| Summary: | Sea ice plays an important role in polar ecosystems, biogeochemical cycling, and regulating Earth's climate. In recent years, sea ice has formed later in the winter, melted earlier in the spring, and covered less total area than previously observed. Because sea ice meltwater possesses a unique noble gas signature, noble gas tracers are a valuable resource to identify and monitor sea ice melt. This study aimed to elucidate the behavior of noble gases Ne, Ar, Kr, and Xe in meltwater by continuously measuring the noble gas content of meltwater during the melting process using equilibrator inlet mass spectrometry (EIMS). We first assessed the capabilities of the EIMS analytical system to measure noble gases under unique experimental conditions and explored a variety of methods for melting ice in order to attain sufficient meltwater for analysis. We then conducted two ice melt experiments during which meltwater was analyzed in two sampling periods. Data from the second sampling period was jeopardized due to warming of meltwater prior to sampling, but data from the first sampling period illuminated changing noble gas content throughout the melting process. Concentrations of the heavy noble gases Ar, Kr, and Xe decreased steadily throughout the first sampling period, indicating that Ar, Kr, and Xe are preferentially released from ice during the melting process. The quantity of Ne in meltwater initially increased, peaked midway through sampling, then decreased. This suggests that Ne, a smaller noble gas, was preferentially retained in the ice early in the melt process. We also found that meltwater analyzed early in the melting process was oversaturated by all noble gases while meltwater analyzed later in the melting process was undersaturated in noble gases. Our data illuminates differences in the behavior of small and large noble gases and thus demonstrates that the size of a gas atom is a key determining factor in how the gas is released from ice as it melts.
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