To investigate AAIW variability, time series of the AAIW salinity minimum were constructed by extracting the salinity minimum from the depth range 500–1200m of every float profile. (The lower limit of 1200m was set by the lowest profiling depth of the majority of floats, the upper limit by the shallowest depth of the AAIW salinity minimum in the tropics.) With a typical sampling interval of 50m in and below the permanent thermocline Argo floats do not necessarily resolve the minimum salinity if it falls between two observation levels. Cubic spline interpolation to 10m intervals was used to improve the resolution