Southern Ocean Carbon and Nitrogen Isotopic Ratios Crosta, X.; Shemesh, A. Crosta, X. Shemesh, A. earth science/paleoclimate/paleoceanography (delta 15N,organic matter,null,per mil AIR,null,paleoceanography,null,null,N,diatom-bound organic matter) earth science/paleoclimate/paleoceanography (delta 13C,organic matter,null,per mil PDB,null,paleoceanography,null,null,N,diatom-bound organic matter) earth science/paleoclimate/paleoceanography (depth,null,null,centimeter,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleocean earth science/paleoclimate/paleocean (SO136-111>LATITUDE -56.67>LONGITUDE 160.23) (IO1270-10>LATITUDE -52.33>LONGITUDE 20.78) Oceanic nutrient cycling in the Southern Ocean is supposed to have an important impact on glacial-interglacial atmospheric CO2 changes and global climate. In order to characterize such nutrient cycling over the last two climatic cycles, we investigated carbon and nitrogen isotopic ratios of diatom-bound organic matter (d13Cdiat and d15Ndiat respectively) in two cores retrieved form the Atlantic and Indian sectors of the Antarctic Ocean. The two cores show the same isotopic patterns. d13Cdiat values are depleted during glacial periods and enriched during interglacial periods indicating lower productivity during cold times. d15Ndiat values are enriched during glacial periods and depleted during interglacial periods arguing for greater nitrate utilization during cold times. Taken at face value, this apparent contradiction leads to opposite conclusions on the role of the Southern Ocean biological pump on the atmospheric CO2 changes. But, the two sets of data can be reconciled by a ""sea ice + mixing rate scenario"" that calls upon a balance between the effect of cutting off gas transfer at the ocean-atmosphere boundary and the effect of reducing vertical transport of nutrients through the pycnocline. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Crosta, X. Investigator : Shemesh, A. 2002-07-01 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/2559 https://www1.ncdc.noaa.gov/pub/data/paleo/paleocean/sediment_files/complete/io127010-tab.txt https://www1.ncdc.noaa.gov/pub/data/paleo/paleocean/sediment_files/complete/so136111-tab.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/crosta2002 https://www1.ncdc.noaa.gov/pub/data/paleo/paleocean/sediment_files/complete/io127010-tab.txt https://www1.ncdc.noaa.gov/pub/data/paleo/paleocean/sediment_files/complete/so136111-tab.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/crosta2002 English https://www.ncdc.noaa.gov/paleo/study/2559 https://www1.ncdc.noaa.gov/pub/data/paleo/paleocean/sediment_files/complete/io127010-tab.txt https://www1.ncdc.noaa.gov/pub/data/paleo/paleocean/sediment_files/complete/so136111-tab.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/crosta2002 Crosta, X., and A. Shemesh. 2002. Reconciling down-core anti-correlation of diatom carbon and nitrogen isotopic ratios from the Southern Ocean. Paleoceanography 17(1):1010. 20.78 -56.67 160.23 -52.33