The University of Southampton
University of Southampton Institutional Repository

Warm ocean processes and carbon cycling in the Eocene

Warm ocean processes and carbon cycling in the Eocene
Warm ocean processes and carbon cycling in the Eocene
Sea surface and subsurface temperatures over large parts of the ocean during the Eocene epoch (55.5–33.7?Ma) exceeded modern values by several degrees, which must have affected a number of oceanic processes. Here, we focus on the effect of elevated water column temperatures on the efficiency of the biological pump, particularly in relation to carbon and nutrient cycling. We use stable isotope values from exceptionally well-preserved planktonic foraminiferal calcite from Tanzania and Mexico to reconstruct vertical carbon isotope gradients in the upper water column, exploiting the fact that individual species lived and calcified at different depths. The oxygen isotope ratios of different species' tests are used to estimate the temperature of calcification, which we converted to absolute depths using Eocene temperature profiles generated by general circulation models. This approach, along with potential pitfalls, is illustrated using data from modern core-top assemblages from the same area. Our results indicate that, during the Early and Middle Eocene, carbon isotope gradients were steeper (and larger) through the upper thermocline than in the modern ocean. This is consistent with a shallower average depth of organic matter remineralization and supports previously proposed hypotheses that invoke high metabolic rates in a warm Eocene ocean, leading to more efficient recycling of organic matter and reduced burial rates of organic carbon.
Eocene, planktonic foraminifera, biological pump, stable isotopes, carbon cycling temperature
1364-503X
20130099
John, Eleanor. H.
523adad7-e7a0-4d24-a2ff-1d5b2ef099eb
Pearson, Paul N.
76269a23-3411-45a1-bc81-b3a668ef1d13
Coxall, Helen K.
aeeac8f5-cc62-4861-8805-4a2027b33b6c
Birch, Heather
2d2443a9-212e-4df8-a10a-0ff8815f15aa
Wade, Bridget S.
882ef710-e0e7-46a1-b382-eb48b1b31a03
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022
John, Eleanor. H.
523adad7-e7a0-4d24-a2ff-1d5b2ef099eb
Pearson, Paul N.
76269a23-3411-45a1-bc81-b3a668ef1d13
Coxall, Helen K.
aeeac8f5-cc62-4861-8805-4a2027b33b6c
Birch, Heather
2d2443a9-212e-4df8-a10a-0ff8815f15aa
Wade, Bridget S.
882ef710-e0e7-46a1-b382-eb48b1b31a03
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022

John, Eleanor. H., Pearson, Paul N., Coxall, Helen K., Birch, Heather, Wade, Bridget S. and Foster, Gavin L. (2013) Warm ocean processes and carbon cycling in the Eocene. Philosophical Transactions of The Royal Society A, 371 (2001), 20130099. (doi:10.1098/rsta.2013.0099).

Record type: Article

Abstract

Sea surface and subsurface temperatures over large parts of the ocean during the Eocene epoch (55.5–33.7?Ma) exceeded modern values by several degrees, which must have affected a number of oceanic processes. Here, we focus on the effect of elevated water column temperatures on the efficiency of the biological pump, particularly in relation to carbon and nutrient cycling. We use stable isotope values from exceptionally well-preserved planktonic foraminiferal calcite from Tanzania and Mexico to reconstruct vertical carbon isotope gradients in the upper water column, exploiting the fact that individual species lived and calcified at different depths. The oxygen isotope ratios of different species' tests are used to estimate the temperature of calcification, which we converted to absolute depths using Eocene temperature profiles generated by general circulation models. This approach, along with potential pitfalls, is illustrated using data from modern core-top assemblages from the same area. Our results indicate that, during the Early and Middle Eocene, carbon isotope gradients were steeper (and larger) through the upper thermocline than in the modern ocean. This is consistent with a shallower average depth of organic matter remineralization and supports previously proposed hypotheses that invoke high metabolic rates in a warm Eocene ocean, leading to more efficient recycling of organic matter and reduced burial rates of organic carbon.

Full text not available from this repository.

More information

Published date: 16 September 2013
Keywords: Eocene, planktonic foraminifera, biological pump, stable isotopes, carbon cycling temperature
Organisations: Geochemistry

Identifiers

Local EPrints ID: 356912
URI: https://eprints.soton.ac.uk/id/eprint/356912
ISSN: 1364-503X
PURE UUID: 14e50ee8-b918-4e13-b60f-1bc9cf524e7f

Catalogue record

Date deposited: 17 Sep 2013 08:52
Last modified: 15 Sep 2017 16:33

Export record

Altmetrics

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×