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Arctic and sub-arctic watersheds are undergoing significant changes due to recent climate warming and degrading permafrost, engendering enhanced monitoring of arctic rivers. Smaller catchments provide understanding of discharge, solute flux and groundwater recharge at the process level that contributes to an understanding of how larger arctic watersheds are responding to climate change. The North Klondike River, located in west central Yukon, is a sub-alpine permafrost catchment, which maintains an active hydrological monitoring station with a record of >40 years. In addition to being able to monitor intra-annual variability, this data set allows for more complex analysis of streamflow records. Streamflow data, geochemistry and stable isotope data for 2014 show a groundwater-dominated system, predominantly recharged during periods of snowmelt. Radiocarbon is shown to be a valuable tracer of soil zone recharge processes and carbon sources. Winter groundwater baseflow contributes 20 % of total annual discharge, and accounts for up to 50 % of total river discharge during the spring and summer months. Although total stream discharge remains unchanged, mean annual groundwater baseflow has increased over the 40-year monitoring period. Wavelet analysis reveals a catchment that responds to El Niño and longer solar cycles, as well as climatic shifts such as the Pacific Decadal Oscillation. Dedicated to Professor Peter Fritz on the occasion of his 80th birthday.

This study presents noble gas characteristics of porewater in the Ordovician low-permeability drill cores, which were vacuum-sealed in Al-foil bags and collected over a decade ago on the eastern flank of the Michigan Basin. Noble gas ratios and concentrations reveal crustal noble gas features as well as radiogenic 4He, 40Ar, and 136Xe components. The measured noble gas ratios in this study agree with measurements previously made in the Ordovician brine samples from the western flank of the Michigan Basin. However, unlike water samples from the western Michigan Basin, no mantle-featured noble gas components are found in the Ordovician rock porewater from this site. The Ordovician porewater residence time is quantitatively estimated with both He and Xe radiogenic ingrowth, yielding an average of 251 million years (m.y.). This porewater residence time estimate is comparable with the previous He accumulation time estimate at the same study site that yielded 260 m.y. The radiogenic noble gas ingrowth demonstrates long-term confinement of porewater and concomitant gases within the Ordovician low-permeability rock investigated. The remarkable preservation of gases in these well-sealed vapor-barrier Al-foil bags provides an economical and efficient possibility for noble gas out-diffusion sampling from drill cores.

Noble gas isotopes are being increasingly applied in groundwater and fugitive gas tracing and dating studies. Analyzing all five stable noble gases is important to acquire as much geological information...

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