Unprecedented set of dissolved manganese data in the North Atlantic Ocean (US GEOTRACES cruise)

Science Highlights

8 January 2015

Manganese (Mn) is an essential nutrient for biological growth. In the ocean, manganese distribution is sensitive to several processes: redox conditions, photochemistry, biological activity, abiotic scavenging, and also eolian, hydrothermal and sedimentary sources. All of them are conditioning the concentration of dissolved Mn in the ocean vertical profiles as shown in the east-west ocean section proposed by Wu and co-workers across the Subtropical North Atlantic Ocean (see figure below).

Their simple model calculation suggests that the main actors determining the distribution are:

  • In the surface waters (0-40m): eolian Mn(II) deposition and in-situ photochemical reduction of dioxide of manganese (MnO2).
  • Below the mixed layer (40-200m): the intensity of sunlight available for in-situ MnO2 photochemical reduction.
  • Between 200 and 700 m: regeneration preformed Mn in the source water and lateral inputs from hydrothermal and sedimentary sources.
  • Below 700 m: lateral inputs from hydrothermal and sedimentary sources become predominant.

2014 Wu l

Figure. Vertical distribution of manganese (Mn) along a section across Subtropical North Atlantic. Warm colours (red, orange, etc.) indicate high concentrations. Click here to view the figure larger.

Reference:

Wu, J., Roshan, S., & Chen, G. (2014). The distribution of dissolved manganese in the tropical–subtropical North Atlantic during US GEOTRACES 2010 and 2011 cruises. Marine Chemistry, 166, 9–24. doi:10.1016/j.marchem.2014.08.007. Click here to access the paper.

Latest highlights

Continuous record of the Antarctic Circumpolar Current latitude over the last glacial-interglacial cycles

The meridional positions of the oceanic fronts separating subtropical and Antarctic waters are key to constraining the mechanisms that drive the degassing of deeply-stored CO2 at the end of the glacial periods…

23 Million Years of iron sources reconstructed in the Northwest Pacific Ocean using iron isotopes in a ferromanganese crust

Using iron isotopes and elemental records, Chu and co-workers analysed an iron-manganese crust recovered from the Hongyan Seamount, and reconstructed the sources of dissolved Fe to the Northwest Pacific Ocean…

Variability of the past deep-water masses in the Arabian Sea over the last 41ka

Shukla and colleagues propose a high-resolution authigenic ƐNd record measured from a sediment core located in the eastern Arabian Sea…

Arctic outflows to Davis Strait and the Labrador Sea traced by radionuclide distributions

This study demonstrates that Arctic outflows through the Canadian Arctic Archipelago play a much more significant role than previously recognised.

Rechercher