Paleo-pCO2 Database Middle Miocene Boron Isotope and CO2 Data Foster, G.L.; Lear, C.H.; Rae, J.W.B. Foster, G.L. Lear, C.H. Rae, J.W.B. earth science/paleoclimate/paleoceanography (delta 11B,Trilobatus sacculifer,null,per mil,null,paleoceanography,null,ion chromatography|multiple collector inductively-coupled plasma mass spectrometry,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/climate forcing|climate reconstructions|paleoceanography (age,null,null,million years ago,null,climate forcing|climate reconstructions|paleoceanography,null,null,N,null) earth science/paleoclimate/paleoceanography (delta 11B,Trilobatus sacculifer,two standard deviations,per mil,null,paleoceanography,null,ion chromatography|multiple collector inductively-coupled plasma mass spectrometry,N,null) earth science/paleoclimate/paleoceanography (magnesium/calcium,Trilobatus sacculifer,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 11B of Globigerinoides sacculifer) earth science/paleoclimate/climate reconstructions|paleoceanography (pH,delta 11B,two standard deviations upper bound,dimensionless,null,climate reconstructions|paleoceanography,null,null,N,null) 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 11B of Globigerinoides sacculifer) earth science/paleoclimate/climate reconstructions|paleoceanography (pH,delta 11B,two standard deviations lower bound,dimensionless,null,climate reconstructions|paleoceanography,null,null,N,null) earth science/paleoclimate/climate forcing|paleoceanography (carbon dioxide,bulk atmosphere,null,parts per million,null,climate forcing|paleoceanography,null,null,N,based on 11B of Globigerinoides sacculifer) earth science/paleoclimate/climate forcing (ODP 761C>LATITUDE -16.737167>LONGITUDE 115.535) (ODP 926>LATITUDE 3.72>LONGITUDE -42.92) The middle Miocene Climatic Optimum (17-15 Ma; MCO) is a period of global warmth and relatively high CO2 and is thought to be associated with a significant retreat of the Antarctic Ice Sheet (AIS). We present here a new planktic foraminiferal d11B record from 16.6 to 11.8 Ma from two deep ocean sites currently in equilibrium with the atmosphere with respect to CO2. These new data demonstrate that the evolution of global climate during the middle Miocene (as reflected by changes in the cyrosphere) was well correlated to variations in the concentration of atmospheric CO2. What is more, within our sampling resolution (~1 sample per 300 kyr) there is no evidence of hysteresis in the response of ice volume to CO2 forcing during the middle Miocene, contrary to what is understood about the Antarctic Ice Sheet from ice sheet modelling studies. In agreement with previous data, we show that absolute levels of CO2 during the MCO were relatively modest (350-400 ppm) and levels either side of the MCO are similar or lower than the pre-industrial (200-260 ppm). These new data imply the presence of either a very dynamic AIS at relatively low CO2 during the middle Miocene or the advance and retreat of significant northern hemisphere ice. Recent drilling on the Antarctic margin and shore based studies indicate significant retreat and advance beyond the modern limits of the AIS did occur during the middle Miocene, but the complete loss of the AIS was unlikely. Consequently, it seems that ice volume and climate variations during the middle Miocene probably involved a more dynamic AIS than the modern but also some component of land-based ice in the northern hemisphere. STUDY NOTES: Paleo-CO2 derived from boron isotope measurements on planktonic foraminifera samples from two Ocean Drilling Program cores, contributed to the Paleo-pCO2 Database. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Foster, G.L. Investigator : Lear, C.H. Investigator : Rae, J.W.B. 2018-05-30 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/24330 https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/foster2012boron.txt https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/foster2012boron.xlsx https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/foster2012boron.txt https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/foster2012boron.xlsx English https://www.ncdc.noaa.gov/paleo/study/24330 https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/foster2012boron.txt https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/foster2012boron.xlsx Gavin L. Foster, Caroline H. Lear, James W.B. Rae2012The evolution of pCO2, ice volume and climate during the middle MioceneEarth and Planetary Science Letters341-344243-25410.1016/j.epsl.2012.06.007https://www.sciencedirect.com/science/article/pii/S0012821X12002919 START YEAR: 16380000 cal yr BP * END YEAR: 12280000 cal yr BP -42.92 -16.737167 115.535 3.72