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Abstract 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−1; 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.
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This content will become publicly available on June 11, 2026
Past aquifer responses to climate recorded by fossil groundwater
Billions of people rely upon groundwater for drinking water and agriculture, yet predicting how climate change may affect aquifer storage remains challenging. To gain insight beyond the short historical record, we reconstruct changes in groundwater levels in western North America during the last glacial termination (LGT, ~20 to 11 thousand years ago) using noble gas isotopes. Our reconstructions indicate remarkable stability of water table depth in a Pacific Northwest aquifer throughout the LGT despite increasing precipitation, closely matching independent Earth system model (ESM) simulations. In the American Southwest, ESM simulations and noble gas isotopes both suggest a pronounced LGT decline in water table depth in in response to decreasing precipitation, indicating distinct regional groundwater responses to climate. Despite the hydrologic simplicity of ESMs, their agreement with proxy reconstructions of past water table depth suggests that these models hold value in understanding groundwater dynamics and projecting large-scale aquifer responses to climate forcing.
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- Award ID(s):
- 2102984
- PAR ID:
- 10615897
- Publisher / Repository:
- Science Advances
- Date Published:
- Journal Name:
- Science Advances
- Volume:
- 11
- Issue:
- 24
- ISSN:
- 2375-2548
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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