Geophysical characteristics of permafrost in the Abisko area, northern Sweden

Research on permafrost in the Abisko area of northern Sweden date from the 1950s. A mean annual air temperature of -3 C in the Abisko mountains (i.e. 1000 m a.s.l.)and -1°C beyond the mountain area at an altitude of around 400 m suggests that both mountain and arctic permafrost occur there. Several geophysical surveys were performed by means of resistivity tomography (ERT) and electromagnetic mapping (EM). Wherever possible the geophysical survey results were calibrated by digging tests pits. The results show that permafrost occurs extensively in the mountain areas, especially those above 900 m a.s.l. and also sporadically at lower altitudes. At 400 m a.s.l. permafrost may be up to 30 m thick. Its thickness and extent are determined largely by the very variable local rock and soil conditions. Fossil permafrost is also likely to occur in this area

The Occurrence of Permafrost within the Glacial Domain

The occurrence of permafrost within glacial environments has never been comprehensively defined based on scientific evidence, despite its importance in determining how all the components of the cryosphere associate and interact. Here, the relation between glaciers and permafrost is discussed based on what scientific field they have been traditionally associated with. As the most accepted definition of permafrost is not exclusively linked to the presence of a geological medium, this can also be ice of any origin, including snow and glacial ice. Thus, active glaciers can act as permafrost medium. Indeed, all thermal types of glaciers meet the definition of permafrost as they remain at or below 0 C for certainly more than two consecutive years. Active rock glaciers, regardless of the origin of the ice within, also meet the definition of permafrost. The presence of an active layer is not a prerequisite for the existence of permafrost either. Therefore, a comprehensive definition of permafrost occurrence across the cryosphere is essential to appropriately understand the phenomenon as a whole, not only as seen from our planet but also as it occurs for example on the icy moons of the Solar System and other frozen rocky bodies

Deglaciation Rate of Selected Nunataks in Spitsbergen, Svalbard—Potential for Permafrost Expansion above the Glacial Environment

Spitsbergen has recently experienced a continuous deglaciation process, linked to both glacier front retreat and lowering of the glacier surface. This process is accompanied by permafrost aggradation from the top of the slopes down to the glacier. Here, the authors determine the rate of permafrost expansion in this type of vertical profile. To this end, seven nunataks across the island were analysed using Landsat satellite imagery, a high-resolution digital elevation model (ArcticDEM), and geoinformation software. Over the last 24–31 years, new nunataks gradually emerged from the ice cover at an average linear rate of 0.06 m a1 per degree of increment of the slope of the terrain at an average altitude of approximately 640 m a.s.l. The analysis showed that the maximum rate of permafrost expansion down the slope was positively correlated with the average nunatak elevation, reaching a value of approximately 10,000m2 a1. In cold climates, with a mean annual air temperature (MAAT) below 0 C, newly exposed land is occupied by active periglacial environments, causing permafrost aggradation. Therefore, both glacial and periglacial environments are changing over time concomitantly, with permafrost aggradation occurring along and around the glacier, wherever the MAAT is negative

Permafrost. The contemporary meaning of the term and its consequences

Nowadays the term ‘permafrost’ means the thermal state of the ground, for which the temperature limit value is 0°C remaining for at least two years. It is the effect of the climate where the average annual temperature of the air is –1°C or lower. As a result of air temperature, it does not need to contain ice, so it can no longer be called underground glaciation, and the only processes which are subject to permafrost are aggradation and degradation. Also the occurrence of permafrost in the geographical environment is conditioned neither by the presence of water nor its phase change – freezing, as the cryotic state is its synonym. Although it is known that the majority of permafrost dates back to the Pleistocene, still the determination of its age is difficult because it consists in determining ‘the age of the temperature’, as it were. The maximum thickness of permafrost occurs in the Antarctic, and it is estimated to reach 2600 m. Permafrost covers more than 25% of the Earth surface together with ice-sheets and ice-caps

Probable two-layered permafrost formation, as a result of climatic evolution in mountainous environment of Storglaciären forefield, Tarfala, Northern Scandinavia

The analysis of climate changes in of the Tarfala valley and Kebnekaise Mts area, and changes within the range of the Scandinavian Glaciation shows that even in the warmest period of Holocene there were favourable environmental conditions for permafrost of the Pleistocene origin to be preserved in this area. The results of electrical resistivity surveys together with analysis of available publications indicate that two layers of permafrost can be distinguished in the Storglaciären forefield. The shallower, discountinuous, with thickness ca. 2–6 meters is connected to the current climate, The second, deeper located layer of permafrost, separated with talik, is older. Its thickness can reach dozens of metres and is probably the result of permafrost formation during Pleistocene. The occurrence of two-layered permafrost in the Tarfala valley in Kebnekaise area shows the evolution of mountain permafrost may be seen as analogous to that in Western Siberia. This means that the effect of climate changes gives a similar effect in permafrost formation and evolution in both altitudinal and latitudinal extent. The occurrence of two-layered permafrost in Scandes and Western Siberia plain indicates possible analogy in climatic evolution, and gives opportunity to understand them in uniform way

Two-layered permafrost formation as a result of climate change in a mountainous environment. Example from Storglaciären, Tarfala, Northern Sweden [abstract]

"The most common study of the occurrence of permafrost in the world concerns one layer in the lithosphere inside which the temperature is equal to or lower than 0 C. Like other components of the cryosphere, Permafrost reacts to climatic changes that register in its thermal characteristics." [...] (fragm.

Geophysical methods in research of permafrost in the Tatra Mountains and northern Scandinavia

A set of geophysical methods were implemented in the research conducted on permafrost of the Tatra Mountains and the Abisko area, Northern Sweden. Results of geophysical surveys show evidence of permafrost in both areas. Compara-tive studies on the occurrence of permafrost in the Tatras and in the Abisko area indicate that contemporary active as well as fossil permafrost might occur in both locations. Results of the electric resistivity, electromagnetic, shallow refraction seismic, and ground penetrating radar methods reveal similar results and might be successfully used in indirect research on perma-frost in the mountainous regions

Lattices of Graphical Gaussian Models with Symmetries

In order to make graphical Gaussian models a viable modelling tool when the number of variables outgrows the number of observations, model classes which place equality restrictions on concentrations or partial correlations have previously been introduced in the literature. The models can be represented by vertex and edge coloured graphs. The need for model selection methods makes it imperative to understand the structure of model classes. We identify four model classes that form complete lattices of models with respect to model inclusion, which qualifies them for an Edwards-Havr\'anek model selection procedure. Two classes turn out most suitable for a corresponding model search. We obtain an explicit search algorithm for one of them and provide a model search example for the other.Comment: 29 pages, 18 figures. Restructured Section 5, results unchanged; added references in Section 6; amended example in Section 6.

Permafrost in the Tatra Mts.: genesis, features, evolution

Z początkiem lat 90. zeszłego wieku autor podjął badania nad problemem występowania wieloletniej zmarzliny w Tatrach. W artykule przedstawione są wyniki sondowań sejsmicznych, elektrooporowych, tzw pomiarów BTS oraz analizy klimatu dotyczące poszukiwania i kartowania wieloletniej zmarzliny w Tatrach Wysokich. Publikowane rezultaty prac autora oraz przeprowadzone analizy stanowią podstawę do przybliżonego określenia cech wieloletniej zmarzli-ny, takich jak temperatura, głębokość stropu i spągu zmarzliny, obszar jej występowania, ilość i wiek zawartego w niej lodu. Na tym tle podjęto próbę opisania ewolucji zmarzliny w holocenie, także w odniesieniu do ustępujących lodowców

Ice classification as a basis for determining the borders and area of Antarctica

W artykule przedstawiono nieścisłości związane z klasyfikacją lodu, których skutkiem są poważne trudności w jednoznacznym określeniu granic i powierzchni Antarktydy, a tym samym w traktowaniu Antarktydy jako kontynentu. Zmiana klasyfikacji lodu i przeniesienie go z hydrosfery do litosfery pozwoliłaby na ujednolicenie i uporządkowanie badań lodu we wszystkich subdyscyplinach z zakresu nauk o Ziemi