MARVOR SIVOR VCM: field proven free drifting subsurface float

MARTEC has developed through partnership with IFREMER a Lagrangian subsurface float MARVOR. While drifting at depth, MARVOR is located using the RAFOS technique and comes up to the surface at regular intervals to transmit via ARGOS all gathered data. Quite similar, SIVOR-VCM float is equipped with a vertical current measurement system that adds vertical motion knowledge to the horizontal water displacement provided by the RAFOS system. Some hundreds of floats have already been manufactured and proved to be very reliable. Most of MARVOR floats are programmed to drift at depth for two or three months and spend two or three days at the surface, but some others are deployed inside eddies and surface every month. The first batch of MARVOR was launched at the beginning of 1994, and some of them are still operating after almost five years at sea. The LODYC has been using VCM floats since the beginning of the nineties, mainly in the Greenland and in the Mediterranean seas. The floats have been measuring in situ parameters characterising deep convection in these areas. Large vertical water displacements of several kilometres, evidencing deep convective events, have been observed thanks to the vertical measurement component. This paper presents evaluation of the global behaviour at sea of these floats and gives some statistics information