LAUSR

The Biogeochemical-Argo (BGC-Argo) Program aims at operating a network of profiling floats equipped with sensors of key biogeochemical variables for supporting research activities that address impacts of climate change on oceanic biogeochemical cycles and ecosystems (Claustre et al. 2010; IOCCG 2011; Johnson et al. 2009). Following a series of publications reporting on successful long-term deployments of profiling floats with various biogeochemical sensors (e.g. Boss et al. 2008; Johnson, Riser, and Karl 2010; Körtzinger et al. 2004) and years of international coordination, the BGC-Argo program was officially launched in October 2016, as an extension of the Argo Program (Biogeochemical-Argo Planning Group 2016; Johnson and Claustre 2016). The objectives of the BGC-Argo Program are to establish and sustain an array with 1000 floats within five years. Similar to Argo, this is a coordinated, voluntary, distributed, and multinational network of profiling floats, but with a significant addition of sensors. At the moment, the global network is progressively maturing through a cluster of national projects, e.g. the French SOCLIM project (http://soclim.com), United States’ SOCCOM project (http://soccom.princeton.edu), South Africa’s SOCCO BIO-ARGO project (http://socco. org.za/research/#Bio-optics), and Chinese ReMOCA project in the Southern Ocean; the European REMOCEAN project (http://remocean.eu) and Japanese INBOX project (http://www.jamstec.go.jp/ARGO/inbox) in the subtropical gyres; the United States’ NAAMES project (http://naames. larc.nasa.gov) and UK-BIO-ARGO project in the subpolar gyres; as well as the French NAOS project (http://en.naos-equipex.fr/) in the Mediterranean Sea and Polar Area. As of November 2017, there are 282 such operational floats working in the global ocean, mainly covering the Southern Ocean, Indian Ocean, eastern Pacific, Atlantic, and Mediterranean Sea (Figure 1). Six BGC-Argo core variables have been identified: dissolved oxygen, nitrate (NO3), pH, Chl-a, suspended particles, and downwelling irradiance (Figure 1). The price of a BGC-Argo float varies from around 25 000 USD to more than 120 000 USD, depending on the types and number of sensors. Although its cost is significantly higher than a simple Argo float (around 18 000 USD), which measures temperature, salinity and depth, these additional observations are critical to study the ocean’s biogeochemistry. On 10 and 11 October 2017, the Second Institute of Oceanography of the State Oceanic Administration of China hosted a workshop designed to summarize the latest achievements of the BGC Program, preview the short-term and long-term future perspectives, discuss data quality-control procedures and distribution, introduce some emerging technologies that could upgrade BGC floats in the future, as well as present and exchange new scientific and multidisciplinary applications of BGCArgo observations. More than 15 participants were invited, which included members of the international BGC-Argo steering committee (from Australia, Europe, France, the UK, US, and China), national Argo project representatives from China, manufacturers of floats, sensors, and batteries, as well as other oceanographers and remote-sensing scientists who are interested in Biogeochemical-Argo float data.