Decadal changes in ocean properties revealed by ARGO floats

This paper demonstrates that CTD data from autonomous profiling floats can be used to detect basin-scale changes of water properties on decadal, and potentially shorter, timescales. In the western Indian Ocean at 32°S, the properties of Subantarctic Mode Water have changed such that between 1987 and 2002, salinity has increased by 0.04 at certain temperature levels. Although in this case detailed and high-accuracy data are available from a research cruise, we demonstrate that floats have the following value: real-time float data are of sufficient accuracy to reveal changes in ocean properties on timescales of a decade or less; floats achieve spatial and temporal coverage not possible with research ships, providing vital supporting evidence for the interpretation of cruise CTD data. Floats therefore provide a mechanism for monitoring changes during the interval between dedicated research cruises and for identifying areas in which further cruises are likely to be fruitful.