Abstract
Recent estimations suggest that vast amounts of methane are locked in the Arctic Ocean bottom sediments in various forms of gas hydrates. A potential feedback from a continued warming of the Arctic region is therefore the release of methane to the atmosphere. This study addresses the relationship between a warming of the Arctic ocean and gas hydrate stability. We apply a theoretical model that estimates the base of the gas hydrate stability zone in the Arctic Ocean considering different bottom water warming and sea level scenarios. We model the present day conditions adopting two different geothermal gradient values: 30 and 40°C/km. For each geothermal gradient value, we simulate a rise and a decrease in seafloor temperature equal to 2°C and in sea level equal to 10 m. The results show that shallow gas hydrates present in water depths less than 500 m would be strongly affected by a future rise in seafloor temperature potentially resulting in large amounts of gas released to the water column due to their dissociation. We estimate that the area, where there could be complete gas hydrate dissociation, is about 4% of the area where there are the conditions for gas hydrates stability.
Highlights
Vast quantities of methane are trapped in oceanic hydrate deposits, and there is a concern that a rise in the ocean temperature will induce dissociation of these hydrate accumulations, potentially releasing large amounts of methane into the atmosphere [1, 2]
The gas hydrate stability zone along continental slopes is found to be sensitive to even small changes in ocean bottom temperature [4], and the Arctic Ocean most likely has a larger gas hydrate stability zone compared to other oceans because of its cold water and low geothermal gradients [7]
The gas hydrate stability zone thickness varies widely within Arctic region depending on factors such as ocean bottom water/permafrost temperature, geothermal gradient, salinity of the water, and composition of gas [9]
Summary
Vast quantities of methane are trapped in oceanic hydrate deposits, and there is a concern that a rise in the ocean temperature will induce dissociation of these hydrate accumulations, potentially releasing large amounts of methane into the atmosphere [1, 2]. The gas hydrate stability zone thickness varies widely within Arctic region depending on factors such as ocean bottom water/permafrost temperature, geothermal gradient, salinity of the water, and composition of gas [9] Both permafrost-associated gas hydrates and the shallowest part of the deepwater marine gas hydrate system are susceptible to dissociation (breakdown to methane and water) under conditions of a warming Arctic climate. The dissociation of these hydrate deposits, which release large quantities of methane, could have dramatic climatic consequences that in turn lead to further atmospheric and oceanic warming through accelerated decomposition of the remaining hydrates [7]. The following parameters were adopted to estimate the base of gas hydrate stability zone as described : geothermal gradient, seafloor temperature, bathymetry, and gas composition
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