Research ArticleCLIMATOLOGY

Moisture availability in the southwest United States over the last three glacial-interglacial cycles

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Science Advances  24 Oct 2018:
Vol. 4, no. 10, eaau1375
DOI: 10.1126/sciadv.aau1375
  • Fig. 1 Study site.

    (A) SW United States including the location of GB Pleistocene lakes (https://keck.library.unr.edu/datasets/gbgd.aspx). Yellow star indicates the location of study site. (B) Map of groundwater flow system adapted from (13, 14). Blue arrows indicate regional groundwater flow direction. Thicker arrows indicate the major groundwater flow direction of the AMGFS from the Spring Mountains to DH caves. Paleozoic carbonate rock (green) ridges broadly reflect the spatial extent of a large, connected lower carbonate rock aquifer. Lower Cambrian siliciclastic rock (brown) ridges indicate the location of local aquitards. Yellow star indicates the location of DH caves (located ca. 200 m apart). (C) Cross section of DH2 cave. Dashed lines indicate the location of cores drilled into the hanging cave wall. ESE, east-southeast; WNW, west-northwest.

  • Fig. 2 DH caves water table records.

    DH record [orange; (11)] and DH2 record (black; this study) plotted r.m.w.t. with 2σ uncertainties. Modern water table elevations are identical in both caves (see main text). Arrows represent inferred water table direction. Dashed horizontal bars represent estimated water table minimums, as determined by the presence of thin mammillary calcite layers (see main text). Question marks denote uncertainties in water table minima/maxima. BP, before present (1950 A.D.).

  • Fig. 3 Three hundred fifty thousand years of DH caves water table fluctuations in comparison with local δ18O, solar insolation, and global ice volume.

    NHSI (gold) (24); DH2 cave δ18O (green) relative to Vienna Pee Dee Belemnite (VPDB) (5). Atmospheric Pco2 (red) recorded in European Project for Ice Coring in Antarctica Dome C (25). Global sea level (26) with associated MISs labeled. Water table fluctuations recorded in DH cave [orange; (11)] combined with water table fluctuations recorded in DH2 cave (black; this study) including 2σ uncertainties. DH caves water table fluctuations plotted r.m.w.t. Shaded regions represent glacial periods. Green bar represents the MIS 5a-4 boundary. TI to TIV, terminations I to IV; ppmv, parts per million by volume.

  • Fig. 4 Millennial-scale events recorded in DH caves over the last three glacial periods.

    DH [orange; (11)] and DH2 (black; this study) plotted r.m.w.t. with 2σ uncertainties. Asian monsoon speleothem δ18O values (purple) record the relative intensity of the East Asian monsoon, which is sensitive to North Atlantic variability (36). North Greenland Ice Core Project (NGRIP) ice core record (blue) record relative North Greenland temperatures (30). Large shaded regions represent glacial periods. Yellow bars indicate the timing of Heinrich events (H) 1 to 6 and 11 [determined by (35)]. Green bars indicate North Atlantic cool periods, including those inferred from low monsoon intensity during MIS 6 and MIS 8. VSMOW, Vienna Standard Mean Ocean Water.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/10/eaau1375/DC1

    Supplementary background information

    Fig. S1. U-Th age sampling and extrapolation diagram.

    Fig. S2. Example of OxCal modeled petrographic boundary.

    Fig. S3. DH2 water table record including nonextrapolated U-Th ages.

    Fig. S4. Past regional moisture availability recorded in the GB.

    Fig. S5. Real-color scanned image of core H collected at +9.5 m r.m.w.t.

    Fig. S6. Real-color scanned image of all DH2 cores included in this study.

    Fig. S7. Photo of folia and mammillary calcite in DH cave.

    Table S1. U-Th dating results.

    Table S2. Age and location of petrographic boundaries.

    References (4145)

  • Supplementary Materials

    This PDF file includes:

    • Supplementary background information
    • Fig. S1. U-Th age sampling and extrapolation diagram.
    • Fig. S2. Example of OxCal modeled petrographic boundary.
    • Fig. S3. DH2 water table record including nonextrapolated U-Th ages.
    • Fig. S4. Past regional moisture availability recorded in the GB.
    • Fig. S5. Real-color scanned image of core H collected at +9.5 m r.m.w.t.
    • Fig. S6. Real-color scanned image of all DH2 cores included in this study.
    • Fig. S7. Photo of folia and mammillary calcite in DH cave.
    • Table S1. U-Th dating results.
    • Table S2. Age and location of petrographic boundaries.
    • References (4145)

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