Abstract
Abstract. There are not many studies that report water movement in freezing peat. Soil column studies under controlled laboratory settings can help isolate and understand the effects of different factors controlling freezing of the active layer in organic covered permafrost terrain. In this study, four peat Mesocosms were subjected to temperature gradients by bringing the Mesocosm tops in contact with sub-zero air temperature while maintaining a continuously frozen layer at the bottom (proxy permafrost). Soil water movement towards the freezing front (from warmer to colder regions) was inferred from soil freezing curves, liquid water content time series and from the total water content of frozen core samples collected at the end of freezing cycle. A substantial amount of water, enough to raise the upper surface of frozen saturated soil within 15 cm of the soil surface at the end of freezing period appeared to have moved upwards during freezing. Diffusion under moisture gradients and effects of temperature on soil matric potential, at least in the initial period, appear to drive such movement as seen from analysis of freezing curves. Freezing front (separation front between soil zones containing and free of ice) propagation is controlled by latent heat for a long time during freezing. A simple conceptual model describing freezing of an organic active layer initially resembling a variable moisture landscape is proposed based upon the results of this study. The results of this study will help in understanding, and ultimately forecasting, the hydrologic response of wetland-dominated terrain underlain by discontinuous permafrost.
Highlights
Wetland-dominated terrain underlain by discontinuous permafrost covers extensive parts of northern North America and Eurasia
As theorized by Low et al (1968), liquid water content in frozen soils must have a fixed value for each temperature at which the liquid and ice phase are in equilibrium, regardless of the amount of ice present
Four peat Mesocosms with different initial moisture contents were subjected to freezing to study the impact of soil water content on soil freezing characteristics, freezing induced soil water redistribution, and frost penetration
Summary
Wetland-dominated terrain underlain by discontinuous permafrost covers extensive parts of northern North America and Eurasia. The hydrologic response of these areas is poorly understood, in part due to the lack of understanding of role of individual climatological and soil related factors (e.g., initial moisture conditions) on active layer freeze-thaw processes. In organic-covered permafrost terrain, the topography of the relatively impermeable frost table (defined as the 0 ◦C isotherm) plays an important role in controlling spring runoff (Wright et al, 2009). It is broadly understood that factors such as climate, canopy cover, ground slope, and soil moisture and thermal properties of soil play critical roles in development or degradation of permafrost. Soil moisture profile at the onset of winter governs the ice content in the surface layer of the organic soils. The rate of thaw propagation is affected by the initial soil ice content. Once thaw reaches a certain depth infiltration into organic soils becomes unlimited (Gray et al, 1985, 2001)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
