|One of the last wandering albatrosses we saw on our cruise, captured here at about 40S in the southern Indian Ocean. This species has a strong preference for the cold, deep waters around Antarctica.|
|The starry eyed night shift watch. We love to have meetings at the top of the rosette - not really. Photo courtesy of Joseph Gum.|
|This is the rosette that took us through most of our cruise. Even though it was a backup, it has served us quite well.|
|Natalie inspecting the rosette before deployment.|
|Dave doing prep work.|
Once the rosette is in the water, we change into our normal clothes and head to the computer lab. In the computer lab, we sit at the CTD console, which is a checkerboard of monitors that displays live readouts from the rosette's instruments. For this part of the job, we monitor the rosette as it moves through the water and log all important events. Additionally, we are in constant communication with the winch operator via a speaker phone and guide him as he lowers the instrument to the seafloor.
|The CTD console. This where we sit to monitor the rosette when it is in the water.|
With almost $1M USD worth of instruments (literally) on the line, we can't afford to make any mistakes. If we overshoot and hit the bottom, we can damage the instruments onboard the rosette. With so much at stake, we are always supervised when doing bottom approach.
|Alison draws near to supervise bottom approach.|
The ship's multi-beam is very useful, but it measures seafloor depth over a relatively large area. If the seafloor terrain is very rugged, the multi-beam's depth estimate may be tens of meters different from depth directly beneath the ship or rosette. To obtain a more localized depth estimate, we use an altimeter that is mounted on the bottom of the rosette.
The altimeter onboard the rosette works in a similar fashion to the shipboard multi-beam. However, it is much smaller than the shipboard multi-beam and not nearly as powerful. The altimeter we have been using for most of the cruise can only detect the ocean bottom from 50 meters away. But once it does, it produces the most accurate estimate of distance to the seafloor.
|Hannah working at the CTD console. Courtney provides expert guidance as Charlene looks on.|
To complicate things even further, both the altimeter and ship board multi-beam are known to "misbehave" and produce incorrect information at any given time. On rare occasions, we have to resort to old bathymetry maps to help us figure out the true ocean depth. This was a bit overwhelming at first, but after a few days on the job we learned how to weigh all pieces of information appropriately and make the right decisions.
Once we safely lower the rosette to 10m off the ocean bottom, we fire the first Niskin bottle to collect a water sample. After logging some notes, we then instruct the winch operator to raise the rosette to a new depth, where we would fire another bottle to collect another water sample. We usually do this for 36 different depths, the last one being at the surface.
Lowering the instrument to the ocean bottom and bringing it back to the surface usually takes about 3 hours. It can be a tedious process, but everyday presents a new challenge (usually in the form of equipment malfunction), which keeps things interesting.
As the rosette approaches the surface, we grab our life vests and helmets to help with the rosette recovery. This where we literally get to snatch the rosette out of the water. It's my favorite part of the job. However, I'll continue this discussion in my next blog post, where I will also describe how we collect samples once the rosette is back on the ship.
|Day shift crew recovering the rosette at the end of a cast.|