Estimates of Arctic land surface temperatures during the early Pliocene from two novel proxies
Abstract
During the Pliocene (2.6 to 5 Ma ago) atmospheric CO_2 levels have been estimated as similar to or slightly above present levels (Tripati et al., 2009; Pagani et al., 2010), and yet Earth's climate was considerably different. Recent evidence suggests that although global temperatures were 2–3 °C warmer than pre-industrial, Arctic warming may have been amplified during the Pliocene. Thus precise temperature records of this interval are required to assess the sensitivity of Earth's climate to persistent levels of CO_2 between 365 and 415 ppm.We present records of two independent proxies for terrestrial growing-season temperatures at the Early Pliocene Beaver Pond site on Ellesmere Island. δ^(18)O values of cellulose from well-preserved peat constrain the δ^(18)O values of meteoric water to − 20.7 ± 0.3‰, which we combined with δ^(18)Ovalues of aragonitic freshwater molluscs found within the peat in order to calculate mollusc growth temperatures. This approach results in an average growing-season temperature of 14.2 ± 1.3 °C. Temperatures were independently derived by applying carbonate 'clumped isotope' thermometry to mollusc shells from the same site, indicating an average growing-season temperature of 10.2 ± 1.4 °C. A one-way ANOVA indicates that the differences between the two techniques are not significant as the difference in mean temperatures between both methods is no different than the difference between individual shells using a single technique. Both techniques indicate temperatures ~ 11–16 °C warmer than present (May–Sept temperature = − 1.6 ± 1.3 °C) and represent the first thermodynamic proxy results for Early Pliocene Ellesmere Island.
Additional Information
© 2011 Elsevier B.V. Received 8 August 2010; revised 15 February 2011; accepted 16 February 2011. Editor: P. DeMenocal. Available online 5 March 2011. A.Z.C would like to acknowledge the laboratory assistance of Tim Prokopiuk and David Dettman, David Dettman also provided helpful advice in preparing an earlier version of this manuscript. A.Z.C would also like to acknowledge funding for this project from a GSA Graduate Research Award. A.T. gratefully acknowledges a NSF ADVANCE supported visit by A.T. to the University of Arizona which initiated the collaboration, Jay Quade for facilitating the visit, and financial support by the UCLA Division of Physical Sciences, NERC, and Magdalene College at the University of Cambridge. We would also like to acknowledge the helpful comments of two anonymous reviewers on improving this manuscript. Author contributions: A.Z.C, A.T. and W.P.P conceived the study. N.R. and A.P.B. collected and provided samples and field notes. A.Z.C. conducted the stable isotope analyses on cellulose and on microsampled mollusks. A.T. and R.A.E. conducted the clumped isotope analyses, and these analyses were performed in the laboratory of J.E. W.P.P supervised the stable isotope analyses. A.Z.C wrote the manuscript with contributions from A.T. and R.A.E. All authors commented on the manuscript throughout its development.Additional details
- Eprint ID
- 23917
- DOI
- 10.1016/j.epsl.2011.02.030
- Resolver ID
- CaltechAUTHORS:20110606-141813381
- GSA Graduate Research Award
- NSF
- UCLA Division of Physical Sciences
- NERC
- University of Cambridge Magdalene College
- Created
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2011-06-10Created from EPrint's datestamp field
- Updated
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2021-11-09Created from EPrint's last_modified field
- Caltech groups
- Division of Geological and Planetary Sciences