Neodymium isotopes in the ocean model of the Community Earth System Model (CESM1.3)

Abstract. Neodymium (Nd) isotope ratio (ε_Nd) is a quasi-conservative water mass tracer and has been used increasingly as paleoclimate proxy to indicate the past evolution of ocean circulation. However, there are many uncertainties in interpreting ε_Nd reconstructions. For the purposes of direct comparison between climate models and proxy reconstructions, we implement Nd isotopes (¹⁴³Nd and ¹⁴⁴Nd) in the ocean model of the Community Earth System Model (CESM). Two versions of Nd tracers are implemented: one is the "abiotic" Nd in which the particle fields are prescribed as the particle climatology generated by the marine ecosystem module of the CESM under present day forcing; the other is the "biotic" Nd that is coupled with the marine ecosystem module. Under present day climate forcing, our model is able to simulate both Nd concentrations and εNd in good agreement with available observations. Also, Nd concentration and εNd in our model show similar sensitivities to the total boundary source and the ratio between particle related Nd and dissolved Nd as in previous modeling study (Rempfer et al., 2011). Therefore, our Nd-enabled ocean model provides a promising tool to study past changes in ocean and climate.