Response of Iberian Margin sediments to orbital and suborbital forcing over the past 420 ka
Response of Iberian Margin sediments to orbital and suborbital forcing over the past 420 ka
Here we report 420?kyr long records of sediment geochemical and color variations from the southwestern Iberian Margin. We synchronized the Iberian Margin sediment record to Antarctic ice cores and speleothem records on millennial time scales and investigated the phase responses relative to orbital forcing of multiple proxy records available from these cores. Iberian Margin sediments contain strong precession power. Sediment “redness” (a* and 570–560?nm) and the ratio of long-chain alcohols to n-alkanes (C26OH/(C26OH?+?C29)) are highly coherent and in-phase with precession. Redder layers and more oxidizing conditions (low alcohol ratio) occur near precession minima (summer insolation maxima). We suggest these proxies respond rapidly to low-latitude insolation forcing by wind-driven processes (e.g., dust transport, upwelling, precipitation). Most Iberian Margin sediment parameters lag obliquity maxima by 7–8?ka, indicating a consistent linear response to insolation forcing at obliquity frequencies driven mainly by high-latitude processes. Although the lengths of the time series are short (420?ka) for detecting 100?kyr eccentricity cycles, the phase relationships support those obtained by Shackleton []. Antarctic temperature and the Iberian Margin alcohol ratios (C26OH/(C26OH?+?C29)) lead eccentricity maxima by 6?kyr, with lower ratios (increased oxygenation) occurring at eccentricity maxima. CO2, CH4, and Iberian SST are nearly in phase with eccentricity, and minimum ice volume (as inferred from Pacific ?18Oseawater) lags eccentricity maxima by 10?kyr. The phase relationships derived in this study continue to support a potential role of the Earth's carbon cycle in contributing to the 100?kyr cycle.
Iberian Margin, paleoceanography, orbital forcing, millennial variability
185-199
Hodell, David
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Crowhurst, Simon
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Skinner, Luke
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Tzedakis, Polychronis C.
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Margari, Vasiliki
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Channell, James E.T.
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Kamenov, George
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MacLachlan, Suzanne
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Rothwell, Guy
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March 2013
Hodell, David
fa374377-1c67-459d-ab72-1e556012f3b1
Crowhurst, Simon
386e0ab1-a26d-430d-9229-c049d0c84006
Skinner, Luke
3b31eb32-9abb-43ff-a821-6bccc6cdbe2a
Tzedakis, Polychronis C.
e2de7aa9-aa3b-4463-af61-ca25032f600b
Margari, Vasiliki
d3fbf6a7-c040-420b-92ef-33665caaa449
Channell, James E.T.
55b6c1cc-76e7-4ca5-8186-d9111b9b5158
Kamenov, George
9b2d2154-deba-46b5-8d4d-e081fe425fa4
MacLachlan, Suzanne
a6c1b5e7-066a-45f5-a6bd-15cbcf127758
Rothwell, Guy
fe473057-bf44-46d1-8add-88060037beb5
Hodell, David, Crowhurst, Simon, Skinner, Luke, Tzedakis, Polychronis C., Margari, Vasiliki, Channell, James E.T., Kamenov, George, MacLachlan, Suzanne and Rothwell, Guy
(2013)
Response of Iberian Margin sediments to orbital and suborbital forcing over the past 420 ka.
Paleoceanography, 28 (1), .
(doi:10.1002/palo.20017).
Abstract
Here we report 420?kyr long records of sediment geochemical and color variations from the southwestern Iberian Margin. We synchronized the Iberian Margin sediment record to Antarctic ice cores and speleothem records on millennial time scales and investigated the phase responses relative to orbital forcing of multiple proxy records available from these cores. Iberian Margin sediments contain strong precession power. Sediment “redness” (a* and 570–560?nm) and the ratio of long-chain alcohols to n-alkanes (C26OH/(C26OH?+?C29)) are highly coherent and in-phase with precession. Redder layers and more oxidizing conditions (low alcohol ratio) occur near precession minima (summer insolation maxima). We suggest these proxies respond rapidly to low-latitude insolation forcing by wind-driven processes (e.g., dust transport, upwelling, precipitation). Most Iberian Margin sediment parameters lag obliquity maxima by 7–8?ka, indicating a consistent linear response to insolation forcing at obliquity frequencies driven mainly by high-latitude processes. Although the lengths of the time series are short (420?ka) for detecting 100?kyr eccentricity cycles, the phase relationships support those obtained by Shackleton []. Antarctic temperature and the Iberian Margin alcohol ratios (C26OH/(C26OH?+?C29)) lead eccentricity maxima by 6?kyr, with lower ratios (increased oxygenation) occurring at eccentricity maxima. CO2, CH4, and Iberian SST are nearly in phase with eccentricity, and minimum ice volume (as inferred from Pacific ?18Oseawater) lags eccentricity maxima by 10?kyr. The phase relationships derived in this study continue to support a potential role of the Earth's carbon cycle in contributing to the 100?kyr cycle.
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Published date: March 2013
Keywords:
Iberian Margin, paleoceanography, orbital forcing, millennial variability
Organisations:
Marine Geoscience
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Local EPrints ID: 353618
URI: http://eprints.soton.ac.uk/id/eprint/353618
ISSN: 0883-8305
PURE UUID: 34928c36-728d-4e8a-9c09-8edd64b1c38b
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Date deposited: 11 Jun 2013 14:23
Last modified: 14 Mar 2024 14:07
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Author:
David Hodell
Author:
Simon Crowhurst
Author:
Luke Skinner
Author:
Polychronis C. Tzedakis
Author:
Vasiliki Margari
Author:
James E.T. Channell
Author:
George Kamenov
Author:
Suzanne MacLachlan
Author:
Guy Rothwell
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