Under Pressure

Latitude: 63˚ 24’ S  Longitude: 53˚ 04’ W
 
Today, like many other days, the RVIB Nathaniel B. Palmer and the #icyinverts crew arrived on station—this time several hundred miles off the coast of James Ross Island—and collected animals from the Antarctic seafloor by trawl. While the many of us busied ourselves identifying and sorting latest exciting batch of critters, the ship’s crew prepared to deploy our CTD. The CTD (an acronym standing for “Conductivity, Temperature, Depth”) is an ingenious instrument, lowered off the side of the ship and used to measure physical properties of the water around it as it descends. In addition to measuring the properties in its name, it can be loaded with other sensors—for example, this CTD also measures chlorophyll concentration, important for knowing where plant-like phytoplankton are in the water. The CTD can even collect seawater from particular, pre-programmed depths in specially designed tubes (called Niskin bottles) that surround the sensor array. We typically deploy the CTD as a final procedure before we begin moving to a new sampling site. Even though the data the CTD collects is often very useful, both for the scientists on the ship and others back on shore, its deployment and retrieval is not usually cause for much fanfare, but yesterday’s CTD cast was a bit different…
 
That’s because yesterday, our CTD went down with a rather unusual payload attached to its frame. Bags and bags of Styrofoam cups! No, not for an exciting new experiment, but rather the last step in a long arts and crafts project familiar to many veterans of oceanographic cruises—CTD cups! It is a tradition on cruises like this one to decorate Styrofoam cups for friends and family back home then send them down on a particularly deep CTD cast. Yesterday’s CTD went down to a depth of 1,800 meters (or just over a mile) below the surface. At depths that great, the Styrofoam cups experience pressures hundreds of times greater than they do on the surface, causing the plastic foam to collapse on itself. The decorated cups shrink several times over in size and the designs on them become condensed—essentially like a shrinky-dink, but substituting pressure for heat! As we steamed away to our next site, we not only had new data to pore over, but numerous adorable tiny cups to admire and compare, with thoughts of sharing these mementos and the many memories of this trip with loved ones back on land rising to the surface amidst the excitement of our ongoing adventures.
 
Dr. James Townsend
Postdoctoral researcher
Providence College/Marine Biological Laboratory