noaa-recon-18015 Western North America LGM Ensemble Hydroclimatic Reconstructions Oster, J.L.; Ibarra, D.E.; Winnick, M.J.; Maher, K. Western North America LGM Ensemble Hydroclimatic Reconstructions 2015-02-23 NCDC-Paleoclimatology ONLINE Files Pending https://www.ncdc.noaa.gov/paleo/study/18015 Investigator J.L. Oster Investigator D.E. Ibarra Investigator M.J. Winnick Investigator K. Maher earth science paleoclimate paleoclimatic modeling temperature,null,null,percent,annual,paleoclimatic modeling,null,null,N,ensemble average LGM-modern earth science paleoclimate paleoclimatic modeling precipitation,null,unspecified margin of error,percent,annual,paleoclimatic modeling,null,null,N,ensemble average LGM-modern earth science paleoclimate paleoclimatic modeling precipitation minus evapotranspiration,null,null,percent,annual,paleoclimatic modeling,null,null,N,ensemble average LGM-modern earth science paleoclimate climate reconstructions moisture index,multiple proxies,null,dimensionless,null,climate reconstructions,null,null,N,null earth science paleoclimate paleoclimatic modeling precipitation minus evapotranspiration,null,unspecified margin of error,percent,annual,paleoclimatic modeling,null,null,N,ensemble average LGM-modern earth science paleoclimate paleoclimatic modeling precipitation,null,null,percent,annual,paleoclimatic modeling,null,null,N,ensemble average LGM-modern earth science paleoclimate paleoclimatic modeling temperature,null,unspecified margin of error,percent,annual,paleoclimatic modeling,null,null,N,ensemble average LGM-modern earth science paleoclimate reconstructions precipitation geoscientificInformation Precipitation Reconstruction 23000 cal yr BP 19000 cal yr BP Complete 31.3 47.61 -124.07 -105.14 Continent North America Western North America Oster 2015>LATITUDE >LONGITUDE None Please cite original publication, online resource, dataset and publication DOIs (where available), and date accessed when using downloaded data. If there is no publication information, please cite investigator, title, online resource, and date accessed. The appearance of external links associated with a dataset does not constitute endorsement by the Department of Commerce/National Oceanic and Atmospheric Administration of external Web sites or the information, products or services contained therein. For other than authorized activities, the Department of Commerce/NOAA does not exercise any editorial control over the information you may find at these locations. These links are provided consistent with the stated purpose of this Department of Commerce/NOAA Web site. English DOC/NOAA/NESDIS/NCEI National Centers for Environmental Information, NESDIS, NOAA, U.S. Department of Commerce https://www.ncdc.noaa.gov/data-access/paleoclimatology-data DATA Center Contact Bruce Bauer bruce.a.bauer@noaa.gov paleo@noaa.gov 303-497-6280 303-497-6513

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Boulder CO 80305-3328 USA online ASCII Jessica L. Oster, Daniel E. Ibarra, Matthew J. Winnick and Katharine Maher 2015 Nature Geoscience 10.1038/ngeo2365

The hydroclimate history of North America includes the formation and desiccation of large inland lakes and the growth and ablation of glaciers throughout the Quaternary period. At the Last Glacial Maximum, expanded pluvial lakes in the south and aridity in the northwest suggest that the winter westerly storm track was displaced southwards and migrated northwards as the Laurentide Ice Sheet waned. However, lake highstands do not occur synchronously along zonal bands, in conflict with this hypothesis. Here we compile a network of precipitation proxy reconstructions from lakes, speleothems, groundwater deposits, pack rat middens and glaciers from the western and southwestern US, which we compare with an ensemble of climate simulations to identify the controls of regional hydroclimatic change. The proxy records suggest a precipitation dipole during the Last Glacial Maximum, with wetter than modern conditions in the southwest and drier conditions near the ice sheet, and a northwest-southeast trending transition zone across the northern Great Basin. The models that simulate a weaker and south-shifted Aleutian low-pressure system, a strong North Pacific high-pressure system, and a high above the ice sheet best reproduce this regional variation. We therefore conclude that rather than a uniformly south-shifted storm track, a stronger jet that is squeezed and steered across the continent by high-pressure systems best explains the observed regional hydroclimate patterns of the Last Glacial Maximum. STUDY NOTES: Synthesis of hydoclimatic proxy records for western North America at the Last Glacial Maximum, indicating wet or dry hydroclimatic conditions relative to today from proxy reconstructions. Proxies table contains the locations and hydroclimate state at the LGM from a collection of proxy records.

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