Permafrost in the Yamal‐Gydan area of Western Siberia

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  • This article was downloaded by: [the Bodleian Libraries of the University of Oxford]On: 16 October 2014, At: 10:23Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

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    Permafrost in the YamalGydan areaof Western SiberiaR. I. YunakPublished online: 23 Dec 2008.

    To cite this article: R. I. Yunak (1979) Permafrost in the YamalGydan area of WesternSiberia, Polar Geography, 3:1, 49-63, DOI: 10.1080/10889377909377101

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  • PERMAFROST IN THE YAMAL-GYDAN AREA OF WESTERN SIBERIA

    R. I. Yunak

    From: Yamalo-Gydanskaya oblast' [The Yamal-Gydan area], R. K. Sisko (ed.).Leningrad: Gidrometeoizdat, 1977, pp. 123-137.

    Abstract: The article presents a prcis of available information on permafrostconditions in the tundra environment of the Yamal-Gydan area, much of it collectedduring expeditions of 1970-72; although it never claims to be a study of applied aspects,the article indicates that the present intensive activity in the area in terms of oil and gasexploration is never far from the author's mind. Permafrost temperatures in the area varyfrom -6 to -9C in the north and -1 to -5C in the south. The range of permafrostdepths is quite wide, from a maximum of 450 m (west of Lake Neyto) to 25 min coastal marshes. Groundwater conditions are examined in some detail, with thepossibilities of potential water supply in mind. Variations in the depth and temperatureof the active layer, and the types, amounts and distribution of underground ice arediscussed with a view to possible problems which these phenomena might pose in termsof exploitation. For example, it was calculated that massive underground ice underlies13.2% of the land area (in the Lake Neyto area) and that the ice content of thepermafrost to depths of 2030 m reaches 30-50% of total volume. The implications ofany disruption of the thermal regime are obvious. (The translation is by William Barr,University of Saskatchewan, Saskatoon.)

    The Yamal-Gydan region falls within the zone of continuous permafrost; thelatter binds together the sands and silty clays of the unconsolidated Quaternarydeposits and contains inclusions of ground ice. The building of oil and gas pipelines,roads, settlements and harbors associated with the exploitation of oil and gasdeposits demands a thorough and comprehensive study of the geocryologicalconditions.

    The matter of the history of permafrost development in Western Siberia, whichhas been examined in many previous works [1, 2, 5, 7, 19, 20, 23, etc.], is of greatsignificance to a study of the present cryogenic structure of the permafrost. Themajor elements in the history of the development of the permafrost in theYamal-Gydan area at the present time are presented below.

    The beginning of permafrost formation may be ascribed to the Quaternaryperiod. In the mid-Pleistocene, when a cold marine basin, 50100 m in depth [16,20] occupied the site of present Western Siberia, the sediments clearly were notfrozen. During the Kazan epoch, in association with a marine regression, islandsappeared on the sites of the current highest parts of Yamal and Gydan, and therocks forming them were subjected to active freezing. The mean annual airtemperature at that time dropped to 7C, and the ground temperature to 3 or4C. (According to V. A. Kudryavtseva [15], for permafrost to exist the meanannual air temperature must not exceed 3.6C.) Under these conditions thethickness of the actively frozen materials reached 250300 m. In the southern partsof Taz Peninsula, and in parts of Gydan Peninsula, the rocks did not freeze, sinceaccording to the calculated data the temperature was no lower than 0.5 to 0.9C[23].

    In the second half of the Upper Pleistocene and in the early Holocene, the

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  • majority of the present land area emerged from the sea. The severe climaticconditions existing at this time were conducive to active freezing of the deposits.During the period of the Zyryan Glaciation only the coastal strip of the presentYamal and Gydan lay beneath the sea. Permafrost developed throughout the landarea, but with thicknesses less than in areas farther south. N. A. Shpolyanskayaexplains this phenomenon by the fact that in the northern part of the region thepermafrost represented newly frozen materials, whereas in the south the permafrostwas relic. During the present epoch, with the onset of the cooling trend after theclimatic optimum, when the permafrost noticeably degraded, the freezing of therocks has continued.

    Thus the basic peculiarities of the permafrost have been established over aconsiderable portion of the Quaternary under the influence of various naturalfactors which V. V. Baulin [6] has divided into two groups. In the first group heincludes long-term fluctuations in climate and in the level of heat exchange at theearth's surface, the development of the geomorphological features of the landscape,etc. To assess these factors, operating over hundreds and thousands of years,methods of calculation were used to determine the temperature and thickness of thepermafrost [15, 17, 23]. The second group of factors (short-term fluctuations inclimate, and in the regimes of streams, lakes and bogs) affected the upper horizonsof the permafrost without penetrating to great depths. As a result of changes in theenvironmental conditions over the period of formation of the permafrost, aheterogeneous structure may be observed in the permafrost in the various regions ofthe West Siberian Plain at the present time [11].

    In particular, a continuous, thick mass of contemporary and ancient frozensediments has formed in the Yamal-Gydan area. Hence the bulk of the territoryunder consideration must be included in the northern permafrost zone, delineatedby many researchers on the basis of the stable properties of the permafrost [1, 6, 9,18, 30]. On the basis of less persistent peculiarities of the permafrost conditions,the northern zone is subdivided in turn into two subzones: polygenetic andepigenetic permafrost (Fig. 1). In the first subzone syngenetic frozen materials andmassive ice wedges formed contemporaneously with the sediments are widespread inthe upper layer (515 m). In the second subzone the formation of the permafrostoccurred primarily after the accumulation of the sediments, and only the depositsof the surface facies and in part the peat deposits have frozen syngenetically.

    Temperature and permafrost thicknesses have been taken by N. A. Shpo-lyanskaya [23] as the basic indices in depicting the major trends in the distributionof permafrost. According to her porposed scheme, the region under consideration issubdivided into three geothermal zones (northern arctic, southern arctic andnorthern subarctic). Only the southern part of Yamal lies within a fourth zone, thesouthern subarctic. All these zones combine to form an area of continuouspermafrost. The boundary of this latter area practically coincides with the limit ofthe northern permafrost zone. In this connection the three northern zonesdelineated by N. A. Shpolanskaya occupy almost the same area as the subzone ofpolygenetic permafrost identified by V. V. Baulin and others.

    Thus a zonation of permafrost clearly emerges in the region under examina-tion. The thermal gradient, which has been found to be constant with depth almosteverywhere, indicates a regular increase in temperature and a decrease in permafrostthickness as one goes south, corresponding to zonal changes in other environmental

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  • Fig. 1. Map of permafrost zonal divisions and distribution of underground ice.

    Legend:1Boundaries of subzones;2Subzone of polygenetic permafrost;3Subzone of epigenetic permafrost;4Syngenetic wedge ice;5Epigenetic wedge ice;6Sheet-like ice bodies;7Injection ice.

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  • components, primarily that of climate. Fairly close agreements exist at the presenttime on many questions as to the general trends in the distribution and character ofpermafrost in the area. In particular it is generally accepted that the temperature ofthe permafrost varies between 1 in the south and -9 in the north [24].

    Permafrost Temperature and Thickness

    In conformity with the relief, N. A. Shpolyanskaya [24] identifies two types ofpermafrost developed in interfluves and in river valleys, respectively. The meanannual temperature of interfluve permafrost varies from 8 to 9C in the northto 5C in the south. The temperature of permafrost developed beneath rivervalleys varies from -6C to -8C in the north to -1C to -5C in the south ofthe region.

    Thus major differences in permafrost temperatures may be detected betweenthe upland and lowland areas [24]. The annual amplitude of temperature inpermafrost under conditions of varying relief in the north of Yamal is 4C. Thespatial distribution of temperature in the Yamal-Gydan area is mainly associatedwith the winter heat regime. Here the summer heat exchange noticeably exceedsthat in winter; the difference between the two seasons is from 1 kcal/cm2 in thesouthern parts of the region to 5 kcal/cm2 in the north [24]. The main factor inthe winter heat exchange is the snow cover with its insulating qualities. Hence thedistribution of permafrost temperature corresponds to the snow cover distribution.

    Along with its low temperatures, the permafrost is characterized by fairly greatthickness. Until recently it was generally accepted that permafrost thickness in thenorth of Western Siberia fluctuated between 100-300 m and 500-700 m,increasing regularly from south to north [6, 15, 23, 24, etc.]. According to datagathered by V. T. Trofimov and B. V. Varenyshev [27] as part of complexengineering-geology field investigations carried out in 19691972 on Yamal Penin-sula by the Tyumen' Expedition, and from analysis of data collected earlier byother expeditions, permafrost thicknesses have turned out to be considerably lower.These authors have compiled a map of permafrost thicknesses in Yamal, which,when compared with the geomorphological map, demonstrates very well thedependence of the permafrost thickness on the age and genesis of the geomorpho-logical levels on which these deposits have formed.

    Permafrost thicknesses (according to these data) vary within quite a wide rangein Yamal: from 25 m up to 300400m, and in places even higher. The maximumthickness has been pinpointed west of Lake Neyto (450 m). The greatest permafrostthicknesses coincide with the oldest geomorphological level: the marine terrace ofthe Yamal Transgression, and in the majority of cases they exceed 300 m. Over themajority of the Yamal Peninsula, representing surfaces of the fourth, third, secondand first marine terraces, permafrost thickness varies from 300 to 150 m,corresponding to the decreasing altitude and age of the geomorphological level. Theleast permafrost thicknesses (50 m to 150 m) are typical of the Holocene levels(coastal marshes, floodplains, deltas, etc.). Beneath the present coastal marshes ofthe Kara Sea coast, permafrost thicknesses increase from 210 m at the seawardside to 50-80 m at the landward side, while on the landward areas of the coastalmarshes of Ob' Bay, permafrost thicknesses are 120-200 m.

    A regular variation in permafrost thicknesses has been recorded in the

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  • floodplains of the river valleys (the Yuribey, Seyakha, Kharasavey, Shchuch'ya,Mordyyakha, etc.)- On the upper reaches of the rivers, where the floodplains arenarrower and the streams small, the permafrost thickness differs little from that ofsurrounding areas. In the middle reaches permafrost thicknesses beneath thecentral parts of the floodplains are 50100 m, while in the lowest reaches, wherethe floodplains reach several kilometers in width, permafrost thicknesses decrease to4050 m. V. T. Trofimov and V. B. Varenyshev believe that the permafrostthicknesses, in the case of all wide floodplains, increase from the zone near the riverchannel, where the warming influence of the river water is both constant and ofconsiderable magnitude, to the edges of the floodplain.

    Apart from this they confirm V. V. Baulin's data [6] to the effect thatpermafrost thicknesses are less in the core areas of geological structures than ontheir fringes. However, in their opinion, this decrease in permafrost thickness in thecore areas of structures ought to appear clearly only in the event that the entirestructure lies within a single geomorphological level.

    The continuous extent of thick permafrost within the region is broken by opentaliks only beneath large rivers. Closed taliks exist beneath the channels of smallrivers and lakes deeper than 1.5 m [4, 6, 17]. On the Yamal, Gydan and Tazpeninsulas the majority of rivers have quite low discharges and possess fairly lowwater temperatures; the warming influ...

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