Changes in the geometry and strength of the Atlantic meridional overturning circulation during the last glacial (20–50 ka)
Pierre Burckel1,2,Claire Waelbroeck1,Yiming Luo3,Didier M. Roche1,4,Sylvain Pichat5,Samuel L. Jaccard6,Jeanne Gherardi1,Aline Govin1,Jörg Lippold6,and François Thil1Pierre Burckel et al.Pierre Burckel1,2,Claire Waelbroeck1,Yiming Luo3,Didier M. Roche1,4,Sylvain Pichat5,Samuel L. Jaccard6,Jeanne Gherardi1,Aline Govin1,Jörg Lippold6,and François Thil1
Received: 26 Feb 2016 – Discussion started: 11 Mar 2016 – Revised: 11 Sep 2016 – Accepted: 29 Sep 2016 – Published: 08 Nov 2016
Abstract. We reconstruct the geometry and strength of the Atlantic meridional overturning circulation during the Heinrich stadial 2 and three Greenland interstadials of the 20–50 ka period based on the comparison of new and published sedimentary 231Pa / 230Th data with simulated sedimentary 231Pa / 230Th. We show that the deep Atlantic circulation during these interstadials was very different from that of the Holocene. Northern-sourced waters likely circulated above 2500 m depth, with a flow rate lower than that of the present-day North Atlantic deep water (NADW). Southern-sourced deep waters most probably flowed northwards below 4000 m depth into the North Atlantic basin and then southwards as a return flow between 2500 and 4000 m depth. The flow rate of this southern-sourced deep water was likely larger than that of the modern Antarctic bottom water (AABW). Our results further show that during Heinrich stadial 2, the deep Atlantic was probably directly affected by a southern-sourced water mass below 2500 m depth, while a slow, southward-flowing water mass originating from the North Atlantic likely influenced depths between 1500 and 2500 m down to the equator.
In this paper, we compare new and published Atlantic sedimentary Pa/Th data with Pa/Th simulated using stream functions generated under various climatic conditions. We show that during Greenland interstadials of the 20–50 ka period, the Atlantic meridional overturning circulation was very different from that of the Holocene. Moreover, southern-sourced waters dominated the Atlantic during Heinrich stadial 2, a slow northern-sourced water mass flowing above 2500 m in the North Atlantic.
In this paper, we compare new and published Atlantic sedimentary Pa/Th data with Pa/Th simulated...