Date: Tue, 19 Feb 2002 17:43:36 +0000 From: "Sirovic, Ana" Subject: Message 10 February 19 2002, 12:25 68 degrees 05.11 S latitude 70 degrees 28.05 W longitude (somewhere off Adelaide Island) Air surface temperature: 0.5 degrees C Sea Surface Temperature (SST): -1.2 degrees C Wind speed: 46 knots, 005 degrees Air pressure: 985.2 mBar Greetings! We're in a little bit of a storm right now. The waves are giving us quite a roll and some pitch, the main deck is pretty wet, the wind is breaking the caps of the waves and is blowing them off quite violently. It's actually kind of nice to stand out on the deck, sheltered from the wind observing its strength. It's too rough to do any kind of mooring operations, so we're headed to Adelaide in hope of some shelter. It's pretty amazing how different this is from the weather we encountered last night! Most of the day yesterday the wind was below 5 kn and by the evening we were moving through perfectly still waters. It was like going through glass. We came to the ice edge, too. There were a bunch of penguins and seals hanging out on the ice floes, it was very cool. As we started into the ice the conditions changed very quickly, the ice going from a very thin layer with some floes into a well packed, thicker ice. At that point we turned around because we realized there will be no way for any moorings to get deployed there. Earlier in the day yesterday, however, 2 WHOI moorings were deployed, as well as a few floats. So today, I'll tell you all about the floats! You can see one be deployed by Josh (Spillane, the marine tech, on the left) and Breck (Owens, the scientist in charge of the floats, with his back turned) on today's picture. The deployment procedure is quite simple: as the ship slows down to ~2 kn, the float is lowered to the water using a string. This has to be done pretty gently because the top cap of the float is held on by vacuum so it can be fairly easy to pop (there are some pressure buildup issues inside the float so it's safer to have it this way). The float is programmed to go down to 250 m depth and there it flows with the currents. Every 5 days is goes down to 600 m or the bottom (whichever comes first) and then goes up to the surface taking measurements. It has conductivity, salinity, and temperature sensors (they're in the white area barely visible to the left of the antenna), so once it reaches the surface it talks to a satellite and sends its location and the profile information. The cool part (theoretically) is that this then gets sent via email to Breck, and he has a little programming script that checks the data and does the analysis. Currently there are some issues with what happens to the float if it gets stuck in the bottom but eventually he should be able to send commands back to the float, i.e. have a real 2-way communication. Now you must be wondering 'but how does the float sink and come up to surface?' Well, in the white part at the bottom there is a bladder. This bladder gets filled with oil from the main chamber or the oil gets sucked back into the float, depending on whether the float needs to go up or down in the water column, thus giving it more or less buoyancy. Currently the best information available on currents in the ocean is for the surface layer. Floats like these are an attempt to better understand the circulation at depth and there are currently thousands of such floats drifting at various depths of the world's ocean. So, this is how it all should work. This morning, Breck got the news that there is something wrong with the software and the floats he deployed so far are basically useless. It's quite unfortunate to come all this way and have it all be in vain! But such is science! I'll sign off here and go enjoy (!?) the storm outside! Ana