Abstract

Paleorecharge and paleo-ground-water flow patterns are reconstructed for the past 31 k.y. for the N aquifer in the Black Mesa basin, northeastern Arizona, by 14C dating of groundwater and numerical simulation of ground-water flow and 14C transport. Paleorecharge rates varied significantly and correlate with 18O and D records of paleotemperatures in the N aquifer waters as well as other proxy records of regional paleoclimate and an atmospheric general circulation model. Recharge rates were two to three times higher than today during the late Wisconsin when inferred temperatures were 5–6 °C cooler, but about 50% lower during early to mid-Holocene when inferred summer temperatures were 2–4 °C warmer. The pulse of the highest estimated recharge between 14 and 17 ka may be related to the northward migration of the southern branch of the split jet stream. Model simulations suggest that thousands of years are required for water levels to fully respond to the changes in recharge, and that water levels fluctuated from 60 m higher to 6 m lower than today.

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