Will climate change impacts the biogeochemical cycles of essential micronutrients?

Trace metals are important micronutrient for marine microbial life. They support many metabolic reactions necessary for bacteria, phytoplankton and zooplankton, however, some trace metals such as Cu or Zn may have toxic effects at high concentrations. The processes shaping trace metals distribution and cycling in the ocean are still poorly understood. Furthermore, the evolution of trace metals distributions as a consequence of climate change has never been investigated.

This work aims at characterizing the potential impacts of climate change on the global biogeochemical cycling of essential trace metals. We use a state-of-the-art global ocean biogeochemical model representing a suite of trace elements (Fe, Cu, Zn, Co, Mn) to investigate how their distribution and inventories may change in response to the RCP8.5 climate change scenario. The changing ocean circulation in this scenario may result in surface stratification, resulting in changes in biological pump strength, oxygen distribution and particle loadings. In regions affected by external inputs, surface concentration of micronutrient may increase as a result of surface stratification. On the other hand, surface micronutrient concentrations may decrease in the open ocean as a result of the decline in vertical supply of nutrients. We use an extended Redfield ratio calculation in order to characterise the changes in trace metal concentrations and highlight the regions where trace metal cycling is the most affected by climate change. Results show that cobalt and manganese concentrations display important evolutions in the Arctic whereas zinc is mostly impacted in the Southern Ocean. Our results suggest that changes to the ocean physics and productivity will impact trace metals differently depending on their role and biogeochemical drivers.