Ship-Based Observation

A ship-based observation is an in-situ measurement made from a research or merchant vessel, the oldest and still a core component of the ocean observing system. Research vessels run CTD casts, water sampling, underway thermosalinograph and pCO2 lines, and mooring servicing; merchant ships of opportunity collect XBT transects and surface meteorology under the Voluntary Observing Ship scheme. Ship data give the multi-parameter, full-depth, calibrated measurements that autonomous platforms cannot match, and they provide the reference samples that anchor float and satellite calibration. The constraint is cost and coverage: ship time is scarce, so repeat hydrographic lines are sparse in space and time.