Reconciliation of marine and terrestrial carbon isotope excursions based on changing atmospheric CO2 levels

Schubert, Brian A.; Jahren, A. Hope

doi:10.1038/ncomms2659

Cited by 71 publications

(72 citation statements)

References 57 publications

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“…Evidence for increasing discrimination with higher CO 2 has also been found in chamber and field studies on C 3 plants under altered CO 2 conditions as well as from paleo data (26,27), although exceptions to this pattern have also been found (28). In a compilation of prior work, Schubert and Jahren (26) find a best-fit sensitivity of ∼0.014‰ ppm −1 at 355 ppm, which also matches well with the sensitivity we require to match the atmospheric δ 13 C trend.…”

Section: Discussionmentioning

confidence: 61%

Atmospheric evidence for a global secular increase in carbon isotopic discrimination of land photosynthesis

Keeling

Graven

Welp

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

207

175

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A decrease in the 13 C/ 12 C ratio of atmospheric CO 2 has been documented by direct observations since 1978 and from ice core measurements since the industrial revolution. This decrease, known as the 13 C-Suess effect, is driven primarily by the input of fossil fuel-derived CO 2 but is also sensitive to land and ocean carbon cycling and uptake. Using updated records, we show that no plausible combination of sources and sinks of CO 2 from fossil fuel, land, and oceans can explain the observed 13 C-Suess effect unless an increase has occurred in the 13 C/ 12 C isotopic discrimination of land photosynthesis. A trend toward greater discrimination under higher CO 2 levels is broadly consistent with tree ring studies over the past century, with field and chamber experiments, and with geological records of C 3 plants at times of altered atmospheric CO 2 , but increasing discrimination has not previously been included in studies of long-term atmospheric 13 C/ 12 C measurements. We further show that the inferred discrimination increase of 0.014 ± 0.007‰ ppm −1 is largely explained by photorespiratory and mesophyll effects. This result implies that, at the global scale, land plants have regulated their stomatal conductance so as to allow the CO 2 partial pressure within stomatal cavities and their intrinsic water use efficiency to increase in nearly constant proportion to the rise in atmospheric CO 2 concentration. Significance Climate change and rising CO 2 are altering the behavior of land plants in ways that influence how much biomass they produce relative to how much water they need for growth. This study shows that it is possible to detect changes occurring in plants using long-term measurements of the isotopic composition of atmospheric CO 2 . These measurements imply that plants have globally increased their water use efficiency at the leaf level in proportion to the rise in atmospheric CO 2 over the past few decades. While the full implications remain to be explored, the results help to quantify the extent to which the biosphere has become less constrained by water stress globally. IntroductionThe accumulation of excess CO 2 in the atmosphere over the past century has been associated with a closely related decrease in the

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Section: Discussionmentioning

confidence: 61%

Atmospheric evidence for a global secular increase in carbon isotopic discrimination of land photosynthesis

Keeling

Graven

Welp

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

207

175

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“…Previous experiments have shown an increase in carbon isotope fractionation by land plants in response to increasing atmospheric pCO 2 concentration (Feng and Epstein, 1995). During the PETM, a massive input of 13 C-depleted carbon to the exogenic carbon reservoirs would necessitate a rise in atmospheric pCO 2 , which in turn could amplify the δ 13 C signal by ∼1-2h through increasing photosynthesis fractionation (Schubert and Hope Jahren, 2013). In summary, the larger excursion observed in the δ 13 C BC and δ 13 C TOC could bias the true magnitude of the CIE due to severe environmental disturbance during the PETM.…”

Section: Magnitude Of Ciementioning

confidence: 98%

Structure of the carbon isotope excursion in a high-resolution lacustrine Paleocene–Eocene Thermal Maximum record from central China

Chen

Wang

et al. 2014

Earth and Planetary Science Letters

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“…Such changes have been variously interpreted to record a change in environmental variables, including plant species composition (e.g., Feakins et al, 2013;, water availability (e.g., Stewart et al, 1995), atmospheric oxygen concentration (Tappert et al, 2013), the isotopic composition of CO 2 in the atmosphere (d 13 C CO 2 ) (e.g., Jahren et al, 2001), and atmospheric pCO 2 (e.g., Schubert and Jahren, 2013). Changes within an isotope record from a single locality may reflect changes in local climate and vegetation, and so multiple high-resolution records from diverse environments are necessary to analyze for changes in global climate.…”

Section: Introductionmentioning

confidence: 99%

Global increase in plant carbon isotope fractionation following the Last Glacial Maximum caused by increase in atmospheric pCO2

Schubert

Jahren

2015

Geology

Self Cite

102

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Changes in the carbon isotope composition of terrestrial plant tissue (d 13 C) are widely cited for evidence of shifts in climate, vegetation, or atmospheric chemistry across a wide range of time scales. A global compilation of d 13 C data from fossil leaves and bulk terrestrial organic matter (TOM) spanning the past 30 k.y., however, shows wide variability and no discernable trend. Here we analyze these data in terms of a relative change in net carbon isotope fractionation between the d 13 C value of plant tissue and that of atmospheric CO 2 [D 13 C = (d 13 C CO 2 -d 13 C)/(1 + d 13 C/1000)] and identify a global 2.1‰ shift in leaf and TOM D 13 C that is synchronous with a global rise in pCO 2 documented from ice core data. We apply a relationship describing the effect of pCO 2 on D 13 C to the global record of D 13 C change documented here to reconstruct pCO 2 levels across the past 30 k.y. Our reconstructed pCO 2 levels are in excellent agreement with the ice core data and underscore the potential of the global terrestrial d 13 C record to serve as an accurate pCO 2 proxy.

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Reconciliation of marine and terrestrial carbon isotope excursions based on changing atmospheric CO2 levels

Cited by 71 publications

References 57 publications

Atmospheric evidence for a global secular increase in carbon isotopic discrimination of land photosynthesis

Atmospheric evidence for a global secular increase in carbon isotopic discrimination of land photosynthesis

Structure of the carbon isotope excursion in a high-resolution lacustrine Paleocene–Eocene Thermal Maximum record from central China

Global increase in plant carbon isotope fractionation following the Last Glacial Maximum caused by increase in atmospheric pCO2

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