NOAA Teacher at Sea
Debra Brice
Onboard R/V Roger Revelle
November 11-25, 2003
Mission: Ocean Observation
Geographical Area: Chilean Coast
Date: November 15, 2003
Data from the Bridge
1. 151700Z Nov 03
2. Position: LAT: 19-50.1’S, LONG: 085-03.3’W
3. Course: 189-T
4. Speed: 12.3 Kts
5. Distance: 295.6 NM
6. Steaming Time: 24H 00M
7. Station Time: 00H 00M
8. Fuel: 4233 GAL
9. Sky: OvrCst
10. Wind: 110-T, 09 Kts
11. Sea: 110-T, 2-3 Ft
12. Swell: 200-T, 3-5 Ft
13. Barometer: 1018.9 mb
14. Temperature: Air: 23.5 C, Sea 19.0 C
15. Equipment Status: NORMAL
16. Comments: None.
Science and Technology Log
We arrived at the Stratus Buoy at 1:30pm. We had some problems putting out the zodiac and will have to go and do a survey of the buoy up close tomorrow. Dr. Weller’s group will be calibrating the instruments on the buoy all day tomorrow and the following day they will be taking it out of the water in preparation to store it and ship it home. The new Stratus Buoy will be deployed in a couple of days. We continued to release radiosondes at 6 hour intervals. We are finished drooping surface drifters for awhile as well as ARGO floats. Dr. Weller did 2 CTD casts tonight to 4000m and we attached our styrofoam cups to the CTDs. I have attached some photos of our cups and my wig head after their trip into the abyss. We filmed a video of the cast that should be up in a couple of days.
A CTD stands for Conductivity, Temperature and Density. Sea water conducts electricity as a function of the amount of dissolved salts, in other words it will be a better conductor of an electrical current if it has a higher amount of salts dissolved in it. The density is calculated based on the salinity and the temperature. The salinity is calculated using the conductivity and temperature. Warm water is less dense than cold water and water with a higher salinity is more dense than water with a lower salinity. Evaporation removes water but leaves behind the salts and creates more dense water at the surface. The densest (heaviest) water sinks and the less dense water rises and you get stratification or layering of different water masses. The wind does cause mixing of the surface layer but this varies with wind speed and can vary in depth between 1 meter to 1500 meters in some areas. The CTD that we just took shows a very shallow mixed layer and we will be analyzing it a bit more closely later today. I have included a picture of the temperature/salinity/density plot from the CTD cast. The green line represents density, which is increasing from the surface down. The red line is salinity which is decreasing from the surface down but you can see some variations which show different water masses and some mixing. The brown is conductivity and the blue is temperature. We sent down the styrofoam cups and the wig heads as a demonstration of the effects of pressure. All of the air piled on top of us from the surface of the earth up into the stratosphere equals one atmosphere, but water is much more dense so if you go down 33 feet you are under 2 atmospheres of pressure and another atmosphere for every 33 feet. So how many atmospheres were our cups under? E-mail me (Debra.Brice@noaa.gov)and let me know your answer?
Personal Log
Long day punctuated by being on watch. Food is wonderful, the cooks are really creative and we have enjoyed all the meals. After dinner a lot of people will go into the lounge and watch DVDs or play board games. Most of us read or check e-mail. There is always something to do or sea and sometimes it is just nice to go outside and watch the sunset or the cloud shapes. At the CTD cast we had a spotlight on the water where the CTD went in and it attracted quite a group of large squid up to the surface. They were over 3 feet long and quite fast. The buoy has a group of 4 boobies that live on or near it feeding on the fish that gather around it. They will be most unhappy when we take it out but they will have a nice new one soon. Well, my watch is almost over and I am fading fast and this will be a busy day coming up…rumor has it that those styrofoam “cup of soup” cups shrink really well, hmmmm we need to do some more experiments on pressure……can we carve some pieces of packing styrofoam…..getting a bit carried away here:)
Cheers