| Gas bubbles in ice hold relevance to the origin and process of formation, distinguishing between an atmospheric or dissolved origin. An extraction line was built to isolate gases from ice, and tested using glacial, aufeis and ground ice from the Canadian Arctic. A newly developed mass spectrometry technique was used to analyze the gases for gas ratios of three principal atmospheric gases (N2, O2, and Ar) as well as 18O and 15N of these gases. O2/Ar and N2/Ar ratios demonstrate differences between atmospheric gas in glacial ice and gases exsolved from freezing water, due to the difference in their relative solubilites. Glacial and ground ice contained higher oxygen-18 values than the atmosphere and aufeis ice. Results for glacier ice show that isotopic and gas ratios of atmospheric gas entrapped during glacial ice formation change through gravitational settling. Aufeis ice bubbles originate as dissolved gas with alteration by excess air addition and/or mixing with snow pack. In the ground ice sampled, low oxygen concentrations and high delta 18O values, indicate respiration prior to formation. |
