The oxygen isotopic composition and temperature of southern ocean bottom waters during the Last Glacial Maximum

Malone, M., Martin, J., Schönfeld, Joachim, Ninnemann, U., Nürnberg, Dirk and White, T. (2004) The oxygen isotopic composition and temperature of southern ocean bottom waters during the Last Glacial Maximum Earth and Planetary Science Letters, 222 (1). pp. 275-283. DOI 10.1016/j.epsl.2004.02.027.

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We provide two new determinations of the oxygen isotopic composition of seawater during the last glacial maximum (LGM). High-resolution oxygen isotopic measurements were made on interstitial waters from Ocean Drilling Program (ODP) Sites 1168 and 1170 in the southeast Indian Ocean sector of the Southern Ocean. We use a diffusion–advection numerical model to calculate the glacial–interglacial change in bottom-water δ18Osw from the pore water δ18O profiles; the first such determinations from this part of the oceans. Statistical analyses of the model runs indicate that Circumpolar Deep Water (CDW) δ18Osw changed by 1.0–1.1±0.15‰ since the last glacial maximum (LGM). Our results are consistent with a previous calculation from a South Atlantic Southern Ocean location (ODP Site 1093) also situated within CDW. The new values determined in this study, together with previous estimates, are converging on a global average Δδ18Osw of 1.0–1.1‰.

Using the calculated bottom-water δ18Osw, we have extracted the temperature component from the benthic foraminiferal δ18O record at Sites 1168 and 1170. Since the LGM, bottom waters at these two sites warmed by 2.6 and 1.9°C, respectively. The absolute temperature estimates for the LGM (−0.5°C [Θ=−0.6°C] at Site 1168 and −0.2°C [Θ=−0.4°C] at Site 1170) are slightly warmer than those reported from previous studies using the same technique, but are consistent with more homogenous deep-ocean temperatures during the LGM relative to the modern.

Document Type: Article
Keywords: δ18O; paleoceanography; last glacial maximum; Southern Ocean; pore water; Ocean Drilling Program
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Refereed: Yes
DOI etc.: 10.1016/j.epsl.2004.02.027
ISSN: 0012-821X
Projects: ODP
Date Deposited: 24 Mar 2009 23:56
Last Modified: 15 Nov 2016 14:17

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