Owing to its propensity to adsorb onto surfaces, Th is a great element to study the role of particles in the ocean. By coupling radioactive and stable Th isotopes, one can estimate particle sinking rates and elemental input fluxes to the ocean. Other radiogenic isotopes, such as 10Be and 7Be and isotopes of radium, can also be used to study ocean processes.
Massive amounts of Pb have been released to the environment when leaded gasoline was being used (from the 1920s). In that regard, Pb can be thought of as one of the great geophysical experiment (like atomic bombs and radioactive tracers, CFCs and the ozone hole, CO2 emissions and climate change). The big question is "where is this Pb now"? Pb isotopes also carry regional signatures. Can these isotopic signatures help us reconstruct fluxes and the fate of Pb in the ocean, across decades and hudrends to thousands of kilometers? Pb is just the "tip of the iceberg" when it comes to metal pollution. The biogeochemical cycles of many other elements are seriously impacted by anthropogenic activities, but little is known about the impact of these activities on large spacial scales and long time scales, that is space and time scales that transcend the short-sightedness of political boundaries.
Although many climate models exist, these models are not all created equal and the forecasts they generate vary consierably. Which model forecast should one believe? Do all models have the same scientific value? What are the biases and can the root causes for these biases be identified? How can models be used to understand the carbon cycle and heat uptake by the ocean? In spite of their limitations, climate and ocean models are poweful and phyiscally consistent tools to understand the environment around us.
To deliver the green transition, achieve decarbonization and meet our net-zero emission targets, we will need to mine more in the next 30 years than in the last 100 years. This means that the demand for minerals, the type of minerals and the intensity with which mineral will be extracted, processed, traded, transformed, recycled and disposed will change. One must not only develop frameworks to understand how elements move through our economy, but also how to meet the demand in a sustainable way. Sustainable development also implies a smarter way to interact with our environment. Ecosystems add value to our society by providing key services. Understanding these services, and possibly developing ways to engineer them in our built environment (to capture carbon, extract metals, decontaminate sites, etc.) is key for our future and will play a role to achieve zero-pollution.
The domain of Earth Science is undergoing a data revolution, in that the field is transitioning from being data poor to being, in some instances, "data overwhelmed"! New sensors, remote sensing, improved data access and cloud computing represent new opportunities to study the Earth, quantify biogeochemical processes, and ultimately manage resources, but tools are required to interpret these new data streams.