Date: Thu, 14 Feb 2002 21:07:22 +0000 From: "Sirovic, Ana" Subject: Message 07 February 14 2002, 17:15 68 deg 05.58 S latitude 70 deg 31.16 W longitude (Marguarite Bay) Air surface temperature: -1.1 degrees C Sea Surface Temperature (SST): -1.3 degrees C Wind speed: 19 knots, 250 degrees Air pressure: 985.7 mBar Hi! I have fully recovered from my short spout of seasickness and have been doing great last couple of days so now I'm ready for another extensive report of the events on the ship. The spirits on the ship, I dare say, have been pretty high, most of this probably due to the fact that we have had 2 gorgeous days! All day today we could see Alexander Island 60 mi away as we were passing through, sometimes very dense, brash ice. The scenery has been about as amazing as Antarctic gets: blue ocean, clear skies and many small floes and brash (mushy - that's a technical term!) ice. It's quite obvious that the productivity of the area is pretty high because all the floes have a brownish waterline indicating abundance of algal and other microorganismal (is that a real word?) life. There have been many crabeater seals, as well as some leopard seals hanging out on the floes. All the real work in the last couple of day has been done by the physical oceanographers from Woods Hole Oceanographic Institution. They have been recovering their moorings: the current meters that they put down a year ago. They have deployed 6 moorings, 2 lines of 3, one across the mouth of Marguarite Bay and the other off Adelaide Island. Their moorings are quite extensive so I will do my best to depict them for you! The moorings are basically a set of instruments suspended at various depths along a wire that is about 400 m long and is moored to the bottom with a big weight (over 1 ton!). The instruments are of different varieties. Usually there are 2-3 VACMs (vector averaging current meters) at various depths, several T-pods (temperature measuring device), Microcats (conductivity sensors - these are used for determining salinity), ADCP (acoustic Doppler current profiler), acoustic release, some moorings have an ice profiler, and all of them have several (8) smaller floats that help keep the instrument upright, as well as a couple of really large flotation spheres. The top one of those is equipped with an ARGOS - a device that, in case the mooring got detached and floated away would relay to a satellite its location and the scientists would be able to locate and retreive it. OK, now that I've stunned you with all the acronyms, let me try to explain what all those thing really are and how they work (as far as I can do this). The current meters they are using are pretty old technology (you can see one on today's picture; it's the long yellow thing Scott and Ryan are holding -- they're the 2 people on the picture). At one end of the meter there is a little wing the orientation of which determines the flow of the current and this is linked to a magnetic compass (I told you it's old technology!) to figure out the direction of the flow. There is also a part that measures the speed of the flow, and all this information gets written onto a tape. Apparently the computers that can read this tape are so rare that they did not even bring one on the ship so all the tapes have to be taken back to Woods Hole before they can be analyzed. T-pods and Microcats (the latter is the silver tube strapped to the VACM on the picture) are much more spiffy, as far as modern technology goes. The data they have recorded can be downloaded onto a computer and is available pretty soon after recovery. Temperature and salinity, along with density, are the major parameters that are measured in the ocean. Knowledge of the values of those 3 parameters can tell you a lot about the ocean at a particular location and many an oceanographer has spent his entire career making measurements of those parameters to help us understand the ocean better. Unfortunately it would take much too much time for me to explain how and why those 3 things are so important, so I'll leave that for some other time. For now, I'll just move on to describe the other instruments. ADCP is also a more modern way of measuring currents. It consists of 4 upward looking transducers so it uses acoustics for determining current fields in an area. An advantage of this instrument over a current meter is that it actually gives information on the current field throughout the water column (or in this case in the part of the column above the ADCP), instead of giving a measurement at one spot. The ice profiler was deployed on just a couple of moorings (it's the orange float trailing behind the ship on the picture) and the idea behind it is to look at the ice coverage above the mooring (also using acoustics) and determine the ice thickness at the location. The acoustic realease system is set up to communicate with an instrument on the ship and once you send it a particular release command, it starts a flow of electric current that burns the wire between the instruments and the weights and all the floats make the instruments come to the surface and we can pick them up. Wow! I got tired writing all this, so I'm sure you're pretty tired as a reader by now. So let me move on to less technical stuff, in hope I didn't misrepresent any of the above given that it's not really the area of my expertise. Scott, Ryan, and Jim, along with the marine tech and the marine science tech (Josh and Randy) are quite a team to watch as they recover their moorings. They work very smoothly and they make the recovery look like a game instead of real hard work, what indeed it really is! So far they have recovered 5 of their moorings, and we haven't been able to find the sixth mooring because when we came over the location of its deployment and tried to talk to it, it wasn't responding. We will certainly try and search for it, but this area is known to get icebergs passing through and given that the shallowest part of the mooring at only ay 50m depth, it is possible it got dragged away. Still, we're hoping for the best... In the end, I want to point out that this is the first time that anyone has left this kind of moorings in this area for an entire year so Bob (Beardsley), Dick (Limeburner), Scott (Worrilow), Ryan (Schrawder), and Jim (Ryder) have actually made history in the last couple of days. But while I'm on the topic of not finding moorings, I never told you how the recoveries of my group went 3 days ago! We recovered only one of the 2 instruments we were supposed to recover on that day. We located the other one but after we repeatedly sent it the release command (it has the same acoustic release system as the WHOI mooring), it never came up to the surface. So we signed defeat for now, but we will certainly try to get back there and see if there is anything else we can do. By tomorrow, the physical oceanographers should be done with their recoveries and then we will steam to the shelf break and there we will proceed with the recovery and redeployment of our moorings. So stay tuned for more exciting news from the slightly chilly but very beautiful Antarctic! Ana