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Climate of the Past An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/cp-2017-83
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
29 Jun 2017
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Climate of the Past (CP) and is expected to appear here in due course.
Does δ18O of O2 record meridional shifts in tropical rainfall?
Alan M. Seltzer1, Christo Buizert2, Daniel Baggenstos3, Edward J. Brook2, Jinho Ahn4, Ji-Woong Yang4, and Jeffrey P. Severinghaus1 1Scripps Institution of Oceanography, University of California-San Diego, La Jolla, CA, 92037, USA
2College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR, 97331, USA
3Climate and Environmental Physics, University of Bern, Bern, 3012, Switzerland
4School of Earth and Environmental Sciences, Seoul National University, Seoul, 08826, South Korea
Abstract. Marine sediments, speleothems, paleo lake elevations, and ice core methane and δ18O of O218O atm) records provide ample evidence for repeated abrupt meridional shifts in tropical rainfall belts throughout the last glacial cycle. To improve understanding of the impact of abrupt events on the global terrestrial biosphere, we present composite records of δ18O atm and inferred changes in fractionation by the global terrestrial biosphere (ΔɛLAND) from discrete gas measurements in the WAIS Divide (WD) and Siple Dome (SD) Antarctic ice cores. On the common WD timescale, it is evident that maxima in ΔɛLAND are synchronous with or shortly follow WD CH4 peaks assumed to mark abrupt climate responses to Heinrich events. Based on our analysis of the modern seasonal cycle of gross primary productivity (GPP)-weighted δ18O of terrestrial precipitation (the source water for atmospheric O2 production), we propose a simple mechanism by which ΔɛLAND tracks the centroid latitude of terrestrial oxygen production. As intense rainfall and oxygen production migrate northward, ΔɛLAND should decrease due to the underlying meridional gradient in rainfall δ18O. A southward shift should increase ΔɛLAND. Monsoon intensity also influences δ18O of precipitation, and although we cannot determine the relative contributions of the two mechanisms, both act in the same direction. Therefore, we suggest that abrupt increases in ΔɛLAND unambiguously imply a southward shift of tropical rainfall. The exact magnitude of this shift, however, remains under-constrained by ΔɛLAND.

Citation: Seltzer, A. M., Buizert, C., Baggenstos, D., Brook, E. J., Ahn, J., Yang, J.-W., and Severinghaus, J. P.: Does δ18O of O2 record meridional shifts in tropical rainfall?, Clim. Past Discuss., https://doi.org/10.5194/cp-2017-83, in review, 2017.
Alan M. Seltzer et al.
Alan M. Seltzer et al.

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To explore whether the oxygen-18 to oxygen-16 ratio of atmospheric O2 is sensitive to the position of the tropical rain belts, we 1) present a record of ice core bubble oxygen isotope measurements from two Antarctic ice cores, and 2) examine the sensitivity of oxygen isotopes in precipitation, weighted by photosynthesis, to the location of oxygen production over the modern-day seasonal cycle. We find a strong modern relationship and discuss implications for past shifts in tropical rainfall.
To explore whether the oxygen-18 to oxygen-16 ratio of atmospheric O2 is sensitive to the...
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