NOAA Teacher at Sea
Onboard NOAA Ship Ka’imimoana
July 8 – August 10, 2010
Mission: Tropical Atmosphere Ocean (TAO) cruise
Geographical area of cruise: Equatorial Pacific: 110 deg W Longitude to 95 deg W Longitude
Date: Monday, 19 July 2010
Weather Data from the Bridge
Cloud Cover: 5/8, Cloud Type” Cumulus,
Visibility: 10 Nautical miles,
Wind bearing: 150 degrees,
Wind speed: 20 knots,
Wave height: 2 – 3 feet,
Swell height: 6 -7 feet,
Atmospheric pressure: 1015.5 mb,
Temperature: 24.5 degrees C (76.1 degrees F)
Current Position: 2 degrees North Latitude, 110 degrees West Longitude
Science and Technology Log
I recently had the opportunity to spend some time talking with Senior Survey Technician (SST), Tonya Watson. Tonya was a Cold War Ocean Systems Technician for four and half years in the US Navy, worked for six years at the California State Dept of Water Resources in the benthic macro invertebrate lab and water quality lab, and has been a civilian Wage Mariner in NOAA for six and a half years both on the Hydrographic vessel Rainier and on the Ka’imimoana (KA). She has an Associates of Science degree from Shasta College and triumphs people who have to rely on work experience without the benefit of four year degrees. Her primary responsibility is running the CTD (Conductivity, Temperature, and Density/Depth) sensor array.
Collecting data from the CTD involves lowering a large cylindrical aluminum frame (about 5 feet high and 5 feet in diameter) to a predetermined depth, typically 1000 or 3000 meters (0.6 miles or 1.9 miles), into the sea and slowly retrieving it to the surface, thus creating a classic temperature salinity profile on the way down and collecting water samples for salinity processing on the way up. A typical 3000 meter run takes about 4 hours from start to finish and the CTD is generally deployed at each buoy station and at a number of intermediate latitude coordinates.
The platform has numerous points onto which a variety of sensors and ballast may be secured, such as other current profiling sensors like an ADCP (Acoustic Doppler Current Profiler), or varied optics. The SST monitors the operation of the sensors (when the sensors are actually operating and collecting data) and handles tag lines (lines that control the horizontal position of the CTD) during the deployment and retrieval of the CTD package and communicates via radio with a winch operator who operates a “J” Frame winch from a control station located directly above the Survey Operations room. While the CTD is being deployed, a NOAA Corps conning officer is navigating the ship from a remote helm called the Bridge Wing. This location permits the officer to observe the deployment and attempt to hold the ship as stable as possible using only rudder maneuvering by watching the angle of the CTD cable entering the water. The conning officer has to be paying close attention to the wind direction and local ocean currents – anything that will affect the position and motion of the vessel, in order to avoid having the package get fouled under the boat or in the screws. The whole operation can be likened to a musical trio – each playing a different instrument but working to play in harmony to complement one another and complete the piece of music: The conning officer stabilizing the ship, the hoist operator raising and lowering the CTD, and the SST monitoring and operating the sensors, while all three continuously communicate back and forth. It is a fine example of effective team work.
The CTD also has the ability to collect water samples during the retrieval phase of operation. The sensors send back a continuous stream of data during the entire round trip measuring the conductivity, the temperature, and the density (depth) of the sea water. In addition, there are a number of 5L water sampling bottles (called Niskin Bottles) secured to the CTD platform that can be remotely triggered to close bringing water samples back from specific depths (they are left open on the way down to avoid being crushed by the immense pressure). These water samples are analyzed in the KA’s wet lab for salinity (concentration of salt) in an Autosal.
The results from the lab work are then compared to the CTD conductivity data log for the same depth. Because there is a direct mathematical relationship between electrical conductivity and salt concentration, this procedure compares the two outcomes looking for a high level of precision (an effective way to verifying the accuracy of the electronic data). Also, an important historical database can be created for an area of the ocean not often accessible to many scientists, which can show trends in temperature and salinity.
Once the data is collected the SST uses various software to put the file into a more readable and easier to use format, and distributed via DVD and ftp upload to the various organizations referred to as “”customers. These customers are other government institutions (both US and foreign), universities, or even other research organizations. In addition, much of this data is available online to the general public for those that are interested. Besides the typical CTD measurements that are made during a standard run other instruments can be mounted on the CTD platform. For example, sensors that measure water clarity (transmissometer), dissolved carbon dioxide concentration, dissolved oxygen concentration, and more can be added to the frame.
The first buoy we reached was at 8 deg N, 110 deg W Longitude. There were no problems with this buoy so this visit was simply for a visual inspection and this we accomplished by making several passes circling around it. Since this buoy is moored in French territorial waters (it is not far from the Clipperton Islands, which is owned by France) we had to obtain permission from the French government to be able to do more than cruise straight by the buoy. We did not receive that permission until the morning of the day we were scheduled to reach the buoy. During this time a number of the crew members put fishing lines out off the fantail (the extreme stern) of the ship. The buoys appear to attract various small fish which of course attract bigger fish and so on up the food chain. In a short time they had caught four nice size (3 – 4 feet long) Mahi mahi (also known as the Dolphin Fish). I assume we will be having a fish dinner sometime very soon. After the inspection we ran a CTD to 3000 meters that did not finish until quite late at night.
I already mentioned that we caught a number of Mahi mahi during the day but during the evening CTD run we had a real treat. Normally a large powerful spotlight is pointed at the water’s surface where the CTD is placed into and removed from the water. During this evening run I joined several of the science members of the crew on deck at the ship’s railing watching squid drawn to the bright spotlight in the water. At times we saw 6 or 7 squid at a time near the surface. They appeared a pinkish red color and were up to approximately a foot long or so. After a while we spied a shadowy figure swimming around and when it came close to the surface we realized it was a small shark no doubt drawn by either the light or the prospects of an evening meal.