TSU scientists found that a lake disappeared in the Arctic zone

Scientists at the TSU Laboratory of Biogeochemical and Remote Monitoring of the Environment are examining the highly productive ecosystems of the Arctic and Subarctic. The main objects of study are the lakes, swamps, and drained lakes (hasyray - the depressions of the former lakes, which were deserted due to the melting of the permafrost and thermal erosion of the shores). Recently, scientists discovered a lake in Yamalo-Nenets Autonomous Okrug that disappeared in less than a month - it made its way into the thawed soil and flowed into Taz Bay.

Laboratory Bio-Geo-Clim was created and equipped with the funds of a megagrant allocated by the Russian government. Its leader is Oleg Pokrovsky, a scientist at TSU and the Observatory Midi-Pyrénées of CNRS (Toulouse, France).

- Usually, the formation of a drained lake is quite a long and phased process that takes several decades,- explains Sergey Loyko, the head of a research project, senior researcher at the laboratory. - In this case, everything happened ten times faster. We found this drained lake from space images two years after its formation, when we searched for the young basins of former reservoirs in the Arctic zone of the Russian Federation. The lake disappeared in the summer of 2016, which was quite hot: it existed at the beginning of July, and was no longer there at the end of the month.

To understand where the water went, the scientists went to the location of the former reservoir. A survey of the basin showed that the lake had gone to the Gulf of Ob of the Kara Sea (Taz Bay). At the same time, the scour along which the lake flowed had already managed to overgrow sedge and cereals. This and other studies helped to obtain data on the extent to which the speed of water descent depends on the difference between the lake and the receiving water body - another lake, river, or sea. In the case of a missing water body, this difference was quite significant - about 15–20 meters - and, what is most important, abrupt.

In the bottom sediments of drained lakes, there are a large number of mineral substances that feed the plants. Soon after the draining of the lakes, a real “flash of life” occurs in their place and in the tundra, and forest tundra there appear oases with shrub-meadow vegetation.

The observations of TSU scientists show that in the past 30 years, the formation of drained lakes has become much more active: the number of such sites has almost doubled. The study of old and young basins of the former lakes showed that despite the serious differences in the structure of their upper layers, the number of nutrients below the root-inhabited horizon is about the same.

- These ecosystems can be purposefully activated in order to provoke the growth of green mass,- says Sergey Loyko. - To do this, it is enough to fill the basin with water, creating a dam, and lower it after a few years; later a drained lake covered with grass can be used for summer grazing of deer and harvesting green fodder. However, after the first decades, the productivity of the drained lakes will begin to fall again. Now we are studying how and what the rates of its decrease depend on.

In 2018, the laboratory researchers obtained new data on the geochemical composition of wetlands. Previously, scientists had only information about the meltwaters. This time, they sampled ten marshes in the Nadym and Taz districts of the Yamal-Nenets Autonomous District, as well as at the location of the Khanymey TSU research base. Ice samples in the permafrost peat were collected throughout the depth of the swamp to the very bottom of the mineral. After thawing the samples, scientists analyzed the concentration of 40 chemical elements, and in particular, estimated the level of bioavailable organic carbon, phosphorus, potassium, calcium, cobalt, and iron.

The analysis showed that in the frozen part of the swamp the concentration of nutrients is 20–70 times higher than in the surface layer, which is subject to annual thawing. According to the scientists, if the warming trend continues, substances from the frozen water will begin to be released and pass into the soil. This will lead to an increase in soil fertility and the growth of more lush vegetation, especially in river valleys and drained lakes, where nutrients will be leached from the marshes. As Sergey Loyko notes, these changes are already occurring, in connection with which there has been a steady trend towards the greening of the Arctic, fixed by various scientific groups.

In 2019, TSU scientists will continue their research under the project Biogeochemical Study of the High Biological Productivity of Vegetation in the Subarctic Conditions as a Basis for Creating Environmental Engineering in the Arctic Zone of the Russian Federation.