Oxygen isotopes in tree rings record variation in precipitation δ18O and amount effects in the south of Mexico

Roel J W Brienen; Peter Hietz; Wolfgang Wanek; Manuel Gloor

doi:10.1002/2013JG002304

Oxygen isotopes in tree rings record variation in precipitation δ¹⁸O and amount effects in the south of Mexico

J Geophys Res Biogeosci. 2013 Dec;118(4):1604-1615. doi: 10.1002/2013JG002304. Epub 2013 Dec 6.

Authors

Roel J W Brienen¹, Peter Hietz², Wolfgang Wanek³, Manuel Gloor⁴

Affiliations

¹ Earth and Global Change, School of Geography, University of Leeds Leeds, UK ; Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México Morelia, Mexico.
² Institute of Botany, University of Natural Resources and Life Sciences Vienna, Austria.
³ Department of Microbiology and Ecosystem Science, Division of Terrestrial Ecosystem Research, University of Vienna Vienna, Austria.
⁴ Earth and Global Change, School of Geography, University of Leeds Leeds, UK.

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 of Mimosa acantholoba from southern Mexico record variation in isotopic composition of precipitation and which climatic processes influence oxygen isotopes in tree rings (δ¹⁸O_tr). Interannual variation in δ¹⁸O_tr was highly synchronized between trees and closely related to isotopic composition of rain measured at San Salvador, 710 km to the southwest. Correlations with δ¹³C, growth, or local climate variables (temperature, cloud cover, vapor pressure deficit (VPD)) were relatively low, indicating weak plant physiological influences. Interannual variation in δ¹⁸O_tr correlated 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 strongly ¹⁸O-depleted rain in the region and seem to have affected the δ¹⁸O_tr signal. Large-scale controls on the isotope signature include variation in sea surface temperatures of tropical north Atlantic and Pacific Ocean. In conclusion, we show that δ¹⁸O_tr of M. acantholoba can be used as a proxy for source water δ¹⁸O and that interannual variation in δ¹⁸O_prec is caused by a regional amount effect. This contrasts with δ¹⁸O 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 precipitation δ¹⁸O.

Keywords: dendrochronology; isotope ratios.