Abstract
Based on a regional ice-ocean model, we simulated the state of the water masses of the Arctic Ocean to analyze the transport of dissolved methane on the Arctic shelves. From 1970 to 2019, we obtained estimates of methane emissions at the Arctic seas due to the degradation of submarine permafrost and gas release at the ocean–bottom interface. The calculated annual methane flux from the Arctic shelf seas into the atmosphere did not exceed 2 Tg CH4 year−1. We have shown that the East Siberian shelf seas make the main contribution to the total methane emissions of the region. The spatial variability of the methane fluxes into the atmosphere is primarily due to the peculiarities of the water circulation and ice conditions. Only 7% of the dissolved methane originating from sediment enters the atmosphere within the study area. Most of it appears to be transported below the surface and oxidized by microbial activity. We found that increasing periods and areas of ice-free water and decreasing ice concentration have contributed to a steady increase in methane emissions since the middle of the first decade of the current century.
Highlights
The dramatic loss of the Arctic Sea ice observed during recent decades is the most apparent manifestation of climate change [1,2,3,4]
The vast area of the Arctic shelf seas and the adjacent water area, previously occupied by ice, is ice-free in the recent years of the second decade of the 2000s. The model reproduces this process with a certain degree of error compared to the observations (Figure 2b); the modeling results clearly show the primary trend of significant degradation of the ice cover started in the first decade of 2000, which continues to the present day
We analyzed the methane emission in the Arctic shelf seas due to gas release at the ocean–bottom interface caused by the degradation of submarine permafrost and an increase in its permeability
Summary
The dramatic loss of the Arctic Sea ice observed during recent decades is the most apparent manifestation of climate change [1,2,3,4]. As assessed from satellite data in [4], the declining linear trend of the Arctic ice extent for the total 42-year record since 1978 is rated at 40,000 km per year. By analyzing linear trends separately for decades, the authors have shown an accelerated decrease in sea ice extent in 2009−2018. According to their findings, the Arctic Sea ice decrease is by 5% in autumn–winter and 35% in spring–summer seasons. An assessment based on a satellite-derived global daily sea surface temperature data set [10] has shown that the second decade of the 21st century for the Siberian Arctic seas was significantly warmer than the first decade [11]. The surface temperature of these seas reached maximum values exceeding the climatic monthly average and threshold values calculated on the 90th percentile value of daily temperature for the climate period from 1981 to 2010
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