Abstract: The ocean is under threat from a variety of processes driven by increasing atmospheric carbon dioxide such as ocean warming, changing winds and currents, decreasing pH and oxygen, and less ice cover at high latitudes. However, vast areas of the open ocean are sampled from research ships for chemical and biological properties only once per decade or less, with sampling occurring mainly in summer. Our ability to detect changes in ocean chemical and biological processes that may be occurring are greatly hindered by this undersampling. Robotic platforms carrying chemical and biological sensors that can monitor ocean metabolism, such as rates of oxygen production, nutrient uptake, accumulation of plankton biomass, and respiration, are required. The platforms and sensors must operate for the 5 to 10 year period between research vessel visits with no direct human intervention and little or no chance for sensor recalibration. Here, I’ll describe the BGC-Argo network, which is being implemented to meet this mission. The BGC-Argo array is based on profiling floats that cycle through the upper 2 kilometers of the ocean every 10 days for 4 to 6 years. These floats carry optical sensors for oxygen, nitrate, chlorophyll, and particles, as well as electrochemical sensors for pH and physical sensors for temperature, pressure and salinity. The nitrate and pH sensors used in the array were developed at MBARI. With funding from NSF, NOAA, and NASA, we have deployed 200 floats in the Southern Ocean over the past 6 years. A recent research infrastructure grant from the NSF will extend the Southern Ocean array to the globe with 500 floats additional floats.