Research ArticleCLIMATOLOGY

On the glacial-interglacial variability of the Asian monsoon in speleothem δ18O records

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Science Advances  12 Feb 2020:
Vol. 6, no. 7, eaay8189
DOI: 10.1126/sciadv.aay8189
  • Fig. 1 Comparison of the Chinese speleothem δ18O record and other major paleoclimate records.

    The compiled speleothem δ18O record from southern China (green) (2) follows the 65°N summer insolation (gray) closely, and it is dominated by the 23-ka precessional cycle. However, variation in other major paleoclimate records, such as atmospheric CO2 concentration (blue) (6) and Antarctica surface temperature anomaly (red) (7) retrieved from European Project for Ice Coring in Antarctica (EPICA) Dome C ice core, benthic foraminifera δ18O LR04 stack (purple) (8), and global sea surface temperature (SST) stack (orange) (9), are dominated by the ~100-kyr glacial-interglacial cycle. VPDB, Vienna Pee Dee belemnite; B.P., before the present.

  • Fig. 2 Sample locations.

    The black arrows represent the present-day averaged June-July-August (JJA) wind pattern 10 m above sea level [data from the National Centers for Environmental Prediction/National Center for Atmospheric Research Reanalysis monthly mean (1981 to 2010) (58)]. The insert shows the AM system [modified after (59)]. The circled numbers mark the three strategic cave sites along the monsoon trajectory (1, CBoB; 2, CM; and 3, SEY). The stars mark the Mawmluh (21, 26), Hulu (60), Dongge (2, 61, 62), and Sanbao (1, 2) caves; and squares mark marine sediment cores SO93-126KL (27) and SO189-39KL (39) for reference.

  • Fig. 3 Weakened ISM during the LGM and glacial boundary conditions.

    (A) The compiled speleothem δ18O record from Hulu Cave (2, 60), Dongge Cave (61, 62), and Sanbao Cave, with the Sanbao record shifted positively by 1.6‰ to align it with the other two cave records from southern China (1). (B) The 65°N summer (JJA) insolation. (C) The combined speleothem records from CBoB (red) and Mawmluh (orange) (21, 26) caves. The Mawmluh record is shifted negatively by 2.1‰ after correcting it for temperature effect on calcite δ18O, and the orange dot marks the mean value of a modern stalagmite (see the Supplementary Materials). (D) G. ruber δ18O record, retrieved from sediment core SO93-126KL, as a proxy for ISM intensity (27). (E) Atmospheric molecular oxygen δ18O record (δ18Oatm), retrieved from the Antarctica Siple Dome ice core (38). (F) Tropical Indian Ocean SST reconstructed from sediment core SO189-39KL (39). (G) Benthic foraminifera δ18O LR04 stack (8).

  • Fig. 4 Spatial-temporal comparison of speleothem δ18O records from mainland Southeast Asia over the past 40 ka.

    The records obtained from the CBoB and Mawmluh (21, 26) (site 1), CM (site 2), and SEY (site 3) caves are shown in red, pink, and purple, respectively. Note that the δ18O in those records from locations other than CBoB has been corrected for temperature effect during calcite precipitation (see details in Materials and Methods). We further smoothed each record using 1000-year averages (thick lines). The shaded envelopes indicate the range of 1σ uncertainty of the δ18O values. The comparison shows a broad 18O-depletion trend from coastal sites to inland, associated with the progressive rainout effect on water isotopes. In addition, the isotopic gradient was larger during the LGM compared with today.

  • Fig. 5 Spatial-temporal comparison of speleothem δ18O records from the SEY, Dongge (2) and Sanbao (1) caves in southern China during MIS 5.

    The summer (21 July) insolation at 65°N (the gray curve) is also plotted for comparison. To facilitate the comparison, we aligned the speleothem δ18O values during MIS 5c with the insolation peak. The dashed lines, drawn from the MIS 5c insolation peak, indicate the difference among the three records in their amplitudes of δ18O minima during MIS 5.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/6/7/eaay8189/DC1

    Supplementary Text

    Fig. S1. Locations of the study sites.

    Fig. S2. Climatology of relevant cities.

    Fig. S3. Images of stalagmite samples.

    Fig. S4. Age models.

    Fig. S5. Replication test on stable isotope data from PDM02.

    Fig. S6. Scatter plot of δ18O versus δ13C.

    Fig. S7. The three obtained speleothem δ18O records.

    Fig. S8. Comparison of the CBoB and Mawmluh cave records.

    Fig. S9. Comparison of orbital AM records and Vostok atmospheric molecular oxygen δ18O record.

    Fig. S10. Spatial-temporal comparison of speleothem δ18O records from the coastal Indian Ocean and southern China.

    Fig. S11. Ice volume and temperature effects.

    Fig. S12. Spatial-temporal comparison of speleothem δ18O records from mainland Southeast Asia over the past 40 ka.

    Fig. S13. Calculation of rainfall δ18O gradient across mainland Southeast Asia.

    Table S1. A list of the studied speleothem samples and their cave locations.

    Table S2. Rainfall oxygen isotopic compositions across mainland Southeast Asia.

    Table S3. Calculations of water vapor loss over the CBoB site.

    Data S1. 230Th dating results, with errors within 2σ (95% in confidence).

    Data S2. Stable isotope compositions.

    References (6391)

  • Supplementary Materials

    The PDF file includes:

    • Supplementary Text
    • Fig. S1. Locations of the study sites.
    • Fig. S2. Climatology of relevant cities.
    • Fig. S3. Images of stalagmite samples.
    • Fig. S4. Age models.
    • Fig. S5. Replication test on stable isotope data from PDM02.
    • Fig. S6. Scatter plot of δ18O versus δ13C.
    • Fig. S7. The three obtained speleothem δ18O records.
    • Fig. S8. Comparison of the CBoB and Mawmluh cave records.
    • Fig. S9. Comparison of orbital AM records and Vostok atmospheric molecular oxygen δ18O record.
    • Fig. S10. Spatial-temporal comparison of speleothem δ18O records from the coastal Indian Ocean and southern China.
    • Fig. S11. Ice volume and temperature effects.
    • Fig. S12. Spatial-temporal comparison of speleothem δ18O records from mainland Southeast Asia over the past 40 ka.
    • Fig. S13. Calculation of rainfall δ18O gradient across mainland Southeast Asia.
    • Table S1. A list of the studied speleothem samples and their cave locations.
    • Table S2. Rainfall oxygen isotopic compositions across mainland Southeast Asia.
    • Table S3. Calculations of water vapor loss over the CBoB site.
    • Legends for data S1 and S2
    • References (6391)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Data S1 (Microsoft Excel format). 230Th dating results, with errors within 2σ (95% in confidence).
    • Data S2 (Microsoft Excel format). Stable isotope compositions.

    Files in this Data Supplement:

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