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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Volume 12, issue 6
Clim. Past, 12, 1281–1296, 2016
https://doi.org/10.5194/cp-12-1281-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Clim. Past, 12, 1281–1296, 2016
https://doi.org/10.5194/cp-12-1281-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 02 Jun 2016

Research article | 02 Jun 2016

Last Glacial Maximum and deglacial abyssal seawater oxygen isotopic ratios

Carl Wunsch1,a Carl Wunsch
  • 1Department of Earth and Planetary Sciences, Harvard University, Cambridge, USA
  • aalso at: Department of Earth, Atmospheric and Planetary Sciences, MIT, Cambridge, USA

Abstract. An earlier analysis of pore-water salinity (chlorinity) in two deep-sea cores, using terminal constraint methods of control theory, concluded that although a salinity amplification in the abyss was possible during the LGM, it was not required by the data. Here the same methodology is applied to δ18Ow in the upper 100 m of four deep-sea cores. An ice volume amplification to the isotopic ratio is, again, consistent with the data but not required by it. In particular, results are very sensitive, with conventional diffusion values, to the assumed initial conditions at −100 ky and a long list of noise (uncertainty) assumptions. If the calcite values of δ18O are fully reliable, then published enriched values of the ratio in seawater are necessary to preclude sub-freezing temperatures, but the seawater δ18O in pore fluids does not independently require the conclusion.

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This paper examines the oxygen isotope data in several deep-sea cores. The question addressed is whether those data support an inference that the abyssal ocean in the Last Glacial Maximum period was significantly colder than it is today. Along with a separate analysis of salinity data in the same cores, it is concluded that a cold, saline deep ocean is consistent with the available data but so is an abyss much more like that found today. LGM model testers should beware.
This paper examines the oxygen isotope data in several deep-sea cores. The question addressed is...
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