Exploring the possibility of using Argo float data to validate bathymetric data

The Argo Program

Argo is an international program aimed at seeding the global ocean with 3000 profiling floats which measure temperature and salinity from surface to 2000 meters depth. As these floats are autonomous and tend to drift with the currents while at the surface and at parking depth, they are prone to beaching or grounding. Though such instances are rare, the data from such floats when grounded can be used to cross compare the bathymetry at the location. Such an attempt was made with the help of a Argo float (WMO 2901253) deployed by the Indian National Centre for Ocean Information Services (INCOIS).

Using Argo floats to contribute to bathymetry studies

This APEX-9A float was deployed in the northern Bay of Bengal (90º E, 19º N) and interestingly, it was found to travel along the edge of continental shelf and slope along which the bottom depth data is obtained. Fig 1 shows the trajectory of the float during its life time. The profiling depth data (which was originally set to 2000 dbars) from this float which can be considered as bathymetry was obtained based on the location information fixed by the ARGOS satellites. The location class (set by the Argos satellites) information is also used for obtaining the correct position while obtaining the depth data. The pressure data recorded by the Argo float is converted to depth using Saunders et al., (1981) algorithm before undertaking comparison. The data thus obtained is compared with existing best available bathy datasets namely modified Etopo2, GEBCO, Smith and Sanwell.