25 May 2021

Robert Frei from IGN receives 6.2 mio. DKK from the Independent Research Fund Denmark


Robert Frei will investigate the relationship between bioproductivity and water column redox in paleo oceans with the help of cadmium of chromium isotopes with the ultimate goal to reconstruct climate change back in time.

​There is an increased knowledge that World’s ocean surface waters are depleted in cadmium relative to deep ocean waters. This is because photosynthetic organisms consume cadmium, and this uptake of cadmium is accompanied by an isotope fractionation, which renders the surface waters isotopically heavy.

Robert Frei in the lab. Photo: Kent Pørksen
Robert Frei in the lab. Photo Kent Pørksen.

Within the framework of the applied project, Robert Frei will apply cadmium of chromium isotopes to marine sedimentary archives.

The project builds on the development of the cadmium isotope system for its use as a paleo-bioproductivity tracer and to combine it with other tracers, such as the chromium isotope system. The idea is to apply the double isotope tracer to reconstruct compositional changes in surface waters of paleo-oceans.

Cadmium substitutes for calcium in calcium carbonate, which is the major constituent of limestone. In a similar way, chromium is incorporated as chromate ion in carbonates. These geochemical affinities leads Robert Frei and his group to apply the combined cadmium-chromium isotope tracer to marine carbonates which are likely to mirror the compositions in surface waters of past oceans, with respect to bioproductivity levels and redox.

Finally, this new approach can be used to characterize and reconstruct parameters which controlled and triggered climate fluctuations in the past.