Potential of ikaite to record the evolution of oceanic δ18O
- 1Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK
- 2School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
- 3Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK
- 4School of Ocean Sciences, University of Wales, Menai Bridge, Anglesey LL59 5AB, UK
- 5University of Bremen, FB5 Geosciences, Box 330440, 28334 Bremen, Germany
- 6Council for the Central Laboratory of the Research Councils, Daresbury Laboratory, Warrington, Cheshire WA4 4AD, UK
Abstract
A challenge in the quest to understand the sensitivity of the climate system is the separation of the competing effects of ice volume or sea level, salinity, and temperature on foraminiferal δ18O. We present precipitation experiments on the mineral ikaite, a hydrated form of calcium carbonate found in organic carbon–rich deep-marine sediments, that show that the hydration waters within the ikaite crystal capture the δ18O of seawater (δ18Osw) with a fractionation factor of 1.0029 (±0.0002). The δ18Osw measures the volume of continental ice, with an overprint of local salinity. Isolation of δ18Osw by analysis of the hydration waters of sedimentary ikaite preserved at temperatures <4 °C could be exploited to create a record of sea level during the Pleistocene. Preliminary data of δ18Osw from hydration waters of ikaite at the Last Glacial Maximum agree with estimates from modeling of pore waters that Antarctic Bottom Water was +1.4‰ ± 0.2‰ heavier.
Footnotes
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- Accepted 3 February 2006.
- Received 8 November 2005.
- Revision received 2 February 2006.
- The Geological Society of America, Inc.
