Inverse response of 231Pa/230Th to variations of the Atlantic meridional overturning circulation in the North Atlantic intermediate water
This study aims to provide a more detailed understanding of the behavior of ²³¹Pa/²³⁰Th under varying ocean circulation regimes. The North Atlantic provides a unique sedimentary setting with its ice-rafted detritus (IRD) layers deposited during glacial times. These layers have been found north of 40...
Published in: | Geo-Marine Letters |
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Main Authors: | , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Springer
2020
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Subjects: | |
Online Access: | https://boris.unibe.ch/141787/2/S%C3%BCfke2020_published.pdf https://boris.unibe.ch/141787/8/Manuscript_Suefke_postprint.pdf https://boris.unibe.ch/141787/ |
Summary: | This study aims to provide a more detailed understanding of the behavior of ²³¹Pa/²³⁰Th under varying ocean circulation regimes. The North Atlantic provides a unique sedimentary setting with its ice-rafted detritus (IRD) layers deposited during glacial times. These layers have been found north of 40° N (Ruddiman Belt) and are most pronounced during Heinrich Stadials. Most of these sediments have been recovered from the deep North Atlantic basin typically below 3000 m water depth. This study reports sedimentological and sediment geochemical data from one of the few sites at intermediate depth of the open North Atlantic (core SU90-I02, 45° N 39° W, 1965 m water depth) within the Ruddiman Belt. The time periods of Heinrich Stadials 1 and 2 of this core were identified with the help of the major element composition by XRF scanning and by IRD counting. Along the core profile, the sedimentary ²³¹Pa/²³⁰Th activity ratio has been measured as a kinematic proxy for the circulation strength. The ²³¹Pa/²³⁰Th record shows highest values during the Holocene and Last Glacial Maximum, above the natural production ratio of these isotopes. During Heinrich Stadials 1 and 2, when Atlantic meridional overturning circulation was most reduced, the ²³¹Pa/²³⁰Th record shows overall lowest values below the production ratio. This behavior is contrary to classical findings of ²³¹Pa/²³⁰Th from the northwestern Atlantic where a strong Holocene circulation is associated with low values. However, this behavior at the presented location is in agreement with results from simulations of the ²³¹Pa/²³⁰Th-enabled Bern3D Earth system model. |
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