Influence of Atlantic Meridional Overturning Circulation changes on deglacial deep-water ecosystems off NW-Africa

The Atlantic Ocean is an important component of the global climate system. In this ocean basin, the Atlantic Meridional Overturning Circulation (AMOC), partially driven by the formation of North Atlantic Deep Water (NADW) in the northern hemisphere, uptakes an important percentage of the anthropogenically induced excess heat of our planet and distributes it around the globe through a complex ocean circulation system that influences global warming rate (e.g. Cummins et al., 2016; Levitus et al., 2000). As described in Chapter 2 and Chapter 4, the instrumental record of AMOC strength provides evidence of a potential decrease or weakening also known as “AMOC slowdown” in the 19th and 20th centuries, synchronous with the increasing trend of CO2 in the atmosphere, as well as greenhouse gases concentrations (Caesar et al., 2021; Dima et al., 2021; IPCC, 2022; Rahmstorf et al., 2015). Furthermore, AMOC will very likely decrease in the 21st century (IPCC, 2023). However, the instrumental AMOC record is still too short to fully understand the effects of such slowdown in the climate system, therefore our knowledge must rely on paleoceanographic proxies. Although controversial, AMOC slowdown has been recorded by different proxies in the last 30,000 years, offering the opportunity to observe the effects of this slowdown in the deep ocean through the marine fossil record. This is discussed in detail in the Introduction of Chapter 4. The last deglaciation period in the Eastern North Atlantic (NE Atlantic) starts after the end of the Last Glacial Maximum (LGM, ⁓ 19 kyrs BP). Temporary returns to cold periods occurred during the Heinrich Stadial 1 (HS1, ⁓18.3 – 15.4 Kyr BP) and Younger Dryas (YD, ⁓12.9 – 11.7 Kyr BP), and between these two cold periods, the Bølling–Allerød warming (B-A) was a transient warming time in the northern hemisphere. The record of AMOC, includes kinematic proxies like 231Pa/230Th (Böhm et al., 2015; Gherardi et al., 2005; McManus et al., 2004), paleo-circulation proxies like the radiogenic neodymium ...