Publication Abstracts

Dyez et al. 2018

Dyez, K.A., B. Hönisch, and G.A. Schmidt, 2018: Early Pleistocene obliquity-scale pCO2 variability at ∼1.5 million years ago. Paleoceanogr. Paleoclimatol., 33, no. 11, 1270-1291, doi:10.1029/2018PA003349.

In the early Pleistocene, global temperature cycles predominantly varied with ∼41-kyr (obliquity-scale) periodicity. Atmospheric greenhouse gas concentrations likely played a role in these climate cycles; marine sediments provide an indirect geochemical means to estimate early Pleistocene CO2. Here we present a boron isotope-based record of continuous high-resolution surface ocean pH and inferred atmospheric CO2 changes. Our results show that, within a window of time in the early Pleistocene (1.38-1.54 Ma), pCO2 varied with obliquity, confirming that, analogous to late Pleistocene conditions, the carbon cycle and climate co-varied at ∼1.5 Ma. Pairing the reconstructed early Pleistocene pCO2 amplitude (92 ±13 µatm) with a comparably smaller global surface temperature glacial/interglacial amplitude (3.0 ±0.5 K), yields a surface temperature change to CO2 radiative forcing ratio of SO[CO2] ∼ 0.75 (±0.5) °C/Wm-2, as compared to the late Pleistocene SO[CO2] value of ∼1.75 (±0.6) °C/Wm-2. This direct comparison of pCO2 and temperature implicitly incorporates the large ice sheet forcing as an internal feedback and is not directly applicable to future warming. We evaluate this result with a simple climate model, and show that the presumably thinner, though extensive, northern hemisphere ice sheets would increase surface temperature sensitivity to radiative forcing. Thus, the mechanism to dampen actual temperature variability in the early Pleistocene more likely lies with Southern Ocean circulation dynamics or antiphase hemispheric forcing. We also compile this new carbon dioxide record with published Plio-Pleistocene δ11B records using consistent boundary conditions and explore potential reasons for the discrepancy between Pliocene pCO2 based on different planktic foraminifera.

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BibTeX Citation

  author={Dyez, K. A. and Hönisch, B. and Schmidt, G. A.},
  title={Early Pleistocene obliquity-scale pCO2 variability at ∼1.5 million years ago},
  journal={Paleoceanography and Paleoclimatology},

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RIS Citation

ID  - dy08000i
AU  - Dyez, K. A.
AU  - Hönisch, B.
AU  - Schmidt, G. A.
PY  - 2018
TI  - Early Pleistocene obliquity-scale pCO2 variability at ∼1.5 million years ago
JA  - Paleoceanogr. Paleoclimatol.
JO  - Paleoceanography and Paleoclimatology
VL  - 33
IS  - 11
SP  - 1270
EP  - 1291
DO  - 10.1029/2018PA003349
ER  -

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