Continental shelves and shelf seas play a central role in the global carbon cycle. However,

their importance with respect to trace element and isotope (TEI) inputs to ocean basins

is less well understood. Here, we present major findings on shelf TEI biogeochemistry

from the GEOTRACES programme as well as a proof of concept for a new method to

estimate shelf TEI fluxes. The case studies focus on advances in our understanding of TEI

cycling in the Arctic, transformations within a major river estuary (Amazon), shelf sediment

micronutrient fluxes and basin-scale estimates of submarine groundwater discharge. The

proposed shelf flux tracer is 228-radium (T1/2 =5.75 yr), which is continuously supplied to

the shelf from coastal aquifers, sediment porewater exchange and rivers. Model-derived shelf

228Ra fluxes are combined with TEI/ 228Ra ratios to quantify ocean TEI fluxes from the

western North Atlantic margin. The results from this new approach agree well with previous

estimates for shelf Co, Fe, Mn and Zn inputs and exceed published estimates of atmospheric

deposition by factors of approximately 3–23. Lastly, recommendations are made for additional

GEOTRACES process studies and coastal margin-focused section cruises that will help refine

the model and provide better insight on the mechanisms driving shelf-derived TEI fluxes

to the ocean.

This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element

chemistry’.