International Polar Year GEOTRACES: An international study of the biogeochemical cycles of Trace Elements and Isotopes in the Arctic and Southern Oceans

Project Description
The community of marine biogeochemists is developing a new international research initiative (the GEOTRACES program) that aims to identify, characterize and quantify processes that control the distribution of key trace elements and isotopes (TEIs) in the global ocean and their sensitivity to changing environmental conditions. Doing so will elucidate the supply of micronutrients to phytoplankton, contaminant dispersal in the ocean, and tracers of past and present ocean conditions. This initiative is prompted by the increasing recognition that TEIs are playing a crucial role as regulators and recorders of important biogeochemical and physical processes that control the structure and productivity of marine ecosystems, the dispersion of contaminants in the marine environment, the level of greenhouse gases in the atmosphere, and global climate. The primary objectives for the global GEOTRACES program are: •Determine global ocean distributions of selected TEIs •Evaluate the oceanic sources, sinks, and internal cycling of these TEIs and thereby characterize more completely their global biogeochemical cycles •Provide a baseline distribution as reference for assessing past and future changes. Specific objectives for polar GEOTRACES research include: •Characterize sources, sinks and internal cycling of trace elements that serve as essential micronutrients, including sources of material delivered to the ocean by rivers (primarily Arctic) and by glacial weathering (primarily Antarctic) of adjacent land masses •In collaboration with companion IPY initiatives, establish the role of micronutrient trace elements in regulating the structure and variability of polar marine ecosystems, with implications for interests ranging from fisheries (primarily Arctic) to the ocean-atmosphere exchange of carbon dioxide (primarily Southern Ocean). The IPY offers the opportunity to obtain synoptic TEI distributions among all major Polar ocean basins. The strong projects that have been proposed for the synoptic studies (Arctic and Antarctic) within IPY will offer the hydrographic and biological context that is needed for a robust interpretation of the TEI fields. Individual IPY – GEOTRACES proposals (EoIs) have been submitted to ICSU to: •Make GEOTRACES part of the synoptic studies planned for the polar oceans •Arctic: join forces with SNAPSHOT, SPACE, SEARCH and CARE, under the coordination of iAOOS, to achieve a detailed picture and improved understanding on the distribution of trace elements and their isotopes along - shelf-deep basin sections - sections across major pathways of Arctic ocean circulation •Southern Ocean: join forces with complementary IPY projects in physical and biological oceanography to perform multiple transects. Present options are: - Three dedicated GEOTRACES sections across “chokepoints” constraining the flow of the Antarctic Circumpolar Current: (1) an international program (BONUS; on a French vessel) studying together the South African margin/upwelling effect on water masses and the GoodHope/CLIVAR section down to 50°S, 0°W, (2) an international program aboard the Polarstern (German research vessel) connecting with the BONUS transect along 0° W and also working across the Drake Passage, and (3) a US study south of New Zealand. - Ancillary meridional sections where micronutrient cycling can be studied within the context of other programs (e.g., SASSI, CLIVAR, SCACE) - Both dedicated and ancillary cruises would be coordinated under the CASO (Climate in Antarctica and the Southern Ocean) umbrella to maximize interdisciplinary benefits from Southern Ocean research during the IPY.

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