Gas-emission craters on Yamal and Gydan Peninsulas – future lakesтезисы доклада Электронная публикация

Работа с тезисами доклада

[1] Gas-emission craters on yamal and gydan peninsulas – future lakes / Y. Dvornikov, M. Leibman, A. Khomutov et al. // The 2nd Asian Conference on Permafrost (ACOP2017) July 2 – July 6 2017, Sapporo, Japan. — Hokkaido University, Sapporo, Japan, 2017. We hypothesize that some of the lakes on the Yamal Peninsula have a non-thermokarst origin (specifically, they are not resulting from subsidence caused by the ground ice thaw). In 2013, gas emission craters (GEC) on Yamal and Gydan peninsulas were formed (Kizyakov et al., 2015). Members of our research group have visited Yamal GEC in 2014 (Leibman et al. 2014) and since then we continued monitoring of this feature. In summer of 2016 our group has also visited a GEC on Gydan peninsula close to a Antipayuta settlement. In 2015 collected were water samples for dissolved methane tests from Yamal GEC. Observed concentrations were 614 nmol/L at the next to water surface and 10350 nmol/L at the depth of 14.5 m of the Yamal GEC lake (the maximal measured depth in 2015 was 23 m). Herewith, the mean dissolved methane concentration in nearest lakes was only 84 nmol/L. It can be concluded that after the event of avalanche-like gas emission and crater formation, the source of methane from the bottom kept active for some time providing gas seepage into the water column of the GEC lake. While the maximum measured depth of Yamal GEC lake was 23 m in 2015, in 2016, the maximum measured depth in the center of GEC lake was about 8 m. At the same time, the area of GEC increased twofold. The maximum measured depth of the lake in Gydan GEC was only 3.5 m. Therefore, during first years of their lifetime the GEC lakes are being filled with water and coastal sediments. Isotope samples taken from both GEC lakes have shown that the isotopic composition of the water is closer to that in tabular ground ice found in this region than to the composition in the nearest lakes. But from year to year the isotopic composition is becoming “lighter”. We then can conclude, that during first years the main source of the water in GEC lakes is thawing ice-bearing permafrost. In addition, thawing of permafrost delivers a huge amount of suspended and particulate matter to the GEC lakes. Studied GEC-lakes water has a higher concentration of major ions, dissolved organic carbon, total suspended matter compared to regular lake water. But we expect that in the nearest future, after the feature stabilizes, the geochemistry of GEC lakes approach that of the regular Yamal – Gydan lakes. Moreover, our bathymetric surveys in lakes of central Yamal have revealed that 18% of measured lakes have crater-like features with much higher depths than the average depth of the lake. These crater-like features are relatively small in area compared to total lake area and can be linked to either the thaw of permafrost underneath or to gas emission. These are the gaps that we need to bridge working on the GEC related issues. This work is supported by RSF grant 16-17-10203 and by Government of Yamal.

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