The ocean provides critical services to life on the planet, absorbing 93% of the heat caused by humans as well as a quarter of human carbon dioxide (CO2) emissions each year. However, rising ocean temperatures and CO2 levels also change the marine environment: pH and oxygen levels fall, ocean currents change, and nutrient fluxes and concentrations are shifting, all with effects on ecosystems and the cycles of oxygen, nitrogen, and carbon throughout the ocean and atmosphere. Until recently, observing these biogeochemical (BGC) changes across remote ocean areas with seasonal to interannual resolution has been impractical due to the prohibitive costs associated with large-scale ship operations. Now robotic profiling floats have been developed that are equipped with chemical and biological sensors, and which can operate independently for years. These robotic systems provide us the ability to observe changing ocean chemistry and biology in real time. This proposal will provide the funds to operate for five years an array of 500 such profiling floats that are distributed across the global ocean. <br/><br/>The Global Ocean Biogeochemistry (GO-BGC) Array was funded through the NSF Mid-scale Research Infrastructure-2 program to deploy 500 biogeochemical (BGC) profiling floats around the globe. Each float will be equipped with a suite of chemical and biological sensors for oxygen, nitrate, pH, chlorophyll fluorescence, optical backscatter, and, in most cases, irradiance. The unprecedented real-time data stream from the GO-BGC Array will enable observation of ocean biogeochemical changes with seasonal to interannual resolution through the upper 2 km of the ocean, driving a transformative shift in scientific and public understanding of marine biogeochemical cycling and ocean health at the global scale. However, the MSRI-2 project does not provide funds to operate the array. Operational costs are centered on the expenses needed to transmit the large data stream from floats through the Iridium satellite communication system and the expenses to operate a data system that quality controls the incoming measurements and distributes the resulting, science quality data in real time. These data are then available without restriction. This proposal will provide the needed costs to transmit data from the GO-BGC array. It will support the quality control of float data streams to ensure that a high quality, science-ready data set is easily available to the community.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.