YAKUTSK, December 8. /TASS/. The erosion processes in the Arctic, caused by the global warming and the permafrost's thawing, threaten local residents, as well as the flora and fauna, leading expert of the North-Eastern Federal University and the Melnikov Permafrost Institute Nikita Tananayev told TASS.
At most hydrological stations in the permafrost zone, scientists can see increased water consumption in winters, which means that perennially frozen grounds, underlying riverbeds, may disappear gradually.
"In Russia's northeast, over recent two decades, numerous communities have reported damage from the coastal erosion," the expert said. He recalled a significant damage to the Yakut village of Zyryanka in 2003 due to the spring flood and collapsed banks of the Kolyma River. Later, protective dams were built along the river there. Similar dams now protect settlements in the middle reaches of the Lena and on the Vilyui River - in the western part of Yakutia.
Scientists say that higher temperatures in the upper layers of cryolithozone, which takes 65% of the Russian territory, will affect stability of foundations and engineering structures. These processes develop actively: the share of deformed buildings has reached 40%.
Cryogenic factors are reasons for 23% of failures in the oil and gas industry's technical systems and for 29% of hydrocarbon production's loss. The potential damage to buildings and structures from the permafrost melting in the Russian Federation's Arctic zone is estimated at 5-7 trillion rubles ($79-111 billion) to 2050, where 700 billion rubles ($11 billion) is an estimated damage to the housing sector.
Changing rivers
In beds of northern rivers, seasonal and, in some places, perennially frozen grounds are located near the bottom, he continued. "The changes we can see at most hydrological stations in the cryolithozone are: an increase in winter water consumption associated with the permafrost melting. One is a direct consequence of the other. We can see bigger winter runoffs, and water levels get higher. Thus, the riverbed area reduces and is subject to freezing in winter," he added.
The riverbed relief is developing more actively, the scientist said. "It is quite possible that frozen soils underlying riverbeds will practically disappear from the bottom layer, and will remain only deep under riverbeds. In that case, the development of river valleys in the permafrost zone, strange as it may seem, will not differ in any way from rivers in temperate latitudes," he added. In this case, floodplain massifs and secondary streams in branched beds of northern rivers will develop more actively.
The climate warming changes the hydrological conditions - precipitation, evaporation, water movements on the surface of the earth and under it. "Additionally, and this is specifically important for Yakutia and generally for the Northern regions, the permafrost has been degrading. Noteworthy, the permafrost underlies more than 25% of the Northern hemisphere and 65% of the Russian territory," he told TASS.
Permafrost degradation
The impact of future changes depends on the territory where they are observed, as well as on the position in the relief, the scientist explained. For example, in intertidal spaces and slopes, the combination of climatic and hydrological changes will decrease the soil moisture in the upper horizon - in top 20 cm.
"This will mean that the slope surface runoff (the fastest) will be less frequent in regions underlain by the permafrost. Accordingly, erosion forms on the slopes will develop less actively. And the slopes - it's a paradox - will get more stable in terms of flowing water," he added.
On the other hand, in the Arctic continues a physical degradation of the permafrost - developing thermokarst and large landslides. In Northern regions, this may be due to hotter summers or due to bigger precipitation in areas where summer temperatures have not grown noticeably.
Sediments brought directly into rivers get bigger and they contact landslide slopes - directly or via more active stream erosion along disturbed slopes. "It is in such thermal tanks or on slopes, where the soil's upper part slides down under the gravity, where stream erosion processes will be active. Sediments that move from the slopes and get into rivers, will transform their reliefs," the scientist said. When the permafrost thawing under the slopes ends, the slopes will stabilize, and the flow of sediments will stop. So far, however, the transforming river valleys may have a negative impact on riverine settlements.
In warmer climates, river floodplains will thaw, losing permafrost. "It is difficult to predict how this will affect coastal erosion and flooding. The thawing floodplains will make lower river shores due to the loss of soil. For the Lena River's middle course, near Yakutsk, we know - the lower the banks, the lower are their erosion rates. Therefore, there we can expect a decrease in the rate of coastal erosion in the future," he said. However, if floodplains are flooded more often, the process may be compensated with bigger amounts of sediments on the floodplain, and in that case the threat to Northern shores will remain, he said in conclusion.