Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.geogr.msu.ru/structure/labs/geos/personal/belova/Belova_IPY-2012_Abstract_01519.pdf Дата изменения: Sun Jul 1 02:38:55 2012 Дата индексирования: Tue Oct 2 12:45:03 2012 Кодировка:

Massive Ice Beds of South-Western Coast of Kara Sea and Their Role in Coastal Dynamics N. Belova Lomonosov Moscow State University, Faculty of Geography, Moscow, Russia Cryolithological composition and in particular the presence of massive ground ice in the coastal bluffs significantly influences the morphology and evolution of the Arctic coasts. Massive ice beds were studied at two key sites of Russian Arctic coasts ­ at the western coast of Baydaratskaya Bay (Ngoyu-Yacha river mouth) and at Kharasavey settlement, West Yamal. The studied sites are now the areas of active gas infrastructure development. In 1980-s coastal dynamics monitoring networks were established at both of these sites. Observations are carried out using the method of repeated geodetic leveling from constant benchmarks. Multi-temporal aerospace imagery is also used here for coastal dynamics investigations. As a result the speed of coastal retreat at different coastal sections was obtained. This study presents the comparison of data on coastal retreat rates with the cryolithological structure of the coastal bluffs. At the at the western coast of Baydaratskaya Bay massive ice beds play more significant role in coastal bluff retreat to compare with their role near the Kharasavey settlement. At the NgoyuYacha river mouth massive ice beds exposures in sandy bluffs 10-25 m high cause maximum mean annual rates of coastal retreat ­ up to 2.0-2.1 m/year for the 41-yr period. In some decades almost the same rates were observed at the low coastal bluffs with wedge ice (at laida). At the Kharasavey settlement there is another situation. The highest coastal retreat rates (up to 2.2 m per year for the 1981-2008 yrs. period) were observed for the coastal bluffs up to 12 m high composed by silty clays with high ice content and ice wedges at the top of the bluff. Here niches made by waves at the base of the cliffs fall down after a rupture along ice-wedge planes. But massive ice beds in certain years cause the speeds not less to compare with the western coast of Baydaratskaya Bay ­ up to 7 m per year. Sporadic occurrence of massive ice beds leads to underestimation of their influence on coastal dynamics, because in different years they are revealed in different sections of the coast. At the Kharasavey coast human impact on the coastal dynamics is higher to compare with Baydaratskaya Bay western coast ­ active development at the coastal zone of Kharasavey area has started 27 years earlier. With the beginning of gas pipeline laying-out across the Baydaratskaya Bay in 2008 the coastal processes at this section would certainly change. At Baydaratskaya Bay western coast massive ice beds are responsible for the maximum mean annual coastal retreat rates, which are 2.3 times higher to compare with average retreat rates along this coastal section. Near Kharasavey settlement coastal bluffs with massive ice beds are characterized by less speeds of coastal erosion to compare with the icy silt clays bluffs with wedge ice or with the sections subjected to strong human impact. Nevertheless the areas of massive ice beds distribution in both regions should be ascribed as unstable, as in different years coastal retreat rates grow up dramatically after exposing of new massive ice beds.