Research ArticleEARTH SCIENCES

High-latitude warming initiated the onset of the last deglaciation in the tropics

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Science Advances  11 Dec 2019:
Vol. 5, no. 12, eaaw2610
DOI: 10.1126/sciadv.aaw2610
  • Fig. 1 The Rwenzori Mountains and geomorphic maps of field areas.

    (A) The Rwenzori Mountains (boxed) occur on the border between Uganda and the Democratic Republic of the Congo. (B) They are an uplifted horst of basement rock in the western branch of the East African Rift System. We targeted two separate catchments for glacial chronology: (C) the lower Mubuku valley and (D) the Moulyambouli valley. Sample locations are yellow circles. 10Be ages are in years ago with internal, 1σ uncertainties. Numbers in gray are the map ID number of samples in tables S1 to S3. One outlier (sample 19) is shown in italics.

  • Fig. 2 The Rwenzori (Mahoma 1 to 4 and Moulyambouli moraines) and recalculated tropical South American LGM moraine chronologies.

    (A) Light blue circles are individual Rwenzori 10Be ages. Dark blue circles are mean moraine ages. (B) Rwenzori moraine ages as normalized probability (camel) plots with 1σ, internal uncertainties highlighted in blue. (C) Recalculated tropical South American 10Be ages (see the Supplementary Materials for details; ID numbers in this figure correspond to assigned IDs in site descriptions in the Supplementary Materials). Light green circles are individual 10Be ages, and dark green circles are mean moraine ages. For both the Rwenzori and tropical South American moraine chronologies, gray circles mark the outermost moraine in a given catchment, if dated. Red circles mark the onset of recession from or from near the LGM maximum ice extent in each catchment. (D) Mean moraine ages grouped by original study. The red-shaded area highlights the onset of glacial recession in the Rwenzori and tropical South America. The gray bar indicates the timing of the CO2 rise at ~18.2 ka (34).

  • Fig. 3 Global boundary conditions during the LGM and Rwenzori moraine ages.

    (A) NH high-latitude summer insolation (blue), mean annual equatorial insolation (orange), and integrated SH high-latitude summer insolation (pink) (54); (B) global sea level (28); and (C) normalized GHG forcing from CO2, methane, and N2O (2931). Atmospheric CO2 concentration is shown independently (linked black circles). (D) The Rwenzori glacial chronology (as in Fig. 2) indicates expanded ice coincident with low values of each of the global boundary conditions (A to C). The red-shaded area and gray bar indicate the onset of tropical glacial recession and rapid atmospheric CO2 rise, respectively, as in Fig. 2.

  • Fig. 4 Longitudinal temperature changes at the onset of the last deglaciation from syntheses of global temperature records.

    (A) Average NH and SH temperature changes relative to changes in the low latitudes. All values plotted versus the net fraction of glacial-interglacial temperature change, as in (7). (B) Organic geochemical temperature reconstructions from tropical African lakes Tanganyika (light blue) (35) and Sacred (red) (36), as plotted by Loomis et al. (33). (C) Tropical moraine ages as in Fig. 2, with tropical South American mean moraine ages at the top and Rwenzori moraine ages (with 1σ error) below.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/12/eaaw2610/DC1

    Supplementary Text

    Fig. S1. Camel plots showing probability-distribution curves for individual moraine ages with sample age statistics.

    Table S1. Sample information for Moulyambouli and Mahoma moraines.

    Table S2. Calculated 10Be ages from the Moulyambouli and Mahoma moraines.

    Table S3. Distribution of 10Be ages from the Moulyambouli and Mahoma moraines as presented in fig. S1.

    Table S4. Recalculated 10Be ages of tropical South American moraines.

    Table S5. Calibration dataset for Kelly et al. (21) as provided for use with version 3 of the online exposure age calculator described by Balco et al. (51) and subsequently updated.

    References (5566)

  • Supplementary Materials

    The PDFset includes:

    • Supplementary Text
    • Fig. S1. Camel plots showing probability-distribution curves for individual moraine ages with sample age statistics.
    • Legends for tables S1 to S5
    • References (5566)

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    Other Supplementary Material for this manuscript includes the following:

    • Table S1 (Microsoft Excel format). Sample information for Moulyambouli and Mahoma moraines.
    • Table S2 (Microsoft Excel format). Calculated 10Be ages from the Moulyambouli and Mahoma moraines.
    • Table S3 (Microsoft Excel format). Distribution of 10Be ages from the Moulyambouli and Mahoma moraines as presented in fig. S1.
    • Table S4 (Microsoft Excel format). Recalculated 10Be ages of tropical South American moraines.
    • Table S5 (Microsoft Excel format). Calibration dataset for Kelly et al. (21) as provided for use with version 3 of the online exposure age calculator described by Balco et al. (51) and subsequently updated.

    Files in this Data Supplement:

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