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Meromictic Lakes Garrow and Sophia in the Canadian Arctic Archipelago were sampled to establish the origin and age of their waters by isotopic studies. The ?&,OW*8O values reflect the permanent stratification of the waters in both lakes. The mixolimnia contain waters with an isotopic signal between -13.16 and -2 1.98o/oo, coherent with the values for precipitation in these high latitudes. The short residence time of the water in this layer makes it possible to record episodic variations of the freshwater inputs to the lakes. In the chemoclines, the Al80 values increase to -10% concomitantly with a rise in chloride content to 42 g-liter-'. This corresponds to a conservative mixing of surficial and deep waters. In the monimolimnia, hypersaline waters (up to 2.5 times the salinity of seawater) show negative 6180 values (ca. -8%~). These waters result from brine production during permafrost growth in the watershed, according to a Rayleigh process. The brines drained toward the deepest part of each lake, after postglacial uplift, and became isolated. 14C dating of total inorganic carbon in the Lake Garrow monimolimnion gave an age of 2,580 + 260 years B.P. In Lake Sophia, the deep waters exhibit recent 14C activity (12 1.4% modern carbon) that suggests recent infiltration of seawater into the lake basin.

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Meromictic lakes in the Arctic Archipelago were analyzed to determine whether the isotope content of the water molecule might confirm their oceanic origin. The 25 m bottom layer of Lake Garrow, on Little Cornwallis Island, is filled with a homogeneous sodium chloride solution with 2.6 times the chloride concentration of seawater (52 g L−1). Its δ18O value is around −10‰ with respect to V-SMOW, and its δ2H is eight times the oxygen value (~ −85‰). In Lake Sophia on Cornwallis Island, the deep stratum (25 m thick) is less concentrated (35 g L−1 Cl−1) and shows slightly higher δ18O and δ2H values (−9 and −75‰, respectively).Chemocline and surficial waters result from mixing between bottom waters and meteoric waters. The chemical and isotopic signals are interpreted as evidence of diagenesis through subpermafrost or intrapermafrost freezing of aquifers once filled with seawater, at some time during postglacial emergence.

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