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Understanding the processes associated with the formation and decomposition of gas hydrates on the arctic shelf
Gas hydrates are primarily located in oceans along continental margins and in permafrost regions with low temperature and high pressure. As an important energy source, hydrates have gathered significant attention from global scientific community. Gas hydrates are also of significant theoretical and practical interest due to their potential influence on climate change, especially in the Arctic shelf region with huge hydrate potential. However, the understanding of the formation and decomposition mechanisms of hydrate in sediments remains unclear. This paper seeks to bridge this knowledge gap by comprehensive examining the formation/decomposition mechanisms of hydrate from both laboratory experiments and geological reservoir perspective regarding changes in the subsea permafrost–hydrate system existing in the largest, shallowest shelf in the Arctic Ocean; the East Siberian Arctic Shelf (ESAS). This study investigates key natural processes associated with the formation and decomposition processes of methane and carbon dioxide hydrates, particularly in the dynamic Arctic shelf region, which plays a crucial role in increasing methane emissions into the atmosphere. Using a specialized laboratory setup, we conducted model experiments to observe dynamic processes at temperature and pressure ranges ambient for the Arctic shelf sediments and performed spectroscopic analyses of gas hydrate structures formed on actual sediment sample. Our findings reveal several novel and important phenomena: the formation of gas hydrate shells around bubbles, the emergence of elongated bubbles and stable bubble clusters, the behavior of both slow-rising and high-velocity bubbles, and the presence of bubbles partially filled with gaseous and liquid hydrocarbons. Furthermore, we documented the formation of stable channels in the sediment layers created by bubbles ascending from decomposing hydrates. The new feature of microparticle/fine particle bubble tail could play a role in formation of coarse sand patches found in the Laptev Sea cold seepage areas. These results showcase a range of intriguing and, in some cases, unexpected processes occurring within the hydrate-bubbles sediment system of the Arctic shelf, providing valuable new insights. The results of this study can be used to improve climate change models. Additionally, these findings may enhance methods for remote acoustic assessment of gas fluxes from sediments into the water column. Further research in this direction will be important for clarifying the entire chain of complex dynamic processes occurring on the Arctic shelf and identifying their impact on the environment.