The resilience and sensitivity of Northeast Atlantic deep water εNd to overprinting by detrital fluxes over the past 30,000 years

No detectable Weddell Sea Antarctic Bottom Water export during the Last and Penultimate Glacial Maximum

“…3 and 4). Therefore, the ε Nd evolution trend across the two terminations was reliably capturing a porewater signature 29 .…”

“…A previous record from the South Atlantic (Site MD07-3076, 44°4.46′S, 14°12.47′W, 3770-m depth) reported early deglacial ε Nd of~−5.5 46 . Potentially, Nd can be released from marine sediments to deep marine bottom water under very sluggish circulation regimes 24,29 . In marine settings such as the North Pacific 28 or North Atlantic 29 , where this process has been observed, the porewater signature (i.e., the ε Nd signal extracted here) is expected to be altered away from bottom water ε Nd toward other non-hydrogenetic sedimentary phases such as volcanic debris within the sediment 29 .…”

“…Potentially, Nd can be released from marine sediments to deep marine bottom water under very sluggish circulation regimes 24,29 . In marine settings such as the North Pacific 28 or North Atlantic 29 , where this process has been observed, the porewater signature (i.e., the ε Nd signal extracted here) is expected to be altered away from bottom water ε Nd toward other non-hydrogenetic sedimentary phases such as volcanic debris within the sediment 29 . If the early deglacial South Atlantic and Drake Passage water column signatures on the order of −5.5 46 to −6.0 45 were equally representative for our core sites in the Atlantic sector of the SO, then the radiogenic glacial and deglacial signatures on the order of~−4 were affected by such porewater alteration, changing the authigenic ε Nd to some degree away from ambient bottom water compositions.…”

“…Consequently, the seawater-derived authigenic Pb isotope signature in deep marine sediments in the Southern Ocean can be controlled both by changes in the upper and lower overturning cells. In contrast to authigenic Pb, the Nd isotope signal of the same deep marine authigenic Fe-Mn oxyhydroxide fraction only records bottom or porewater compositions 28,29 . Taking advantage of the different behavior of Pb and Nd in seawater, past seawater Pb isotopic compositions extracted from the authigenic Fe-Mn oxyhydroxide fraction in deep marine sediments 30 hence provide insights into isotopic changes of the entire water column, while the Nd isotopic composition extracted from deep marine sediments is controlled by bottom water conditions.…”

Ice-rafted debris as a source of non-conservative behaviour for the εNd palaeotracer: insights from a simple model

“…The potential significance of localised highly nonconservative behaviour of neodymium isotopes for palaeoceanography has been raised by recent geochemical studies on sediment cores from the eastern North Atlantic (Roberts and Piotrowski 2015;Blaser et al 2019). The extensive sea-ice in the North Atlantic during the last glaciation resulted in the widespread deposition of ice-rafted debris (IRD).…”