Decadal cyclicity of regional mid-Holocene precipitation: Evidence from Dominican coral proxies

The stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotopic compositions of four Holocene specimens of Montastraea sp. and Siderastrea sp. coral skeletons from the Dominican Republic were analyzed to examine decadal-scale fluctuations in regional precipitation. The specimens range in length from 47 to 197 years individually and range in age from ∼7.2 to 5.2 kyr. Oscillations in the δ¹³C and δ¹⁸O of coral skeletons from the Holocene Enriquillo Valley occur with a seemingly consistent frequency of 15-20 years. For one coral (∼6 ka) this decadal to multidecadal mode of variability is statistically significant. The decadal to multidecadal mode of stable isotopic variability may represent cyclic fluctuations in mid-Holocene migration of the Intertropical Convergence Zone (ITCZ) or in the hydrogeology of the region as governed by fluctuations in the passage of tropical storms and hurricanes. Regional temperature is believed to act as only a secondary control on the δ¹⁸O values of these corals. However, ITCZ migration and/or oscillations in storm frequency at this site may ultimately reflect decadal-scale patterns in greater tropical North Atlantic sea surface temperatures. The length and resolution of climate variability represented in this study indicate a persistent decadal to multidecadal mode of Atlantic climate fluctuation throughout the mid-Holocene that is indistinguishable from observed historical climate.