AMOC variability before, during, and after the Northern Hemisphere Glaciation onset from Nd isotopes

The Atlantic Meridional Overturning Circulation (AMOC) is a critical component of the global thermohaline ocean circulation system, distributing heat, salt, greenhouse gases, and biologically important nutrients throughout the basin, with numerous feedback processes that relate the AMOC to global climate. Here, we reconstruct glacial-interglacial changes in AMOC through the initiation of the Northern Hemisphere glaciation ( 2.4 Mya). We use Nd isotope measurements from fish debris over the interval of 1.6 to 2.9 Mya, from ODP Site 1090 (42° 54.82'S, 8°53.98'E, 3702 m) located in Cape Basin in the southeast Atlantic Ocean. Site 1090 is an ideal location for developing a greater understanding of this critical time interval because it lies near the lower boundary of the southern-flowing North Atlantic Deep Water (NADW), which drives the global oceanic thermohaline circulation, and Circumpolar Deep Water (CDW). Previously, Pena and Goldstein (2014) showed that Nd isotopes at this site are sensitive and faithful indicators of changes in NADW and CDW over the Mid-Pleistocene Transition ( 600 to 1100 ka). Understanding how the AMOC has shifted since the onset of the Northern Hemisphere Glaciation is critical because it will provide insight as to how ocean circulation and climate are related through this important event.