COASTAL GEOSYSTEMS OF THE KARA SEA IN A CHANGING CLIMATE

Current climate changes cause an increase both in coastal retreat rates and in sediment intake of the water area. The presence of ground ice in coastal outcrops additionally accelerates these processes. The researchers identify two morphological types of coastal zone destruction for the Western part of the Arctic — linear and volumetric. The retreat rate in some areas reaches 3 m/year and above. Together with terrigenous material, organic matter, gases, occluded in ice and sediments, and low-valent metal ions (mainly Fe (II)) enter the water, thus causing a change in physicochemical parameters of the coastal zone environment. The researches performed geochemical studies of ground ice and host sediments on three sections of the Kara Sea coast (Spindler area; Marre-Sale subsoil; Sopochnaya Karga subsoil). The results allowed developing a geochemical model of changes in the geosystems of the coastal-shelf zone under current climate warming conditions in the Arctic. The researchers have identified processes causing changes in coastal geosystems: a decrease in the concentration of oxygen in water due to the oxidation of substances coming from decaying coastal deposits, the drift of fine particles into coastal waters, and the release of gases during destruction of permafrost and ground ice. The volume of oxygen consumed during coastal destruction is comparable in order of magnitude with its volume obtained in the process of photodissociation of water in the upper atmosphere. The oxidation of Fe (II) during thawing of the permafrost requires the amount of oxygen contained in about 1 km3 of water. In the absence or limitation of the rapid exchange of water masses inside the basin, the oxygen contained in seawater will be completely exhausted for iron oxidation, which will lead to both complete stagnation of the coastal biota and development of anaerobic processes. Significant variations in the CH4 concentrations in sediments and ice indicate possible accumulations of these gases in “traps” inside frozen rocks. Their destruction can be dangerous for coastal geosystems.

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