July 27, 2008
Today Jim Dunn, Will Ostrom and Rick Krishfield from WHOI will recover a mooring that has been sitting underwater up here in the Arctic collecting data for the past year. The mooring has several data collectors on it: among them are a upward-looking sonar to measure ice thickness and a MMP that travels up and down the mooring line collecting CTD (conductivity (a measure of salinity), temperature and depth) and water current information. This system allows scientists to collect data 27/7/365 in this remote and inhospitable climate and adds data over time to our "ocean water sandwich". Click here to see a schematic drawing of the mooring.
Uh huh, you say. So what? Well- you know that arcade game where you put your money in to try to pick up *your* prize out of a jumbled mess of objects in a glass box using a joy stick and a claw? Now image that the glass box is the Arctic ocean and *your* prize is a 3800 meter-long mooring. There may be significant ice in the way.
To win the game, you have to locate it, steam an icebreaker over the location, breaking and moving any ice that may be in the way, then send an acoustic signal to a hook on the bottom telling it to let go of the anchor and send *your* prize to the top.
Once the top float is at the ocean surface , it is hooked and brought on board. This is not quite as easy as it sounds..... Today is relatively calm with no ice but some wind, so hooking top flotation sphere (or top float) takes about half an hour of dangling and ship maneuvering. Your prize is 30 feet below the ship deck.
Once the orange top float is brought on board, the rest of the mooring can be recovered.
This is a long process, taking about 6 hours. 3800 meters of wire must be reeled on board. The MMP is recovered, and finally it is time to bring in the glass flotation spheres (glass balls), all 58 of them. Each ball provides 50 pounds of buoyancy. This 2900 pounds of buoyancy plus an additional 2500 pounds provided by the top float give the mooring a total off 5400 pounds of buoyancy.
Question: WHY is so much buoyancy needed? (Hint: the anchor on the bottom weighs 4000 pounds).
Stay tuned--tomorrow they will put the whole thing back in for another year of data collecting under the ice.