Eastern Arctic Seas Research Articles

Mechanisms responsible for degradation of submarine permafrost on the eastern arctic shelf of Russia

In 2011, a marine interdisciplinary expedition on the R/V Akademik M.A. Lavrentyev was carried out in the eastern Arctic seas. The expedition was conducted within the framework of the project of targeted basic investigations under the aegis of the Russian Founda� tion for Basic Research. These investigations regis� tered intense methane blowouts related to degradation of submarine permafrost (SMPF) in these basins. The mechanisms responsible for their degradation are determined by paleogeographic factors and recent sedimentation, as well as by structural features of the Arctic region. Under continuing degradation of sub� marine permafrost, methane emission should inten� sify. This process results in the formation of significant values of both gas and water, which migrate upward through the sedimentary section of the shelf and along the bedding surfaces from coastal heated areas to colder deeper parts of the basins forming subhorizon� tal convective cells, thus, stimulating permafrost deg� radation even under negative bottom temperatures. Submarine permafrost rocks are widespread mostly on the shelf in the eastern sector of the Russian Arctic region. This is explained by the peculiar paleogeo� graphic development of the region: due to the absence of the ice shield during the Quaternary glacial epochs, the shelf was dominated by subaerial settings with low temperatures. Alternation of subaerial and marine environments on the shelf resulted in the formation of a stratified sedimentary sequence. The regressive cycles (cooling epochs) were accompanied by intense frosting of the primary surface and formation of com� pact dehydrated members (for example, during the last Late Quaternary regression). On the contrary, the transgressive cycles (warming epochs) were marked by accumulation of unconsolidated sediments. In these periods, stable negative temperatures of the bottom water favored conservation of the stratified structure in the sedimentary section [1, 2].

Polychlorinated naphthalenes in air and snow in the Norwegian Arctic: a local source or an Eastern Arctic phenomenon?

PCNs were measured in air and snow during separate field campaigns at Ny-Ålesund (April 2001) and Tromsø (February/March 2003) in the Norwegian Arctic. Air concentrations ranged from 27 to 48 and 9 to 47 pg ΣPCN m −3 for Ny-Ålesund ( n=6) and Tromsø ( n=10), respectively. These concentrations (including the tri-chlorinated naphthalenes) greatly exceeded concentrations previously measured in the Canadian Arctic, but did fall within the upper range of concentrations observed over the eastern Arctic Ocean and regional seas. Local sources appear to be affecting concentrations observed at both sites, with the presence of several hexa-chlorinated naphthalenes at Tromsø probably attributed to local/regional sources. Use of air mass back trajectories at Tromsø revealed that background air concentrations in the Norwegian Arctic are likely to range between <9 and 20 pg ΣPCN m −3 and that contemporary concentrations derived close to potential sources (i.e. arctic towns) may equal or exceed those of PCBs. The mean concentration in surface snow was 350 and 240 pg ΣPCN L −1 (meltwater) (or 0.014 and 0.01 pg g −1 (snow)) at Ny-Ålesund and Tromsø, respectively. The wide variation in concentrations observed between fresh snowfalls could be explained by different snow densities (as a surrogate of snow surface area), rather than attributed to varying air concentrations. A statistically significant inverse relationship was found between snow density and concentrations of tri- to penta-chlorinated homologues and compliments similar findings for the polychlorinated biphenyls (PCBs). This suggests that the vapour-sorbed quantity changes rapidly with snow ageing/compaction; with implications for the fate of these chemicals in the Arctic.