jabbrv-ltwa-all.ldf jabbrv-ltwa-en.ldf Previous attempts to explain the distribution of Neodymium (Nd) and its isotopes in the ocean, a tracer for past global Meridional Overturning Circulation (MOC) changes, primarily focused on a top-down approach using reversible scavenging. This approach assumes that Nd is supplied to the ocean through terrestrial sources at the surface, and reversible particulate scavenging and sinking of Nd on particles explains observations of linearly increasing dissolved Nd concentrations with depth. Here, we explore a conceptually different model: the bottom-up hypothesis and irreversible scavenging. A benthic flux (BF) is assumed to be the sole source of marine Nd at the seafloor; vertical diffusion leads to upward transport and adsorption onto particles, with a constant adsorption coefficient (kp) as the only loss term. This model is explored in a simple one-dimensional (vertically resolved) version and a three-dimensional global general circulation numerical model. Results indicate that the observed distribution of Nd in the ocean is well reproduced globally using a constant BF of 20 pmol cm-2 yr -1 and irreversible scavenging. Our results suggest that bathymetry and lateral transport play important roles in determining Nd water column distribution in the pelagic ocean.