XBT (eXpendable BathyThermographs) transect AX01 runs between Greenland, Iceland, and Denmark. It is located across the northward upper transport to the Nordic Seas and Arctic Ocean and provides the data necessary to monitor the subpolar gyre. The data is also used to study ocean current transport on seasonal time scales and to perform comparisons between an intake temperature sensor (Thermosalinograph, installed in the ships used for these transects) and the XBTs, in order to assess possible temperature biases. Additionally data from AX01 helps to document the ocean heat storage and global transport of heat and fresh water, which is crucial to improving climate prediction models that are initialized with temperature profiles. The seasonal to interannual variability in upper ocean heat content and transport is monitored to understand how the ocean responds to changes in atmospheric and oceanic conditions and how the ocean response may feedback to the important climate fluctuations such as the North Atlantic Oscillation.