Ground ice and soluble cations in near‐surface permafrost, Inuvik, Northwest Territories, Canada

The distribution of segregated ice and soluble ions in near‐surface permafrost were investigated in hummocky terrain near Inuvik, Northwest Territories. Soil water content profiles from analyses of drill cores indicate that ice‐poor permafrost developed beneath a permafrost table aggrading at approximately 4 cm/a, but an ice‐rich zone, 10 to 20 cm thick, was observed beneath a permafrost table that had remained stable for about a decade. Ice‐rich intervals 10 to 30 cm thick were observed immediately beneath both a thaw unconformity formed in 1981 and an older, deeper unconformity. In profile, the correspondence between zones of cation and ice enrichment suggests soluble materials were incorporated into permafrost during development of near‐surface aggradational ice. Moisture enrichment below an experimentally degrading permafrost table was negligible. Similar ice contents beneath the present permafrost table and the deep thaw unconformity, and the preservation of ice‐poor intervals immediately above the 1981 and deep thaw unconformities indicate limited vertical ice enrichment. The estimated rates of ice accumulation in two‐decade‐old permafrost are on the order of mm/a, but ice accumulation above older unconformities indicates that, in aggregate, these initial rates decrease with time. The ground ice and soluble cations sequestered in near‐surface permafrost comprise an important pool of water and nutrients that may be released into the active layer during periods of deeper thaw. Copyright © 2003 John Wiley & Sons, Ltd.