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 climate(1), but the absolute changes in solar intensity over the range of decades to millennia are small(2) 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 zone(3), whose northward migration stops near the southern shoreline of Arabia in the present climate(4). 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 delta O-18 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 delta O-18 record with the Delta C-14 record from tree rings(5), which largely reflects changes in solar activity(6,7). 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.