NOAA Teacher at Sea
Leyf Peirce
Onboard NOAA Ship Rainier
July 6 – 15, 2004
Mission: Hydrographic Survey
Geographical Area: Eastern Aleutian Islands, Alaska
Date: July 9, 2004
Time: 16:00
Latitude: N 55°26.60
Longitude: W 159°33.97
Visibility: < 1 foot
Wind direction: 221
Wind speed: 13 knots
Sea wave height: 0 – 1 foot
Swell wave height: 1 –2 feet
Sea water temperature: 10.6 °C
Sea level pressure: 1016.0 mb
Air temperature: 11.7 °C
Cloud cover: fog
Science and Technology Log
Most of my day was spent exploring the pages within Nathaniel Bowditch’s The American Practical Navigator: An Epitome of Navigation. I took notes mostly from a chapter titled “The Oceans”. It primarily discussed oceanography and the branches that are studied as a part of oceanography: geography, geology, chemistry, physics, and biology, “with their many subdivisions, such as sedimentation, ecology, bacteriology, biochemistry, hydrodynamics, acoustics, and optics” (427). With the main focus on the physical characteristics of the ocean, this chapter further detailed the importance of understanding salinity, density, temperature, and pressure—the main factors that affect most of the oceans’ behavior. There are several concepts within this chapter that can be watered down for my sixth, seventh, and eighth graders, however the one most applicable to hydrographic research is the study of the speed of sound waves within salt water. Because echo sounding is used to chart the ocean floor, the speed of sound within saltwater is essential to ultimately creating nautical charts. According to Bowditch, the speed of sound within a given fluid can be calculated using the following equation:
U = 1449 + 4.6T – 0.055T2 + 0.0003T3 + 1.39(S – 35) + 0.017D
In this equation:
U = sound of speed (m/s)
T = temperature (°C)
S = salinity (psu)
D = depth (m)
Using this information, one can calculate the speed of sound given different parameters. These measurements are determined using a CTD test (conductivity—which correlates with salinity, temperature, depth test) and a depth probe about every 4 hours that we are conducting hydrographic research. This information is then accounted for when employing the echo sounding devices. This equation can also easily be used by 7th and 8th graders. I plan on gathering real data and using these concepts in my classes along with graphing the data and outcomes.
While I read a lot today, I also got to tour the engine room. I have seen many engines and know the basics of how they work, thanks to my Mechanical Engineering degree, but I have never seen one so powerful! The twin 1200 horsepower engines can have up to 210 RPM. There are also two generators aboard the ship. What amazed me most on my tour was the control room where the control board looked like ones I have seen in museums—I thought that they would have moved to computers by now! One of the engineers assured me that this switch would be made in the near future.
Personal Log
I woke up this morning to what seemed like even thicker fog—this is the third foggy day in a row! Feeling a new energy from sleeping so well, I decided to try to work out on the treadmill in the ships workout room. I was told about there being a TV and VCR, and knowing that the workout room is on the same level as the engine room, I decided to take a movie with me and play it very loud. While the movie and TV worked great, the treadmill was a whole new experience. In all my years of exercising and training, I have never been on a treadmill that pitches and rolls with a boat! I felt as if my running counted as twice the exercise since I was not only running forward on the treadmill, but I was also adjusting every step with the motion of the ship—a very odd experience! After 45 minutes of exercise, I decided I had enough. The rest of the day was spent reading Nathaniel Bowditch’s The American Practical Navigator: An Epitome of Navigation, thinking of ideas for incorporating the concepts into next year’s curriculum, and playing cribbage, a card game the other Teacher at Sea, Sena Norton, taught me. Lt. Slover also informed me that I will be going on one of the launches tomorrow to help conduct research! While he was reviewing the small boat safety, the fog lifted to reveal beautiful snow covered mountains and islands—we had stopped the hydro research with the Rainier and were headed to our anchor point near Egg Island. We are expected to anchor around 21:00, with a possible stop for fishing along the way. Just finished dinner, I am now sitting in the chart room, looking out the window at dramatic cliffs plummeting into the sea—a reminder that these islands are, in fact, formed from a volcanic chain. I can’t believe how green these islands are—I must be sure to take plenty of pictures. As I day dream at these islands that are reminiscent of the islands in the BVI’s, the fog horn goes off again—the first time in a few hours. I guess this is the changing weather of the Alaska coast line; I just hope that tomorrow there is no fog when we are out on the launches.
Question of the Day:
My sister, Dr. Shayn Peirce at the University of Virginia, emailed me some interesting questions. P.S. Shyla Allen was a great source for these answers:
Dr. Peirce’s questions:
“My questions for you…can the echo scanner detect a whale on the bottom of the ocean? If so, how do they know it’s a whale and not a rock bump in the ocean floor or something else.
2nd question: what is the difference in echo scanning that you’re doing on the boat and ultrasound that they use in biomedical diagnostics…(to image babies in the womb or ovarian cysts?) Both involve acoustic imaging…is the frequency or wavelength of the sound emitted and detected different? Obviously the biomedical application requires a much smaller resolution with less depth penetration while the ocean application requires large penetration depth and not as much resolution…by the way what is the resolution of the echo signal…a few square feet of the ocean floor? Could you pick up the signal of that 1 foot long wench you dropped in the BVIs at 150 ft ocean depth?”
Answers:
1) Yes, the equipment here can detect a whale at the bottom of the ocean. In fact, it can even detect a wreck very well! I saw an image yesterday of a wreck and you could see the mast and bowsprit and everything—very detailed! I am trying to get a copy of that picture. Usually the whale will be moving, so that motion will also be picked up and cause more “static” in the data that needs to be cleaned. This rarely happens though.
2a) The echo sounding aboard the Rainier and ultrasound that they use for biomedical diagnostics are actually the same process, just with different frequencies!
2b) The resolution of what is done aboard this ship depends on water depth and the size of the footprint left by the scanner; the deeper the water, the larger the footprint, and the less resolution. However, they are required to have a resolution of 3 pings per 2 square meters in a depth of 40 meters or less (given the equipment used, there are up to 240 pings in a 160 degree swath). 40 meters is chosen because that is the maximum draft of a tanker vessel. P.S. Allen told me that, unfortunately, the 1 foot wench I lost somewhere in the BVI’s is probably long gone and undetectable by the equipment used aboard this ship. However, in shallow water, she has been able to see not only lobster pots, but their mooring lines as well. Their mooring lines have about the same diameter as the mooring line we descended in the Caymans on our dive trip. I also asked if the equipment could pick up a diver. P.S. Allen said yes, but that it is VERY bad for your body—so much power!