by Clare Johnson
There are now two more bright yellow robots ‘swimming’ in the North Atlantic Ocean. On Friday we deployed an Argo float (picture below). These yellow tubes containing a host of complex electronics are designed to dive to 2000m, sit there for 10 days drifting with the water, then to rise back to the surface. Every time the floats dive/rise they measure the temperature and salinity of the water, and every time the floats are at the surface they transmit this data and their position via satellite back to scientists on land. They then dive back to 2000m and repeat the cycle over and over again until they run out of life. There are around 3880 Argo floats all over the world monitoring various oceans and transmitting the data back to scientists.
The second yellow robot deployed was a glider (picture below). This glider is a different make than those deployed/recovered on the Discovery cruise, with slightly different capabilities. However, it works in a near identical way: using buoyancy changes to dive to 1000 m and then rise back to the surface again measuring the temperature and salinity of the water as it goes. At the surface in the same way as an Argo float the glider transmits the data and its position to scientists on land. The difference between a glider and an Argo float is that scientists can ‘talk’ to a glider whilst it is out in the ocean, give it instructions and determine in what direction the glider should go in. So while the Argo float is happily left to its own devices, the glider has a piloting team in America and China checking it is ok and deciding where it should go next.
The big advantage of autonomous instruments like Argo floats and gliders is that they can collect a huge amount of data when scientists and ships are not at sea. Particularly they give us valuable information about inaccessible areas – for example the subpolar North Atlantic in winter when the weather is often too bad for ship work. To me it feels as if the development of gliders within the last few years is an exciting step forward for marine science. However, when it is my turn to pilot and the glider gets into difficulty at 4am in the morning and texts me to say that there is a problem that I need to get up and sort out immediately, I am less enthusiastic!!! The glider that we recently deployed should be collecting data between Scotland and south of Iceland for the next 6-12 months before it is picked up.
PS In case anyone is wondering why some gliders are yellow and others bright pink, both colours are thought to be as visible as possible in the ocean so it is a matter of choice to which colour you go for!
Pic 1: An Argo float being deployed off the back of Pelagia. Thanks to Colin for the photo.
Pic2: The Slocum Glider with proud scientists Heather and Dalai just before it was carefully lowered over the side.