title: Oxygen isotopes in tree rings record variation in precipitationδ18O and amount effects in the south of Mexico.
abstract: [1] Natural archives of oxygen isotopes in precipitation may be used to study changes in the hydrological cycle in the tropics, but their interpretation is not straightforward. We studied to which degree tree rings ofMimosa acantholobafrom southern Mexico record variation in isotopic composition of precipitation and which climatic processes influence oxygen isotopes in tree rings (δ18Otr). Interannual variation inδ18Otrwas highly synchronized between trees and closely related to isotopic composition of rain measured at San Salvador, 710 km to the southwest. Correlations withδ13C, growth, or local climate variables (temperature, cloud cover, vapor pressure deficit (VPD)) were relatively low, indicating weak plant physiological influences. Interannual variation inδ18Otrcorrelated negatively with local rainfall amount and intensity. Correlations with the amount of precipitation extended along a 1000 km long stretch of the Pacific Central American coast, probably as a result of organized storm systems uniformly affecting rainfall in the region and its isotope signal; episodic heavy precipitation events, of which some are related to cyclones, deposit strongly18O-depleted rain in the region and seem to have affected theδ18Otrsignal. Large-scale controls on the isotope signature include variation in sea surface temperatures of tropical north Atlantic and Pacific Ocean. In conclusion, we show thatδ18OtrofM.acantholobacan be used as a proxy for source waterδ18O and that interannual variation inδ18Oprecis caused by a regional amount effect. This contrasts withδ18O signatures at continental sites where cumulative rainout processes dominate and thus provide a proxy for precipitation integrated over a much larger scale. Our results confirm that processes influencing climate-isotope relations differ between sites located, e.g., in the western Amazon versus coastal Mexico, and that tree ring isotope records can help in disentangling the processes influencing precipitationδ18O.
authors.affiliation: Earth and Global Change, School of Geography, University of Leeds Leeds, UK ; Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México Morelia, Mexico.
authors.forename: Roel J W
authors.initials: RJ
authors.lastname: Brienen
authors.affiliation: Institute of Botany, University of Natural Resources and Life Sciences Vienna, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Hietz
authors.affiliation: Department of Microbiology and Ecosystem Science, Division of Terrestrial Ecosystem Research, University of Vienna Vienna, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wanek
authors.affiliation: Earth and Global Change, School of Geography, University of Leeds Leeds, UK.
authors.forename: Manuel
authors.initials: M
authors.lastname: Gloor
keywords: dendrochronology; isotope ratios