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Understanding Thermokarst Lakes: Their Expansion, Impact on Microbial Communities and Contribution to Greenhouse Gas Emissions

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Mason Walker
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Understanding Thermokarst Lakes: Their Expansion, Impact on Microbial Communities and Contribution to Greenhouse Gas Emissions

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An Overview of Thermokarst Lake Development

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Thermokarst lakes are an integral part of permafrost regions. These bodies of water are formed by the thawing of ice-rich permafrost or the melting of massive ground ice. A recent study analyzed thermokarst lakes in a specific region, focusing on their number density, area density, and size characteristics. The analysis revealed the distribution of small, medium, and large lakes in different sub-regions, with a noteworthy increase in both lake number and area from 1988 to 2020.

Interestingly, the emergence and expansion rates of the lakes varied between different phases and sub-regions. The study also highlighted the seasonal variation, permafrost characteristics, terrain, and climate data as influential factors on thermokarst lake development. It was found that thermokarst lakes are widely developed in warm permafrost regions with low ground ice content.

Impact of Marine Water Inundation on Microbial Communities

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Thermokarst lakes and lagoons are not only important geological features but are also home to diverse microbial communities. A study investigated the effect of marine water inundation on microbial community composition in Arctic coastal thermokarst lakes and lagoons. It was discovered that microbial structures in the uppermost lagoon sediment influenced by marine water inflow were significantly different from those deeper in the lagoon sediment and from those of the lakes.

Furthermore, the diversity of core microbial consortia community decreased compared with the lake sediments. This indicates that transitions from thermokarst lake to lagoon can substantially alter microbial communities.

Thermokarst Lakes and Greenhouse Gas Emissions

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Thermokarst lakes also play a significant role in greenhouse gas emissions, specifically methane (CH4) and carbon dioxide (CO2). A study explored the relationship between lake size and aerobic methane oxidation in sediments, as well as the production of CO2. The study found that CO2 production was stronger in the upper sediments of smaller lakes, while methane oxidation rates were faster in larger lakes due to higher oxygen concentration. These findings highlight the role of thermokarst lakes as crucial hotspots for greenhouse gas emissions.

Climate Change and Groundwater Storage

Climate change has been identified as a major driver of groundwater storage recharge and discharge in the Qinghai Tibetan Plateau. Changes in precipitation, evapotranspiration, and permafrost are among the regional drivers influencing groundwater quantity evolution dynamics. To monitor regional groundwater evolution more effectively, future research has been proposed to develop advanced coupled cryosphere-groundwater numerical modeling methods.

Permafrost Degradation and Thermokarst Processes on Sediment Transport

Finally, the impacts of permafrost degradation and thermokarst processes on sediment transport cannot be overlooked. With a warming and wetting climate, thermokarst processes will increase the occurrence of mass movements until the slopes are stabilized. This underlines the pressing need for a deeper understanding of thermokarst landscapes and related permafrost erosion processes.

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