dynamics of permafrost active layer were carried out in the eight summer periods in the Recherche Fiord border (the Bellsund southern region).

Transkrypt

1 Janina REPELEWSKA-PĘKALOWA Department of Geomorphology Institute of Earth Sciences Maria Curie-Skłodowska University Akademicka Lublin, P O L A N D Wyprawy Geograficzne na Spitsbergen UMCS. Lublin, 1994 SUMMER THAWING OF GROUND IN CALYPSOSTRANDA IN THE RECHERCHEFJORDEN REGION (SPITSBERGEN) INTRODUCTION The polar summer is a period of intensive activity of morphogenetic processes resulting from snow melting and ground thawing. A large amount of water causes the development of erosion, washing and creeping processes. The temperature increase causes heat wave penetration and thawing of the permafrost upper layer called the permafrost active layer. In this layer vertical movements of ground, implying freezing and thawing alternately, as well as heaving and drying, take place. That causes formation and development of patterned ground as well as solifluction which are the typical phenomena for the periglacial zone. The sine qua non condition for the development of most morphogenetic processes is ground thawing, that is why the studies aiming at the determination of this process intensity, are significant. This problem was investigated by the Spitsbergen Polish Expeditions exploring the Hornsund and Kaffióyra regions (Jahn, 1983; Grześ, Wójcik et al. 1991). This problem had to be included also in the programme of Geographical Expeditions organized by Maria Curie-Sklodowska University (Repelewska-Pękalowa, 1992). The studies on the dynamics of permafrost active layer were carried out in the eight summer periods in the Recherche Fiord border (the Bellsund southern region). G E N E R A L CHARACTERISTICS O F T H E STUDY AREA Calypsostranda, a coastal plain situated in the foreland of the Scott and Renard glaciers was the study area. According to the regional division of Spitsbergen, it is a north-west part of Wedel Jarlsberg Land. Its width is about 2 km and length 5 km. In the north side it is enclosed by the active cliff in Skilvika and in the north-east by a dead cliff separated by a zone of beaches and contemporary storm ridges (Fig. 1). 93

2 Calypsostranda constitutes a complex of raised marine terraces, 3 to 100 m high, formed in Pleistocene and Holocene (Landvik et al. 1988; Salvigsen et al. 1991). The largest area is occupied by the terrace m a.s.l., formed in Early Holocene (Repelewska-Pękalowa, Pękala 1990). It is cut by glacial, nival and melt-permafrost rivers (Repelewska-Pękalowa, 1987). Calypsostranda plain is built of marine, glacial, fluvioglacial deposits resting on the ground course of Tertiary rocks. Quaternary rocks, whose thickness is several meters are represented by sands with gravels, marine silts and boulder clays (Dallman et al. 1990). Permafrost thickness is from 100 to 460 m (Liestol 1977). From a geobotanical point of view (Święs 1988) the area is an example of lichen and moss grown tundra. RESEARCH M E T H O D S A sounding method using steel rods was applied. Apart from that, the Danilin frostmeters were used. These are the methods frequently used. Soundings were made several times during the polar summer from 1986 to They were applied in the whole area of Calypsostranda. The measuring points constituted systematic series of N-S and E-W aspects and on different aspects of slopes: northern, southern, eastern and western. A sounding system consisted of over 300 points. At the same time the measurements of ground thermal currents (Gluza, 1990, Gluza et al. 1988) and observations of essential meteorological elements were carried out. THICKNESS O F P E R M A F R O S T ACTIVE LAYER A N D RATE O F ITS D E V E L O P M E N T It is known that ground thawing starts when the snow cover dissappears and develops, reaching its maximum in the middle of August. It is a time function (Jahn 1982, Jahn & Walker, 1983). However, the course and rate of this process are differentiated. There are many reasons for it, of which the increase of air and ground temperature recorded in the summer are essential. The effect of this factor due to an air free flow was almost the same in the whole area of Calypsostranda. Also the sediments deposited on the surface possess similar characteristics (Repelewska-Pękalowa, Pękala 1993). Therefore great differentiation of the active layer thickness had to be caused by other factors. The development of ground thawing process was observed during the eight seasons. A large number of data concerning the tundra geocomplexes characteristic for Calypsostranda was collected (Repelewska-Pękalowa, Gluza, 1988; Repelewska-Pękalowa, Magierski, 1989; Repelewska-Pękalowa, Paszczyk, 1990; Paszczyk, Repelewska-Pękalowa 1991; Repelewska-Pękalowa, Pękala 1993). 94

3 The most representative sites-geocomplexes connected with the terrace m a.s.l. are: - a flat surface close to the terrace edge, modelled by washing and niveo-eolian processes with poor vegetation (point 1); - patterned grounds, periodically waterlogged with the mobile water in the covers, moss grown on the peat layer (point 2); - active patterned grounds with the mobile water in the covers without a compact vegetation cover (point 3); - a small stream flowing over the surface without a compact vegetation cover (point 3a); - a peat islet of about 50 m 2 area within a shallow lakelet (point 4); - a plain at the dead cliff foot in the vicinity of a beach, without compact vegetation, a changing level of underground waters (point 5); - surfaces of differentiated aspects: N, S, W, E but of similar slopes inclination, covered with poor vegetation; Summer thawing of the ground on Calypsostranda in presented in Tables 1 and 2. One should emphasize the enormous differentation of this process intensity as stated in the earlier publications. The deepest thawing took place in the complexes characterized by the presence of mobile water in covers which can be explained by an easy transfer of heat through it. Thawing on the slope of aspect S, strongly heated and dispossessed of snow cover early, was also quite deep. The smaliest intensity of the summer thawing process was observed in places where stagnant water constituted an isolating layer, in places covered with peat and vegetation and where the snow lay for a long period. This situation is well illustrated by the distribution of thermoisoplets (Gluza et al. 1988) showingmore difficult penetration of heat inside and formation of specific temperature stratification (Fig. 2). Studies on chemical properties of permafrost active layer waters (Magierski et al. 1990, Repelewska-Pękalowa, Magierski 1989) showed poor mineralization of Calypsostranda underground waters and allowed to make some observations concerning mobile waters in the permfrost active layer. It can be stated that water dislocates along the permafrost roof forming a dynamic two-phase system. As long as the flow exists, the permafrost roof starts melting continuously. In summer the main cause is the plus temperature of water but in autumn it is the decrease of water solidification point due to higher mineralization, the so called the cryochemical effect" (Pulina, 1984, Repelewska-Pękalowa, Magierski, 1989). It is not easy to determine the thawing rate. It becomes possible only when the beginning of measurements is synchronized with the process start. For technical reasons it was possible only in 1987 (Repelewska-Pękalowa, Gluza 1988). From 95

4 the observations made then (Tab. 3) it was stated that thawing proceeded quickly where it was delayed for some reason. The maximum rates were on the average from 4.5 to 5.9 cm/a day and night. The thawing process could proceed at the rate increasing gradually and then decreasing or at the rate changing stepwise. Such a situation took place in the summer 1987 (Tab. 3). The taxonomic analysis of the data collected in the long measuring period (Paszczyk, Repelewska-Pękalowa 1991) shows that thawing has a phase character. The following phases can be distinguished: initial, transient, stagnation and dying out of the process (Fig. 3). Similar remarks refer to coastal plain Kaffióyra (Wójcik et al. 1990). A relatively long period of studies provided a large number of numerical data characterizing development of the permafrost active layer. Their elaboration required application of statistical analysis methods such as analyses of regression, variance and correlation as well as computer processing of empirical data. It was possible to obtain the isolines of the studied area. The attempt was made to reconstruct the initial period of thawing and to determine the average thickness of permafrost active layer as well as thickness anticipated on the last day of the astronomical summer (Fig. 4). The hierarchic classification methods were used to divide the studied region into areas of similar thawing regime (Repelewska-Pękalowa, Paszczyk, 1990). CONCLUSIONS The measurements of permaforst active layer thickness to determine size and rate of the summer thawing were carried out in the eight summer periods. These were the periods with different meteorological conditions which are responsible for these processes. The surprising fact is enormous differentiation of parameters characteristic for the permafrost active layer dynamics assigned to a relatively small study area. This is the evidence for a large influence of local factors such as: the extent of underground water mobility, vegetation, as well as aspect, which clearly results from the analyses of the data from the whole study period. This fact is also important because of the utilitarian character of the studies which have become more and more important recently. The evidence of their are the publications presented at the International Conferences on Permafrost as well as the works of the International Permafrost Association. REFERENCES DaUmann W. K., Hjelle A., Ohta Y., Salvigsen O., BjornerudM. G., Hauser E. C., Maher H. D., Craddock C., 1990: Geological M a p Svalbard 1: В 11G Van Keulenfjorden. Norsk Polarinstitult, Oslo. 96

5 Grześ M., 1985: Warstwa czynna wieloletniej zmarzliny na zachodnich wybrzeżach Spitsbergenu. Przegl. Geogr. t. 57, z. 4: Gluza A. F., 1990: Distribution of the ground temperature in July, August and September 1988 on Calypsostranda (Southern Bellsund-Western Spitsbergen). Wyprawy Geograficzne na Spitsbergen, UMCS Lublin: Gluza A., Repelewska-Pękalowa J. & Dąbrowski К., 1988: Thermic of permafrost active layer - Spitsbergen. V International Conference of Permafrost, Trondheim, Proceeding vol. 1, Jahn A., 1982: Soil thawing and active layer of permafrost in Spitsbergen. Acta Univ. Wratisl. No. 525: Jahn A., Walker H. J., 1983: The active layer and climate. Z. f. Geomorph. Suppl. Bd. 47: LandvikJ. Y., Mangerud J. & Salvigsen O., 1988: Glacial history and permafrost in the Svalbard area. V International Conference on Permafrost, Trondheim. Proceedings vol. 1: LiestolO., 1977: Pingos, springs and permafrost in Spitsbergen. Norsk Polarinstitutt Arbok 1975: Magierski./., Michalczyk Z., Repelewska-Pękalowa J., 1990: Water affluence of permafrost layer. Wyprawy Geograficzne na Spitsbergen, U M C S Lublin: Paszczyk J., Repelewska-Pękalowa J., 1991: The phases of summer thawing on the coastal plain Calypsostranda (Spitsbergen). Wyprawy Geograficzne na Spitsbergen, UMCS Lublin: Pękala К., Repelewska-Pękalowa J., 1990: Relief and stratigraphy of Quaternary deposits in the region of Recherche Fiord and southern Bellsund (Western Spitsbergen). Wyprawy Geograficzne na Spitsbergen, UMCS Lublin: Pulina M., 1984: The effect of cryochemical processes in the glaciers and the permafrost in Spitsbergen. Polish Polar Research, 5, 3-4. Repelewska-Pękalowa J., 1987: Rozwój równiny nadmorskiej pod wpływem procesów erozji (na przykładzie Calypsostrandy), rejon Bellsundu, Zachodni Spitsbergen. XIV Sympozjum Polarne, Lublin: Repelewska-Pękalowa J., 1992: Scientific results of Polar Expedition of Maria Curie-Skłodowska University in Lublin, Wyprawy Geograficzne na Spitsbergen UMCS Lublin, Repelewska-Pękalowa J. & Gluza A., 1988: Dynamics of permafrost active layer-spitsbergen V International Conference on Permafrost, Trondheim, Proceedings vol. 1; Repelewska-Pękalowa J., Magierski J., 1989: Czynna warstwa zmarzliny: dynamika i właściwości chemiczne wód, Calypsostranda, sezon letnio-jesienny 1988 r. Wyprawy Geograficzne na Spitsbergen, UMCS Lublin: Repelewska-Pękalowa./., Paszczyk./., 1990: Dynamics of permafrost active layer based on the statistical analysis. Wyprawy Geograficzne na Spitsbergen, UMCS Lublin: Repelewska-Pękalowa J., Pękala К., 1993: The influence on solifluction rates, Spitsbergen, Svalbard. Akademie der Wissenschaften und der Literatur, Mainz Palaoklimaforschung vol. 11. Special Issue: ESF Project European Palaeoclimate and M a n " 6; Święs F., 1988: Zróżnicowanie geobotaniczne tundry na południowym wybrzeżu Bellsundu (Spitsbergen Zachodni). Wyprawy Geograficzne na Spitsbergen, UMCS Lublin: Salvigsen O., Elgersma A., Landvik J. Y., 1991: Radiocarbon dated raised beaches in northwestern Wedel Jarlsberg Land, Spitsbergen Svalbard. Wyprawy Geograficzne na Spitsbergen, UMCS Lublin: Wójcik G., Marciniak К., Przybylak R., 1990: A dynamics of summer ground thawing due to meteorological conditions on the basis of Kaffióyra plain studies (NW Spitsbergen in period ). Wyprawy Geograficzne na Spitsbergen, UMCS Lublin:

6 STRESZCZENIE W sezonach letnich prowadzono na równinie nadmorskiej Calypsostranda w rejonie fiordu Recherche badania zmierzające do określenia wielkości i tempa letniego rozmarzania gruntów. Stosowano metodę sondowania przy użyciu stalowych prętów oraz posługiwano się zmarzlinomierzami Danilina. Punkty w których kilkakrotnie w ciągu każdego sezonu wykonywano pomiary były zlokalizowane w obrębie geokompleksów reprezentatywnych dla badanego terenu. Średnia wielkość letniego rozmarzania wahała się w granicach od 30 cm do 170 cm (Tab. 1) cm zaś maksymalna miąższość warstwy rozmarzniętej wynosiła od 60 cm do 196 cm (Tab. 2). Jak wynika z analizy danych, na stosunkowo niewielkiej powierzchni wielkość letniego rozmarzania gruntu była ogromnie zróżnicowana. Duży wpływ na tempo i rozmiary tego procesu miały czynniki lokalne: obecność ruchomych wód w pokrywach, roślinność oraz ekspozycja. Praca wykonana w ramach realizacji projektu badawczego (grant KBN) nr

7 Fig. 1. Location of study area 10VII 15 20VIT 25 1VIII 5 lovni 15 20VIII Fig. 2. Thermoisopleths of the grounds (points 4) - after Gluza et al

8 27 VI 4 VII 6 VII 8 VII 12 VII 25 VII 1 VIII hn I. t 1 M h-> 1 h- -H > M M hh t- ГЧ 4- > ve > oe > гч > i Ti > > n ^ ta- м с- ИН Nx кн Нм И i к ИН I 1 1 > > 1Г г- > О гч / jzm > > 4 VIII /йп 5 VIII й 7 VIII й 17 VIII й / 20 VIII й 31 VIII ł-" m i i / 1 А ПЛ С PD Fig. 3. Diagram of ground thawing division into periods A, B, C, D-the distinguished phases of the active layer development, (after Paszczyk & Repelewska-Pękalowa, 1991) 100

9 A В С Fig. 4. Dynamics of the permafrost active layer: A. Reconstruction of the beginning of a thawing period (dates) B. Average rate of thawing (cm/day) C. Prognostic thickness of permafrost active layer on the last day of astronomical summer in cm (after Repelewska-Pękalowa & Paszczyk, 1990) 101

10 Tab. 1. Summer thawing of the ground - Calypsostranda (mean values in cm) Place Years Point a Aspect of slopes N S E W

11 Tab. 2. Extreme thickness of permafrost active layer - Calypsostranda (in cm) Place Years Point ! a Aspect of slopes N S E w Tab. 3. Rate of summer thawing, Calypsostranda, summer 1987 (after Repelewska-Pękalowa & Gluza, 1988) Period total period J Place mean values cm/24-hour Point j Point i Point Point 3 a Point ! Points Aspect of slopes S N W E