Coral δ18O evidence for Pacific Ocean mediated decadal variability in Panamanian ITCZ rainfall back to the early 1700s

Article history: Received 25 June 2015 Received in revised form 22 January 2016 Accepted 1 February 2016 Available online 11 February 2016 In Central America, seasonal and interannual shifts in the position of the Intertropical Convergence Zone (ITCZ) control the hydrologic budget. To better understand long-term changes in regional ITCZ-driven precipitation we re-examined a coral δO record froma Porites lobata coral headnear Secas Island (Core ID: S1) (7°59′N, 82°3′W) in the Gulf of Chiriquí on the Pacific side of Panamá. Linsley et al., (1994) originally published the 277-year time series and first described the presence of a narrow-band decadal cycle (period near 9–12 years) in δO. The original study did not present potential drivers for the decadal cycle, although they ruled out the influence of the sun spot cycle. Our re-analysis of this record supports the original interpretation that coral δO is largely responding to variations in precipitation and associated river discharge, but with a new proposed mechanism to explain the decadal mode. There is no similar decadal cycle in gridded instrumental sea surface temperature from the area, suggesting that the decadal coral δO signal results from hydrologic changes that influence coastal δOseawater. The decadal component in S1 δO is also coherentwith a decadal mode embedded in the Pacific Decadal Oscillation (PDO) Index thatwe suggest has tropical origins.We speculate that the coral's temporary δOdeviation (1900–1930) in thedecadalmode fromthe correspondingbands in rainfall and the PDO can be ascribed to a weak PDO in addition to local Panama gapwind variability and its effect onmoisture transport from the Atlantic to the Pacific. Ultimately, the Secas Island coral δO series records ITCZ-driven precipitation dictated by both the Atlantic and Pacific basins. © 2016 Elsevier B.V. All rights reserved.