Award: OCE-1130870

Project Outcomes This project organized a research cruise as part of the on-going US contribution to the international GEOTRACES program which seeks to understand some of the fundamental processes controlling the chemistry of Earth?s oceans. The larger international program has been designed to unravel what controls the inputs and outputs of chemicals to the oceans – from the land, from the air and also from the seafloor: not just through sediments but also through volcanoes and hot-springs on the deep ocean floor. A particular highlight of this project was that we were able to study, in detail, the site of the largest hot spring or "hydrothermal" inputs anywhere in the deep ocean. This led to a particularly surprising result – from enrichments of the metals iron and manganese in a lens of water centered at about 2500m deep (approximately 1 and a half miles down) we were able to show that inputs of chemicals from hydrothermal vents along the East Pacific Rise volcanic chain off the coast of Chile and Peru were swept for more than 4000km (2500 miles) west across the Pacific Ocean, at least as far as Tahiti which was as far west as our cruise extended during nearly 2 months continuously at sea. What has been particularly important from these results is the realization that if these chemical inputs can travel so far, they can also have an impact on the Earth system at a truly global scale. In the southern Ocean, biological productivity is limited by a lack of a vital nutrient – iron. From our demonstration that hydrothermal inputs of iron can travel such long distances through the ocean, we now calculate that this should include a supply of iron from deep in the Pacific up into the southern ocean?s sunlit surface waters. As a result, we have been able to calculate that the iron from seafloor hydrothermal venting may underpin as much as 30% of all the biological productivity in the Southern Ocean, presently. Of course, this is only the first exciting result arising from our research cruise. We anticipate many more. In total more than 60 separate scientists were involved in separate projects that were directly related to the cruise – both those involved in the sampling out at sea and those who have been busy analyzing samples back ashore. The results from all their separate specialist measurements are beyond the scope of this report, but we are busy editing that work into a special volume of scientific research papers and we expect many more highlights still to come. Our project also provided excellent training opportunities for more than a dozen young research scientists, both at graduate student level and beyond, helping to grow the next generation of US ocean scientists and leadership. Last Modified: 08/22/2016 Submitted by: Chris German