The chemical development of a hypersaline coastal basin in the High Arctic

Abstract

We investigated a hypersaline, seasonally isolated marine basin (SIMB) in the Canadian High Arctic to elucidate the role of brine rejection, tidal forcing, and groundwater input over the formation of hypersalinity. Analyses of physical parameters and seasonal sampling of ionic and isotopic composition were carried out on a coastal basin near Shellabear Point, Melville Island, Northwest Territories (75°N, 113°W). Observations reveal daily and seasonal variability in the water column due to a seasonal tidal connection during the ice‐free season, which lasts substantially longer than the period of freshwater inflow from the catchment. An ice formation model of the volume of brine rejected from surface ice formed from marine water indicates that rapid saline enrichment of the basin due to ice formation is possible from tidally replenished marine water, and that the current hypersalinity may have formed in less than a decade. Modeled isotopic composition of brines are consistent with observations and provide an alternative to freshwater isotopic dilution suggested by other workers. A tidal connection is a critical consideration in lake evolution, and many hypersaline polar lakes could have developed their current chemical composition before full marine isolation. By contrast, in some coastal lakes, marine stratification caused by ice shelves before isolation provides a setting for minimal brine formation and subsequent meromictic conditions to develop. Hence, the marine setting at the time of isolation represents a key factor in explaining divergent lake chemical evolution in the High Arctic.