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1. GEOTRACES Reflections

   https://doi.org/10.5670/oceanog.2024.405  

   Anderson, Robert (January 2024, Oceanography)

   GEOTRACES is an international program that has benefited from contributions by investigators in 35 nations. The program mission is 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. This perspective first summarizes the historical motivation for the program, and then describes selected research highlights, focusing on recent findings related to iron. The patchy distribution of iron in the ocean indicates a short residence time, at the low end of the range of residence times estimated in models. Iron removal from the ocean must, therefore, be rapid. Recent results from the North Atlantic Ocean suggest that the formation of particulate authigenic iron phases may be a factor contributing to iron removal that is faster than previously thought. This article also identifies several areas where advancements are expected through modeling and synthesis efforts. 

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2. A Young Scientist’s Perspective on GEOTRACES

   https://doi.org/10.5670/oceanog.2024.403  

   Halbeisen, Dylan (January 2024, Oceanography)

   GEOTRACES is an international endeavor to elucidate the biogeochemical cycles of trace elements and their isotopes in the ocean. Inherently, this interdisciplinary program provides ample opportunities for students to develop professional, academic, and seagoing skills. This perspective recalls first-hand experiences gained from five years in the GEOTRACES community, spanning undergraduate and graduate research, including international engagement in Germany and seagoing oceanography in the South Pacific and Southern Ocean. Description of these opportunities reveals the framework that makes the GEOTRACES program a success and the culture that will ensure its ongoing legacy. 

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3. The GEOTRACES Intermediate Data Product 2017

   https://doi.org/10.1016/j.chemgeo.2018.05.040  

   Schlitzer, Reiner; Anderson, Robert F.; Dodas, Elena Masferrer; Lohan, Maeve; Geibert, Walter; Tagliabue, Alessandro; Bowie, Andrew; Jeandel, Catherine; Maldonado, Maria T.; Landing, William M.; et al (August 2018, Chemical Geology)
4. GEOTRACES: Ironing Out the Details of the Oceanic Iron Sources?

   https://doi.org/10.5670/oceanog.2024.416  

   Conway, Tim; Middag, Rob; Schlitzer, Reiner (January 2024, Oceanography)

   Dissolved iron (dFe) is an essential micronutrient for phytoplankton, with vanishingly low oceanic dissolved concentrations (pico- to nanomoles per kg) known to limit growth—and thus influence primary productivity and carbon cycling—over much of the surface ocean. However, because of the considerable challenges associated with contamination-free sample collection and accurate analysis of such low dFe concentrations, the first reliable dFe measurements came only in the 1980s. Further, by 2003, despite several decades of research, there were only ~25 full-depth oceanic dFe profiles worldwide, with dust considered to be the main oceanic dFe source. Since 2008, facilitated by the extensive field campaign and rigorous intercalibration of the international GEOTRACES program, there has been an “explosion” in the availability of oceanic dFe data, with hundreds of profiles now available. Concurrently, there has been a paradigm shift to a view of the marine Fe cycle where multiple sources contribute, and some forms of dFe can be transported great distances through the intermediate and deep ocean. Here, we showcase the GEOTRACES dFe datasets across the different ocean basins, synthesize our current multi-source view of the oceanic Fe cycle, spotlight sediments as an important dFe source, and look to future directions for constraining oceanic dFe boundary exchange. 

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5. Intercalibration: A Cornerstone of the Success of the GEOTRACES Program

   https://doi.org/10.5670/oceanog.2024.404  

   Aguilar-Islas, Ana; Planquette, Hélène; Lohan, Maeve; Geibert, Walter; Cutter, Gregory (January 2024, Oceanography)

   The international GEOTRACES program was developed to enhance knowledge about the distribution of trace elements and their isotopes (TEIs) in the ocean and to reduce the uncertainty about their sources, sinks, and internal cycling. Recognizing the importance of intercalibration from the outset, GEOTRACES implemented intercalibration efforts early in the program, and consensus materials were generated that included the full range of TEIs dissolved in seawater, in suspended particles, and from aerosols. The GEOTRACES section cruises include “crossover station(s)” that are occupied by two or more sections and whereby all aspects of sample collection, preservation, and processing can be compared and intercalibrated. Once datasets are generated, an international intercalibration committee reviews intercalibration reports and works with the community to address issues and provide intercalibrated data for intermediate data products. This process has resulted in a highly cooperative community that shares advances in protocols to strengthen capacity building and GEOTRACES outcomes, including an unprecedented oceanic atlas of TEIs, with data quality that is state-of-the-art. This article outlines the development and implementation of the successful GEOTRACES intercalibration process. 

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