Thermal states, responsiveness and degradation of marginal permafrost in Mongolia

• Published in: Permafrost and periglacial processes 2018-10, Vol.29 (4), p.271-282
• Main Authors: Ishikawa, Mamoru, Jamvaljav, Yamkhin, Dashtseren, Avirmed, Sharkhuu, Natsagdorj, Davaa, Gamboo, Iijima, Yoshihiro, Baatarbileg, Nachin, Yoshikawa, Kenji
• Format: Article
• Language: English
• Subjects: Air temperature; Boreholes; Ecosystems; Enthalpy; Environmental factors; Frozen ground; Geologic depressions; Ground temperatures; local and regional characteristics, marginal permafrost, multi‐borehole observations, permafrost degradation, thermal responsiveness; Permafrost; Permafrost temperatures; Regions; Sensible heat; Solar radiation; Temperature fluctuations; Winter ice
• ISSN: 1045-6740; 1099-1530
• DOI: 10.1002/ppp.1990

Ground thermal conditions in marginal permafrost in Mongolia were assessed using ground temperatures measured year‐round at 69 borehole sites. Permafrost is continuous in northern Mongolia and exists as sporadic/isolated patches in the south. Ground temperatures are strongly controlled by local environmental factors, such as topographic depressions that concentrate cold air during winter, ice‐rich strata that prevent penetration of sensible heat, and tree cover that reduces incident solar radiation. Permafrost temperatures are typically between −1 and 0°C; colder permafrost (< −2°C) occurs in the northern extent of continuous permafrost and at high elevations in the sporadic/isolated permafrost zones. Relict permafrost, which is thermally disconnected from seasonal air temperature fluctuations, is present near the latitudinal and elevational limits of perennially frozen ground. Cold and thermally responsive permafrost is dominant in the continuous and discontinuous zones, while warm and thermally unresponsive permafrost is dominant in the sporadic and isolated zones. Overall, the climate‐driven permafrost in the colder regions is stable, while the ecosystem‐driven permafrost in the warmer regions is degrading.