Using Radium-228 (228Ra) activity as an indicator of coastal water mass influence and a compilation of Neodymium (Nd) parameters in the first 100 m, Chen and co-authors propose that more stratified regions are generally associated with low surface Nd concentrations and that lateral mixing of Nd from coastal surface current is not the only mechanism determining the basin scale variations of surface water Nd concentrations. Their strong hypothesis is that upper ocean vertical supply may be an as yet neglected primary factor in controling this distribution. Consequently, the estimated required input flux of Nd to the surface layer to maintain the observed concentrations could be nearly two orders of magnitudes larger than riverine/dust flux, and also larger than the model-based estimation on shelf-derived coastal flux.
Chen, T.-Y., J. Rempfer, M. Frank, R. Stumpf, and M. Molina-Kescher (2013), Upper ocean vertical supply: A neglected primary factor controlling the distribution of neodymium concentrations of open ocean surface waters?, J. Geophys. Res. Oceans, 118, 3887–3894, DOI:10.1002/jgrc.20288.