{"NOAAStudyId":"23550","contactInfo":{"address":"325 Broadway, E/NE31","city":"Boulder","constraints":"Please cite original publication, online resource, dataset and publication DOIs (where available), and date accessed when using downloaded data. If there is no publication information, please cite investigator, title, online resource, and date accessed. The appearance of external links associated with a dataset does not constitute endorsement by the Department of Commerce/National Oceanic and Atmospheric Administration of external Web sites or the information, products or services contained therein. For other than authorized activities, the Department of Commerce/NOAA does not exercise any editorial control over the information you may find at these locations. These links are provided consistent with the stated purpose of this Department of Commerce/NOAA Web site.","country":"USA","dataCenterUrl":"https://www.ncdc.noaa.gov/data-access/paleoclimatology-data","email":"paleo@noaa.gov","fax":"303-497-6513","longName":"National Centers for Environmental Information, NESDIS, NOAA, U.S. Department of Commerce ","phone":"303-497-6280","postalCode":"80305-3328","shortName":"DOC/NOAA/NESDIS/NCEI","state":"CO","type":"CONTACT INFORMATION"},"contributionDate":"2018-03-09","dataPublisher":"NOAA","dataType":"CLIMATE FORCING","dataTypeInformation":"https://www.ncdc.noaa.gov/data-access/paleoclimatology-data/datasets/climate-forcing","difMetadataLink":"http://www1.ncdc.noaa.gov/pub/data/metadata/published/paleo/dif/xml/noaa-forcing-23550.xml","doi":null,"earliestYearBP":1243250,"earliestYearCE":-1241300,"entryId":"noaa-forcing-23550","funding":[],"investigators":"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.","mostRecentYearBP":111320,"mostRecentYearCE":-109370,"onlineResourceLink":"https://www.ncdc.noaa.gov/paleo/study/23550","originalSource":null,"publication":[{"abstract":"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.","author":{"name":"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. Wilson"},"citation":"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. Wilson. 2017. Causes of ice age intensification across the Mid-Pleistocene Transition. Proceedings of the National Academy of Sciences, 114(50), 13114-13119. doi: 10.1073/pnas.1702143114","edition":null,"identifier":{"id":"10.1073/pnas.1702143114","type":"doi","url":"http://dx.doi.org/10.1073/pnas.1702143114"},"issue":"50","journal":"Proceedings of the National Academy of Sciences","pages":"13114-13119","pubRank":"1","pubYear":2017,"reportNumber":null,"title":"Causes of ice age intensification across the Mid-Pleistocene Transition","type":"publication","volume":"114"}],"reconstruction":"Y","scienceKeywords":null,"site":[{"NOAASiteId":"19232","geo":{"geoType":"Feature","geometry":{"coordinates":["12.75","-78.73"],"type":"POINT"},"properties":{"easternmostLongitude":"-78.73","maxElevationMeters":"-2827","minElevationMeters":"-2827","northernmostLatitude":"12.75","southernmostLatitude":"12.75","westernmostLongitude":"-78.73"}},"locationName":"Ocean>Pacific Ocean>North Pacific Ocean","mappable":"Y","paleoData":[{"NOAADataTableId":"35393","coreLengthMeters":null,"dataFile":[{"NOAAKeywords":["earth science>paleoclimate>climate forcing>carbon dioxide"],"fileUrl":"https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/Paleo-pCO2/chalk2017odp999boron.txt","linkText":"ODP999 Boron Isotope and CO2 Data","urlDescription":"NOAA Template File","variables":[{"cvAdditionalInfo":null,"cvDataType":"CLIMATE FORCING|CLIMATE RECONSTRUCTIONS|PALEOCEANOGRAPHY","cvDetail":null,"cvError":null,"cvFormat":"Numeric","cvMaterial":null,"cvMethod":null,"cvSeasonality":null,"cvShortName":null,"cvUnit":"calendar year before present","cvWhat":"age variable>age"},{"cvAdditionalInfo":"G. ruber white sensu stricto; 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