NOAA/WDS Paleoclimatology - ODP1094 South Atlantic Diatom Carbon and Nitrogen Isotope Data

High-resolution d13C and d15N records of diatom-bound organic matter (d13CD, d15ND) from ODP site 1094, South of the Polar Front, are combined with reconstructions of summer sea surface temperature and winter sea-ice to establish changes in surface water characteristics associated with the main climatic events of the past 640 ka. The six glacial-interglacial d13CD cycles show excellent agreement with SPECMAP d18O and Vostok CO2 content, suggesting that global physical processes rather than local biological factors were the main influences on d13CD. By contrast, there is weak correspondence between the Vostok dust record and the d13CD and d15ND records. The data do not support the hypothesis that glacial iron fertilization of the Southern Ocean was the main factor lowering atmospheric CO2, if dust accumulation represents iron input. The records indicate that sea ice cover, water column stratification and iron addition from deep water mixing are more likely to explain our observations.