Changing sea-surface and deep-water conditions in the southern Cape Verde Basin during the mid-Pleistocene to Holocene

Reconstruction of the Atlantic Meridional Overturning Circulation (AMOC) based on long-term records spanning multiple glacial-interglacial transitions is essential for understanding the interplay between ocean dynamics and global climate change. However, despite valuable previous studies, many uncertainties remain, especially regarding the distribution of glacial water masses in the Atlantic and the AMOC intensity. Such long-term reconstructions are highly constrained by sedimentary geochemical records. Here, we present isotope, geochemical, and micropaleontological records from the core ANS-33047 retrieved from the southern part of the Cape Verde Basin at a water depth of 4027 m. The data reflect the glacial–interglacial changes in surface and near-bottom conditions in the area over the last 513 kyr. Within the upper ocean layer, enhanced bioproductivity associated with northward ITCZ migration has been determined during MIS 13/12, early MIS 11, 9, 7, and MIS 1. A gradual deepening of the mixed layer is inferred from MIS 5 to the present. Stronger deep-water upwelling and shoaling of the mixed layer over the study site preceded these intervals. In the deep-water environment, we propose three different regimes within the interglacials: a “classical model” and “local productivity effect” associated with a stronger advection of paleo-NADW into the study area (MIS 11, 5, 1, warm early phases of MIS 9 and 7, MIS 13/12 boundary), as well as “amplified paleo-AABW influence” (late MIS 13 and 7). The bottom-water chemistry was affected by organic matter degradation coinciding with intervals of northward ITCZ migrations and enhanced surface bioproductivity. The most prominent signal of southern-sourced deep water was reconstructed during the late MIS 12, MIS 8, and at the MIS 10/9 boundary. During MIS 3 and sub-stage 12b, the study area was bathed by a mixture of paleo-NADW and paleo-AABW. A comparison of the carbon isotope records from the northeastern and southeastern equatorial Atlantic demonstrates a larger difference in the deep-water properties within glacials in contrast to interglacials.