Dissolved noble gas and isotopic tracers reveal vulnerability of groundwater in a small, high‐elevation catchment to predicted climate changes

摘要: [1] Noble gas concentrations and multiple isotopic tracers in groundwater stream water at a small, high-elevation catchment of the Sierra Nevada Mountains constrain recharge conditions subsurface residence times different components. We identify three sources that contribute to flow: (1) seasonal with short travel times, (2) elevated radiogenic 4He has experienced longer flow paths, (3) upwelling deep fluids have “magmatic” helium carbon isotope signatures. Results from our study illuminate two important aspects hydrological system will direct impact on how this responds climate change: alluvial aquifer occurs primarily lower slopes is therefore sensitive changes snowline elevation western part very young provides little buffering capacity. Although apparent ages indicate range less than year several decades, recharges seasonally dominates aquifer. Noble temperatures are close mean annual air temperature, 5°–11° higher would be expected for influx snowmelt. Excess concentrations, indicating entrapment bubbles during recharge, through bedrock fractures. Instead, likely over vegetated areas slopes, as indicated by δ13C-dissolved inorganic values consistent incorporation CO2 soil respiration.