1 From Ocean Sensors to Traceable Knowledge by Harmonizing Ocean Observing Systems Joaquín del Rio

ii Society is requesting more than ever being better informed on the state and effects of Earth’s changing oceans. This has direct implications on ocean observing systems, including scientific planning and technology. For instance better knowledge implies that data on health, climate and overall dynamics of our oceans have a known level of quality, be up-to-date, be easily discoverable, be easily searchable both in time and space, and be human- and machine-readable in order to generate faster decisions when and where needed. Requirements with respect to spatial regions and scales (seas and ocean basins, from millimeters to hundreds of kilometers), time scope and scales (past, present, future, from microseconds to decades) indeed have direct implications on observing systems ' spatio-temporal sampling capabilities. Possibly high spatial and temporal resolution also means unprecedented amounts of data, communication bandwidth and processing power needs. Technological implications are thus quite substantial and in this short article we will try to provide a review of some initiatives of global and local focus that are aiming to respond to at least some of these needs, startin