Float Lifetime
The average life of the latest model APEX Argo floats are around 3.7 years or approximately 135 cycles. These statistics are for floats with the standard alkaline battery configuration from an analysis by Kobayashi et al (2009). To read more download the paper here. In the Australian Argo program we deploy our floats with a combination of lithium and alkaline battery packs which extends float lifetime. Our floats usually last 5 years and we have several floats that are approaching their 7th birthday and are still returning good data! Data measured by Argo float 5900032 is shown below as an example. These long time series incorporate around 240 profiles.
- Time series from a long lived float for temperature with depth (above) and salinity with depth (below)
Floats that have been profiling for many years will eventually start to suffer from a phenomenon known as 'energy flu'. This often precedes float death and is associated with a drop in battery voltage. An example float record below shows the shortened profiles at the end of the time series that are characteristic of diagnosing 'energy flu'.
- Time series for a float suffering from energy flu, salinity (above) and density (below). The black dots indicate the water depth at which measurements are made. You can see that the sampling density is greater in the top 100 m of the water column.
