A drifting instrument is not a fixed station

A rising temperature series from a drifting instrument can record a journey across ocean structure rather than local warming. This essay contrasts ice-tethered profilers with anchored instruments and uses an explicitly invented water-mass crossing to separate spatial variation from change through time. It also explains why a fixed mooring can record a displaced current or layer, so anchoring does not remove every interpretive ambiguity. Position, pressure, temperature, salinity, currents, and repeated profiles constrain different alternatives. Maps and depth-distance sections can reveal coverage changes hidden by monthly means, while many neighbouring profiles do not become independent basin-wide samples. Published Arctic ocean assessments provide context for combining viewpoints. The practical implication is to retain platform movement and instrument geometry as explanatory evidence, not remove them from the story.