Millennial-scale variations of the Holocene North Atlantic mid-depth gyre inferred from radiocarbon and neodymium isotopes in cold water corals
TISNERAT-LABORDE, Nadine
Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] [LSCE]
Géochrononologie Traceurs Archéométrie [GEOTRAC]
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Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] [LSCE]
Géochrononologie Traceurs Archéométrie [GEOTRAC]
TISNERAT-LABORDE, Nadine
Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] [LSCE]
Géochrononologie Traceurs Archéométrie [GEOTRAC]
Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] [LSCE]
Géochrononologie Traceurs Archéométrie [GEOTRAC]
PONS-BRANCHU, Edwige
Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] [LSCE]
Géochrononologie Traceurs Archéométrie [GEOTRAC]
Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] [LSCE]
Géochrononologie Traceurs Archéométrie [GEOTRAC]
FRANK, Norbert
Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] [LSCE]
Géochrononologie Traceurs Archéométrie [GEOTRAC]
Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] [LSCE]
Géochrononologie Traceurs Archéométrie [GEOTRAC]
DAPOIGNY, Arnaud
Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] [LSCE]
Géochrononologie Traceurs Archéométrie [GEOTRAC]
Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] [LSCE]
Géochrononologie Traceurs Archéométrie [GEOTRAC]
DUTAY, Jean-Claude
Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] [LSCE]
Modélisation du climat [CLIM]
Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] [LSCE]
Modélisation du climat [CLIM]
BLAMART, Dominique
Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] [LSCE]
Paléocéanographie [PALEOCEAN]
Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] [LSCE]
Paléocéanographie [PALEOCEAN]
DOUVILLE, Eric
Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] [LSCE]
Géochrononologie Traceurs Archéométrie [GEOTRAC]
< Réduire
Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] [LSCE]
Géochrononologie Traceurs Archéométrie [GEOTRAC]
Langue
EN
Article de revue
Ce document a été publié dans
Quaternary Science Reviews. 2019-05, vol. 211, p. 93-106
Résumé en anglais
Variations in North Atlantic Ocean mid-depth circulation during the Holocene are poorly understood. It is believed that they had a significant influence on the properties of water entering the Nordic Sea by redistributing ...Lire la suite >
Variations in North Atlantic Ocean mid-depth circulation during the Holocene are poorly understood. It is believed that they had a significant influence on the properties of water entering the Nordic Sea by redistributing heat and freshwater, potentially affecting deep-water formation and climate. To improve our knowledge of the NE Atlantic mid-depth circulation, radiocarbon and neodymium isotope analyses have been then carried out on precisely dated (U-Th) L. pertusa and M. oculata coral fragments from two sediment cores taken at ∼750 m water depth on the SW Rockall Trough margin. Cold-water coral (CWC) εNd values vary between −12.2 ± 0.3 and −16.6 ± 0.4 and result from variable contributions of unradiogenic mid-depth subpolar gyre (mid-SPG) water (∼-15) and more radiogenic Eastern North Atlantic Water (ENAW) (∼-11) which is transported northward to the Rockall Trough by boundary currents along the European margin. Increased coral εNd reflects a westward contraction of the mid-SPG water and a higher proportion of ENAW. The mid-Holocene (from 8.8 to 6.8 ka BP) is marked by unradiogenic coral εNd (from −16.6 ± 0.4 to −14.6 ± 0.5) indicating a greater eastward extension of the mid-SPG. This is followed by a shift from 6.8 to 5 ka BP toward more radiogenic εNd values (from −15.4 ± 0.3 to −13.3 ± 0.2) suggesting a westward contraction of the mid-SPG and a higher proportion of ENAW. The mid-Holocene long-term change in εNd is characterized by millennial variations of up to 2.5 epsilon units well marked during the Late Holocene, indicating that eastward extension of the mid-SPG coeval with warm periods in northern Europe (e.g. the Medieval Climatic Anomaly and the Roman Warm Period). Most of the CWC-derived Δ14C values match the global ocean values indicating that the water masses bathing the corals were generally well ventilated; the exceptions are a few short intervals of eastward extension of the mid-SPG, which are characterized by lower Δ14C during the late Holocene. We propose that these minor Δ14C fluctuations in the Rockall Trough may be related to local changes in the mixed layer depth or to variability in the advection of water from the Labrador Sea where deep convection gives rise to thermocline waters that are relatively depleted in terms of Δ14C.The eastward extension of the mid-SPG between 8.8 and 6.8 ka BP is associated with the Holocene climatic optimum, concurrent with a maximum strength of the Iceland-Scotland Overflow Water (ISOW), which is indicative of an increase in the Atlantic Meridional Overturning Circulation (AMOC). This period is followed by a transition in the North Atlantic circulation, which occurred around 6.8 ka BP, and coincides with the onset of Labrador Sea Water formation, a decrease of the ISOW strength and a contraction of the mid-SPG leading to a greater intrusion of saline subtropical water into the subpolar Atlantic.< Réduire
Mots clés
PANOPLY
Mots clés en anglais
Panoply
Cold-water corals
Rockall Trough
Holocene
Nd isotopic composition
radiocarbon
North Atlantic gyre dynamics.
Project ANR
IPSL Climate graduate school - ANR-17-EURE-0006
LabEx Institut Pierre Simon Laplace (IPSL): Understand climate and anticipate future changes - ANR-10-LABX-0018
LabEx Institut Pierre Simon Laplace (IPSL): Understand climate and anticipate future changes - ANR-10-LABX-0018