Water sources and composition of dissolved gases and bubbles in a saline high Arctic spring.

We investigate the water sources for a perennial spring, "Little Black Pond," located at Expedition Fiord, Axel Heiberg Island in the Canadian High Arctic based on dissolved gases. We measured the dissolved O2 in the likely sources Phantom Lake and Astro Lake and the composition of noble gases (3He/4He, 4He, Ne,36Ar, 40Ar, Kr, Xe), N2, O2, CO2, H2S, CH4, and tritium dissolved in the outflow water and bubbles emanating from the spring. The spring is associated with gypsum-anhydrite piercement structures and occurs in a region of thick, continuous permafrost (400-600 m). The water columns in Phantom and Astro lakes are uniform and saturated with O2. The high salinity of the water emanating from the spring, about twice sea water, affects the gas solubility. Oxygen in the water and bubbles is below the detection limit. The N2/Ar ratio in the bubbles and the salty water is 89.9 and 40, respectively, and the relative ratios of the noble gases, with the exception of Neon, are consistent with air dissolved in lake water mixed with air trapped in glacier bubbles as the source of the gases. The Ne/Ar ratio is ~62% of the air value. Our results indicate that about half (0.47±0.1) of the spring water derives from the lakes and the other half from subglacial melt. The tritium and helium results indicate that the groundwater residence time is over 70 years and could be thousands of years.