The knowledge of soil thermal properties is important for determining how a soil will behave under changing climate conditions, especially in the sensitive environment of permafrost affected soils. This paper represents the first complex study of the interplay between the different parameters affecting soil thermal conductivity of soils in Antarctica. Antarctic Peninsula is currently the most rapidly warming region of the whole Antarctica, with predictions of this warming to continue in the upcoming decades. This study focuses on James Ross Island, where the Abernethy Flats automatic weather station is located in a lowland area with semi-arid climate. Air and ground temperature, soil heat flux and soil moisture during the thawing season were monitored on this site from 2015 to 2023. Moreover, two approaches to determining soil thermal conductivity were compared - laboratory measurements and calculation from field data. During this period, mean annual temperatures have increased dramatically for both air (from-6.9 degrees C in 2015/2016 to-3.8 degrees C in 2022/2023) and ground (from-6.5 degrees C to-3.2 degrees C), same as active layer thickness (from 68 cm to 95 cm). Average soil thermal conductivity for the thawing period reached values between 0.49 and 0.74 W/m.K-1 based on field data. Statistically significant relationships were found between the seasonal means of volumetric water content and several other parameters - soil thermal conductivity (r = 0.91), thawing degree days (r = -0.87) and active layer thickness (r = - 0.88). Although wetter soils generally have a higher conductivity, the increase in temperature exhibits a much stronger control over the active layer thickening, also contributing to the overall drying of the upper part of the soil profile.

Permafrost has become increasingly unstable as a result of surface warming; therefore it is crucial to improve our understanding of permafrost spatiotemporal dynamics to assess the impact of active layer thickening on future hydrogeological processes. However, direct determinations of permafrost active-layer thermal properties are few, resulting in large uncertainty in forecasts of active layer thickness. To assess how to reduce the uncertainty without expanding monitoring efforts, a total of 1,728 numerical 1D models were compared using three error measures against observed active layer temperature data from the Qinghai-Tibetan Plateau. Resulting optimized parameter values varied depending on the error measure used, but agree with reported ones: bulk volumetric heat capacity is 1.82-1.94 x106Jm3 K, bulk thermal conductivity 1.0-1.2 W/m K and porosity 0.25-0.45 (-). The active layer thickening rate varied significantly for the three error measures, as demonstrated by a similar to 15 years thawing time-lag between the error measures over a 100 years modeling period.

Accurate information on the distribution of permafrost and its thermal and hydrological properties is critical for environmental management and engineering development. This study modeled the current state of permafrost on the Qinghai-Tibet Plateau (QTP), including the spatial distribution of permafrost, active-layer thickness (ALT), mean annual ground temperature (MAGT), depth of zero annual amplitude (DZAA) and ground-ice content using an improved Noah land surface model (LSM). The improved model was examined at a typical permafrost site and then applied to the entire QTP using existing gridded meteorological data and newly developed soil data. The simulated permafrost distribution and properties were validated against existing permafrost maps in three representative survey areas and with measurements from 54 boreholes. The results indicate that the Noah LSM with augmented physics and proper soil data support can model permafrost over the QTP. Permafrost was simulated to underlie an area of 1.113 x 10(6) km(2) in 2010, accounting for 43.8% of the entire area of the QTP. The modeled regional average ALT and MAGT were 3.23m and -1.56 degrees C, respectively. Spatially, MAGT increases and DZAA becomes shallower from north to south. Thermally unstable permafrost (MAGT above -0.5 degrees C) is predominant, accounting for 38.75% of the whole permafrost area on the QTP. Ice-rich permafrost was mainly simulated around lakes across the north-central QTP.

Rapid and extensive snowmelt occurred during 2 days in March 2013 at a low-Arctic study site in the ice-free part of southwest Greenland. Meteorology, snowmelt, and snow-property observations were used to identify the meteorological conditions associated with this episodic snowmelt event (ESE) occurring prior to the spring snowmelt season. In addition, outputs from the SnowModel snowpack-evolution tool were used to quantify the snow-related consequences of ESEs on ecosystem-relevant snow properties. We estimated a 50-80% meltwater loss of the pre-melt snowpack water content, a 40-100% loss of snow thermal resistance, and a 4-day earlier spring snowmelt snow-free date due to this March 2013 ESE. Furthermore, the accumulated meltwater loss from all ESEs in a hydrological year represented 25-52% of the annual precipitation and may potentially have advanced spring snowmelt by 6-12 days. Guided by the knowledge gained from the March 2013 ESE, we investigated the origin, past occurrences, frequency, and abundance of ESEs at spatial scales ranging from local (using 2008-2013 meteorological station data) to all of Greenland (using 1979-2013 atmospheric reanalysis data). The frequency of ESEs showed large interannual variation, and a maximum number of ESEs was found in southwest Greenland. The investigations suggested that ESEs are driven by foehn winds that are typical of coastal regions near the Greenland Ice Sheet margin. Therefore, ESEs are a common part of snow-cover dynamics in Greenland and, because of their substantial impact on ecosystem processes, they should be accounted for in snow-related ecosystem and climate-change studies.

Two 30-m deep permafrost temperature-monitoring boreholes were installed in bedrock, one at Marble Point and one in the Wright Valley, in the Ross Sea region of Antarctica. A soil climate-monitoring station in till is located near each borehole. The ground surface temperature (GST) was highly correlated with the air temperature at both sites in 2008. Thermal offsets were small (< 1 degrees C) in the till and negligible in the boreholes. The active layer was thicker in the boreholes than in the till, presumably because of the higher thermal diffusivity of the rock. The measured depth of zero annual temperature amplitude was around 27 m at Wright Valley and 25 m at Marble Point. Permafrost thickness was estimated at about 680 m at Wright Valley and 490 m at Marble Point. The GST history, reconstructed using an inversion procedure, suggests a slight cooling from 1998 to 2003 followed by a slight warming to 2008. Longer temperature records or deeper boreholes would be required to establish if long-term climate change has occurred. Copyright (c) 2011 John Wiley & Sons, Ltd.

The impact of vegetation cover on the active-layer thermal regime was examined in an alpine meadow located in the permafrost region of Qinghai-Tibet over a three-year period. A high vegetation cover (93%) delayed thawing and freezing at a given depth relative to sites with lower covers (65%, 30% and 5%). Low vegetation covers exhibited greater annual variability in soil temperatures, and may be more sensitive to changes in air temperature. Low vegetation covers are also linked to higher thermal diffusivity and thermal conductivity in the soils. The maintenance of a high vegetation cover on alpine meadows reduces the impact of heat cycling on the permafrost, may minimise the impact of climate change and helps preserve the microenvironment of the soil. Copyright (C) 2010 John Wiley & Sons, Ltd.