What Are The Implications Of Thermokarst Lake Expansion On The Talik Formation And Subsidence Patterns In Ice-rich, Thaw-sensitive Deposits Of Late Pleistocene Age Cryotic Soils In The Continuous Permafrost Zone Of The Alaskan Arctic, And How Might These Changes Impact Regional Greenhouse Gas Emissions And Carbon Cycling?

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The expansion of thermokarst lakes in the Alaskan Arctic has significant implications for talik formation, subsidence, and regional greenhouse gas emissions, influencing carbon cycling in several interconnected ways:

  1. Talik Formation and Subsidence:

    • Thermokarst lakes contribute to the formation of talik, a thawed layer within permafrost, primarily through the warming effect of lake water. This thawing is more pronounced in larger and deeper lakes, leading to deeper talik development over time.
    • As permafrost thaws, the melting of ice within the soil causes subsidence, lowering the ground surface. This subsidence can create a positive feedback loop, as lower areas may retain more water, facilitating further lake expansion and thawing.

  2. Greenhouse Gas Emissions:

    • Thawing permafrost releases stored carbon as CO2 and methane. Thermokarst lakes act as sources of these gases, with methane production being significant in waterlogged environments due to anaerobic decomposition.
    • The type of lake ecosystem (e.g., fen vs. bog) and water depth may influence the dominance of CO2 or methane emissions, though methane is typically more prevalent in wet conditions.

  3. Carbon Cycling Implications:

    • The release of ancient carbon from thawing permafrost contributes to climate change, potentially outweighing the carbon sequestration by new vegetation in thawed areas.
    • The transformation of landscapes into wetlands may alter carbon cycling dynamics, though the net effect remains a significant release of stored carbon.

  4. Feedback Loops and Regional Impacts:

    • The expansion of thermokarst lakes accelerates permafrost thaw, creating a self-reinforcing cycle that enhances greenhouse gas emissions and climate change.
    • Regional factors, such as the continuous permafrost zone in Alaska, exacerbate these effects due to the large carbon stocks in Late Pleistocene soils, which are highly vulnerable to rapid thaw.

In conclusion, thermokarst lake expansion in the Alaskan Arctic drives talik formation and subsidence, leading to increased greenhouse gas emissions and altered carbon cycling. These processes create a feedback loop that accelerates climate change, with significant implications for regional carbon budgets and global climate projections.