperatures, as well as in the development of periglacial phenomena. Statistically, closer dating of the onset permafrost formation, more identi-fication of permafrost remains with richer proxy information about paleoenvironment, and more dating information enable higher resolution for paleo-permafrost reconstruction. Based on the scenarios of persistent climate warming of 2 2 -2 .6 °C in the next 50 years, and in combination of the monitored trends of climate and permafrost changes, and model predictions suggest an accelerated regional degradation of plateau pemafrost. Therefore,during the first half of the 21st century, profound changes in the stability of alpine ecosystems and hydro（geo）logical environments in the source regions of the Yangtze and Yellow rivers may occur. The foundation stability of key engineering infrastructures and sustainable eco-nomic development in cold regions on the QTP may be affected.

Water Chemistry and Hydrometeorology in a Glacierized Catchment in the Polar Urals,Russia

This study aims to determine the relationships between local meteorological conditions,proglacial river discharge and biogeochemical processes operating in a periglacial basin located in the Polar Ural mountain range, Russia. Fieldwork was conducted in the catchment of Obruchev Glacier(13 km2) during the summer peak flow period in 2008. River discharge was dominated by snowmelt and changed from 3300 l s-1 to less than 1000 l s-1. The mean daily air temperatures of stations situated in the mountain tundra and near Obruchev Glacier from July 11 th to August 1st 2008 were 14.4°C and 10.3°C, respectively. The glacial river had low total dissolved solids varying from 4.5 to 9 mg l-1 and coefficients of correlation between Na+ and Cl-, K+ and Cl-, as well as NH4+ and Cl- were 0.94, 0.90 and 0.84, respectively. Rainfall events affected the snowmelt initiation and provided an essential part of the discharge during the intense snowmelt period, which occurred from July 11 th to July 18 th 2008. Data showed that Na+ and K+ in the surface water derived from snowmelt rather than chemical weathering of silicates. Also, it was obtained that NO3- derived from the melting snowpack, whereas ammonification occurring under the snowpacks was the primary source for NH4+.

Cryotic climate conditions and their eventual implication in the high-mountain surface of the Nevado de Toluca volcano, Mexico

The state of the cryosphere in tropical regions is of great importance because the temperature around the glaciers, permafrost and snow cover always fluctuates near the melting point. These thermal conditions and their high sensitivity to climate change cause the accelerated disappearance of these elements;therefore, it is important to know the climatic factors that regulate them, as well as the physical characteristics of each cryospheric element. Unlike glaciers, permafrost and snow cover have not been widely studied. In recent decades, the study of the glacial and periglacial environment has been carried out in intertropical mountains. However, despite the altitude of their relief and the frequent occurrence of snowfall in tropical high mountains, the conditions that determine such events have been barely analyzed;and in the case of Mexico, the volume of snowfall and its thickness have not been quantified either, as well as their corresponding duration. Consequently, this work is aimed to analyze the temperature and precipitation conditions that determine the snowfall at the higher part of the Nevado de Toluca volcano;at the same time, the conditions of the cryotic climate and their possible implication on the surface are studied. The analysis of data from 1965 to 2016, using frequency statistics, allowed to realize that snowfall occurs with low intensity, its accumulation being less than 10 cm thick and 10 mm of snow water equivalent, which causes the snowpack to stay only a few weeks on average. At the same time, it was determined that there is a significant increase in the number of freeze-thaw cycles. Therefore, due to the climate conditions and their influence on the mountain surface, it is probable that the bedrock is subject to a greater gelifraction dynamics, and the unconsolidated soil surface increases;the combination of the above could cause a greater geomorphological dynamic over time, particularly due to debris flows, and by water and wind erosion of the surface. This work is intended to serve as a reference for the high mountain environment in the intertropical regions.

伊尔加兹山脉冰缘地貌发育和土壤形成及其气候的影响(土耳其黑海西岸)

The main aims of the current study are to determine the morphological features of the periglacial landforms(non-sorted step,mud circle,stony earth circle,thufur,and congeliturbation)located on the Ilgaz Mountains,examine the physicochemical and mineralogical properties with pedological processes of the soils,and assess of the effects of climatic conditions controlling the development of landforms.The Ilgaz Mountains(2587 m a.s.l.),located in the Western Black Sea Region,within the Anatolian Mountains,are important in terms of periglacial landforms(mud circles,stony earth circles,thufurs,non-sorted steps,non-sorted stripes,congeliturbation deposits,and block currents).The descriptive statistics of 123 periglacial landforms measured by fieldworks were analyzed.The distribution of freezing and thawing in the Ilgaz Mountains throughout the year was evaluated,and it was found that freezing takes place between December and March,freezing-thawing takes place in April,May,October and November,and thawing takes place between June and October.Accoding to soil properties,organic matter content changes from 1.88%to 12.72%in non-sorted step soils,while it is between 2.03%and 12.24%in stony earth circle soils.The organic matter is observed to be close to congeliturbation deposits at lower ratios compared to non-sorted steps,stony earth circles and mud circles.The soil reactions on stony earth circles and non-sorted steps vary between slightly acidic and slightly alkaline.On the other hand,soil samples taken from the mud circles are different from those taken from the non-sorted steps and stony earth circles.Their soil reaction is acidic,and pH changes between 4.86 and 6.25.The lime content also varies between 2.81%and 32.08%,with an average of 12.02%.The texture properties of soils are dominantly loam and clay loam,as in the non-sorted steps,stony earth circles,and mud circles.Considering their mineralogical properties,the XRD study was carried out to determine the primer mineral types and abundance degrees of soils of periglacial landforms.Quartz,muscovite and albite minerals were found in soils in the stony earth circle,while quartz,muscovite,orthoclase and albite minerals were determined as primary minerals in soils formed on the thufur landforms.