A dynamic physical model for soil temperature and water in Taylor Valley, Antarctica

A.G Fountain,H Basagic,H.W Hunt,P.T Doran

doi:10.1017/s0954102010000234

A.G Fountain, H Basagic + Show 2 more

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https://doi.org/10.1017/s0954102010000234

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Abstract

AbstractWe developed a simulation model for terrestrial sites including sensible heat exchange between the atmosphere and ground surface, inter- and intra-layer heat conduction by rock and soil, and shortwave and longwave radiation. Water fluxes included snowmelt, freezing/thawing of soil water, soil capillary flow, and vapour flows among atmosphere, soil, and snow. The model accounted for 96–99% of variation in soil temperature data. No long-term temporal trends in soil temperature were apparent. Soil water vapour concentration in thawed surface soil in summer often was higher than in frozen deeper soils, leading to downward vapour fluxes. Katabatic winds caused a reversal of the usual winter pattern of upward vapour fluxes. The model exhibited a steady state depth distribution of soil water due to vapour flows and in the absence of capillary flows below the top 0.5 cm soil layer. Beginning with a completely saturated soil profile, soil water was lost rapidly, and within a few hundred years approached a steady state characterized by dry soil (< 0.5% gravimetric) down to one metre depth and saturated soil below that. In contrast, it took 42 000 years to approach steady state beginning from a completely dry initial condition.

Highlights

The McMurdo Dry Valleys of Antarctica comprise the largest ice-free area on the Antarctic continent
Parameter values used in the original model formulation of Matthias (1990) are included for comparison, and these generally fall within the range for the McMurdo Dry Valley sites, except for rock/soil albedo which is highest at the agricultural site
The simulation model fitted the observed soil temperature data well, except that the model tended to overestimate surface temperatures in winter by a few degrees. This problem may have resulted from errors in specifying the depth distributions of rocks and water, which control thermal properties, but which were not based on information specific to our sites

Summary

Introduction

The McMurdo Dry Valleys of Antarctica comprise the largest ice-free area on the Antarctic continent. They are important for the study of life in extreme environments (Priscu & Christner 2004), as a physical analogue for Mars (McKay et al 2005), and potentially as a source of information about ancient Earth climates (Sugden et al 1995). Buried ice has been found in the Dry Valleys but its age is controversial (Sugden et al 1995, Hindmarsh et al 1998, Ng et al 2005). The rate of vapour transport through overlying till provides one approach for estimating ice age, but published models for soil temperature and water in the Dry Valleys The rate of vapour transport through overlying till provides one approach for estimating ice age, but published models for soil temperature and water in the Dry Valleys (e.g. Hindmarsh et al 1998, McKay et al 1998, Schorghofer 2005, Kowalewski et al 2006, Hagedorn et al 2007) are deficient because they do not deal mechanistically with exchanges between soil and atmosphere, and do not treat soil water dynamically

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