THE EFFECT OF HUMAN ACTIVITIES ON MOISTURE-CONTENT OF SOILS AND UNDERLYING PERMAFROST FROM THE MCMURDO SOUND REGION, ANTARCTICA

Soils and the underlying permafrost from undisturbed sites and sites t hat had been disturbed by construction activities at Marble Point and Pram Point in the McMurdo Sound region were sampled from excavated pit s and drill cores. Gravimetric moisture (ice) contents and particle si ze distribution were determined. Volumetric moisture contents were cal culated from these results. At undisturbed sites soil moisture content s within the active layer (to c. 60 cm depth) were low and ranged from 0.5% by weight at the soil surface to 10% above the permafrost. The p ermafrost was generally completely saturated with ice, but sometimes c ontained considerable excess ice, with ice contents rising as high as 80% by volume. At disturbed sites, soil moisture contents within the a ctive layer were similar to those of the undisturbed sites (generally <10% by weight) but within the permafrost, moisture contents were lowe r and less variable than in the undisturbed sites, rarely exceeding 20 % by weight. The release of considerable quantities of water from the permafrost as a result of land disturbance during construction activit ies caused stream flows, soil shrinkage, land slumping and salinisatio n, resulting in significant permanent environmental damage. At Marble Point there has been no significant re-establishment of icy permafrost in the disturbed soils in the 30 years since land disturbance occurre d.