Beschreibung:
<jats:title>Abstract</jats:title><jats:p>Constraining the magnitude of past hydrological change
may improve understanding and predictions of future shifts in water
availability. Here we demonstrate that water-table depth, a
sensitive indicator of hydroclimate, can be quantitatively
reconstructed using Kr and Xe isotopes in groundwater. We present
the first-ever measurements of these dissolved noble gas isotopes in
groundwater at high precision (≤0.005‰
amu<jats:sup>−1</jats:sup>; 1σ), which reveal
depth-proportional signals set by gravitational settling in soil air
at the time of recharge. Analyses of California groundwater
successfully reproduce modern groundwater levels and indicate a
17.9 ± 1.3 m (±1 SE) decline in water-table depth in Southern
California during the last deglaciation. This hydroclimatic
transition from the wetter glacial period to more arid Holocene
accompanies a surface warming of 6.2 ± 0.6 °C (±1 SE). This new
hydroclimate proxy builds upon an existing paleo-temperature
application of noble gases and may identify regions prone to future
hydrological change.</jats:p>