Inverse response of 231Pa/230Th to variations of the Atlantic meridional overturning circulation in the North Atlantic intermediate water

• Published in: Geo-Marine Letters
• Main Authors: Süfke, Finn, Schulz, Hartmut, Scheen, Jeemijn, Szidat, Sönke, Regelous, Marcel, Blaser, Patrick, Pöppelmeier, Frerk, Goepfert, Tyler J., Stocker, Thomas F., Lippold, Jörg
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer 2020
• Subjects: North Atlantic
• Online Access: https://oceanrep.geomar.de/id/eprint/48719/; https://oceanrep.geomar.de/id/eprint/48719/10/S%C3%BCfke2020_Article_InverseResponseOf231Pa230ThToV.pdf; https://oceanrep.geomar.de/id/eprint/48719/2/367_2019_634_MOESM1_ESM.pdf; https://oceanrep.geomar.de/id/eprint/48719/3/367_2019_634_MOESM2_ESM.xlsx; https://doi.org/10.1007/s00367-019-00634-7

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.