Imprint of Holocene climate variability on cold-water coral reef growth at the SW Rockall Trough Margin, NE Atlantic

U-Th ages and temperatures derived from Li/Mg have been measured on coral fragments of Lophelia pertusa and Madrepora oculata collected from two sediment cores, which were taken from cold-water coral (CWC) mounds at 700-790 m water depth at the SW Rockall Trough margin. Our data, combined with previ...

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Bibliographic Details
Published in:Geochemistry, Geophysics, Geosystems
Main Authors: Bonneau, Lucile, Colin, Christophe, Pons-Branchu, Edwige, Mienis, Furu, Tisnerat-Laborde, Nadine, Blamart, Dominique, Elliot, Mary, Collart, Tim, Frank, Norbert, Foliot, Lorna, Douville, Eric
Format: Article in Journal/Newspaper
Language:English
Published: 2018
Subjects:
Earth and Environmental Sciences
CARBONATE-MOUND DEVELOPMENT
DEEP-SEA CORALS
NORTH-ATLANTIC
NORTHEASTERN ATLANTIC
LOPHELIA-PERTUSA
LABRADOR SEA
LATE PLEISTOCENE
CIRCULATION
RECONSTRUCTION
HYDRODYNAMICS
Arctic
Rockall Trough
Labrador Sea
Lophelia pertusa
North Atlantic
Online Access:https://biblio.ugent.be/publication/8587312
http://hdl.handle.net/1854/LU-8587312
https://doi.org/10.1029/2018GC007502
https://biblio.ugent.be/publication/8587312/file/8587313
Description
Summary:U-Th ages and temperatures derived from Li/Mg have been measured on coral fragments of Lophelia pertusa and Madrepora oculata collected from two sediment cores, which were taken from cold-water coral (CWC) mounds at 700-790 m water depth at the SW Rockall Trough margin. Our data, combined with previous published data, have allowed us to first estimate the occurrence of CWC at the SW Rockall Trough margin during the Holocene and, second, to better constrain the environmental conditions driving variability in CWC growth. CWC abundance is marked by a pronounced increase in the mid-Holocene (similar to 6 ka) and is modulated by millennial-scale variability throughout the late-Holocene. The mid-Holocene proliferation of CWC coincides with lowest IRD abundances and a major reorganization of the circulation at thermocline depth in the Rockall Trough, marked by the progressive replacement of the fresh-cold Sub-Arctic Intermediate Water (SAIW) by the saltier and nutrient-rich Eastern North Atlantic Water (ENAW). This event must have established a modern-like winter mixed layer and thermocline structure, generating suitable conditions for enhanced surface productivity, downslope transport of food particles, bottom current acceleration at mound depth and thus CWC growth. Several short time intervals of decreased CWC occurrences closely match prominent increases in North Atlantic drift ice and storminess in Northern Europe. We, therefore, propose that high detrital supply and/or changes in the vertical density gradient associated with millennial-scale ice-rafted detritus (IRD) events are the likely controlling factors for CWC growth and subsequent mound formation on the SW Rockall Trough margin.

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