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Descent toward the Icehouse: Eocene sea surface cooling inferred from GDGT distributions

Descent toward the Icehouse: Eocene sea surface cooling inferred from GDGT distributions
Descent toward the Icehouse: Eocene sea surface cooling inferred from GDGT distributions
The TEX86 proxy, based on the distribution of marine isoprenoidal glycerol dialkyl glycerol tetraether lipids (GDGTs), is increasingly used to reconstruct sea surface temperature (SST) during the Eocene epoch (56.0–33.9 Ma). Here we compile published TEX86 records, critically reevaluate them in light of new understandings in TEX86 palaeothermometry, and supplement them with new data in order to evaluate long-term temperature trends in the Eocene. We investigate the effect of archaea other than marine Thaumarchaeota upon TEX86 values using the branched-to-isoprenoid tetraether index (BIT), the abundance of GDGT-0 relative to crenarchaeol (%GDGT-0), and the Methane Index (MI). We also introduce a new ratio, %GDGTRS, which may help identify Red Sea-type GDGT distributions in the geological record. Using the offset between TEX86H and TEX86L (?H-L) and the ratio between GDGT-2 and GDGT-3 ([2]/[3]), we evaluate different TEX86 calibrations and present the first integrated SST compilation for the Eocene (55 to 34 Ma). Although the available data are still sparse some geographic trends can now be resolved. In the high latitudes (>55°), there was substantial cooling during the Eocene (~6°C). Our compiled record also indicates tropical cooling of ~2.5°C during the same interval. Using an ensemble of climate model simulations that span the Eocene, our results indicate that only a small percentage (~10%) of the reconstructed temperature change can be ascribed to ocean gateway reorganization or paleogeographic change. Collectively, this indicates that atmospheric carbon dioxide (pCO2) was the likely driver of surface water cooling during the descent toward the icehouse.
greenhouse climates, Eocene, organic biomarkers
0883-8305
1000-1020
Inglis, Gordon N.
d78ea396-b651-452f-bf6d-fe9d5008e4b1
Farnsworth, Alexander
42c07817-9776-49d0-af90-e562d8b85482
Lunt, Daniel
91e85848-e555-4925-8fc6-3253b54877c8
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022
Hollis, Christopher J.
203511ab-eec4-41c5-b718-622189de5dfc
Pagani, Mark
fea192f2-422c-4380-a5be-f6e2e75398e6
Jardine, Phillip E.
59e357df-ec61-435c-ac71-917450c944c7
Pearson, Paul N.
76269a23-3411-45a1-bc81-b3a668ef1d13
Markwick, Paul
fb6da003-9a49-4b6d-b6d7-29c15c3c9226
Galsworthy, Amanda M. J.
18e556da-f81c-4724-830e-07bf2fc51a97
Raynham, Lauren
289d9b5d-9f4d-4230-bd9a-c0e3c140f15c
Taylor, Kyle. W. R.
e15699ea-3d42-472d-868a-13b46cc1b96d
Pancost, Richard D.
5914e19e-7777-4304-9fd8-86e2e9cfe8a1
Inglis, Gordon N.
d78ea396-b651-452f-bf6d-fe9d5008e4b1
Farnsworth, Alexander
42c07817-9776-49d0-af90-e562d8b85482
Lunt, Daniel
91e85848-e555-4925-8fc6-3253b54877c8
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022
Hollis, Christopher J.
203511ab-eec4-41c5-b718-622189de5dfc
Pagani, Mark
fea192f2-422c-4380-a5be-f6e2e75398e6
Jardine, Phillip E.
59e357df-ec61-435c-ac71-917450c944c7
Pearson, Paul N.
76269a23-3411-45a1-bc81-b3a668ef1d13
Markwick, Paul
fb6da003-9a49-4b6d-b6d7-29c15c3c9226
Galsworthy, Amanda M. J.
18e556da-f81c-4724-830e-07bf2fc51a97
Raynham, Lauren
289d9b5d-9f4d-4230-bd9a-c0e3c140f15c
Taylor, Kyle. W. R.
e15699ea-3d42-472d-868a-13b46cc1b96d
Pancost, Richard D.
5914e19e-7777-4304-9fd8-86e2e9cfe8a1

Inglis, Gordon N., Farnsworth, Alexander, Lunt, Daniel, Foster, Gavin L., Hollis, Christopher J., Pagani, Mark, Jardine, Phillip E., Pearson, Paul N., Markwick, Paul, Galsworthy, Amanda M. J., Raynham, Lauren, Taylor, Kyle. W. R. and Pancost, Richard D. (2015) Descent toward the Icehouse: Eocene sea surface cooling inferred from GDGT distributions. Paleoceanography, 30 (7), 1000-1020. (doi:10.1002/2014PA002723).

Record type: Article

Abstract

The TEX86 proxy, based on the distribution of marine isoprenoidal glycerol dialkyl glycerol tetraether lipids (GDGTs), is increasingly used to reconstruct sea surface temperature (SST) during the Eocene epoch (56.0–33.9 Ma). Here we compile published TEX86 records, critically reevaluate them in light of new understandings in TEX86 palaeothermometry, and supplement them with new data in order to evaluate long-term temperature trends in the Eocene. We investigate the effect of archaea other than marine Thaumarchaeota upon TEX86 values using the branched-to-isoprenoid tetraether index (BIT), the abundance of GDGT-0 relative to crenarchaeol (%GDGT-0), and the Methane Index (MI). We also introduce a new ratio, %GDGTRS, which may help identify Red Sea-type GDGT distributions in the geological record. Using the offset between TEX86H and TEX86L (?H-L) and the ratio between GDGT-2 and GDGT-3 ([2]/[3]), we evaluate different TEX86 calibrations and present the first integrated SST compilation for the Eocene (55 to 34 Ma). Although the available data are still sparse some geographic trends can now be resolved. In the high latitudes (>55°), there was substantial cooling during the Eocene (~6°C). Our compiled record also indicates tropical cooling of ~2.5°C during the same interval. Using an ensemble of climate model simulations that span the Eocene, our results indicate that only a small percentage (~10%) of the reconstructed temperature change can be ascribed to ocean gateway reorganization or paleogeographic change. Collectively, this indicates that atmospheric carbon dioxide (pCO2) was the likely driver of surface water cooling during the descent toward the icehouse.

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e-pub ahead of print date: 27 July 2015
Published date: July 2015
Keywords: greenhouse climates, Eocene, organic biomarkers
Organisations: Geochemistry

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Local EPrints ID: 379714
URI: https://eprints.soton.ac.uk/id/eprint/379714
ISSN: 0883-8305
PURE UUID: 37f0ccc5-c0d4-4eea-a9f8-847dc7ab1e28

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Date deposited: 28 Jul 2015 08:43
Last modified: 17 Jul 2017 20:41

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Contributors

Author: Gordon N. Inglis
Author: Alexander Farnsworth
Author: Daniel Lunt
Author: Gavin L. Foster
Author: Christopher J. Hollis
Author: Mark Pagani
Author: Phillip E. Jardine
Author: Paul N. Pearson
Author: Paul Markwick
Author: Amanda M. J. Galsworthy
Author: Lauren Raynham
Author: Kyle. W. R. Taylor
Author: Richard D. Pancost

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