In geology, permafrost or permafrost soil is soil at or below the freezing point of water (0 °C or 32 °F) for two or more years. Ice is not always present, as may be in the case of nonporous bedrock, but it frequently occurs and it may be in amounts exceeding the potential hydraulic saturation of the ground material. Most permafrost is located in high latitudes (i.e. land in close proximity to the North and South poles), but alpine permafrost may exist at high altitudes in much lower latitudes. The extent of permafrost can vary as the climate changes. Today, approximately 20% of the Earth's land mass is covered by permafrost (including discontinuous permafrost) or glacial ice. A glacier is a large, slow-moving mass of ice, formed from compacted layers of snow that slowly deforms and flows in response to gravity and high pressure. The word glacier comes from French via the Vulgar Latin glacia, and ultimately from Latin glacies meaning ice.
Glacier ice is the largest reservoir of fresh water on Earth, and second only to oceans as the largest reservoir of total water. Glaciers cover vast areas of polar regions, are found in mountain ranges of every continent, and are restricted to the highest mountains in the tropics. The processes and landforms caused by glaciers and related to them are referred to as glacial. The process of glacier growth and establishment is called glaciation. Glaciers are sensitive monitors of climate conditions and are crucial to both world water resources and sea level variation.
This new book presents the latest research on both permafrost and glaciers.
Chapter 1 - Designing infrastructure and assessing hazard for risks mapping in mountainous environments is a challenging task for every engineer and geoscientist. Steep and sometimes unstable terrain, heterogeneous geological settings, harsh climatic conditions with strong winds, rain, snow (including drifts and significant snow loads) and large temperature variations between summer and winter play key roles in the design process. Not only is a structure directly influenced by these factors in terms of foundation conditions, for example, but also indirectly by rock fall, debris flows or snow avalanches. The difficulties related to foundations in permafrost are largely controlled by the fact that the ground is frozen and may contain ice in various forms, such as ice rich layers, pore ice in coarse soils, ice lenses in fine soils or ice-filled joints in fractured rocks. The ground ice is the main problem affecting mountain infrastructure due to its susceptibility to creep, accrete and melt, hence changing the soil structure. In addition, the top layer thaws during the summer months further changing the strength and deformation characteristics of the ground. Climate change adds even more uncertainties to the foundation and load conditions of any mountainous infrastructure in the long term and needs to be addressed early in the design process. The ground is therefore in a transient state that has to be considered and characterised adequately.
Unique geotechnical characteristics and important features of permafrost soils and rocks, which focus on mountain permafrost, are highlighted related to the design and the construction of mountain infrastructure. The main objective of this chapter is to help with the design process, prolong the service life of structures and to lower the risks and damage potential when dealing with infrastructure located in, or in the proximity of, mountain permafrost environments.
Chapter 2 - This chapter briefly reviews current state-of-the-art in modeling permafrost in numerical weather prediction models (NWPMs), chemistry transport models (CTMs) and in general circulation models (GCMs) and earth system models (ESMs) for projecting the global climate. Pros and cons of various methods are assessed. Deficits of GCM/ESMs permafrost modeling practice are discussed based on gridded observed soil-temperature data; deficits of the treatment of permafrost in NWPMs and CTMs are elucidated by examples of site-by-site evaluations. In addition, the uncertainty in simulated soil moisture and heat fluxes due to uncertainty in soil physical and plant-physiological parameters is illustrated. The consequences of incorrect simulation of or even neglecting of permafrost processes for simulated weather and climate are discussed. Extreme changes in permafrost distribution and active layer depths, as they are associated with wildfires/fires and their impact on the simulated atmospheric conditions, are addressed as well. Finally the great challenges for improving permafrost simulations (grid resolution, lack of horizontally and vertically high resolved soil data, uncertainty in soil parameters, organic soils) in GCMs, ESMs, CTMs and NWPMs and how to address these challenges is outlined.
Chapter 3 - Bacterial strains resistant to beta-lactams, aminoglycosides, tetracycline, chloramphenicol, sulphathiazole and trimethoprim were isolated from more than 60 samples of Arctic and Antarctic permafrost subsoil sediments dated from 5 thousand to 3 million years of age. About 30% of the isolated strains were cross-resistant to two and more antibiotics of different classes. The diversity of multidrug-resistant ancient bacteria, the genetic structure of resistance determinants and their association with different mobile elements were studied.
Principal attention was given to multidrug-resistant strains of Gram-negative bacteria belonging to genera Acinetobacter, Pseudomonas, Psychrobacter, Stenotrophomonas, and Xanthomonas. It was shown that multidrug resistance of some strains of Acinetobacter sp. can be transferred by transformation of chromosomal genes and most probably results from expression of efflux pumps. The authors also revealed that many of the strains contained antibiotic resistance genes closely related to those of modern bacteria. In particular, among different strains resistant to streptomycin, they identified strains with strA-strB genes, strains with aadA genes and strains containing both types of genes. Genes closely related to tetR-tet(H) genes were detected in a strain of Psychrobacter psyhrophilus resistant to tetracycline and streptomycin. Finally, the authors demonstrated that many of the resistance determinants are associated with mobile elements such as plasmids and transposons.
The results of the study strengthen the hypothesis that antibiotic resistance genes were present in natural bacterial populations long before the 'antibiotic era'. Also, the association of the resistance determinants with different mobile elements confirm an important role of horizontal transfer in distribution of these genes among environmental bacteria.
Chapter 4 - Pleistocene periglacial features were studied in different areas of Hungary in comparison with Canadian recent cryogenic features. Pleistocene periglacial activity forms an important component of the landscape of the Carpathian Basin. There is a general consensus about the study and interpretation of cryogenic deformation structures (e.g., frost fissures, cryoturbations and involutions) being helpful in paleoenvironmental reconstructions. During the glacial periods of the Pleistocene, the Carpathian Basin was ice-free and subject to a cryogenic environment that produced various periglacial features. The reason for the cold climate during these glacial periods is the Basin's unique geographic setting. The Carpathians, which surrounds this large basin, creates an almost closed climatic situation, producing climatic conditions not found elsewhere in Europe. In effect, the climate in Hungary during the glacial periods of the Pleistocene was somewhat similar to the recent climate of the dry tundra regions of North Siberia. But according to other researchers, the Carpathian Basin was mostly devoid of permafrost during the Quaternary. Previous researches described so many relict forms in different geomorphic positions, but none of these have been revised according to the most recent research methods and permafrost nomenclature. Our review addresses past periglacial processes and their coupling to paleoclimate. Permafrost distribution in Canada shows a latitudinal zonation. The main annual temperature associated with these permafrost zones are 0° to -5.5°C (SPZ), -5.5° to -8.3°C (WPZ) and -8.3° to -17°C (CPZ). Sand wedges, frost cracks and ice wedges all develop in permafrost environments and are currently actively forming in the Continuous Permafrost Zone in Canada. The well-developed sand-wedge polygons, frost cracks, ice wedge casts and cryoturbated soils found in Hungary suggest that the Carpathian Basin was a permafrost-affected area during a cold, glacial part of the Weichselian (Late Pleniglacial, 22,000-18,000 years BP). At that time this area was most likely underlain by continuous permafrost.
Chapter 5 - This paper reviews our current knowledge on periglacial landforms and processes on Disko Island, central West Greenland. Disko Island is located on the southern limit of the continuous permafrost zone, and permafrost and periglacial processes are therefore sensitive to future climate warming. The landscape of Disko Island contains a wide variety of periglacial landforms such as rock glaciers, pingos, palsas, patterned ground and active layer phenomena. Also, weathering processes and fluvial and coastal landforms and processes related to cold-climate environments are widespread.
Until now, most research has concerned the incidence, morphology and palaeoclimatic significance of rock glaciers. Although this research has improved our understanding of the late-Holocene history, there are limited studies on other process-landform interrelations, making holistic geomorphological reconstructions of the landscape evolution difficult.
Disko Island contains 247 glaciers larger than 1 km2, and 75 of these are classified as surge-type glaciers. The recession after surge events leaves proglacial areas prone to formation of periglacial landforms, providing good conditions for field studies on landform evolution on decadal and centennial timescales.
Chapter 6 - Recent studies have described mountain permafrost degradation due to global warming in many mountain regions, such as European mountains, the Tibetan Plateau, the Tien Shan and mountainous areas of Mongolia. In this chapter, the authors describe the recent mountain permafrost degradation in the Nepal Himalayas and the Russia Altai Mountains. The Nepal Himalayas is one of the largest mountainous areas of the world. In 1973, the permafrost lower limit was estimated to be 5200-5300 m above sea level (ASL) on southern-aspect slopes in the Khumbu Himal, the eastern part of the Nepal Himalayas. Using ground-temperature measurements, the mountain permafrost lower limit on slopes with the same aspect was estimated in 2004. The results indicate that the permafrost lower limit was
5400-5500 m ASL in 2004. The permafrost lower limit was estimated to be 5400 to 5500 m on slopes with a southern aspect in the Khumbu Himal in 1991 using seismic reflection soundings. Thus, it is possible that the permafrost lower limit has risen 100-300 m between 1973 and 1991, followed by a stable limit of 5400 to 5500 m over the last decade. The Russia Altai Mountains is located on the southern fringe of the Siberia Plain. The altitudinal range of sporadic/patchy permafrost zone and that of discontinuous/continuous permafrost zone are 1800-2000 m ASL and above 2000 m ASL, respectively. The mean annual air temperature at Russian meteorological stations in Russian Altai exhibited remarkable warming trends. The authors observed the phenomena relating to permafrost degradation, such as landslide influenced by antecedent permafrost degradation, and rapid degradation of pingos around the lower limit of discontinuous/continuous permafrost zone.
Chapter 7 - Since 1973 one drillhole (5-14 warm times / 6-15 glacials) and 39 expeditions in the Himalayas, Tibet, the Karakorum, the Kuen Lun, the Tienshan, the Sayan Mountains, the Altai and other parts of Central Asia contributed to detailed knowlegde about extension (2.4 Mio km2) and thickness (800-1000 m) of High Asian inland-ice. The data are best for the Last Glacial Period (Würm, Marine Isotop Stage (MIS) 4-2). The author thinks that during the last 2.75 Ma conditions that are comparable to the LGP ocurred several times in Central Asia. Geometric boundary conditions that resulted from the low latitude caused a substantial albedo-induced impact on the energy budget of the Earth during glacial times. The vast extension of the ice-sheets and the high elevation (~6000 m asl) contributed to this. A substantial albedo-induced cooling of the atmosphere is inferred.
Chapter 8 - Glacial ice was for a long time considered only as an extremely stable, frigid and static environment. However, recent investigations showed that glacial ice and glaciers are much more dynamic at the microscale, as well as at the geomorphological level, than previously assumed. Particularly in polythermal glaciers, characterized by a warm core, quick seismic shifts can occur and cause displacements of cryokarst formations and glacial ice masses. Increased pressure at the base of the glaciers can generate subglacial ice melting. These waters, supplemented with supraglacial melt-waters and groundwater, soak rocks and sediments below the glacier and become enriched with local solutes and suspended sediments. When frozen together with the base of the glacier, they constitute the subglacial environment.
Until recently, subglacial environments were thought to be abiotic. However, recent studies revealed the existence of aerobic heterotrophic bacterial communities able to survive the dynamic processes of thawing and freezing. To our knowledge, until our investigations, there were no reports on the presence of fungi in subglacial ice. Given the known adaptive behaviour of many fungi to low water activity (aw) and a wide range of temperatures, the authors assumed that various types of ice can represent potential natural habitats for diverse halotolerant fungi. To evaluate this hypothesis, media with lowered aw and incubations at low and "normal" temperatures were chosen to provide a selective advantage for the recovery of culturable fungi from supra- and subglacial environments of four different polythermal Arctic glaciers (Svalbard, Norway).
The dominant taxons isolated were basidiomycetous and ascomycetous yeasts, melanized yeast-like fungi, mainly represented by the genera Cladosporium and Aureobasidium and different species of the genus Penicillium. The fungal counts detected in the subglacial samples were two orders of magnitude greater when compared with those recovered from supraglacial samples, mainly due to yeasts (with counts reaching 4 x 106 CFU L-1). Five ascomycetous and twenty-two basidiomycetous yeast species were isolated, including three new species. According to species diversity and abundance, the majority of species were assigned to the hymenomycetous yeasts (Filobasidium/Cryptococcus albidus taxa of the Tremellales). The stable core of the subglacial yeast communities were represented by Cr. liquefaciens, Rhodotorula mucilaginosa, Debaryomyces hansenii and Pichia guillermondii.
Among the isolated filamentous fungi the prevailing genus was Penicillium, with twenty-four different species being identified and a new species, P. svalbardense being described. The dominant species was P. crustosum, representing on the average half of all isolated strains from the studied glaciers. In contrast to yeasts, primarily associated with the clear subglacial ice, the highest counts for penicillia were obtained for debris-rich subglacial ice.
Enriched fungal populations in subglacial environments may represent a significant reservoir of biological activity with the potential to influence glacial melt-water composition, release of nitrogen and carbon in the polar environment and seeding of oceans with microbial life.
Chapter 9 - Many supraglacial lakes have appeared and expanded in the Himalayas since the 1950s by glacial retreat, probably due to global warming after the Little Ice Age. Some of these lakes have produced glacial lake outburst flood (GLOF) events since the 1960s, which have occurred, on average, once every three years somewhere in the Himalayas. The three glacial lakes, Tsho Rolpa (water level 4,580m a.s.l.) and Imja (5,009m a.s.l.) in the Nepal Himalayas, and Lugge (4,539m a.s.l.) in the Bhutan Himalayas, were typical supraglacial lakes in the 1950s to 1960s, but, at present, are moraine-dammed by the subsequent horizontal expansion, enough to touch the side moraine. The lakes were investigated from the hydrological and hydrodynamic viewpoints by field observations from 1995 to 1997, and in 2001 and 2002. In particular, Tsho Rolpa has the highest potentiality of GLOF, since the lake water directly contacts the end moraine, in addition to sufficient water pressure (maximum depth, 131m). Hence, the hydrodynamics of the lake were explored in the pre-monsoon season of 1996 by mooring current meters, temperature loggers and turbidimeters under water, and by obtaining vertical profiles of water turbidity and temperature. As a result, a dynamic model of the lake basin expansion, related to calving at the glacier terminus, was proposed.
A comparison of the thermal structure between Tsho Rolpa, Imja, and Lugge shows a definite difference in the lake hydrodynamics associated with the lake expansion rate. The end-moraine and the dead-ice zone of Imja are 10-25m higher than the lake level. The topographic screening of the end moraine on valley winds, commonly blowing along the elongated lakes, tends to decrease wind velocity near the lake surface, which weakens vertical thermal circulations inducing the ice melt below the lake bottom. The characteristic thermal structure of Imja Lake was probably produced by such a screening effect. A three-dimensional numerical simulation of wind around Imja definitely shows the upwind topographic screening effect. The hydrodynamics of Tsho Rolpa was simulated by creating a three-dimensional lake basin of actual size in the calculation domain. In the simulation, a return current, activated by the inflow-outflow system of the lake, was observed. Spatial distributions of the concentration and size for suspended sediment were also simulated, which was reasonable in pattern to the observation.
Chapter 10 - This study identifies 75 surge-type glaciers on Disko Island (Qeqertarsuaq), central West Greenland, using old maps, aerial photographs, satellite imageries and field observations. The surge-type glaciers comprise about 30% of the glaciers larger than 1 km2
and 59% of the glacierised area. The duration of the surge cycle is at least 100 years or more, which is relatively long compared to surge clusters in other parts of the world. The surge events are very dramatic and include some of the longest frontal advances ever recorded such as 10.5 km advance of Kuannersuit Glacier in 1995-98, where the glacier advance velocity reached at least 70 m d-1. The surge-type glaciers are responsible for valley floor geomorphology such as complex moraine systems and extensive dead ice areas. This implies that glacier surging has to be considered when glacier recession is related to climatic fluctuations.
In: New Permafrost and Glacier Research Edltors: Max I. Krugger and Harry P. Stern
ISBN: 978-1-60692-616-1 ©2009 Nova Science Publishers, Inc.
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