δ18O of Marine‐Influenced Tectona grandis L. f. From Equatorial Indonesia: A Local Rainfall Amount and Remote ENSO Indicator

• Published in: Paleoceanography and paleoclimatology Vol. 39; no. 5
• Main Authors: Nurhati, I. S., Evans, M. N., Cahyarini, S. Y., D’Arrigo, R. D., Yoshimura, K., Herho, S. H. S.
• Format: Journal Article
• Language: English
• Published: 01.05.2024
• Subjects: dendrochronology; ENSO; Indonesia; proxy system modeling; stable isotopes; Tectona grandis L. f. (teak)
• ISSN: 2572-4517; 2572-4525
• DOI: 10.1029/2023PA004758

The hydroclimatic response of the El Niño‐Southern Oscillation (ENSO) to external radiative forcing remains controversial and difficult to project with confidence for the 21st century. Annually resolved paleoclimatic reconstructions spanning the pre‐ and post‐industrial eras from the Indonesian maritime continent may provide hindcasting and diagnostic targets. Here we report δ18O observations from dendrochronologically dated teak (Tectona grandis L. f.) α‐cellulose samples collected at Muna Island, Sulawesi (5.3°S, 123°E, elevation 10 m), for November‐April growing seasons during the period 1969/70–2004/5. Age‐modeled, annually averaged α‐cellulose δ18O anomalies are significantly correlated with simulated α‐cellulose δ18O at the study site. We show that the correlation is largely explained by the amount effect in local and regional precipitation δ18O. Significant correlation with SST anomalies over the study period suggest that replicated multicentury α‐cellulose records from this archive may be interpreted as ENSO indicators. Plain Language Summary Does El Niño change when the energy balance of the climate is altered? This study sets the stage for addressing this question by developing an indirect record of El Niño from the oxygen isotopic composition of Indonesian trees growing adjacent to the warm equatorial western Pacific Ocean. The data are consistent with modeling of the record as a function of local precipitation amount, and the pattern of ocean surface temperature changes El Niño events produce. Extension of these records hundreds of years into the past should enable us to detect hypothesized changes in El Niño event occurrence over the recent geological past. Key Points We developed a modern composite oxygen isotopic record from cross‐dated teak samples from Muna, Sulawesi (5.3°S, 123°E) Observations are consistent with data simulations, and a primary response to rainfall amount Significantly correlated with ENSO, the data point to future analysis of its forced response and the unforced variation over centuries