David Tourtellot: Draggin’ The Line, July 21st, 2018

NOAA Teacher at Sea

David Tourtellot

Aboard NOAA Ship Thomas Jefferson

July 9-26, 2018

Mission:  Hydrographic Survey – Approaches to Houston

Geographic Area of Cruise: Gulf of Mexico

Date: July 21st, 2018

Weather Data from the Bridge

Latitude: 29° 11.6357’ N

Longitude: 093° 55.9746’W

Visibility: 10+ Nautical Miles

Sky Condition: 6/8

Wind: Direction: 224°    Speed: 8.5 knots

Temperature:

Seawater: 30.4°C

Air: Dry bulb:31.5°C          Wet bulb: 28.5°C

 

Science and Technology Log

In my previous post, I discussed the ship’s sonar. This time, I’ll go into more detail about the tools the Thomas Jefferson is using to complete its mission. The sonar that the ship uses is multi-beam echosounder sonar, which sends the pings down to the seafloor and receives echoes in a fan shape, allowing the ship to survey a wide swath beneath the ship.

Multibeam Sonar

An illustration of a ship using multi-beam sonar. Image courtesy of NOAA

In addition to the multi-beam sonar, NOAA Ship Thomas Jefferson utilizes two towfish, or devices that are towed in the water behind the ship.

The first is the side scan sonar. Like the multi-beam, this device uses pings of soundwaves to create images of its surroundings. However unlike the multi-beam, the side scan doesn’t capture any data from the area underneath it. Instead, it collects data to its sides.  The side scan is connected to the ship via a cable, and is dragged through the water 6-15 meters above the seafloor. It is great for measuring the intensity of the return of the ping, which provides insights into the makeup of the seafloor.

The side scan towfish

The side scan towfish

The second towfish that the Thomas Jefferson is using is the MVP (like many things on the ship, MVP is an acronym, for Moving Vessel Profiler). The MVP truly gives the ship some of its most valuable data. As I discussed in my previous blog post, in order for us to accurately calculate the distance that the sonar’s pings are traveling, we need to know the amount of time it takes them to travel, as well as the velocity, or the speed, at which they’re moving. The singarounds I mentioned in my last post measure sound velocity, but only at the face of the sonar. Water conditions are not uniform – at the surface, water tends to be warmer, with less salinity. As you get deeper, however, the water tends to be colder and saltier. This means that the velocity of sound changes the deeper you get. Most of the time, the MVP rides just under the surface of the water, but periodically it will get cast down, to approximately 1 meter above the seafloor. It measures the water conditions of the entire water column from the surface to the seafloor, allowing us to calculate sound velocity all the way down.

MVP

The MVP towfish as it is being lowered into the water

The MVP measures the same water qualities as the CTD (a device I discussed in an earlier blog post), however, the MVP has a distinct advantage over the CTD. In order to use a CTD, the ship has to come to a stop while the CTD is lowered into the water. The MVP, however, can be used while the ship is in motion, which greatly increases productivity.

When surveying, many on the crew say it’s like mowing the lawn. The ship will capture a long stretch of data, called a line, and then turn around, and capture another stretch. 4% of these lines are cross lines, which run perpendicular, across a wide swath of lines of captured data. Cross lines allow the survey department to double check that the data they’ve captured is accurate.

Mowing the Lawn

A display of the lines of survey data the ship has captured. Cross lines can be seen running perpendicular to the majority.

 

Personal Log

TJ Bridge Daylight

The bridge of NOAA Ship Thomas Jefferson in the daylight

A couple of days ago, I went up to the bridge shortly after sunset, and I was surprised what I saw. All the lights were off, and the screens of the various instruments had been covered by red filters. I was told that this is for maintaining night vision when on watch. Red light interferes least with our night vision, so anything that gives off light is switched to red.

Bridge at night

The bridge of NOAA Ship Thomas Jefferson at night

While on the bridge, I had the opportunity to ask ENS Garrison Grant (who had recently been selected for a promotion to Lieutenant Junior Grade – congratulations Garrison!) a little about the NOAA Corps. I must admit that I was largely unfamiliar with them before joining the Thomas Jefferson.

The NOAA Corps as we know it today began in 1970, though its roots are much older. As president, Thomas Jefferson (for whom NOAA Ship Thomas Jefferson is named) created the United States Survey of the Coast, which would later evolve into the United States Coast & Geodetic Survey. Their early operations were not unlike the survey work that NOAA Ship Thomas Jefferson is doing today, though their tools were more primitive: surveyors wanting to determine the depths of America’s bodies of water didn’t have the benefit of sonar, and instead used lead lines – lead weights tied to the end of ropes. These surveyors would also play a vital role in our military history. They would often assist artillery, and survey battlefields. This is what led to the United States Coast & Geodetic Survey (and later, the National Oceanic and Atmospheric Administration) to gain a commissioned uniformed service. Due to the rules of war, captured uniformed service members could not be tried as spies.

To join the NOAA Corps today, you need to first have a bachelor’s degree. ENS Grant received his degree from Stockton University in Marine Sciences, but he says that it isn’t a requirement that the degree be in a maritime field. He says that some of his classmates had degrees in fields such as English or Communications. After getting a degree, you then apply to join the NOAA Corps (anyone interested should check out this website: https://www.omao.noaa.gov/learn/noaa-corps/join/applying). If selected, you would then complete the Basic Officer Training Class (BOTC), which generally takes about 6 months. After that, you’d be given your first assignment.

 

Did you know? Before NOAA Ship Thomas Jefferson was operated by the National Oceanic and Atmospheric Administration, it belonged to the U.S. Navy and was known as the U.S.N.S. Littlehales

Vickie Obenchain: Starting a Hydrographic Survey, June 28, 2018

NOAA Teacher at Sea

Victoria Obenchain

Aboard NOAA Ship Fairweather

June 26 – July 6, 2018

 

Mission: Arctic Access Hydrographic Survey

Geographic Area of Cruise: Northwest Alaska

Date: June 28th, 2018

Weather from the Bridge

  • Latitude: 54o 25.5’ N
  • Longitude: 134o 13.7’ W
  • Wind Speed: 13 Knots
  • Wind Direction: South, Southwest
  • Temperature: 12.2 oC
  • Visibility: 10 nautical miles
  • Wave Height: 1 foot
  • Current Sky Conditions: Overcast

 

Science and Technology Log

This morning I spent some time on the bridge with the officers. NOAA Ship Fairweather is manned day and night with men and women making sure we are safely on course. While the ship is equipped with GPS, the ship is also full of experienced mariners who plot our position on paper nautical charts to help guarantee the technology is working correctly and helps the officers orient themselves with the area.  Every 15 minutes, an officer plots our position either by using GPS coordinates, radar returns, or fixed land triangulation using an alidade. This last mode of determining our coordinates, at least to me, is the most difficult. You must use 3 fixed land points on either side of the ship, determine their direction using the compass on the alidade and then using sliding protractors plot our triangulated position on the chart. Both Executive Officer (XO) Michael Gonsalves and ENS Cabot Zucker have been incredibly helpful in teaching me these different plotting techniques.

plotting our course

XO Gonsalves in the foreground and ENS Zucker in the back plotting our course.


Today we are headed to the Queen Charlotte-Fairweather Fault System. This is a strike slip fault line extending 746 miles off shore of Vancouver Island to the Fairweather range in southeast Alaska.  USGS has partnered with NOAA Ship Fairweather to help to create part of a comprehensive map of one of the fastest moving underwater tectonic plates in the world, moving of a slip rate of 2 inches a year. Over the next 24 hours they will survey the area using multibeam sonar to help complete the mapping which as taken almost 4 years to complete.

To start this, the survey team had to deploy a Moving Vessel Profiler (MVP) into the water. The MVP follows behind the ship and by detecting water temperature and salinity of the water, the MVP can then determine the speed of sound in water needed to accurately detect the sea floor. With this knowledge the survey team can correctly calibrate their sonar to map the sea floor. Below you will see Sam Candio and Simon Swart of the survey team deploying the MVP.

 

Next blog will cover the amazing people working with the sonar, all times of day and night to make the sea floor maps! (Stay tuned!!)

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Another short term visitor on this ship is a college student from Loyola University Chicago, Paul Campion, who is on board doing an internship with NOAA. Each year NOAA accepts approximately 130 college sophomores into their two-year-long Hollings internship program to give students an opportunity to take part in research, gain job experience and see what NOAA does.  While on board, Paul has been working with the survey team to learn how they do their work, as well as create his own project.  Paul has been looking at the electronic navigational charts (ENC) used today by most mariners which show the depth of the sea floor. As NOAA Ship Fairweather surveys an area, these ENC’s can then be updated with more accurate and up to date data. While some areas may remain the same, some areas may show changes or even characteristics which may not have been mapped prior and need to be highlighted.  Paul has been working to help create an efficient way to show where the ENCs are different to the new NOAA Ship Fairweather data and may need to be altered or updated.

Paul Campion

Paul Campion pointing out a beautiful glacier!

Personal Log

Since we are out in the sea, and do not have neighboring island chains around us, the boat has been tossed around a bit more and is definitely rolling around in the waves. Luckily, I have not been sick… yet. I have been taking sea sickness pills, and making sure I get plenty of fresh air, but the boat is definitely more difficult to work in. You find yourself moving both with the boat’s inertia and then having to fight against it to move. Walking uses walls and railings, sitting requires holding on to the closest counter top or nailed down object and to get into rooms you need to shove doors away from you to open them, yet hold on so they don’t swing completely away from you and slam the opposite wall. It is kind of challenging and yet amusing.

After lunch today, I went to take a shower. I was given some good advice since I had not done this when the boat was in open water. These words of advice included: Use the walls, kind of squat down to lower your center of gravity, don’t take a razor with you (nothing good will come of that), and if the soap drops be especially careful! All things I took to heart and I am glad to report I am clean, unscratched and ready for another day.

 

Heather O’Connell: Sound in Seawater and Sleeping at Sea, June 8, 2018

NOAA Teacher at Sea

Heather O’Connell

NOAA Ship Rainier

June 7 – 21

Mission: Hydrographic Survey

Geographic Area of Cruise: Seattle, Washington to Southeast, Alaska

Date: 6/8/18

Weather Data from the Bridge: Latitude: 48.15° N, Longitude: 122 ° South 58.0’  West, Visibility: 8 nautical miles, Wind: 24 knots, Temperature: 14.2° C

Science and Technology Log

I was fortunate enough to sit in on a survey orientation for new survey technicians and junior officers with Lieutenant Steven Loy. He was on Rainier as the Field Operations Officer, F.O.O., in the past and is currently here as an augmenter filling the role of Senior Watch Officer since he has navigated through the Inside Passage several times. In his two hour orientation, he shared a wealth of knowledge and discussed how multibeam sonar and ultrasounds are two opposite ends to the ultrasonic pulse spectrum.

Multibeam sonar sends out sound and measures the time it takes to return to calculate the depth of the ocean floor. The accuracy of the depth data generated from the multibeam sonar relies on the sound speed profile of the water. The combined effects of temperature, salinity and pressure generate a sound speed profile. Because of the inherent importance of this profile, there are several different ways to measure it. The sound velocity profiler measures this right at the interface of the multibeam sonar. C.T.D.s., or conductivity temperature and depth machines, measure water profile while the ship is stopped. M.V.P.s, or moving vessel profilers, take the water profile as the vessel is moving. Lastly, XBTs are expendable bathythermographs that measure temperature while the ship is in motion.

Sound is affected by different variables as it is energy that travels through a medium as a wave. Lieutenant Loy shared an informative website, The Discovery of Sound in the Sea, where I was able to enhance my understanding. Sound can travel through a liquid, such as water, a gas like air, or a solid like the sea floor. On average, sound travels about 1500 meters per second in sea water. However, the rate changes at different times of day, various locations, changing seasons and varying depths of the water. By looking at sound speed at one particular place in the ocean, you can determine how the different variables affect this sound. Usually, as depth increases, temperature decreases, while salinity and pressure increase.

A multi-beam sensor has a metal plate receiver and a transmitter perpendicular to one another. This array geometry enhances sound.  The sound velocity profiler is next to the receiver and measures right at the interface. To determine the speed of sound right where the beam is generated, sonar is used to measure speed sound across a known distance. This information is then utilized in the overall determination of the depth of the ocean floor. Once this cast is taken, the Seafloor Information System (SIS), can adjust sonar measurements accordingly.

Another way to measure the sound profile of water includes a C.T. D.  This device measures the conductivity, temperature and depth of the water. Conductivity measures the electrical current of the water. The more dissolved salt, or ions in solution, the greater the conductivity and salinity of the water. The depth of the water is directly related to the pressure of the water. Salinity, temperature and pressure affect the sound speed profile of water. This machine has a high data rate that goes up and down the water column. The titanium C.T.D. operates at a high pressure and costs about forty thousand dollars. This accurate technology can only be utilized when the boat is stopped and is used on the smaller survey launches.

C.T.D. used for sound speed profile of water

C.T.D. used for sound speed profile of water

A third method of measuring sound profile is the M.V.P., moving vessel profiler, which takes the data when the ship is moving. These are calibrated before a survey begins and are an efficient way to collect data. An expansive crane lowers the metal torpedo with the sensor off the fantail, the overhanging back part of the ship, into the water to collect the data. The fish is programmed to stop twenty meters above the ocean floor, at which point it returns to its docked position. On ship Rainier, the deck department deploys the fish with a cable wire and the plot room with the survey technicians controls the sensor.  

Boatswain Kinyon and Survey Technicians Finn and Stedman releasing the torpedo of the M.V.P. into the water

Boatswain Kinyon and Survey Technicians Finn and Stedman releasing the torpedo of the M.V.P. into the water

Another way to collect the sound profile of water with a moving vessel is to use an expendable probe. As temperature decreases, the sound speed decreases. Since temperature is the most important factor affecting the speed of sound, an X.B.T., Expendable Bathythermograph, or expendable probe created by the military. With bathy relating to depth and thermo meaning heat, this measures the temperature of the water at a cost of about one hundred dollars. These probes descend at a known rate, so, depth is a function of time.

Sources – Discovery of Sound in the Sea

Personal Log

We left port yesterday at 16:30, which has been a highlight of my NOAA Teacher at Sea Experience thus far. Before leaving port, all hands were assigned a different assignment to help with the launch. I watched the crew bring in the gangway that connects the ship to the port then disassemble it. The crew with hard hats and orange work vests took down poles and neatly tied up different sections by knotting ropes. We slowly progressed out of the port after a cargo ship passed us.  

The deck crew preparing to leave port

The deck crew preparing to leave port

Once the ship picked up speed and the ocean breeze was in my hair, I felt a new kind of freedom. With the Seattle skyline behind us and the beautiful green peninsulas in front of us, I was content to be moving forward. Everyone seemed to feel relieved once we were underway. I felt gratitude as I enjoyed watching the sunset from the flying bridge, the area of the ship above the bridge at the front of the ship.

Seattle Skyline

Seattle Skyline

After sunset, I returned to my berth, or sleeping quarters, located in the bow of the ship on the C-deck. I heard the constant white noise of the propellers that got much louder when the pitch, or angle, of them changed. This sound of seawater combined with the rocking motion of the ship lulled me to sleep on our first night at sea.

20180607_203558.jpg

Sunset

Did You Know?

Juneau, the American capital of Alaska, can only be entered by plane or boat. It is inaccessible by roads due to large mountain ranges on either side.