Impact summary (3938/4000 characters, with spaces)
Although of primary interests to marine trace metal chemists contributing to the GEOTRACES
program, the benefits of this work will extend beyond advances in academic research. The
following areas will be particularly concerned.
i.
Environmental and climate change: problems and remediation strategies
a. Iron fertilization: Iron addition was proposed as a geo-engineering solution to pump
carbon out of the atmosphere into the ocean. It is not clear how to quantify the
benefits of such schemes and how to weight the negative aspects, such as the
development anoxic conditions and its influence on sea life. This project will provide
a better understanding of iron remineralization on large scales, on interior iron
transport and on the relationships between iron and other metals.
b. Acidification: Changing seawater pH changes metal speciation and bioavailability.
pH and redox conditions also control sedimentary metal cycling and the dissolution
of carbonates. Acidification changes the lysocline depth and can influence
sediment-water column metal exchange. This project will provide a baseline
assessment of current relationship between pH-gradients in the sea and ocean
interior metal cycling.
c. Ecosystems: Micronutrients like Fe, Zn, Cd, Mn and Ni are important to maintain
phytoplankton growth and thus to support the marine ecosystem. By analyzing the
large-scale subsurface signature of these metals, the project will inform on the role
of micronutrients on surface. A better understanding of ecosystems will help better
manage fisheries and international marine resources.
ii.
Deep-sea resource exploitation and management
a. Deep-sea mining: It has been known for decades that marine deposits are rich in
valuable metals. About 30 years ago, deep-sea mining was deemed not profitable. It
was cheaper to exploit land-based resources. Today, our economies rely on access
to critical metals. With prices going up and the risk that metal supply is used as a
geopolitical weapon in international negotiations, countries and corporations are
looking again in the potential of deep-sea mining. The results from this project will
provide a large-scale picture on the processes controlling the deep-sea distribution
of metals, information that will help identify, evaluate and, in time, mitigate the
influence of deep-sea mining on ecosystems and on the metal budget of the ocean.
iii.
Earth system modeling and forecasting
a. Carbon export: The flux of particulate carbon is a critical quantity to assess the
strength of the biological pump and its role in the global carbon cycle. It is, however,
a difficult quantity to observe and model. No model currently simulates the dynamics
of marine particles with any confidence. Since some metals scavenge on particles,
tracing the interior distribution of metals helps constrain particles dynamics, the
particle flux and its spatial pattern, provided one can separate the influence of
transport on concentrations. This work will explicitly quantify the role of advection.
By focusing on modeling the distribution of metals better, one will achieve a better
understanding and representation of carbon export and ultimately on the fate of
atmospheric CO2 and on the functioning of ecosystems.
b. Ocean interactions with its boundaries: Our understanding of the interactions
between submerged landmasses (continental shelves, mid-ocean ridges,
seamounts, bottom boundary layer) and the ocean is generally poor. Our ability to
model these interactions is commensurate with our understanding of these
processes. This work will provide estimates of the fraction of trace elements that
cannot be explained by advection. It will then be possible to interpret this “residual”
fraction using a combination of trace metals and ancillary isotopic data. By
investigating the spatial gradient of these residuals, the project will contribute a
much greater understanding of these land-ocean interactions.