Effects of short-term variability of meteorological variables on soil temperature in permafrost regions

Abstract

Abstract. Effects of the short-term temporal variability of meteorological variables on soil temperature in northern high latitude regions have been investigated. For this, a process-oriented land surface model has been driven using an artificially manipulated climate dataset. Climate variability mainly impacts snow depth, and the thermal diffusivity of lichens and bryophytes. This latter effect is of opposite direction in summer and winter in most regions. These impacts of climate variability 5 on insulating surface layers together substantially alter the heat exchange between atmosphere and soil. As a result, soil temperature is 0.1 to 0.8• C higher when climate variability is reduced. Earth system models project warming of the Arctic region but also increasing variability of meteorological variables and more often extreme meteorological events. Therefore, our results show that projected future increases in permafrost temperature and active-layer thickness in response to climate change 10 will be lower i) when taking into account future changes in short-term variability of meteorological variables, and ii) when representing dynamic snow and lichen and bryophyte functions in land surface models.

Protection of Permafrost Soils from Thawing by Increasing Herbivore Density

“…In this study we use a version of the land surface scheme JSBACH 22,36,37 that has recently been advanced by several processes which are particularly important in cold regions, including coupling of soil hydrology and vertical heat conduction via latent heat of fusion 20 and the effects of ice and water content on soil thermal properties 20 , as well as a new dynamic snow model for soil insulation 21,25 . The version used here in particular also includes a dynamic biogeochemical model of lichens and bryophytes 21 which simulates both the extent of lichens and bryophytes and their impact on the vertical heat conduction 21,25 . In total, five snow layers, one bryophyte/lichens layer, and seven soil layers are used in an implicit numerical scheme to solve the heat conduction equation with phase change 21,23 .…”

“…20,21,25 . This model version has been intensively evaluated in terms of cold regions physical processes at site level and pan-Arctic scale 20,21,24,25 . Additional evaluation plots can be found in the supplemental information.…”

“…In order to address these questions, here we use snow depth and soil temperature observations in concert with the land surface model JSBACH that is state-of-the-art in terms of process representations for cold regions 20,21 . This model has been extensively evaluated at site level, regional scale, and global scale [20][21][22][23][24][25] . Model results central for this study (snow depth, land surface temperature, and mean annual ground temperature) as well as the insulation efficiency of snow are additionally evaluated against observations and discussed in light of other global model results in the Supplementary Information.…”

“…The height of the thermal soil layers increase with depth from 6 cm to 30 m reaching 53 m in total 21 . Soil depth until bedrock, which is the maximum depth of hydrological soil layers considered in the model, is additionally prescribed 25 and usually ranges between 0.5-4 m in northern permafrost regions 26,27 . The model assumes homogeneous soil conditions within a grid cell, and thermal and hydrological parameters have been derived using pedo-transfer functions 20 based on soil texture type information from the Harmonized World Soil Database at 1 km horizontal resolution 28 .…”

Impact factors and dynamic simulation of tillage-layer temperature in frozen-thawed soil under different cover conditions

“…Shati et al [17] studied the relationship among soil temperature (at depth of 5 cm) and snow depth, air temperature (at 2 m above the surface), and their results showed that there was a time-dependent, non-linear relationship between soil temperature (at depth of 5 cm) and air temperature (at 2 m above the surface) and the snow cover played a crucial role in the relationship. Beer et al [18] studied the permafrost in the northern hemisphere, and based on meteorological data, the addition of external conditions, such as surface vegetation and snow coverage, was shown to improve the simulation and prediction accuracy of soil temperature changes in frozen-thawed soils. Michalska et al [19] considered that the daily variation of soil temperature in shallow layers showed a continuously fluctuating trend, with good correlation with daily total solar radiation.…”