Characteristics of Water‐Heat Exchanges and Inconsistent Surface Temperature Changes at an Elevational Permafrost Site on the Qinghai‐Tibet Plateau. Issue 18 (17th September 2018)

• Record Type: Journal Article
• Authors: Luo, D. L.; Jin, H. J.; He, R. X.; Wang, X. F.; Muskett, R. R.; Marchenko, S. S.; Romanovsky, V. E.
• Is Part Of: Journal of geophysical research. Volume 123:Issue 18(2018)
• Page Start: 10, 057
• Page End: 10, 075
• Publication Date: 2018-09-17
• Subjects: elevational permafrost -- surface temperature -- soil heat flux -- radiation budget -- hydrothermal processes -- albedo; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2018JD028298
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Increase of surface temperatures has long been recognized as an unequivocal response to radiative forcing and one of the most important implications for global warming. However, it remains unclear whether the variation of ground surface temperature ( GST ) and soil temperatures is consistent with simultaneous changes of the near‐surface air and land (or skin) surface temperatures ( T a and LST ). In this study, a seven‐year continuous observation of GST, T a, and surface water and heat exchange was carried out at an elevational permafrost site at Chalaping, northeastern Qinghai‐Tibet Plateau. Results showed a distinct retarding of warming on the ground surface and subsurface under the presence of dense vegetation and moist peat substrates. Mean annual T a and LST increased at noteworthy rates of 0.22 and 0.32 °C/a, respectively, while mean annual GST increased only at a rate of 0.057 °C/a. No obvious trends were detected for the four radiation budgets except the soil heat flux ( G ), which significantly increased at a rate of 0.29 W · m −2 · a −1, presumably inducing the melting of ground ice and resulted in much higher moisture content through the summers of 2015 and 2016 than preceding years and subsequent 2017 at the depths between 80 and 120 cm. However, no noticeable immediate variations of soil temperatures occurred owing to the large latent heat effect (thermal inertia) and the extending zero‐curtain period. We suggest that a better protected eco‐environment, particularly the surface vegetation, helps preserving the underlying permafrost, and thus to mitigates the potential degradation of elevational permafrost on the Qinghai‐Tibet Plateau. Key Points: Near‐surface air and land surface temperatures increased significantly, but ground surface and soil temperatures increased insignificantly Seasonal thawing layer deepened evidently by increasing of soil moisture content Soil heat flux increased significantly as the trend of annual albedo decreased