The oceans store a large amount of heat and dissolved chemical substances. Their circulation in the oceans has a large impact on the global climate. The purpose of this research program is to elucidate the distribution and temporal changes in heat and chemical materials such as carbon dioxide in the oceans. For this purpose we deploy Argo floats, which drift in the mid-layer of the ocean and surface periodically, to measure and automatically transmit oceanographic data. We also conduct basin-scale repeat hydrography using research vessels, to obtain high-quality physical and chemical parameters along trans-oceanic sections. We also deploy mooring buoys, to measure heat flux between atmosphere and ocean in the Kuroshio Extension region. Research is also in progress on a dynamically consistent data assimilation technique that integrates these observational data with the results of numerical simulations.