It's a bird! It's a plane! No it's a glider!!

It has been a lively couple of days on the R/V Armstrong. Yesterday was the surface mooring deployment which was super exciting, and the excitement continued today with the glider deployment! There were a total of three gliders that got put in the water today along with the hybrid profiling mooring (HYPM), but that’s something to be explained in another blog post. Today, the focus is on gliders.

Two days ago, I got to speak with Collin Dobson who is in charge of all the gliders (I nicknamed him the “glider G.O.A.T”) about how gliders function and collect data. Contrary to what you may think, gliders don’t actually fly.  They manipulate buoyancy to navigate the water column. To do this, each glider has an oil reservoir and a pitch battery that move throughout the glider to change its volume which changes its density to either sink or float. To sink, the oil reservoir retracts, and the pitch battery moves forward an inch to become negatively buoyant and sink, and to float back up, the oil expands out of the reservoir and the pitch battery moves back. The wings are attached to the glider to prevent the glider from sinking straight down to the sea floor and there is also a rudder on the tail to help the glider sink at an angle. While it has a crush depth of 1200m, the glider only dives down to 980m and it does so at an angle of 26 degrees. When the gliders come back up, they don’t always surface, each time they go down to depth and come up to reach 50m is called a “yo” and they have two yos per dive segment before they resurface.  There is an air bladder in the tail that helps the glider reach the surface and only that tail comes out of the water, and once that tail is out of the water the glider can “call home.” During these calls home, the gliders send OOI back information on their condition and every tenth point of data it collects.

Collin posing with  gliders

               

There are two types of gliders that we have on the cruise with us: the profiling glider and the open ocean glider. The profiling glider functions near the surface mooring and the hybrid profiling mooring (HYPM) collecting data from the surface to 200m and has most of the sensors for data collection with a CTD instrument which measures salinity temperature and depth, PAR (Photosynthetically active radiation) sensor, an oxygen optode, and a SUNA nitrate sensor. Open ocean gliders basically act as data mules for subsurface moorings that cannot transmit data on their own. They operate on triangular routes collecting data throughout the range of 50-980m. These gliders also have the sensors that most oceanographic instruments have including an oxygen optode, a ctd, and bb3 which samples chlorophyll and backscatter amongst other things.

For our project, we've modified the open ocean gliders to have oxygen optodes in a special place at the top of the glider so that it can measure oxygen in the air when the glider surfaces, which allows us to better calibrate the oxygen sensors throughout the year

Before going in the water all gliders get named pictured is 515 named "Aurora" and our project glider 525 which is named "Homefry" by the BCP team

             

 With all the gliders in the water in the water, including the one funded by out project, the day comes to a close, only with more deployments tomorrow!

Signing off for today,

Thanda

Team BCP with our project glider Homefry