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Climate of the Past An interactive open-access journal of the European Geosciences Union
Clim. Past, 13, 1323-1338, 2017
https://doi.org/10.5194/cp-13-1323-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
11 Oct 2017
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, 3012 Bern, 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 O2 (δ18Oatm) 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 δ18Oatm and inferred changes in fractionation by the global terrestrial biosphere (ΔεLAND) 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 ΔεLAND are synchronous with or shortly follow small-amplitude WD CH4 peaks that occur within Heinrich stadials 1, 2, 4, and 5 – periods of low atmospheric CH4 concentrations. These local CH4 maxima have been suggested as markers of 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 ΔεLAND tracks the centroid latitude of terrestrial oxygen production. As intense rainfall and oxygen production migrate northward, ΔεLAND should decrease due to the underlying meridional gradient in rainfall δ18O. A southward shift should increase ΔεLAND. 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 ΔεLAND unambiguously imply a southward shift of tropical rainfall. The exact magnitude of this shift, however, remains under-constrained by ΔεLAND.

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, 13, 1323-1338, https://doi.org/10.5194/cp-13-1323-2017, 2017.
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Short summary
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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