Collaborative Research: GEOTRACES Arctic Section: The Geochemistry Size-fractionated Suspended Particles Collected by in-situ Filtration

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An investigator from Woods Hole Oceanographic Institution participating in the 2015 U.S. GEOTRACES Arctic expedition will collect and analyze suspended particulate matter in the Western Arctic Ocean to better understand cycling of trace elements in the region. In common with other multinational initiatives in the International GEOTRACES Program, the goals of the U.S. Arctic expedition are to identify processes and quantify fluxes that control the distributions of key trace elements and isotopes in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions. Some trace elements are essential to life, others are known biological toxins, and still others are important because they can be used as tracers of a variety of physical, chemical, and biological processes in the sea. Particles are a key parameter for the GEOTRACES program because of their role as sources, sinks, and in the cycling of trace elements. Results from this study will be shared through outreach to native groups in Alaska. The project will involve training of graduate and undergraduate students.Particle cycling in the Arctic Ocean is profoundly different from other ocean basins. Extremely low primary production in the perennially ice-covered central Arctic leads to a very weak biological pump. With little particle flux coming from above, the dominant source of particles to the Arctic Basin appears to be lateral transport from the margins, and these laterally transported particles have much higher lithogenic content than is typically found in particles in other ocean basins. The different source and composition of particles in the Arctic potentially sets up a completely different dynamic for the removal of particle-reactive trace elements and their isotopes from the water column than is currently understood. There has yet to be a comprehensive survey of the concentration and composition of suspended particles in the Arctic. In this study, the size-fractionated suspended particles will be analyzed for major phases and trace element composition, measurements needed to determine scavenging removal of particle reactive elements and provide insight into the mechanisms controlling the biological pump.