The survey technician team collects data on the bathymetric seafloor using a precise timing and ranging system. Multibeam echosounders emit different frequencies to capture different particles in the water (fish, plankton, gases like oxygen), as well as the bathymetry of the seafloor (basically, what the bottom of the floor is made up of.) This will then provide a 3-D picture of the seafloor. A larger version of this, called Kongsberg ME70, was used during the Deepwater Horizon Spill tracking the oil and methane gas. Often, sea floor mapping occurs at night in designated locations.
What is Bathymetry?
Bathymetry is the study of underwater depths of lakes, rivers, or oceans.
What is Sonar?
Sonar (SOund NAvigation and Ranging) is used to not only measure the water’s depth but to also detect objects underwater. This is done by emitting sound pulses under water and measuring their return after being reflected.
Sophie Caradine-Taber, Survey Technician
Sophie got her degree in biology and environmental studies. She got her start at the National Marine Fisheries Service working for NOAA on a hydrographic survey vessel on the Bering Sea in Alaska for four and half years. Her job on Pisces is part of the survey technician team that does seafloor mapping.
Makailyn is on Pisces collecting Environmental DNA (eDNA) for the University of West Florida’s lab under Dr. Alexis Janosik. Makailyn graduated from UWF with a degree in marine biology, and worked as a research technician under Dr. Janosik. She has volunteered for numerous career opportunities, including this trip and sea turtle monitoring. Her goal is to attend graduate school and get a job as a researcher in either lab or field work.
ENS Grace Owen, Junior Officer
Grace is a Junior Officer for NOAA Corps. She is from North Carolina, and didn’t originally start her path on the ocean, but towards the mountains. She went to college in Colorado and worked as a climbing guide. She felt like she needed to do something more, and began looking at the Coast Guard. This is when she discovered the NOAA Corps and she felt like it aligned more with her values. Grace learned that she didn’t have enough STEM credits to join NOAA, so she moved to Florida to attend the University of Miami and got her graduate degree in exploration science. Training for the NOAA Corps takes around 5 months at the Coast Guard Academy. Once training is completed officers can then go to driving and navigating vessels for NOAA. Grace also has her pilots license and her next goal is to attend NOAA flight school with the future hopes to fly for the NOAA Hurricane Hunters. She even says there is a hurricane name in rotation named “Grace” that has yet to be used, and that would be super neat if she was the one who helped find it.
Student Questions of the Day
Jonathan asks: Have you ever found a sunken ship in the ocean?
Sophie works with sea floor mapping, and last year NOAA’s hydrographic ship on Lake Erie found 5 shipwrecks.
Anabelle asks: What is daily life like on the ship?
Sophie calls each ship she is on home, because she spends most of the year on them. She works the 12am-12pm shift 7 days a week. She tries to stay in touch with family, and reads a lot of books on her down time while on the ship. If they port between legs for the weekend she tries to make sure she takes time for herself.
Levi asks: How many years did it take to be able to drive a ship?
Grace states that the NOAA Corps training is 5 months, but once you’re on a ship that is when the real training takes place. Officers will do 2 years on a ship and then usually 3 years off on land assignments.
Ethan asks: What challenges are there when driving the ship?
Grace states that part of the challenges of driving the large ships are learning the physics and maneuvering of the vessel. NOAA is also mostly male dominated, but she feels confident in what she does and it has been an easy fit for her.
I am enjoying learning all the different backgrounds of everyone on this ship. Even though it is predominately men, I am impressed with the determination that the four women of the crew have. Myself and Makailyn are guests aboard Pisces, but it was nice to see how the women fit in on the ship and are respected. Everyone on board continues asking how I am doing, and making sure I am learning as much as I can. Chief Survey Technician Todd Walsh even spent days building up an extravagant event by having me deploy an Expendable Bathythermograph Sensor (XBT). Todd had convinced me that it was going to be like an “explosion” when it went off, and I was in charge of it. He even gave me a training pamphlet that I studied, and he had me convinced that I must be crazy to agree to do this but I am here for the experience… right? Little did I know that the entire ship was in on the joke. After all the hype of how things could go dangerously wrong, training on how it could backfire, and the special safety attire the day of; the device literally just dropped into the ocean falling out of the holder. Todd… I will get you back!
Several on the ship are looking forward to the end of leg 3 to have a few days off before they are back at it to finish the last leg of this mission. Today I heard the countdown, “2 days and a wake up”. The crew spends so much time out here they look forward to a few days off the ship and a chance to see family. The current scientists will go back to their land jobs after this leg and new scientists will finish the last leg of this mission. Today was by far the prettiest day we have had yet. The ocean has finally calmed down and the Sun is shining bright. This evening it was as if the ocean came alive. We saw whales, dolphins, mahi-mahi, a shark and a trigger fish. I was able to do some laundry on the boat which was great because I tried to pack as light as possible so that I didn’t have to check in luggage at the airport. I am trying to do a little grading when I get a chance. There will only be 10 days left of school when I return. I have missed the students and have really enjoyed reading the letters they wrote me to bring along. Below, you will see a drawing that a student did for me to give to the ship. It is amazing and she is so talented!
Future Weather Forecast: Showers likely and 70% possibility of afternoon thunderstorms
Science and Technology Log – and a Little History
Shipwrecks & Sonar
Lake Erie has an astonishing 2,000-plus shipwrecks which is among the highest concentration of shipwrecks in the world. Nobody knows the exact number of shipwrecks that have occurred in Lake Erie, but estimates range from 500 to 2000. Only about 400 of Lake Erie’s wrecks have ever been found. There are schooners, freighters, steamships, tugs and fishing boats among them.
So why does Lake Erie have more known shipwrecks per square foot than most any other body of water – with the possible exception of the English Channel? At its deepest point, Lake Erie is only 210 feet. Its shallowness is one of the reasons so many ships have sunk.
Hydrographers have found their share of ships over the years! I am unable to identify where, however, the TJ found a shipwreck recently. The following shows various multibeam echo sonar images of items found on the seafloor. Not all have been found in Lake Erie. 😊
Side scan sonar is a specialized sonar system for searching and detecting objects on the seafloor. Like other sonars, a side scan sends out sound energy and analyzes the return signal (echo) that bounced off the seafloor or other objects. Side scan sonar typically consists of three basic components: a towfish, a transmission cable and the topside processing unit. In a side scan the energy that is sent out is in the shape of a fan. This fan of energy sweeps the seafloor from directly under the towfish to either side. The width of the fan is about the length of a football field.
The strength of the return echo is recorded creating a “picture” of the ocean bottom. For example, objects or features that stick out from the seafloor create a strong return (creating a light area) and shadows from these objects create little or no return signal (creating a dark area).
NOAA hydrographic survey units use side scan sonar systems to help find and identify objects. The shape of the seafloor and objects can be seen well with a side scan sonar. This technology, however, does not give scientists information with respect to how deep the object is. That is why the side scan sonar is often used along with the multibeam echo sonar.
NOAA Ship Thomas Jefferson field work is focused in the Great Lakes for the 2022 field season. Thomas Jefferson’s hydrographers are surveying the floor of Lake Erie in the vicinity of Cleveland, South Bass Island and Presque Isle, PA. They are identifying hazards and changes to the lake floor and will provide this data to update NOAA’s nautical charts to make it safe for maritime travel.
So why did NOAA decide to focus on this part of Lake Erie? “The Port of Cleveland is one of the largest ports on the Great Lakes and ranks within the top 50 ports in the United States. Roughly 13 million tons of cargo are transported through Cleveland Harbor each year supporting 20,000 jobs and $3.5 billion in annual economic activity.” The Office of Coast Survey continues to explain that “most of this area has not been surveyed since the 1940’s, and experiences significant vessel traffic.”
A Little Bit of History – Have you ever been to Put-in-Bay, South Bass Island?
Our National Anthem, a naval officer with the middle name “Hazard”, the War of 1812, and Lake Erie have connections.
So, what does all of this have to do with Lake Erie? In 1812, America found itself at war with Britain. They were at war for three reasons: 1) The British were trying to limit U.S. trade, 2) they were also capturing American seamen and making them fight for the British (this is called impressment), and 3) they did not like the fact that America wanted to expand its territory. Both the British and the Americans were anxious to gain control of Lake Erie. Late in the summer of 1813, American troops were moved into Put-in-Bay on South Bass Island, Lake Erie. They hoped to cut off the supply routes to the British forts.
On the morning of September 10, 1813, British naval forces attacked. Commander Oliver Hazard Perry was on his flagship (a flagship is the ship that carries the commanding officer), the USS Lawrence. (Isn’t “Hazard” a great middle name for someone in the Navy!) He directed his fleet into the battle, but because of light winds, the sailing ships were slow to get into a position where they could fight. His ship suffered heavy casualties. Perry’s second flagship, the USS Niagara, was slow to come into range to help. Four-fifths of Perry’s crew were killed or wounded. He made the decision to surrender his ship, the USS Lawrence, and move his remaining crew and battle flag to the USS Niagara. He was rowed half a mile under heavy fire, bearing his now-famous blue and white battle pennant with the words “Don’t Give Up the Ship.”
The British thought Perry and the rest of the American fleet would retreat after the surrender of the USS Lawrence. Perry, however, decided to rejoin the battle. At 3:00 pm, the British fleet surrendered, marking the first time in history that an entire British naval squadron had surrendered to an American vessel. Huzzah!! Huzzah!!
Perry wrote to General William Henry Harrison (who eventually became the 9th President of the United States):
We have met the enemy and they are ours. Two ships, two brigs, one schooner and one sloop.
Yours with great respect and esteem, O.H. Perry
Oliver Hazard Perry was awarded the Congressional Gold Medal in 1814 for his actions in the Battle of Lake Erie and the War of 1812. You can visit Perry’s Victory and International Peace Memorial on South Bass Island, Lake Erie.
“Perry’s Victory and International Peace Memorial commemorates the Battle of Lake Erie that took place near Ohio’s South Bass Island, in which Commodore Oliver Hazard Perry led a fleet to victory in one of the most decisive naval battles to occur in the War of 1812.” (Wikipedia)
This video gives you a nice overview of the War of 1812:
Oh, so you might be wondering what all of this has to do with our National Anthem? The poem that eventually became our National Anthem was written during the War of 1812. It was written in 1814 by a young lawyer named Francis Scott Key during the battle of Fort McHenry.
Watch this video for information about Mr. Key and our National Anthem:
Did you know that our National Anthem actually has four verses, but most of us only know the first one? Look it up!
I’ve been part of the mission leg that is surveying off the coast of Presque Isle – as the survey around South Bass Island had been completed prior to me coming aboard. The area around Presque Isle also has important historic roots.
Presque Isle State Park is a 3,200-acre sandy peninsula that arches into Lake Erie and is 4 miles west of Erie, PA. According to a tourist website, “As Pennsylvania’s only “seashore,” Presque Isle offers its visitors a beautiful coastline and many recreational activities, including swimming, boating, fishing, hiking, bicycling, and in-line skating.” Recorded history of Presque Isle began with the Erielhonan, a Native American tribe who gave their name to Lake Erie. Erielhonan is the Iroquoian word for “long tail”. The French first named the peninsula in the 1720s; presque-isle means peninsula or “almost an island” in French. It served as a base for Commodore Oliver Hazard Perry’s fleet in the War of 1812.
In the 19th century, Presque Isle became home to several lighthouses and what later became a United States Coast Guard station. In 1921, the peninsula became a state park. The Presque Isle peninsula formed because of glaciation and is constantly being reshaped by waves and wind. Since 1967, the park has been named one of the best places in the United States for watching birds.
During the War of 1812, Presque Isle played a part in the victory over the British in the Battle of Lake Erie. Oliver Hazard Perry, commander of the American fleet, made strategic use of the bay as a place to construct six of the nine ships in his fleet. The “Little Bay” near the tip of the peninsula where the ships sheltered was later named “Misery Bay” because of the hardships during the winter of 1813–1814, after the men returned there from battle. Many men suffered from smallpox and were kept in quarantine near the bay. A great many infected men died and were buried in what is now called Graveyard Pond.
After the Battle of Lake Erie on September 10, 1813, Perry’s two largest ships, the USS Lawrence and USS Niagara, were badly damaged, and intentionally sunk in Misery Bay. Both ships were eventually raised. The Lawrence burned while on display at the 1876 Centennial Exposition and parts of the Niagara were eventually used to build a replica of the current Niagara, based in Presque Isle Bay.
For the Little Dawgs . . .
Q: Where is Dewey? Hint: This controller is used to move a heavy object.
A: Dewey is sitting on the piece of technology that is used to control the davits. Davits are hydraulic machines that take the small boats on and off the ship.
This time-lapse video shows the crew using the davits to pick up and then redeploy one of the small boat launches. (Video taken by Physical Scientist Dan Garatea)
Human-Interest Poll (HIP)
Miss Parker makes a lot of yummy desserts! I recently asked the crew to list their favorite.
Meet the Crew
Dan Garatea and Surafel Abebe are physical scientists (PS) who work in Silver Spring, MD for NOAA’s Office of Coast Survey (OCS) where they plan hydrographic surveys for chart updates. They research and develop the plans and instructions for NOAA ships, contractors, other governmental agencies, and other interested parties to develop hydrographic priorities. When on board during a survey, they manage and provide guidance for the surveys in the field.
It is nice being home. I do, however, miss the crew aboard Thomas Jefferson. They are now back out surveying on the Lake Erie after a much needed shoreleave. I am having fun thinking about how I will use what I learned during this adventure to enrich the K-8 STEAM curriculum of the Dalton Local School District.
Allow me to provide a summary of the survey and what was accomplished on this leg. June 9, we departed from Galveston and made our way out to sea. The survey started the next day. We traveled 1,866.6 nautical miles (or 2,148.04 miles) along the continental shelf. That’s like driving from Florida to California! On this leg of the survey we (they) deployed 169 cameras, 22 CTDs, 13 bandit reels, and 12 XBTs (still don’t know what that is). We collected 15 eDNA samples (go Caroline!) and mapped 732 nautical miles. This year’s survey started in April, and this was the last leg. We’re making our way back to Pascagoula (yes, I can pronounce it now), a near 28 hour transit. We will be docking and unloading at the Gulf Marine Support Facility. The next survey on the Pisces starts next week, deploying Remote Operated Vehicles (ROVs). The science never stops, folks.
The SEAMAP Reef Fish Survey began as a fish trap survey in 1980’s and transitioned to a video survey in 1991, and the technology continues to evolve year after year. This over thirty years of data provides abundance and distribution information on Gulf of Mexico reef fish. Reef fish abundance and size data are generated directly from the videos. So though the work feels slow, it is essential. An index of abundance for each species is determined as the maximum number of a fish in the field of view in a single video frame. Here are some snippets of the footage recording during our trip.
*NOTE: The tiger shark shot was not from our leg of the survey, but too cool not to include.
This survey combined with all research approaches (i.e. traps, bandit reels, eDNA) allows for a comprehensive stock assessment of the fish populations in the Gulf of Mexico. Stock assessments collect, analyze, and report demographic information to estimate abundance of fish, monitor responses to fishing, and predict future trends. This significant data is used in managing fish populations and preserving our oceans resources.
One of the scientific operations I have not yet mentioned is bathymetric mapping. Senior Survey Technician Todd Walsh works the night shift running the mapping show – multibeam echo-sounder hydrographic survey to be precise. An echo-sounder determines the depth of the seafloor by measuring the time taken for sound echoes to return. The technology is impressive. Todd is straight up 3D mapping the bottom of the ocean. He watches it come to life, line by line. That’s freaking cool. I see you, Todd.
Though mapping occurred overnight, Todd was sure to point out any interesting finds in the morning. The Pisces mapped an area south of the Flower Garden Banks National Marine Sanctuary and found an impressive geological feature hosting two mud volcanoes. A mud volcano is a landform created by the eruption of mud or slurries, water and gases. Man, the ocean floor is like a whole other world. It was so interesting to watch the mapping unfold right before your eyes. Maybe the seafloor will be my next destination.
The long days take their toll. This crew has worked so hard and is ready to decompress. Some have been out here for months and are counting down the days. You really can’t blame them. You ask anyone out here, “how many days?” and you will hear “three days and a wake up.” “Two days and a wake up.” “One day and a wake up.” They have all earned some serious rest and recovery, and long awaited time with their families and friends. I mean, I’d like to call them friends, but I get it, you can have lots of friends.
I cannot believe it is already my last day out here. Though each day felt like 100 hours, somehow it still flew by. The last CTD hauled out of the water last night marked the end of the SEAMAP survey. I cheer and shout in solitude and run round giving high fives. Good work, everyone! They are all exhausted, but certainly excited and proud of the work they have accomplished. Listen guys, if you aren’t proud, let me remind you that you most certainly should be.
The last day is the first sunrise I didn’t catch – sleeping in was just too tempting. Friends at home have to literally drag me out of bed to catch a sunrise, but out here, it just feels right. We ease into our day and clean and prepare the working spaces and equipment for arrival. I mop. That’s about all I am good for. TAS card. I spend the day roaming as usual, this time reflecting on my arrival and experience at sea. Time slows down even more (if you can believe that) when it’s your last day. I do my best to take in every last moment. I balance the day with some relaxation, a nice game of “bugs” with my pals, a good deal of snacking, revisiting the views, and saying my goodbyes.
Though thrilled to be heading back, most everyone finds their way outside for the last sunset. I soak up every colorful ripple. Mother Nature does not disappoint in those last hours. Dolphins put on a show jumping out of the water at a distance. The stars start to appear, not a cloud in the sky. I stargaze for what felt like hours. We’re greeted by multiple shooting stars. These are the moments I live for – when I feel most at rest. I am overcome with humility and gratitude.
I consider myself lucky to have met and worked with the Pisces crew. Every person on this trip has left an impression on me. From day one, the crew has been so welcoming and willing to let me participate, committed to providing me an exceptional experience. For that, I am grateful. I had so much fun learning from each department and goofing off with the best of them. The work that goes in to the research is remarkable, from navigation, the science, to vessel operations. I learned much more than expected. It’s hard to summarize my experience, but here are some valuable takeaways, in no particular order.
NOAA research is vital in protecting our most precious natural resource.
Ocean conservation is the responsibility of every one of us.
Remember why you do the job you do and the impact you have.
Never pass up an opportunity to learn or do something new.
Everyone should have the opportunity to connect to our natural world.
You can never see too many sunsets.
Expose your toes to the great outdoors.
I can’t express enough how grateful I am to have been selected for the NOAA Teacher at Sea Program and be a part of its mission. The experience was so much more than I could have even imagined. Participating in the research was so rewarding, and offered valuable insight into fisheries research and scientific operations. The questions never stopped coming. The novelty of the work kept me hooked. If there is one thing above all that I took away from this trip is – never stop learning. Continuous learning is what enhances our understanding of the world around us, in so many ways, and why I love what I do.
I look forward to sharing my experience with the many students I have the opportunity to work with, and hopefully inspiring them to continue to learn and grow, building a better understanding and appreciation for our planet. NOAA, your investment in me will not go unnoticed. The biggest THANK YOU to all involved in making this experience a reality.
We ride together, we die together. Pisces for life. – Junior
I have been immersed in many science concepts in my very first day on the ship. Science is everywhere from how the engine works to navigating the ship to mapping the lake/ocean floor. I guess first I’ll start with explaining the science behind the research that the NOAA Ship Thomas Jefferson does in Lake Erie.
NOAA’s Ship Thomas Jefferson uses technology called multibeam sonar to map the seafloor and detect objects in the water column or along the seafloor. It is mounted on the bottom of the ship, also known as the ship’s hull. A multibeam sonar sends out multiple, simultaneous sonar beams (or sound beams) in a fan-shaped pattern which allows it to cover the space both directly under the ship and out to each side and then listen for reflections (echo).
Why are sound waves used in water but not radar or light waves?
Because sound waves travel farther in the water than radar and light waves, and sound waves are created by vibrations. That means that sound waves travel faster in denser substances because the molecules are densely packed together. When one molecule vibrates the amount of time to vibrate neighboring molecules is shorter, meaning sound travels faster. What a great way to talk about different waves here but I am going to leave it here for curious readers like yourself to explore!
So, sound waves. If you were to compare one bottle of water with one bottle of air, the one bottle of water would have 800 times more particles than the bottle it has air (According to Scientific American).
Here it comes to the question. Do sound waves travel differently in saltwater than freshwater? The answer is yes! Because seawater has more particles due to salt (salinity) than freshwater. Remember, the more particles there are in a substance, the faster the sound can travel through it. The comparison can be extended among sea, ocean and freshwater systems.
Many sea mammals use sonar to communicate with each other. Take the humpback whales, for example. Researchers believe that humpback whales’ low frequency sounds can travel more than 10,000 miles in the ocean. Imagine you are a whale singing, how far can you reach out? Mind blowing!
This also reminds me of the science behind human hearing. Our ear detects the sound vibrations that travel from the air through the ear canal and strike the eardrum and vibrate. These vibrations are then passed to three tiny bones in the middle ear. Those tiny bones then amplify the sound by sending out sound waves to the FLUID-FILLED hearing organ called the cochlea. Meaning, we as humans, eventually use water to amplify what we heard outside in the air.
What a great way to learn the physics of sound within real-world applications. I challenge you to find out more real-world applications of sound.
While I have so many science concepts to talk about, I also have so many other things to talk about.
Let me start off by saying what I did when I got on the ship prior to our departure the next day. First, I received Covid-19 testing prior to boarding and thankfully after getting a negative result, I was allowed on the ship. The OOD (Officer of the Deck) showed me my stateroom (where I sleep). It is like a bunkhouse with two people and I chose to sleep on the top. Between two staterooms, there is one common bathroom with showers. Every room has safety equipment, refrigerators, lockers etc. It was really way better than I expected.
Anyway, soon after one of the ship’s deck officers told us that we were meeting at a restaurant for dinner at 7pm. While I was enjoying my hot fried coconut jumbo shrimp ( it was so hot that it didn’t cool even 15 minutes later!), one of the crew members asked my name. I responded to him in a way that could be pronounced in English. After waiting a couple of seconds, he responded “ Benim adim Justin, sen Türkçe biliyor musun?” With the shock that Justin gave me, I couldn’t say a single word. Justin said – “My name is Justin, and do you speak Turkish?” He knew that I am of Turkish origin and wanted to make sure I could speak. If the time of this conversation is around 8 pm then we had so much deep conversation that we couldn’t keep track of time and realized it was around midnight when we got back to the ship. His wife is Turkish and he knows how to speak Turkish very well. Imagine how odd it is to meet a person on a ship who happens to know how to speak Turkish in a place far from Turkey. Justin is an electronics technician (ET) for the ship. Ohh I forgot to tell you, we also went bowling after the restaurant.
When I got to my stateroom, it was well past midnight. Even though I drove 4 hours on the road and was worn out from the day, spending more than 9 hours with this incredible team recharged me. I couldn’t be more excited about what my days will look like onward.
I put my head down and could hear the loud generator noise. I was so tired that I could not get up to put my ear plugs on. I slept like a torn out elephant until the next morning!
I ate my veggie burger with scrambled eggs in the mess deck (crew eating area) for breakfast, spinach ravioli for lunch, and baked salmon with alfredo sauce macaroni and potatoes for dinner. Believe it or not, their mess deck is sooo awesome that I picked one convenient spot as my “office” desk. You can find every type of snack (that includes ice cream), tea, coffee… in this small place. There are coffee makers, water fill stations, soda machines just to name a few. NOAA is clearly taking care of their crew very well. Keep up the good work NOAA!
We departed around 2:30 pm from Cleveland and headed out to the Lake where we started to survey. About an hour and a half later, the ship started sending out multibeam sound waves and our official work started. Again, there is more talk about the crew, the work they do, and how I feel. I think I will intentionally make you curious more about my adventures and stop here.
Did you know?
First Fact: The last time a NOAA ship visited the Great Lakes was in the early 1990s which means updated nautical charts of the Great Lakes are long overdue. Ohio’s primary economic force comes from manufacturing, and many factories rely on water systems in Ohio such as the Ohio River and Great Lakes. Updating nautical charts for the Great Lakes is significant, not only for Ohioans, but also the entire nation.
Second Fact: Water in the Great Lakes (consists of five lakes: Superior, Huron, Michigan, Erie and Ontario) comes from thousands of streams and rivers and the flow of water continues to move eastward. Lake Superior drains into Lake Michigan/Huron via the St. Mary’s River. Lake Huron drains into Lake Erie via the St. Clair and Detroit Rivers. Lake Erie drains into Lake Ontario via the Niagara River. The entire system eventually flows to the Atlantic Ocean via the St. Lawrence River. Four of the five lakes are shared by two nations, the U.S. and Canada; only Lake Michigan is entirely within the U.S.
Latitude & Longitude: 43◦ 53.055’ N 124◦ 47.003’W Windspeed: 13 knots Geographic Area: @10-15 miles off of the Oregon/California coast Cruise Speed: 12 knots Sea Temperature 20◦Celsius Air Temperature 68◦Fahrenheit
Navigation is how Fairweather knows its position and how the crew plans and follows a safe route. (Remember navigation from the last post?) But what “drives” where the ship goes is Hydrographic survey mission. There is a stunning amount of sea floor that remains unmapped, as well as seafloor that has not been mapped following a major geological event like an earthquake of underwater volcano.
Why is Hydrography important? As we talked about in the previous post, the data is used for nautical safety, creating detailed maps of the ocean floor, setting aside areas are likely abundant undersea wildlife as conservation areas, looking at the sea floor to determine if areas are good for wind turbine placement, and most importantly to the residents off the Pacific coast, locating fault lines — especially subduction zones which can generate the largest earthquakes and cause dangerous tsunamis.
In addition to
generating the data needed to update nautical charts, hydrographic surveys
support a variety of activities such as port and harbor maintenance (dredging),
coastal engineering (beach erosion and replenishment studies), coastal zone
management, and offshore resource development. Detailed depth information and
seafloor characterization is also useful in determining fisheries habitat and
understanding marine geologic processes.
The history of hydrographic surveys dates back to the days
of Thomas Jefferson, who ordered a
survey of our young nation’s coast. This began the practice and accompanying sciences
of the coastal surveys. The practice of
surveys birthed the science of Hydrography (which we are actively conducting
now) and the accompanying science of Bathymetry (which we will go into on the
next post.) This practice continues of
providing nautical charts to the maritime community to ensure safe passage into
American ports and safe marine travels along the 95,000 miles of U.S. Coastline.
Want to learn more about Hydrographic Survey history? Click on THIS LINK for the full history by the NOAA.
Scientists have tools or equipment that they use to successfully carry out their research. Let’s take a look at a few of the tools hydrographic survey techs use:
Want to learn more about the science of SONAR? Watch the video below.
On board Fairweather (actually underneath it) is the survey tool call a TRANSDUCER which sends out the sonar pulses.
The transducer on Fairweather is an EM 710- multibeam echo sounder which you can learn more about HERE.
The Transducer is located on the bottom of the ship and sends out 256 sonar beams at a time to the bottom of the ocean. The frequency of the 256 beams is determined by the depth from roughly 50 pings per second to 1 ping every 10 seconds. The active elements of the EM 710 transducers are based upon composite ceramics, a design which has several advantages, which include increased bandwidth and more precise measurements. The transducers are fully watertight units which should give many years of trouble-free operation. This comes in handy since the device in on the bottom of Fairweather’s hull!
Here is the transducer on one of the launches:
The 256 sonar beams are sent out by the transducer simultaneously to the ocean floor, and the rate of return is how the depth of the ocean floor is determined. The rate of pulses and width of the “swath” or sonar beam array is affected by the depth of the water. The deeper the water, the larger the “swath” or array of sonar beams because they travel a greater distance. The shallower the water, the “swath” or array of sonar beams becomes narrower due to lesser distance traveled by the sonar beams.
The minimum depth that this transducer can map the sea floor is less than 3 meters and the maximum depth is approximately 2000 meters (which is somewhat dependent upon array size). Across track coverage (swath width) is up to 5.5 times water depth, to a maximum of more than 2000 meters. This echo sounder is capable of reaching deeper depths because of the lower frequency array of beams.
The transmission beams from the EM 710 multibeam echo sonar are electronically stabilized for roll, pitch and yaw, while they receive beams are stabilized for movements. (The movement of the ship) What is roll, pitch, and yaw? See below – these are ways the Fairweather is constantly moving!
Since the sonar is sent through water, the variable of the water
that the sonar beams are sent through must be taken into account in the
Some of the variables of salt water include: conductivity
(or salinity) temperature, depth, and density.
Hydrographic scientists must use tools to measure these factors in sea water, other tools are built into the hydrographic survey computer programs.
One of the tools used by the hydrographic techs is the XBT or Expendable Bathy Thermograph that takes a measurement of temperature and depth. The salinity of the area being tested is retrieved from the World Ocean Atlas which is data base of world oceanographic data. All of this data is transmitted back to a laptop for the hydrographers. The XBT is an external device that is launched off of the ship to take immediate readings of the water.
Launching the XBT: There is a launcher which has electrodes on it, then you plug the XBT probe to the launcher and then XBT is launched into the ocean off of the back of the ship. The electrodes transmit data through the probe via the 750-meter copper wire. The information then passes through the copper wire, through the electrodes, along the black wire, straight to the computer where the data is collected. This data is then loaded onto a USB then taken and loaded into the Hydrographic data processing software. Then the data collected by the XBT is used to generate the sound speed profile, which is sent to the sonar to correct for the sound speed changes through the water column that the sonar pulses are sent through. The water column is all of the water between the surface and seafloor. Hydrographers must understand how the sound moves through the water columns which may have different densities that will bend the sound waves. By taking the casts, you are getting a cross section “view” of the water column on how sound waves will behave at different densities, the REFRACTION (or bending of the sound waves) effects the data.
See how the XBT is launched and data is collected below!
Videos coming soon!
The other tool is the MVP or moving vessel profiler which takes measurements of conductivity, temperature, and depth. These are all calculated to determine the density of the water. This is a constant fixture on the aft deck (the back of the ship) and is towed behind the Fairweather and constantly transmits data to determine the speed of sound through water. (Since sonar waves are sound waves.)
The sonar software uses this data to adjust the calculation of the depth, correcting for the speed of sound through water due to the changes in the density of the ocean. The final product? A detailed 3d model of the seafloor!
All of this data is run through the survey software. See screen shots below of all the screens the hydrographers utilize in the course of their work with explanations. (Thanks Sam!) It’s a lot of information to take in, but hydrographic survey techs get it done 24 hours a day while we are at sea. Amazing! See below:
Did You Know? An interesting fact about sonar: When the depth is deeper, a lower frequency of sonar is utilized. In shallower depths, a higher sonar frequency. (Up to 900 meters, then this rule changes.)
Question of the Day: Interested
in becoming a hydrographic survey tech?
See the job description HERE.
Challenge yourself — see if you can learn and apply the new terms and phrases below and add new terms from this blog or from your research to the list!
Geographic Area of Cruise: Bering Sea and Bristol Bay, Alaska
Date: July 11, 2019
Weather Data from the Bridge Latitude: 58° 36.7 N Longitude: 162° 02.5 W Wind: 1 knot N Barometer: 1011.0 mb Visibility: 10 nautical miles Temperature: 58° F or 14° C Weather: Partly cloudy, no precipitation
What is NOAA and the Teacher at Sea program?
You may be wondering what, exactly, am I doing going “to sea” with NOAA. First off, NOAA stands for the National Oceanic and Atmospheric Administration and originates back to 1807 with Thomas Jefferson founding the U.S. Coast and Geodetic Survey (as the Survey of the Coast) with a mission to provide nautical charts to the maritime community for safe passage into American ports. Over time, the Weather Bureau was added and then the U.S. Commission of Fish and Fisheries was developed. In 1970, these three agencies were combined under one umbrella organization and named NOAA, an agency that supports accuracy and precision of physical and atmospheric sciences, protection of life and property, and stewardship of natural resources. NOAA is within the Department of Commerce.
NOAA’s Teacher at Sea (TAS) program has existed since 1990, sending over 800 teachers on NOAA research cruises. The TAS mission is “to give teachers a clearer insight into our ocean planet, a greater understanding of maritime work and studies, and to increase their level of environmental literacy by fostering an interdisciplinary research experience.” There is usually just one teacher sent per leg of a mission, that way the TAS gets full exposure to the research process and attention from the crew, scientists and staff on the ship. And it is true, everyone onboard has been friendly, helpful, welcoming, and willing to answer any question I might have, like, where is C deck? (That’s where my stateroom is located).
Science and Technology Log
Now that you understand NOAA’s mission, it should not surprise you that I am on a research cruise that is mapping a part of the seafloor that has not had detailed soundings. “Soundings” means the action or process of measuring the depth of the sea or other body of water. See the map below as that is where I am right now, in Bristol Bay. By the way, NOAA nautical charts are available for free at this NOAA site.
When I’ve told friends, family and students that I was chosen to be on a NOAA research vessel that was compiling a detailed map of the sea floor off of Alaska, it was met with great surprise. “The ocean floor hasn’t been mapped before? How could that be?” In fact, more than 80 percent of the ocean bottom has not been mapped using modern, highly precise technologies. But we do have a very coarse ocean floor – or bathymetric – map, created in the early 1950s by Marie Tharp using sounding data collected by the U.S. military and her collaborator Bruce Heezen. Tharp’s early map of the sea floor beautifully revealed the Mid-Atlantic Ridge and added another piece of evidence in support of the theories of continental drift plate tectonics. There’s a terrific Cosmos: A Spacetime Odyssey episode featuring Tharp.
Why we need a more detailed bathymetry map than the one created by Tharp and Heezen can be explained by the original mission of the early version of NOAA. Jefferson wanted to build a “…survey to be taken of the coasts of the United States…” in order to provide safe passage of ships to ports within the navigable waters of the U.S. As the Bristol Bay chart above shows, there are still coastal areas that have limited to no data. Without detailed charts, mariners cannot know where the shallower waters are (called shoals), or rock obstructions, shifted underwater sand bars, shipwrecks, or other hindrances that cause safety concerns to the movement of boats.
The hydrographic Survey Team on the NOAA Ship Fairweather use several 30 foot boats, called launches, with a multibeam echosounder attached to the hull (the bottom of the ship). The multibeam echosounder uses sonar and is a device useful for both shallow and deep water. In a nutshell, depth measurements are collected by calculating the time it takes for each of the sound pulses to travel from the echosounder through the sea water to the ocean floor and back again. The distance from the instrument to the seafloor is calculated by multiplying the travel time by the speed of sound through seawater, which is about 1,500 meters/second or 4,921 feet/second. Right before a hydrographic survey is started, the team collects information on the conductivity, temperature and depth of the sea water, as temperature and salinity will modify the density and change the travel time of the sonar pulses. The video below can explain the process further.
The software used to collect the soundings is created by the multibeam echosounder manufacturer, so the collection of millions of points on a transect is seamless. Data collection runs are taken over multiple days and several “legs” or extended periods of time when the crew are all out at the same time on the Fairweather. Following collection transects, the data are then post-processed using Caris HIPS and SIPS, which is the software that the Fairweather hydrographers use for data processing.
We’ve motored to a new location, Cape Newenham, which is the name of this mission, so we will be here for about a week. When we got underway, the ship got to really rocking and my stomach could not handle it. I had one bad night but I am now fine and ship shape!
Cape Newenham is at latitude 58°N so we are up close to the Arctic Circle (66.5°N). At this time of year, there are about 5 hours of darkness per night here in Alaska, which is really cool. Compare that what we have in New York…
Did You Know?
You probably know that Charles Darwin was the naturalist on board the HMS Beagle which set sail on December 27,1831. Over the nearly five years the Beagle was at sea, Darwin developed his ideas on natural selection and evolution of species. But what you might not know is that the captain of the Beagle, Robert FitzRoy, was an officer in the Royal Navy, a meteorologist and hydrographer. In fact, the primary mission of the Beagle was to survey the coastline of South America and, in particular, the Strait of Magellan, at the southernmost tip. Better, more accurate charts were needed by the British government, to navigate the treacherous, rough waters of the channels. In addition, FitzRoy was a protégé of Francis Beaufort (who developed the Wind Force Scale which is still used to help explain wind speed) and both worked together to create the science of weather forecasting.
Quote of the Day
“In every outthrust headland, in every curving beach, in every grain of sand there is the story of the earth.” – Rachel Carson
Geographic Area of Cruise: U.S. Southeastern Continental Margin, Blake Plateau
Date: June 5, 2019
Latitude: 29°01.5’ N
Longitude: 079°16.0’ W
Wave Height: 2 feet
Wind Speed: 10 knots
Wind Direction: 128
Visibility: 10 nm
Air Temperature: 27.7°C
Barometric Pressure: 1021.3
Science and Technology Log
What is sonar?
Sonar is the use of sound to describe the marine environment. Sonar can be compared to satellites that use light to provide information about Earth, but instead of light, sound is used. It is used to develop nautical charts, detect hazards under the water, find shipwrecks, learn about characteristics of the water column such as biomass, and map the ocean floor. There are two types of sonar, active and passive. Active sonar is sonar that sends out its own sound wave. The sonar sends a sound wave (ping) out into the water and then waits for the sound to return. The return sound signal is called an echo. By assessing the time, angle, and strength of the return sound wave or echo one can learn many details about the marine environment. Passive sonar does not actively send out a sound ping, but rather listens for the sound from other objects or organisms in the water. These objects may be other vessels and these organisms may be whales or marine ecosystems such as coral reefs.
Sound waves move through the water at different speeds. These speeds are known as frequencies and the unit of measurement for sound is a hertz (Hz). Lower frequencies (example 18 kHz) are able to go farther down because they move slower and have more power behind them. It is like when a car goes down your street, pumping the bass (always seems to happen when I am trying to sleep) and you can hear it for a long time. That is because it is a low frequency and has longer wave lengths. Higher frequencies (example 200 kHz) move faster, but have less power. The sound waves should reach the bottom, an object, or biomass in the water column, but there may be no return or echo. High frequency sound waves are closer together. High frequencies give you a good image of what is happening near the surface of the water column and low frequencies give you a good idea of what is happening near, on, or under the ocean floor.
Type of Sonar on Okeanos Explorer
There are many types of sonar and other equipment aboard Okeanos Explorer for use during mapping operations. All have different capabilities and purposes. Together they provide a complete sound image of what is happening below us.
Kongsberg EM302 Multibeam Sonar
Multibeam sonar sends sound out into the water in a fan pattern below the hull (bottom) of the ship. It is able to map broad areas of the water column and seafloor from depths of 10 meters to 7,000 meters. Only the deepest trenches are out of its reach. It is the most appropriate sonar system to map seafloor features such as canyons and seamounts. The fan like beam it emits is 3-5.5x the water depth with a max swath range of 8 km. However, when you get to its depths below 5,000 meters the quality of the sound return is poor so scientists keep the swath range narrower to provide a higher quality of data return. The widest swath area scientists can use while maintaining quality is a depth of 3,300-5,000 meters. The user interface uses a color gradient to show you seafloor features (red=shallow and purple=deep).
Backscatter uses the same pings from the multibeam. People use backscatter to model or predict physical or biological properties and composition of the sea floor. The coloring typically is in grayscale. A stronger echo looks brighter in the image. A weaker echo looks darker in the image. It gives you a birds-eye view of seafloor characteristics such as substrate density and seafloor features.
An Expendable Bathy-Thermograph (XBT) provides you with information on the temperature gradients within the water. When the temperature profile is applied to a salinity profile (taken from World Ocean Atlas) you are able to determine sound velocity or the rate at which the sound waves can travel through the water. When sound moves through water it does not move in a straight line. Its path is affected by density which is determined by water type (freshwater or saltwater) and temperature. Freshwater is less dense than saltwater and cold water is denser than warm water. The XBT information accounts for sound refraction (bending) through various water densities. When near shore XBTs are launched more frequently because the freshwater inputs from land alter density of the water and temperatures in the water column are more varied. XBTs are launched less frequently when farther from shore since freshwater inputs are reduced or nonexistent and the water column temperature is more stable. However, ocean currents such as the Gulf Stream (affecting us on this cruise) can affect density as well. The Gulf Stream brings warm water from the Gulf of Mexico around the tip of Florida and along the eastern coast of the United States. Therefore, one must also take into account which ocean currents are present in the region when determining the launch schedule of XBTs.
Simrad EK60 and EK80 Split-beam Sonar
Split-beam sonar sends out sound in single beam of sound (not a fan like the multibeam). Each transducer sends out its own frequency (example 18 kHz, 38 kHz, 70 KHz, 120 kHz, and 200 kHz). Some frequencies are run at the same time during mapping operations. Mapping operations typically do not use the 38 kHz frequency since it interferes with the multibeam sonar. Data collected with the use of the EK60 or EK80 provides information about the water column such as gaseous seeps, schools of fish, and other types of dense organism communities such as zooplankton. If you remember my “did you know” from the second blog, I discussed how sonar can be used to show the vertical diurnal migration of organisms. Well the EK60 or EK80 is the equipment that allows us to see these biological water column communities and their movements.
Knudsen 3260 Sub-bottom Profiler
The purpose of using a sub-bottom profiler is to learn more about the layers (up to 80 meters) below the ocean floor. It works in conjunction with the sonar mapping the ocean floor to provide more information about the bottom substrate, such as sediment type and topography features. Sub-bottom data is used by geologists to better understand the top layers of the ocean floor. A very low frequency is used (3.5 kHz) because it needs to penetrate the ocean sediment. It will give you a cross section of the sea floor so floor features can be detected.
Telepresence aboard the ship allows the science team to get mapping products and raw data to land on a daily basis. The science team can also live feed data collection to shore in real time. By allowing a land based shore team to see the data in real time you are adding another system of checks and balances. It is one more set of eyes to make sure the data being collected looks correct and there are no issues. It also allows a more collaborative approach to mapping, since you are able to involve a worldwide audience in the mission. Public viewers can tune in as well. Support for the technology needed to allow telepresence capabilities comes in partnership with the Global Foundation of Ocean Exploration (GFOE). With GFOE’s help, the protocols, high-speed satellite networks, Internet services, web and social media interfaces, and many other tools are accessible when out to sea. The NOAA Office of Exploration and Research (OER) provides the experts needed to develop, maintain, and operate the telepresence systems while at sea, but also at shore through the Exploration Command Centers (ECCs) and the University of Rhode Island’s Inner Space Center.
All in all, the equipment aboard Okeanos Explorer is impressive in its abilities to provide the science team with a high quality and accurate depiction of the ocean floor and water column. The science team aboard is able to interpret the data, clean out unwanted data points, store massive data files on computers, and send it back to land daily, all while rocking away at sea. Very impressive and very cool!
I learned all about memes today. Apparently they are very popular on the ship. So popular, we are even in the middle of a meme contest. For those of you unfamiliar to memes like I was, a meme is a funny picture with a clever caption that makes you laugh or relates to something in your life. After my tutorial in meme making, we had a great time out on the bow of the ship playing corn hole and hanging out. The night was beautiful. The humidity subsided and there was a great breeze. After the sun set, I watched the stars come out and then went inside to learn more about the mapping process. I am starting to get a better understanding of what the science team is doing. You know the how and the why of it all. After I couldn’t keep my eyes open any longer, I made my nightly venture out onto the bow to look from some bioluminescence, the glittering of zooplankton in the night. A magical site. I will leave you wondering how the ocean glitters until one of my future blogs when I describe the process of bioluminescence.
Did You Know?
The SOFAR (Sound Fixing and Ranging) channel occurs in the world’s oceans between depths of 800 to 1000 meters in the water column. Because of the density and pressure around this channel, sound waves travel for an extended distance. It is thought that fin whales travel to this channel to communicate with other fin whales many kilometers away.
Latitude: 57°39.2266’ N Longitude: 152°07.5163’ W Wind Speed: 11.6 knots Wind Direction: NW (300 degrees) Air Temperature: 11.37° Celsius Water Temperature: 8.3° Celsius
Science and Technology Log
Today I went out on a launch for the first time. The plan was to survey an area offshore and then move nearshore at low tide, with the water at its lowest level on the beach of Kodiak Island. Survey Techs, Carl Stedman and Christina Brooks, showed me the software applications used to communicate with the coxswain and collect data. To choose the best frequency for our multibeam pulse, we needed to know the approximate depth of the area being surveyed. If the water is deeper, you must use lower frequency sound waves, since higher frequency waves tend to attenuate, or weaken, as they travel. We chose a frequency of 300 kilohertz for a 60 meter depth. Periodically, the survey techs must cast a probe into the water. The Sea-bird SeaCAT CTD (Conductivity, Temperature, Depth) measures the characteristics of the water, creating a sound velocity profile. This profile can tell us how quickly we should expect sound waves to travel through the water based upon the water’s temperature, salinity, and pressure.
Using the sound velocity profile allows the computer’s Seafloor Information System (SIS) to correct for changes in water density as data is being collected. Once the profile was transmitted to SIS, we were ready to begin logging data.
Imagine that you are mowing your lawn. To maximize efficiency you most likely will choose to mow back and forth in relatively straight paths, overlapping each new row with the previous row. This is similar to how the offshore survey is carried out. As the boat travels at a speed of about 7 knots, the Kongsberg EM2040 multibeam sonar transducer sends out and receives pulses, which together create a swath. The more shallow the water, the wider the base of the swath.
After lunch we changed to a nearshore area closer to Kodiak Island between Sequel Point and Cape Greville. It was important to wait for low tide before approaching the shore to avoid being stuck inshore as the tide is going out. Even so, our coxswain was very careful to follow the edges of the last swaths logged. Since the swath area extends beyond the port and starboard sides of the boat, we could collect data from previously uncharted areas without driving directly above them. In this way we found many rocks, invisible to the naked eye, that could have seriously damaged an unlucky fisherman!
Career Focus – Able Seaman
Our coxswain driving the boat today was Allan Quintana.
As an Able Seaman, Allan is part of the Deck Department, which functions primarily to keep track of the ship, manage the lines and anchoring, and deploy and drive the launches. Allan started out working for the Navy and later transitioned to NOAA. A Miami native, he told me how he loves working at sea, in spite of the long stretches of time away from his friends and family back home.
If you have never been on a boat before, it is a unique experience. Attempts have been made by poets, explorers, scientists, naturalists, and others throughout history to capture the feeling of being at sea. Although I’ve read many of their descriptions and tried to imagine myself in their shoes, nothing compares to experiencing it first-hand.
Standing on the bow of the anchored ship, looking out at the water, my body leaning to and fro, rising and falling, I am a sentient fishing bobber, continuously rocking but not really going anywhere. My head feels somehow both heavy and light, and if I stand there long enough, I just might fall asleep under the spell of kinetic hypnosis. The motion of the launch is different. A smaller boat with far less mass is bullied by the swells. For a new crew member like me, it’s easy to be caught off guard and knocked over, unless you have a good grip. I stand alert, feet apart, one hand clasping a rail, as the more experienced crew move about, casually completing various tasks. I wonder how long it would take to become accustomed to the boat’s rising and falling. Would my body gradually learn to anticipate the back and forth rocking? Would I eventually not feel any movement at all?
Word of the Day
draft – the vertical distance between the waterline and the hull of a boat, a.k.a. the draught
Mission:Mapping Deep-Water Areas Southeast of Bermuda in Support of the Galway Statement on Atlantic Ocean Cooperation
Date: July 30, 2018
Air Temperature: 27.5°C
Wind Speed: 18.17 knots
Conditions: Partly Sunny
Depth: 3742.65 meters
Qimera is a hydrographic processing software that was used during this expedition. This computer program allows scientists to edit and process the survey line data as it was being collected.
To successfully edit incoming multibeam data, it was necessary to isolate a specific section of the line and use Qimera’s 3D Editing Tool. The 3D Editing Tool was utilized to remove outliers that skew the data.
Essentially, each colorful point in the diagram below is a sounding from the multibeam sonar. The soundings are return signals that bounce back and reach the receivers on the sonar. When scientists are previewing and editing data, certain points are considered outliers and are rejected. The rejected points are shown as red diamonds in the diagram below. Once the edits are made, they are saved, and the surface is updated.
It is especially important to ensure that we are collecting as much data as possible as we continue to survey this area. In order to accomplish this, factors such as required resolution, sea state, water depth and bottom type are used to determine line plans. By partially overlapping lines, we ensure there is quality data coverage on the outside beams. More overlap tends to mean denser, high quality coverage which will allow our team to develop accurate maps of the seafloor.
Another program that was used to process data was known as Fledermaus. This interactive 4D geospatial processing and analysis tool is used to reproject Qimera projects as well as export the Daily Product that was completed and sent onshore where it is publicly available. We also projected the edited data on Google Earth (see below) and would include this in the Daily Product that was sent to shore as well.
Now that we have left the survey area, we are transiting back to Norfolk and still collecting and processing data. We are scheduled to arrive early on the 31st and a majority of us will depart that evening. Since we are still collecting return transit data, it is still necessary for processing to occur. Although we’ve been working diligently, we still like to make time for fun. On Friday night, we hosted a Finer Things Club Gathering complete with fancy cheese, crackers, sparkling apple juice, and chocolate! It was great! On Saturday, we played the final cribbage tournament game as well as other board games, and on Sunday we had an ice cream party!
Did You Know?
One of the first breakthroughs in seafloor mapping using underwater sound projectors was used in World War I.
Mission: Hydrographic Survey – Approaches to Houston
Geographic Area of Cruise: Gulf of Mexico
Date: July 24th, 2018
Weather Data from the Bridge
Visibility: 5 Nautical Miles
Sky Condition: 8/8
Wind: Direction: 70.1°, Speed: 13.3 knots
Air: Dry bulb:26.9°C Wet bulb: 24.7°C
Science and Technology Log
Coming to NOAA Ship Thomas Jefferson, I was eager to learn all I could about sonar. I am amazed that we have the ability to explore the ocean floor using sound.
Over the course of my previous blog entries, I have described the tools and processes used to survey using sonar. This time, I am going to try to frame the sounds that the sonars are using in a musical context, in the hope that doing so will help students (and myself) better understand the underlying concepts.
Note – many aspects of music are not standardized. For the purpose of this blog post, all musical tuning will be in equal temperament, at A=440. When I reference the range of a piano, I will be referencing a standard 88-key instrument. Many of the sonar frequencies do not correspond exactly to an in-tune pitch, so they have been written to the nearest pitch, with a comment regarding if the true frequency is higher or lower than the one written.
In sonar and in music, when considering soundwaves it is important to know their frequency, a measure of how many waves occur over the course of a set period of time. Frequency is measured in a unit called Hertz (abbreviated as Hz), which measures how many soundwaves occur in one second. One Hertz is equal to one soundwave per second. For example, if you heard a sound with a frequency of 100Hz, your ears would be detecting 100 soundwaves every second. Musicians also are concerned with frequency, but will use another name for it: pitch. These words are synonymous – sounds that are higher in pitch are higher in frequency, and sounds that are lower in pitch are lower in frequency.
Below are the eight octaves of the note A that are found on a piano, each labeled with their frequency. The notes’ frequencies have an exponential relationship – as you move from low to high by octave, each note has a frequency that is double that of its predecessor.
The highest note on a piano, C, has a frequency of 4186.01Hz
Average, healthy young humans hear sounds ranging from 20Hz to 20,000Hz. All sounds outside of that range are inaudible to people, but otherwise no different from sounds that fall within the human range of hearing. The highest note we would be able to hear would be an E♭, at a frequency of 19,912.16Hz (a frequency of exactly 20,000Hz would fall in between E♭ and E♮, though would be closer to E♭). If put on a musical staff, it would look like this:
The hull of NOAA Ship Thomas Jefferson is equipped with several sonar transmitters and receivers, which can operate at a wide variety of frequencies.
Higher frequencies provide higher resolution returns for the sonar, but they dissipate more quickly as they travel through water than lower frequencies do. Surveyors assess the depth of the water they are surveying, and choose the frequency that will give them the best return based on their conditions. Most of the sonar frequencies are too high for humans to hear. The ship’s multi-beam echo sounder has a variable frequency range of 200,000Hz-400,000Hz, though as I’ve been on board they’ve been scanning with it at 300,000Hz. Likewise, the multi-beam sonars on the launches have also been running at 300,000Hz. The ship has a sub-bottom profiler, which is a sonar used for surveying beneath the seafloor. It operates at a frequency of 12,000Hz, and has the distinction of being the only sonar on the ship that is audible to humans, however, we have not had a need to use it during my time aboard the Thomas Jefferson.
The ship’s side scan towfish (which I described in my previous blog entry) operates at 455,000Hz.
Here, we can see what those frequencies would look like if they were to be put on a musical staff.
Altering the frequency isn’t the only way to affect the quality of the reading which the sonar is getting. Surveyors can also change the pulse of the sonar. The pulse is the duration of the ping. To think about it in musical terms, changing the pulse would be akin to switching from playing quarter notes to playing half notes, while keeping the tempo and pitch the same. Different sonar pulses yield different readings. Shorter pulses provide higher resolution, but like higher frequency pings, dissipate faster in water, whereas longer pulses provide lower resolution, but can reach greater depths.
Mariners have a reputation for being a rather superstitious bunch, so I decided to ask around to see if that held true for the crew of the Thomas Jefferson. Overall, I found that most didn’t strictly adhere to any, but they were happy to share some of their favorites.
Everyone I spoke to told me that it is considered bad luck to leave port on a Friday, though the Commanding Officer, CDR Chris van Westendorp, assured me that you could counteract that bad luck by making three 360° turns to the left as soon as the ship is able. Many on the crew are also avid fishermen, and told me that bringing bananas aboard would lead to a bad catch, and one went so far as to be mistrustful of yellow lighters as well.
Certain tattoos are said to bring good luck – I was told that sailors often have a chicken and a pig tattooed on their feet. According to custom, those animals were often stored in wooden crates that would float if a ship went down, and having them tattooed onto you would afford you the same benefit. When asked if he was superstitious one of our helmsmen Jim proudly showed me a tattoo he has of a dolphin. He explained that having a sea creature tattooed on your body would prevent drowning. “It works!” he said with a grin, “I’ve never drowned!”
Several maritime superstitions deal with foul weather. Umbrellas are said to cause bad weather, as is split pea soup. Whistling while on the bridge is said to “whistle in the winds.” While not a superstition per se, many crew members told me variations of the same meteorological mantra: Red sky at night, sailor’s delight. Red sky in the morning, sailors take warning.
One of the NOAA Corps Officers aboard, ENS Garrison Grant, knew several old superstitions related to shipbuilding. When laying the keel (the first piece of the ship to be put into place), shipbuilders would scatter evergreen boughs and tie red ribbons around it to ward off witches. Historically, having women aboard was considered bad luck, though, conversely it was said that if they showed their bare breasts to a storm, it would subside. This is why several ancient ships had topless women carved into the masthead. Legend has it that in order to assure that a ship would float, when it was ready to be launched for the first time, virgins would be tied to the rails that guided the ship from the ship yard into the water. The weight of the ship would crush them, and their blood would act as a lubricant, allowing the ship to slide into the water for the first time. Yikes! Thankfully, as society became more civilized, this practice evolved into the custom of breaking a bottle of champagne against a ship’s bow!
Did you know? Musical instruments play an important role in ship safety! In accordance with maritime law, ships will use auditory cues to make other vessels aware of their presence in heavy fog. For large ships, this includes the ringing of a gong at regular intervals.
Latest Highlight: During this week’s fire drill, I got to try the fire hose. It was very powerful and a lot of fun!