NOAA Teacher at Sea Wes Struble Aboard NOAA Ship Ronald H. Brown February 15 - March 5, 2012
Mission: Western Boundary Time Series Geographical Area: Sub-Tropical Atlantic, off the Coast of the Bahamas Date: March 2, 2012 Weather Data from the Bridge Position: 26 degrees 19 minutes North Latitude & 79 degrees 55 minutes West Longitude (8 miles west of Florida's coast) Windspeed: 14 knots Wind Direction: South Air Temperature: 25.4 deg C / 77.7 deg F Water Temperature: 26.1 deg C / 79 deg F Atm Pressure: 1014.7 mb Water Depth: 242 m / 794 feet Cloud Cover: none Cloud Type: NA Science/Technology Log: There are four different ship's stations that are involved in a CTD (Conductivity, Temperature, & Depth) operation: the bridge, the survey team, the winch operator, and the computer room. The bridge is responsible to keep the ship on position and stable over a predetermined latitude and longitude. The survey team is responsible for preparing the CTD platform for deployment and securing it back on deck at the completion of the cast. The winch operator controls the actual motion of the CTD platform by the use of a hoist. The computer lab relays commands to the winch and survey team in reference to testing and sampling depths, and when to start and stop the ascent and descent of the platform. The CTD platform can carry many types of instruments depending upon the nature of the research being conducted. During this cruise our platform usually contained two each of a temperature gauge, conductivity gauge (from which you can obtain salinity), and oxygen gauge. In addition there is one pressure gauge and a transmissometer (that measures the turbity of water which is an indicator of the phytoplankton), 23 Niskin water sampling bottles, and two Acoustic Doppler Range finders - one pointing toward the surface and one pointing at the sea floor. [caption id="attachment_9429" align="aligncenter" width="495" caption="The CTD (Conductivity, Temperature, & Depth) platform on the Ron Brown. The long grey cylinders are the water sampling Niskin bottles, the yellow and blue device at the bottom in the Acoustic Doppler Current Profiler (for measuring distance to the sea floor) for measuring the distance to the sea floor during descent phase of a cast, the grey cylinders are weights, and the green cylinder is the power supply."]
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[caption id="attachment_9437" align="aligncenter" width="488" caption="A Niskin Bottle with my Nike shoe for scale"]
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[caption id="attachment_9611" align="aligncenter" width="490" caption="The CTD platform being lowered over the side for start of another cast."]
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[caption id="attachment_9438" align="aligncenter" width="486" caption="The "downlooking" ADCP (Acoustic Doppler Current Profiler mounted on the CTD."]
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[caption id="attachment_9439" align="aligncenter" width="490" caption="The "up-looking" ADCP (Acoustic Doppler Current Profiler) mounted on the CTD"]
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[caption id="attachment_9440" align="aligncenter" width="490" caption="The Niskin Bottle trigger release. This device is used to remotely close the Niskin bottles at depth"]
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[caption id="attachment_9647" align="aligncenter" width="480" caption="The bridge of the Ron Brown during a CTD cast"]
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A CTD cast begins when the ship arrives at prearranged coordinates of latitude and longitude. The bridge will announce that we are "on station".
[caption id="attachment_9645" align="aligncenter" width="490" caption="A photo of the Ron Brown off the coast of Grand Bahama Island"]
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The survey team acknowledges and then raises the CTD platform and places it is the water at the surface for a minute or two. Then after receiving a signal from the computer operator that all functions are operating within normal parameters the platform is lowered to 10 meters and held there for two minutes to allow the instruments to stabilize.
[caption id="" align="aligncenter" width="491" caption="Here I am starting my midnight to 6 :00 am shift at the CTD computer control station in the computer lab of the NOAA Ship Ronald H Brown"]
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[caption id="attachment_9441" align="aligncenter" width="480" caption="The "brains" of the CTD. This device also contains the pressure sensor."]
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After the two minute hold at 10 meters the entire platform is brought back to the surface and the log is started as the package is lowered. The descent begins at about 30 meters/minute and eventually reaches 60 meters/minute. Many of the deep water casts on this cruise were between 4000 m and 5500 meters (about 13000 ft and 18,000 ft) and take over an hour to reach the bottom. While the descent takes place all the instruments are recording data which is stored and plotted in real time at the computer monitor. When the CTD platform is 10 meters from the bottom the descent is stopped and the first water sample is collected by sending a signal that closes the first Niskin bottle. At this point the CTD slowly begins its climb back to the surface (another hour or more) stopping at designated depths to collect water samples.After the last Niskin bottle is closed at the surface, the CTD platform is brought back on deck, the water samples are removed, and the entire platform is prepared for the next cast.
[caption id="attachment_9590" align="aligncenter" width="482" caption="Here I am on the weather deck in my favorite chair on the ship. I enjoy relaxing here in the sun in the morning after a night shift at the CTD computer station."]
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[caption id="attachment_9612" align="aligncenter" width="486" caption="Another beautiful western Atlantic pre-sunset. I enjoyed many of these during the cruise."]
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[caption id="attachment_9649" align="aligncenter" width="520" caption="The early sun rising in the east off the stern of the Ron Brown brings another night of CTD's to an end."]
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