Strong coherence between solar variability and the monsoon in Oman between 9 and 6 kyr ago


Variations in the amount of solar radiation reaching the Earth are thought to influence climate, but the extent of this influence on timescales of millennia to decades is unclear. A number of climate records show correlations between solar cycles and climate1, but the absolute changes in solar intensity over the range of decades to millennia are small2 and the influence of solar flux on climate is not well established. The formation of stalagmites in northern Oman has recorded past northward shifts of the intertropical convergence zone3, whose northward migration stops near the southern shoreline of Arabia in the present climate4. Here we present a high-resolution record of oxygen isotope variations, for the period from 9.6 to 6.1 kyr before present, in a Th–U-dated stalagmite from Oman. The δ18O record from the stalagmite, which serves as a proxy for variations in the tropical circulation and monsoon rainfall, allows us to make a direct comparison of the δ18O record with the Δ14C record from tree rings5, which largely reflects changes in solar activity6,7. The excellent correlation between the two records suggests that one of the primary controls on centennial- to decadal-scale changes in tropical rainfall and monsoon intensity during this time are variations in solar radiation.

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Figure 1: Plot of age versus depth for stalagmite H5.
Figure 2: Profiles of H5 δ18O values and atmospheric Δ14C.
Figure 3: Measured (dashed line) and optimized (solid line) Th–U age scales for stalagmite H5.
Figure 4: Frequency analysis of the H5 δ18O record for the entire sample and for the high-resolution interval.
Figure 5: Cross-spectral analysis30 of the tuned H5 δ18O record for the entire studied sample versus the Δ14C record (ref. 4).


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We thank D. Sanz for caving assistance; R. Eichstädter for technical assistance; M. Stuiver, A. Baker and D. Ford for suggestions; and S. Clemens for comments.

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Correspondence to S. J. Burns.

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Neff, U., Burns, S., Mangini, A. et al. Strong coherence between solar variability and the monsoon in Oman between 9 and 6 kyr ago. Nature 411, 290–293 (2001) doi:10.1038/35077048

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