A calibration of cellulose isotopes in modern prostrate Nothofagus and its application to fossil material from Antarctica.

Autor: Rees-Owen RL; School of Earth and Environment, University of Leeds, Leeds, UK., Newton RJ; School of Earth and Environment, University of Leeds, Leeds, UK. Electronic address: r.j.newton@leeds.ac.uk., Ivanovic RF; School of Earth and Environment, University of Leeds, Leeds, UK., Francis JE; British Antarctic Survey, Cambridge, UK., Riding JB; British Geological Survey, Nottingham, UK., Marca AD; School of Environmental Sciences, University of East Anglia, Norwich, UK.
Jazyk: angličtina
Zdroj: The Science of the total environment [Sci Total Environ] 2021 Feb 01; Vol. 754, pp. 142247. Date of Electronic Publication: 2020 Sep 07.
DOI: 10.1016/j.scitotenv.2020.142247
Abstrakt: Carbon and oxygen isotopes (δ 13 C and δ 18 O) in tree rings are widely used to reconstruct palaeoclimate variables such as temperature during the Holocene (12 thousand years ago - present), and are used increasingly in deeper time. However, their use is largely restricted to arboreal trees, which excludes potentially important data from prostrate trees and shrubs, which grow in high latitude and altitude end-member environments. Here, we calibrate the use of δ 13 C and δ 18 O as climatic archives in two modern species of southern beech (Nothofagus) from Tierra del Fuego, Chile, at the southern limit of their current range. We show that prostrate trees are potentially suitable archives for recording climatological means over longer periods (on the order of decades), which opens up these important environments for tree ring isotope analysis. We then apply our new understanding to a remarkable late Neogene (17-2.5 Ma) fossil Nothofagus assemblage from the Transantarctic Mountains, Antarctica, representative of a prostrate tundra shrub growing during a period of significant ice sheet retreat. The δ 13 C of the fossil cellulose was found to be ~4‰ enriched relative to that of the modern tress. This is likely to be due to a combination of a more positive δ 13 C of contemporaneous atmospheric CO 2 and enhanced water use efficiency at the fossil site. Using the cellulose-δ 18 O in the fossil wood, we are able to reconstruct precipitation oxygen isotopes over the Antarctic interior for the first time for this time period. The results show that δ 18 O precip over Antarctica was -16.0 ± 4.2‰, around 12‰ enriched relative to today, suggesting changes in the hydrological cycle linked to warmer temperatures and a smaller ice sheet.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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