7GLOB_6 (1)

Definition: Permafrost is the subsurface layer of soil that remains at or below 0°C for two or more years and can optionally contain ground ice.
Classification: Permafrost can be categorized as continuous, discontinuous, sporadic, or isolated based on spatial distribution and abundance.
Geographical Extent: Terrestrial permafrost covers up to 24% of the Northern Hemisphere's exposed land area.
Thickness: Ranges from 500 to 1400 m in the Arctic regions to just a few meters in subarctic areas.
Temperature Influences: The surface energy balance plays a crucial role in determining permafrost temperature, thickness, and continuity.

Active Layer: Portion above permafrost that thaws and freezes seasonally; crucial for ecological activity in cold regions.
Talik: A layer of unfrozen ground within a permafrost area, resulting from anomalies in temperature or moisture conditions.

Aggradation: An increase in permafrost extent or thickness.
Degradation: A decrease in extent or thickness, observed to be rapid in recent years.

Consequences of Global Warming:
- Increased temperatures and altered precipitation patterns.
- Changes in albedo (surface reflectivity) contributing to further warming.
- Release of greenhouse gases, particularly methane, from thawing permafrost.

Key Observations:
- High-confidence indication of warming and thawing permafrost in Northern Hemisphere.
- Observations of permafrost temperature increases since the 1980s.

Trends:
- Northern Alaska recorded temperature increases of 2°C to 3°C.
- Evidence of permafrost thawing beyond Alaska in regions such as the Swiss Alps and Tibetan Plateau.

High likelihood of substantial decrease in near-surface permafrost as global temperatures rise; projections indicate decreases from 37% to 81% based on various climate scenarios.
Substantial risks of carbon and methane emissions linked to thawing permafrost.

Effects on Geomorphology:
- Ground subsidence upon thawing of ice-rich layers, leading to landscape changes.
- Thermokarst processes manifesting as depressions and lakes.
Influence on Hydrology:
- Changes in water storage and discharge patterns.
- Increased frequency of wildfires exacerbating thawing.

Ecosystem Changes:
- Over-saturation leading to swamp formation.
- Increase in landslides and erosion rates due to increased terrain subsidence.

Yedoma: Organic-rich permafrost with significant carbon content that releases methane during decomposition.
Carbon Balance: Shift in permafrost changes can modify an ecosystem's role as a carbon sink or source, influencing climate.

Characteristics: Situated beneath the seabed and influenced by sea temperature and historical sea level changes.
- Assessment of methane release potential remains uncertain due to limited observational data.

Various strategies have been developed to address issues arising from thawing permafrost:
- Construction of bridges and elevated tracks to reduce ground contact.
- Passive cooling measures (e.g., ammonia-based heat exchangers).

Building Strategies:
- Structures should be elevated on piles or gravel pads.
- Above-ground placement of utilities to mitigate heat influx.
- Installation of heat transfer systems to manage permafrost temperatures beneath infrastructure.

Notable references include works by Lanz, Harris, and the IPCC, which discuss various aspects of global environmental problems related to permafrost.

The degradation of permafrost presents significant implications for climate change, ecosystems, infrastructure, and the global carbon cycle. Continuous monitoring and adaptive strategies are essential to mitigate its impacts.