Abrupt changes in the deep Western Tropical Atlantic Ocean during the last two glacial periods

Abstract

The Atlantic Meridional Overturning Circulation (AMOC) was recently listed as a tipping element of the climate system. However, large uncertainties are associated to the possibility of a future AMOC shutdown/marked slowdown and to its consequences. Marine sediment cores from the Atlantic Ocean recorded repeated shutdown/marked slowdown events of the AMOC during the last glacial period, holding a wealth of much-needed information not available in the instrumental record. Yet, the paucity of records hampers the detailed characterization of the consequences of such AMOC shutdown/marked slowdown events to the deep ocean. Here we will determine the detailed response of the deep Western tropical Atlantic Ocean to the shutdown/marked slowdown events of the last two glacial periods. Therefore, we will apply the following proxies to a carefully selected depth transect of marine sediment cores from the continental margin of NE South America: (i) stable carbon isotopic composition of epibenthic foraminifera (a proxy for remineralization of organic matter and the source of bottom waters); (ii) neodymium isotopic composition of authigenic phases (a proxy for the source of bottom waters); and (iii) the radiocarbon age difference between coexisting benthic and planktonic foraminifera (a proxy for bottom water age). By doing this, we will provide an in-depth understanding of the responses of the deep Western tropical Atlantic Ocean to abrupt changes in AMOC strength of the two last glacial periods, helping to constrain possible future scenarios for the Atlantic Ocean. (AU)