Publication Date:
2022-05-26
Description:
Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 24 (2009): PA2204, doi:10.1029/2008PA001696.
Description:
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.
Description:
The LSCE-WHOI cooperation has been supported by a NSF-CNRS
cooperative grant NSF INT-0233483. Analytical measurements in LSCE
have been supported by French Programme National d’Etude de la
Dynamique du Climat, Commissariat a` l’Energie Atomique, and Centre
National de la Recherche Scientifique. The
participation of J.F.M. in this project was supported in part by grants from
the U.S.-NSF, WHOI-OCCI, and the Gary Comer Science and Education
Foundation. R.F.’s participation was supported by grants from NSERC and
the Canadian Foundation for Climate and Atmospheric Science.
Keywords:
MOC
Repository Name:
Woods Hole Open Access Server
Type:
Article
Format:
application/pdf
Format:
text/plain
Format:
application/vnd.ms-excel
Format:
application/postscript
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