Dominant Factors Controlling Variability in the Ionic Composition of West Greenland Lakes

Abstract

Over 80 lakes were sampled between the ice margin and the coast in West Greenland between 66 and 67°N and analyzed for their pH, alkalinity, conductivity, and major ions. Most of the lakes (67%) are dilute, circumneutral, and have conductivity values <150 μS cm⁻¹. There are, however, also saline lakes (2000–4000 μS cm⁻¹; NaHCO₃/CO₃, and Mg HCO₃/CO₃-dominated), mainly around the head of the fjord. The main control on lake chemistry in this area is evaporation as indicated by the fossil shorelines surrounding the saline lakes. The high concentrations of Na indicate extensive inputs from either weathering or from eoliantransported silts (loess) derived from the sand outwash plains at the ice sheet margin. The pattern of cation dominance in the freshwater lakes is Ca > Mg > Na > K. Variability in the water chemistry and the dominant controls on water chemistry were examined using PCA and RDA, respectively. There is a clear gradient in lake chemistry from west to east. This trend reflects the split between the dilute coastal lakes (with higher %C1) and the saline lakes close to the head of the fjord. Altitude is also significant and probably reflects reduced weathering rates at upland sites (~500 m) with limited vegetation cover. A number of lakes had high SO₄ concentrations (maximum >10,000 μeq L⁻¹) and were clearly influenced by local geology.