Glacial-interglacial circulation changes inferred from 231 Pa/ 230 Th sedimentary record in the North Atlantic region - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Paleoceanography Année : 2009

Glacial-interglacial circulation changes inferred from 231 Pa/ 230 Th sedimentary record in the North Atlantic region

Résumé

Studies from the subtropical western and eastern Atlantic Ocean, using the 231Pa/230Th ratio as a kinematic proxy for deep water circulation, provided compelling evidence for a strong link between climate and the rate of meridional overturning circulation (MOC) over the last deglaciation. In this study, we present a compilation of existing and new sedimentary 231Pa/230Th records from North Atlantic cores between 1710 and 4550 m water depth. Comparing sedimentary 231Pa/230Th from different depths provides new insights into the evolution of the geometry and rate of deep water formation in the North Atlantic during the last 20,000 years. The 231Pa/230Th ratio measured in upper Holocene sediments indicates slow water renewal above ∼2500 m and rapid flushing below, consistent with our understanding of modern circulation. In contrast, during the Last Glacial Maximum (LGM), Glacial North Atlantic Intermediate Water (GNAIW) drove a rapid overturning circulation to a depth of at least ∼3000 m depth. Below ∼4000 m, water renewal was much slower than today. At the onset of Heinrich event 1, transport by the overturning circulation declined at all depths. GNAIW shoaled above 3000 m and significantly weakened but did not totally shut down. During the Bølling‐Allerød (BA) that followed, water renewal rates further decreased above 2000 m but increased below. Our results suggest for the first time that ocean circulation during that period was quite distinct from the modern circulation mode, with a comparatively higher renewal rate above 3000 m and a lower renewal rate below in a pattern similar to the LGM but less accentuated. MOC during the Younger Dryas appears very similar to BA down to 2000 m and slightly slower below.
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Dates et versions

hal-02959689 , version 1 (09-10-2020)

Identifiants

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J.-M. Gherardi, L. Labeyrie, S. Nave, Raoul François, J. Mcmanus, et al.. Glacial-interglacial circulation changes inferred from 231 Pa/ 230 Th sedimentary record in the North Atlantic region. Paleoceanography, 2009, 24 (2), pp.PA2204. ⟨10.1029/2008PA001696⟩. ⟨hal-02959689⟩
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