Paleo-pCO2 Database ODP999 1.2 Million Year Boron Isotope and CO2 Data Chalk, T.B.; Hain, M.P.; Foster, G.L.; Rohling, E.J.; Sexton, P.F.; Badger, M.P.S.; Cherry, S.G.; Hasenfratz, A.P.; Haug, G.H.; Jaccard, S.L.; Martínez-García, A.; Pälike, H.; Pancost, R.D.; Wilson, P.A. Chalk, T.B. Hain, M.P. Foster, G.L. Rohling, E.J. Sexton, P.F. Badger, M.P.S. Cherry, S.G. Hasenfratz, A.P. Haug, G.H. Jaccard, S.L. Martínez-García, A. Pälike, H. Pancost, R.D. Wilson, P.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/paleoceanography (magnesium/calcium,Globigerinoides ruber white,two standard deviations,millimole per mole,null,paleoceanography,null,null,N,G. ruber white sensu stricto) 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,Globigerinoides ruber white,null,per mil,null,paleoceanography,averaged,multiple collector inductively-coupled plasma mass spectrometry,N,G. ruber white sensu stricto; column chemistry) earth science/paleoclimate/paleoceanography (magnesium/calcium,Globigerinoides ruber white,null,millimole per mole,null,paleoceanography,null,null,N,G. ruber white sensu stricto) 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/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,Globigerinoides ruber white,two standard deviations,per mil,null,paleoceanography,null,multiple collector inductively-coupled plasma mass spectrometry,N,G. ruber white sensu stricto; column chemistry) earth science/paleoclimate/climate forcing (ODP 999A>LATITUDE 12.75>LONGITUDE -78.73) During the Mid-Pleistocene Transition (MPT; 1,200-800 kya), Earth's orbitally paced ice age cycles intensified, lengthened from ~40,000 (~40 ky) to ~100 ky, and became distinctly asymmetrical. Testing hypotheses that implicate changing atmospheric CO2 levels as a driver of the MPT has proven difficult with available observations. Here, we use orbitally resolved, boron isotope CO2 data to show that the glacial to interglacial CO2 difference increased from ~43 to ~75 uatm across the MPT, mainly because of lower glacial CO2 levels. Through carbon cycle modeling, we attribute this decline primarily to the initiation of substantive dust-borne iron fertilization of the Southern Ocean during peak glacial stages. We also observe a twofold steepening of the relationship between sea level and CO2-related climate forcing that is suggestive of a change in the dynamics that govern ice sheet stability, such as that expected from the removal of subglacial regolith or interhemispheric ice sheet phase-locking. We argue that neither ice sheet dynamics nor CO2 change in isolation can explain the MPT. Instead, we infer that the MPT was initiated by a change in ice sheet dynamics and that longer and deeper post-MPT ice ages were sustained by carbon cycle feedbacks related to dust fertilization of the Southern Ocean as a consequence of larger ice sheets. STUDY NOTES: Paleo-CO2 derived from boron isotope measurements on marine sediment core ODP999A for the past 1.2 million years, contributed to the Paleo-pCO2 Database. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Chalk, T.B. Investigator : Hain, M.P. Investigator : Foster, G.L. Investigator : Rohling, E.J. Investigator : Sexton, P.F. Investigator : Badger, M.P.S. Investigator : Cherry, S.G. Investigator : Hasenfratz, A.P. Investigator : Haug, G.H. Investigator : Jaccard, S.L. Investigator : Martínez-García, A. Investigator : Pälike, H. Investigator : Pancost, R.D. Investigator : Wilson, P.A. 2018-03-09 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/23550 https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/chalk2017odp999boron.xlsx https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/chalk2017odp999boron.txt https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/chalk2017odp999boron.xlsx https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/chalk2017odp999boron.txt English https://www.ncdc.noaa.gov/paleo/study/23550 https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/chalk2017odp999boron.xlsx https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/chalk2017odp999boron.txt Thomas B. Chalk, Mathis P. Hain, Gavin L. Foster, Eelco J. Rohling, Philip F. Sexton, Marcus P.S. Badger, Soraya G. Cherry, Adam P. Hasenfratz, Gerald H. Haug, Samuel L. Jaccard, Alfredo Martínez-García, Heiko Pälike, Richard D. Pancost and Paul A. Wilson2017Causes of ice age intensification across the Mid-Pleistocene TransitionProceedings of the National Academy of Sciences1145013114-1311910.1073/pnas.1702143114http://www.pnas.org/content/114/50/13114 START YEAR: 1243250 cal yr BP * END YEAR: 111320 cal yr BP -78.73 12.75 -78.73 12.75