Controls on Western U.S. Interior Water Cycling Over the Holocene: Investigating Water Isotope Trends in iCESM and Ferricrete Proxy Data
Nigro, E., Macarewich, S., Zhu, J., Chamberlain, P.. (2025). Controls on Western U.S. Interior Water Cycling Over the Holocene: Investigating Water Isotope Trends in iCESM and Ferricrete Proxy Data. , doi:https://doi.org/10.5065/vgvh-s059
| Title | Controls on Western U.S. Interior Water Cycling Over the Holocene: Investigating Water Isotope Trends in iCESM and Ferricrete Proxy Data |
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| Genre | Manuscript |
| Author(s) | Emily Nigro, Sophia Macarewich, Jiang Zhu, P. Chamberlain |
| Abstract | Understanding regional water cycle trends is crucial for water resources management in the drought-prone western U.S., but predicting future precipitation changes remains a challenge. The Holocene (~11.7 ka to present) provides a case study for investigating the forcing mechanisms controlling temporal and spatial rainfall patterns in this region, given its rich proxy record and warmer-than-preindustrial temperatures. While most hydrologic proxies are used to reconstruct mean annual precipitation, iron-oxide deposits called ferricretes form from winter streamwater and have been interpreted to reflect summer precipitation changes. Here, we use time slice simulations from the isotope-enabled Community Earth System Model (iCESM1.2) to investigate hydrologic changes and the mechanisms driving the isotopic composition of streamwater in the western U.S. throughout the Holocene. Preliminary model results show a general increase in available moisture in northern Rocky Mountain summers over the Holocene, while δ 18O of precipitation decreases, especially from 9 to 6 ka. These two factors combine to produce a U-shaped trend in winter subsurface drainage δ 18O, with a ~0.5 ‰ increase from 6 ka to preindustrial. Overall, the iCESM1.2 and proxy winter δ 18O trends agree in direction, but changes in the model are muted relative to the strong ferricrete δ 18O increase over time. This work highlights the utility of using isotope-enabled Earth system models in conjunction with proxy evidence and identifies potential reasons for the model–proxy discrepancy. Specifically, this work suggests a likely underestimation of future precipitation response to external forcing in current models, at least in the case of CESM. |
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| Publication Date | Aug 1, 2025 |
| Publisher's Version of Record | https://doi.org/10.5065/vgvh-s059 |
| OpenSky Citable URL | https://n2t.net/ark:/85065/d7639v6g |
| OpenSky Listing | View on OpenSky |
| CGD Affiliations | PPC |