Paleo-pCO2 Database ODP668 Early Pleistocene Boron Isotope and CO2 Data Dyez, K.A.; Hönisch, B.; Schmidt, G.A. Dyez, K.A. Hönisch, B. Schmidt, G.A. earth science/paleoclimate/climate forcing|climate reconstructions|paleoceanography (age,null,null,calendar year before present,null,climate forcing|climate reconstructions|paleoceanography,null,null,N,null) earth science/paleoclimate/climate reconstructions|paleoceanography (pH,delta 11B,null,dimensionless,null,climate reconstructions|paleoceanography,null,null,N,null) earth science/paleoclimate/climate reconstructions|paleoceanography (sea surface temperature,magnesium/calcium,null,degree Celsius,null,climate reconstructions|paleoceanography,null,null,N,null) earth science/paleoclimate/paleoceanography (delta 11B,Trilobatus sacculifer,two standard deviations,per mil,null,paleoceanography,null,thermal ionization mass spectrometry,N,N-TIMS) earth science/paleoclimate/climate forcing|paleoceanography (carbon dioxide,bulk atmosphere,null,parts per million,null,climate forcing|paleoceanography,null,null,N,based on planktic foram delta 11B) earth science/paleoclimate/paleoceanography (magnesium/calcium,Globigerinoides ruber,null,millimole per mole,null,paleoceanography,null,null,N,null) earth science/paleoclimate/climate forcing|paleoceanography (carbon dioxide,bulk atmosphere,two standard deviations lower bound,parts per million,null,climate forcing|paleoceanography,null,null,N,based on planktic foram delta 11B) earth science/paleoclimate/climate forcing|paleoceanography (carbon dioxide,bulk atmosphere,two standard deviations upper bound,parts per million,null,climate forcing|paleoceanography,null,null,N,based on planktic foram delta 11B) earth science/paleoclimate/paleoceanography (delta 11B,Trilobatus sacculifer,null,per mil,null,paleoceanography,averaged,thermal ionization mass spectrometry,N,N-TIMS) earth science/paleoclimate/paleoceanography (magnesium/calcium,Globigerinoides ruber,two standard deviations,millimole per mole,null,paleoceanography,null,null,N,null) earth science/paleoclimate/climate forcing (ODP668B>LATITUDE 4.77>LONGITUDE -20.93) 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 matm) 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 S[CO2]~0.75 (±0.5) degC/Wm-2, as compared to the late Pleistocene S[CO2] value of ~1.75 (±0.6) degC/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 d11B records using consistent boundary conditions and explore potential reasons for the discrepancy between Pliocene pCO2 based on different planktic foraminifera. STUDY NOTES: Paleo-CO2 derived from boron isotope measurements on marine sediment core ODP668 the early Pleistocene 1.53-1.38 ma), plus secondary Mg/Ca-based SST reconstructions, contributed to the Paleo-pCO2 Database NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Dyez, K.A. Investigator : Hönisch, B. Investigator : Schmidt, G.A. 2018-10-31 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/25490 https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/dyez2018odp668boron.xlsx https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/dyez2018odp668boron.txt https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/dyez2018odp668boron.xlsx https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/dyez2018odp668boron.txt English https://www.ncdc.noaa.gov/paleo/study/25490 https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/dyez2018odp668boron.xlsx https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/dyez2018odp668boron.txt Dyez, Kelsey A.; Hönisch, Bärbel; Schmidt, Gavin A.2018Early Pleistocene obliquty-scale pCO2 variability at ~1.5 million years agoPaleoceanography and Paleoclimatology START YEAR: 1535666 cal yr BP * END YEAR: 1384000 cal yr BP -20.93 4.77 -20.93 4.77