Under pressure

By Emma Slater

Photo credit: Ashlie McIvor

During the Extended Ellett line cruise, it is a tradition to attach polystyrene cups to the CTD frame on the deepest cast. Our 19th CTD was going to be the deepest cast so drawing nautical themes on polystyrene cups could commence. The cast was going to drop down to ~2700 m which is about 270 times surface air pressure.

The effect on the polystyrene cups was quite staggering. What makes polystyrene useful is that it is filled with air pockets. This makes it a good insulator, but when put under such high pressure those air pockets are forced out giving us the miniaturised versions you see in the photos. You’ll also notice from one of the photographs how we’ve been doing our laundry…

Unfortunately, during the upcast, the computer in the main lab had trouble firing the Niskin bottles. Once on deck we realised none of the Niskins had closed and so no sampling could be done. After further investigation, the mechanism that releases the bottle endcaps and allows the bottles to close had to be completely replaced for the next station. Thanks to all the preparation ahead of the cruise, we had a spare!

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