Dynamics of the seasonal thawing of frozen ground at the disturbed area, Alexandra Land, Franz-Joseph Land Archipelago Tikhonravova Yana Earth Cryosphere Institute SB RAS, Tyumen, Russia tikh-jana@yandex.ru The Study Region The expedition of the "Russian Arctic" National Park visited the Franz-Joseph Land archipelago in 2014. The geocryological studies were included the assessing of the technogenic impact on the seasonal thawing of frozen ground at Alexandra Land. The study of the dynamics of the seasonally thawed layer was performed at two sites 40х70 m in size of the polar desert at Alexandra Land at 80°38'38" N 46°49'49" E (fig. 1). The first site was presented by natural conditions with mosses and lichens. The second one was covered by the consumer waste of the past dump, barrels of fuels (fig. 2) and the road. The island had been cleaned out of the wastes by 2014. Patches of fuel were removed by bulldozer, but black lenses were seen at the pit profile at depths of 2-5 cm. Also near of the tehnogenic site was observed the geocryology processes: thaw sinks, frost boil, polygonal pattern (fig. 3). Figure 3 – The geocryology processes: thaw sinks (a), frost boil (b), polygonal pattern (c) a b c Figure 2 – The barrels of fuels near the technogenic site Figure 1 – Location of Alexandra Land Island, the Franz-Josef Land Archipelago Figure 3 – Temperature in July and August for past 10 years The Condition The summer of 2014 at the archipelago was extremely cold; the area of sea ice cover was on 30% more than normal cover for the past 40 years in according to the data of the 'Russian Arctic' National Park. The snow didn't melt completely at the island. According to the Ernst Krenkel Observatory [http://www.Rp5.ru], the air temperature was at 1C below than the average temperatures of July-August for 10 years (fig. 3). The Method The traditional method of measuring of active-layer thickness by probing of the bottom of the active layer with a graduated rod could not be used because there are numerous large stones (fig. 4). The active-layer thickness was measured during one month (26 July – 24 August) at tests pits located on a grid with a step of 5 m. The repeated measurements were made at 5 points on the boundaries and in the center of the sites, the distance between the repeated pits was less than 0,5 m. The total water content was determined by point method [Ershov, 1985], samples were taken at the base of active-layer in the beginning and in the middle of the observation period. Figure 4 – The measuring of active-layer thickness at tests pits located The Result The dynamics of the active layer thickness at the sites was shown at the (fig. 1– c). The average depths of thawing were 14.7 cm at the natural site and 24 cm at the technogenic site at the end of July. At the end of August, the differences of the thawing depth decreased and reached 21,4 cm at the natural site and 26,6 cm at the technogenetic site. Minimum depth of thaw was 7 cm, maximum depth of thaw was 33 cm during the study. The sub-zero air temperature were registered at August 16 and the upward freezing begun at August 19 (see fig. 1 – c). The total water content was 20% at the natural and 32% at the technogenic site at July 29. It was 24% at the natural site and 27% at the technogenic site at August 10 [Tikhonravova, 2014]. The Conclude   The depths difference of permafrost roof on the natural and technogenetic sites probably associated with absence of vegetation cover, thus different albedo. The surface of technogenic site had depressed because of continuous dump influence and was further lowered after cleaning up, so it has wetted more. Over the observation period, dynamic of active-layer thawing was slower for the technogenic site because of higher total ice content in compare with natural site. Perhaps, in the beginning of summer thawing rate on the technogenic site was higher, but over time it was decreased because of the total water content increasing with depth. The study had begun when active-layer thickness already reached 11 cm on the natural site and 24 cm on the technogenic site. Also the lenses of oil and bitumen could distort the dynamics of thawing through the shifting of heat exchange within the soil. The research are need continued. Figure 3 – The depths of thaws on the natural and technogenetic sites in 2014, Alexandra Land, Franz Josef Land Research is supported by the Russian Science Foundation grant №14-17-00131 References Ershov E.D. 1985 Laboratory method of study to frozen soils - Moscow: MGU. 350 pp. (in Russia) Tikhonravova Y.V. 2014. The detection of a dependence of speed of thawing permafrost rocks of technogenic pressure on the island of Alexandra Land archipelago Franz-Joseph//Exploration and production of fossil fuels, Geology, geography, biology and ecology. Abstracts of the Sixth conference on the results of the practices – Moscow: «Pero». 173-174 pp. Weather on the island Hayes (http://www.Rp5.ru)