Scientists have found that, according to an extended 20,000-year groundwater record, underground water systems in the Southwest U.S. are more susceptible to climate change than groundwater systems in the Pacific Northwest.
This finding suggests that millions of people who rely on the southwestern aquifers face higher water insecurity as the climate continues to change.
Researchers at the Woodscon Oceanography Institute used cutting-edge technology to analyze fossil groundwater from 17 wells in Washington and Idaho, a technology that measures ancient groundwater level depths through aristocratic isotopes. Their work reveals a clear difference in aquifers’ response to major climate change at the end of the last ice age.
Water table in shape when ice cap
During the last glacier termination (dramatic warming period 20,000 to 11,000 years ago) changes dramatically in western North America. Now, rainfall is raining in the southwest, while today’s rainy Pacific Northwest is still relatively dry.
As global temperatures rise and the ice sheet retreats, these storms move northward. Despite increased precipitation, groundwater levels in the Northwest Pacific Ocean have barely sprouted, showing significant stability throughout the vast climate change.
The Southwest tells a different story completely. Previous research by the same team found that the water table there dropped sharply by nearly 18 meters during the same period.
The mystery of communication feedback
“On average, climate models suggest that the Southwest America may get drier, while the Northwest of the Pacific Northwest may get wetter by the end of the century,” said Alan Seltzer, lead author and associate scientist of the study.
But why are the responses so different in these regions? The team found that the answer lies in what is called “transmittance feedback”, a mechanism in which shallow water tables produce natural stability effects lacking in deeper systems.
Think of it as a bathtub with drainage, which becomes wider as the water level rises. In the Pacific Northwest, water tables are relatively close to the ground, and any increase in rainfall that briefly raises the groundwater level will also increase drainage, thereby lowering the level downward. This is a built-in shock absorber.
In deeper aquifer systems in the southwest, this stabilization mechanism cannot function. Changes in rainfall directly transform into major changes in underground water storage.
Modern Verification of Ancient Data
This study is particularly striking about how close ancient water records are to predictions of complex models of Earth systems. “The model gives almost exactly the same answer as isotope measurements,” Seltzer notes. “This is an exciting result that shows that even relatively simple groundwater models can capture critical dynamics.”
The team used xenon and K k exton isotopes, which like molecular timingists, retained signatures of past groundwater depths through gravity separation in soil air. This novel approach allows them to reconstruct groundwater conditions with unprecedented precision throughout thousands of years.
Major regional differences:
- Despite 10% precipitation, the Pacific Northwest Water Table remains stable
- The Southwest system is very sensitive to rainfall
- Climate models accurately predict two regional responses
- Future forecasts show continuous different patterns
Future water safety
The team extended their analysis to future climate predictions and found that the same regional vulnerabilities persist. Under high emissions schemes, the Southwest Water Table may drop another 5 meters by 2100, while the Northwest system remains relatively stable.
“While this study focuses on western North America, using these model simulations combined with new insights from ancient groundwater level depth records, we were able to map areas of focus globally.”
This work shows that combining paleoclimatic data with modern models can improve global water resource planning, resulting in a 20,000-year perspective on aquifer response to climate change – knowledge becomes increasingly important as water managers plan for an uncertain future.
Related
If our report has been informed or inspired, please consider donating. No matter how big or small, every contribution allows us to continue to provide accurate, engaging and trustworthy scientific and medical news. Independent news takes time, energy and resources – your support ensures that we can continue to reveal the stories that matter most to you.
Join us to make knowledge accessible and impactful. Thank you for standing with us!
