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Glacial-interglacial circulation changes inferred from231Pa/230Th sedimentary record in the North Atlantic region
- Source :
- Paleoceanography. 24
- Publication Year :
- 2009
- Publisher :
- American Geophysical Union (AGU), 2009.
-
Abstract
- [1] 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 Bolling-Allerod (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.
- Subjects :
- 010504 meteorology & atmospheric sciences
North Atlantic Deep Water
Paleontology
Last Glacial Maximum
010502 geochemistry & geophysics
Oceanography
01 natural sciences
Shutdown of thermohaline circulation
13. Climate action
Interglacial
Deglaciation
Thermohaline circulation
14. Life underwater
Glacial period
Younger Dryas
Geology
0105 earth and related environmental sciences
Subjects
Details
- ISSN :
- 08838305
- Volume :
- 24
- Database :
- OpenAIRE
- Journal :
- Paleoceanography
- Accession number :
- edsair.doi...........14fbb964a47d643dde88cd9f79ca8cdd