TY - JOUR
T1 - A mechanistic understanding of oxygen isotopic changes in the Western United States at the Last Glacial Maximum
AU - Tabor, Clay
AU - Lofverstrom, Marcus
AU - Oster, Jessica
AU - Wortham, Barbara
AU - de Wet, Cameron
AU - Montañez, Isabel
AU - Rhoades, Alan
AU - Zarzycki, Colin
AU - He, Chengfei
AU - Liu, Zhengyu
N1 - Funding Information:
This work was supported by NSF grants AGS-1804747 to Tabor and Montañez, AGS-1554998 to Oster, and AGS-1810682 to Liu.
Funding Information:
The CESM project is supported primarily by the National Science Foundation (NSF). This material is based upon work supported by the National Center for Atmospheric Research (NCAR) , which is a major facility sponsored by the NSF under Cooperative Agreement No. 1852977 . Computing and data storage resources, including the Cheyenne supercomputer ( https://doi.org/10.5065/D6RX99HX ), were provided by the Computational and Information Systems Laboratory (CISL) at NCAR. The iCESM1.2 code is publicly available at https://github.com/NCAR/iCESM1.2 . Data used in this manuscript are archived on NCAR Campaign Storage and UConn HPC. Additional data used in this manuscript may be requested from the authors. We thank Juan Lora for discussion about and assistance with atmospheric river tracking. We thank editor Ingrid Hendy for handling our manuscript and the thoughtful comments of two anonymous reviewers.
Funding Information:
This work was supported by NSF grants AGS-1804747 to Tabor and Monta?ez, AGS-1554998 to Oster, and AGS-1810682 to Liu.The CESM project is supported primarily by the National Science Foundation (NSF). This material is based upon work supported by the National Center for Atmospheric Research (NCAR), which is a major facility sponsored by the NSF under Cooperative Agreement No. 1852977. Computing and data storage resources, including the Cheyenne supercomputer (https://doi.org/10.5065/D6RX99HX), were provided by the Computational and Information Systems Laboratory (CISL) at NCAR. The iCESM1.2 code is publicly available at https://github.com/NCAR/iCESM1.2. Data used in this manuscript are archived on NCAR Campaign Storage and UConn HPC. Additional data used in this manuscript may be requested from the authors. We thank Juan Lora for discussion about and assistance with atmospheric river tracking. We thank editor Ingrid Hendy for handling our manuscript and the thoughtful comments of two anonymous reviewers.
Publisher Copyright:
© 2021 Elsevier Ltd
PY - 2021/12/15
Y1 - 2021/12/15
N2 - At the Last Glacial Maximum (LGM), records suggest drier conditions in the northwest United States and wetter conditions in the southwest United States relative to present-day as well as widespread changes in the isotopic composition of water. However, the mechanisms responsible for these changes remain ambiguous. Here, we explore differences in western United States hydroclimate between the LGM and preindustrial with a water isotope tracer enabled Earth System Model. We then use proxy forward models to compare simulated and recorded δ18O in speleothems. We find that the pattern of hydroclimate response in the western United States at the LGM relates to a combination of 1) increased frequency and southward shifted wintertime extratropical cyclones in the North Pacific, 2) greater rainout of moisture as it moves over the continent, and 3) reduced evaporation in the cooler LGM climate. The simulated lower δ18O of precipitation at the LGM relates predominantly to an increase in cool season moisture removal efficiency, with a secondary contribution from relatively more cool season precipitation. Both surface temperatures and North American ice sheets contribute to these hydroclimate changes at the LGM. Comparisons between δ18O from proxy forward models and speleothem records in the western United States show general agreement at the LGM, with increasing depletion moving towards the continental interior. This study highlights the similarities and differences between hydrologic and δ18O changes at the LGM and emphasizes the utility of model-proxy comparison for interpretation.
AB - At the Last Glacial Maximum (LGM), records suggest drier conditions in the northwest United States and wetter conditions in the southwest United States relative to present-day as well as widespread changes in the isotopic composition of water. However, the mechanisms responsible for these changes remain ambiguous. Here, we explore differences in western United States hydroclimate between the LGM and preindustrial with a water isotope tracer enabled Earth System Model. We then use proxy forward models to compare simulated and recorded δ18O in speleothems. We find that the pattern of hydroclimate response in the western United States at the LGM relates to a combination of 1) increased frequency and southward shifted wintertime extratropical cyclones in the North Pacific, 2) greater rainout of moisture as it moves over the continent, and 3) reduced evaporation in the cooler LGM climate. The simulated lower δ18O of precipitation at the LGM relates predominantly to an increase in cool season moisture removal efficiency, with a secondary contribution from relatively more cool season precipitation. Both surface temperatures and North American ice sheets contribute to these hydroclimate changes at the LGM. Comparisons between δ18O from proxy forward models and speleothem records in the western United States show general agreement at the LGM, with increasing depletion moving towards the continental interior. This study highlights the similarities and differences between hydrologic and δ18O changes at the LGM and emphasizes the utility of model-proxy comparison for interpretation.
UR - http://www.scopus.com/inward/record.url?scp=85118529678&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85118529678&partnerID=8YFLogxK
U2 - 10.1016/j.quascirev.2021.107255
DO - 10.1016/j.quascirev.2021.107255
M3 - Article
AN - SCOPUS:85118529678
VL - 274
JO - Quaternary Science Reviews
JF - Quaternary Science Reviews
SN - 0277-3791
M1 - 107255
ER -