XBT Transect

An XBT transect is a repeated line of expendable bathythermograph profiles collected along a fixed shipping route from ships of opportunity. As the ship steams, crew launch XBT probes at set spacing, building an upper-ocean temperature section across a basin without dedicated ship time. High-density lines space probes finely to resolve mesoscale eddies and boundary currents. The global network of these lines under the Ship of Opportunity Program tracks heat transport and interannual change in features such as the East Australian and Kuroshio currents, a multi-decade record that complements Argo’s broad-scale coverage with along-track resolution.