NOAA Teacher at Sea Yaara Crane Aboard NOAA Ship Thomas Jefferson June 22, 2013 – July 3, 2013
The survey boat is moving from its cradle on the deck of the TJ.
Mission: Hydrographic Survey Geographical area of cruise: Mid-Atlantic Date: Wednesday, June 26, 2013
Latitude: 38.84°N Longitude: 75.04°W
Weather Data from Bridge: Wind Speed: 8.35 knots
Surface Water Temperature: 21.29°C
Air Temperature: 22.80°C
Relative Humidity: 82.00%
Barometric Pressure: 1011.36mb
The survey launch on its wayI am talking with the HIC about the notations on the nautical chart for our survey grounds.
Science and Technology Log
As promised, today’s post is going to be about the Hydrographic Survey Launches. The Thomas Jefferson has two of these boats that are generally launched by 8:00am and return to the ship at 5:30pm. On Tuesday, my official role was Hydrographer in Training. I joined HIC Todd and Coxn Junior for a day of surveying on boat 3102. After a morning of seasickness, they returned me to the TJ around 11:30 to recuperate. However, I was still able to experience a little of what they do every day and the hilarious camaraderie between the two!
In general, the survey launches do the same work as the Thomas Jefferson, just on a smaller scale. The TJ can only drive on lines with a minimum depth of 30 feet, but the survey launches can go to a minimum depth of 12 feet which allows them to get much closer to shoals and the coast. Every morning, the launch survey teams have a meeting with the FOO and XO in the survey room to discuss logistics and safety. My boat was headed out to survey grounds on a new sheet near Cape May, New Jersey. Specifically, we were driving lines in the Prissy Wicks Shoal. This particular region has highly variable depths and created quite a challenge for the HIC and Coxn for two reasons: you cannot navigate in straight lines over shoals, and the shoals constantly change so you must drive slowly in case an area is shallower than charted.
Todd is at his workstation in the cabin.
Todd has been a HIC for both the Rainier and the Thomas Jefferson. In this position, he was worked with many Teachers at Sea, and gave me lots of great resources to bring back to school. The HIC sits inside the cabin and makes sure that all of the equipment is working together and logging the correct data. Just like on the ship, he has an MBES, HYPACK, and POS-MV to help him do his job. However, unlike the ship, he does not have an MVP, and must launch a CTD every four hours to measure the sound velocity profile in the water column. Measuring the sound velocity profile is an important part of correcting the MBES data for improved accuracy. Remember, the equipment is very sensitive to changes in the water because the farther the sound waves travel, the more they are affected by changes in the density of the medium through which they travel.
Junior is doing his best to keep us on the line
Junior’s job as Coxn is to work with the HIC to safely navigate the boat on the survey lines. The Coxn has a monitor controlled by the HIC to help him see the current chart and line. Junior gave me the opportunity to try driving, and I barely lasted 15 seconds before I was off the line! Tuesday was particularly complex because we were in a highly trafficked waterway, shoals appeared out of nowhere, and there was a very strong current around the cape. When another boat appears in the line, the Coxn must bring his boat to a standstill while staying on the line so that data collection does not have to stop. If the survey line goes over an area that is particularly shallow, a decision needs to be made about how to get around the shoal without hitting the bottom. A lot of good-natured yelling happens between the Coxn and HIC so that they can hear each other and be in constant communication.
Once the survey launch has returned to the main ship, the data is downloaded onto a server from which the hydrographers can move the data into CARIS. Eventually all of that data will be turned into a new nautical chart to help marine vessels maneuver through the waters.
What looks like highlighting is the multi-beam data from the survey launches. The colors get warmer (red) as the depth gets shallower
Today’s Acronyms and Abbreviations (some old, some new)
HIC – Hydrographer in Charge
Coxn – Coxswain
FOO – Field Operations Officer
XO – Executive Officer
MBES – Multi-Beam Echo Sounder
MVP – Moving Vessel Profiler
HYPACK – Surprise, not an acronym! This is just the name of the software.
POSMV – Positioning Orientation System Marine Vessel
SSS – Side Scan Sonar
CTD – Conductivity, Temperature, and Depth
CARIS – Computer-Aided Resource Information System. This software allows scientists to process the data that comes from HYPACK. Hypack collects data one line at a time, while CARIS allows you to combine the lines into a new nautical chart.
The chart of Prissy Wicks Shoal shows the extreme changes in depths in a very small area.
Personal Log
Well, my bout of seasickness started about half an hour into my time on the survey launch. I started off in the cabin with the HIC, and the swells in the water got to me immediately. I spent the rest of the time on the deck with the Coxn trying to keep my eyes on the horizon. Through it all, I still managed to get a glimpse of some dolphins playing in the swells and saw many different types of boats and ships sailing around. When I was returned to the ship, I immediately felt better. However, the medical officer took precautionary measures and measured my blood pressure (totally normal, as usual for me) and prescribed 1.5 Liters of water before bed for the night. I took a nice long nap, and woke up in time for a delicious vegetable casserole for dinner. I am feeling back to 100% today, and hope to stay awake tonight. The TJ runs 24 hour operations, so I will pop by the bridge and survey rooms to see what it looks like after dark.
This sign is placed in each room as a reminder of what to do in case of emergencies.
Did You Know?
While at sea, it is required to perform at least one safety drill a week. Today, we had a fire drill and an abandon ship drill.
As part of my safety orientation, I had to put on the survival suit. I think I need a smaller size…
NOAA Teacher at Sea Yaara Crane Aboard NOAA Ship Thomas Jefferson June 22, 2013 – July 3, 2013
Mission: Hydrographic Survey
The SSS looks like a fish on a line just before it gets lowered into the water.
Geographical area of cruise: Mid-Atlantic Date: Monday, June 24, 2013
Latitude: 38.81°N Longitude: 75.10°W
Weather Data from Bridge: Wind Speed: 11.54 knots
Surface Water Temperature: 20.41°C
Air Temperature: 24.30°C
Relative Humidity: 86.00%
Barometric Pressure: 1018.16mb
Science and Technology Log
The plan of the day (POD) for today included launching two survey ships (also known as Hydrographic Survey Launches), fixing the MBES, and pulling up anchor. The survey launches must have at least two people aboard: the hydrographer in charge (HIC) and the coxswain. They go out most days collecting data from about 7:30am until 5:30pm. While the Thomas Jefferson (TJ) has been anchored, these small survey boats have still been able to go out and work. I will have more information about these smaller boats in my next post as I plan to go on tomorrow’s survey team to learn what these individuals do each day.
The FRB is put into its cradle using the davit to lift it from the water.
We have been anchored just off the coast of Lewes, DE in the Harbor of Refuge since Saturday morning. The CO (commanding officer) paged me at 12:30 today to observe while we were heaving the anchor in. I was allowed to stand on the bow and lean over the side of ship to watch. Pulling up the anchor was excellent news because it meant that the equipment delivery had arrived and the data collection would be able to begin again. Just after the anchor came up, I watched the FRB (fast rescue boat) make its delivery and be lifted into its cradle by the use of davits overhanging the deck.
The workstation by the bridge has 5 monitors working to make sure the hydrographers are getting clear data. The bottom right monitor shows the current sheet and line we are sailing on.
We then sailed for a while to make it to our survey grounds. The Thomas Jefferson collects data by sailing in specified lines through the ocean; navigating to the beginning of a line takes skill and practice. NOAA assigns survey sheets which are sections of water with hundreds of lines that have earned priority to be charted on a particular leg of a journey. It is imperative that the watch standers on the bridge keep the ship on its planned survey lines to ensure that the entire ocean floor in a specific sheet is covered. If you follow the path of the TJ on NOAA’s shiptracker, you might be able to zoom in to see the TJ going back and forth along these lines that are spaced exactly 120m apart. The 120m lines are carefully determined based on the fact that the SSS can measure 75m in either direction. Due to the nature of acoustic imaging, the farther a sound wave travels, the worse its accuracy will become. Therefore, a 30 m overlap of the SSS data occurs with 120m line spacing and the farthest distances will be able to be analyzed twice. If you remember, the MBES sends out a swath or cone of sound waves, so it will never be able to reach the farthest parts of the lines without being in extremely deep water. If the SSS picks up irregularities towards the edges of the data, the entire ship will have to break course to sweep back over the area in order to collect MBES data on that point.
The side scan sonar is doing its job showing us the sand patterns on the ocean floor. The black in the center of the image is the water column directly underneath the ship which cannot be imaged by the SSS.
Today was the first time that I really had the opportunity to see what this ship is all about, and I look forward to seeing what kinds of objects can be detected on the sea floor.
Personal Log
Yesterday, our kayak adventure around Lewes gave me the opportunity to chat with a lot more people about their backgrounds and roles on the ship. Although everyone is very welcoming, this is certainly a very busy vessel and I appreciated the time to talk with people when I knew I was not interrupting their work. I was buddied up with Eileen, a junior officer, and Steve, the second engineer. Eileen is the newest NOAA Corps Officer on board the TJ, and is in training for many different certifications. She and Charles, another junior officer, need to earn hours towards their FRB certification and spent some time driving the FRB on the ride back from kayaking to the ship. It is jet propelled and extremely responsive and maneuverable. I was able to drive it for a few minutes on my first day, and that thing can really move!
Today’s delicious menu selection
The mess area is still a very exciting area of the ship for me. Normally, I avoid the high school cafeteria but I just can’t get enough on the ship! It probably helps that I am only on the ship for a short amount of time, but so far I have been enjoying all of the food. The chef posts a menu every day, and meals are served at 7:00am, 11:30am, and 4:30pm. Outside of those hours, there is still food available in the form of a salad bar, ice cream bar, cold and hot drinks, cereal, and probably other things I have not yet discovered. All of these options are certainly a necessity because there is no take out or delivery in the middle of the Delaware Bay.
Did You Know?
The anchor of the Thomas Jefferson weighs 3500 pounds. To clean off the mud from a dirty anchor, the ship will drag the anchor at surface level and let the running water of the sea do the cleaning.
The anchor has been dragging in the water for several minutes. You can see that one side still has the mud caked on it from the ocean floor.I am in my safety gear as the crew begins to lift the anchor chain located behind me.
(at Frederick Sound in Keku Strait off Kake, Alaska)
Mission: Hydrographic survey
Geographical area of cruise: Southeast Alaska, including Chatham Strait and Behm Canal, with a Gulf of Alaska transit westward to Kodiak
Log date: June 22, 2013
Weather conditions: 14.08⁰C, overcast skies with increasing cloud coverage, 92.82% relative humidity, 1014.29 mb of atmospheric pressure, light variable winds (speed of less than 3.5 knots with a heading between 10⁰ and 19⁰)
This large cruise ship is one of many seagoing vessels ships in Southeastern Alaska that rely on NOAA-produced nautical charts for safe navigation.
Explorer’s Log: Long days on the trail
Thick fog had settled on Chatham Strait, where the launches would be surveying for the day, as seen from the ship’s anchored location in Bay of Pillars.
When we think about explorers, we usually focus on the “big moments” – the crescendos of excitement that build as the storytellers regale us with tales of daring escapes from danger, amazing sights visible only from the summit, or exotic flavors tasted upon the foreign shore. But life-long explorers know that those moments are far outnumbered by the sometimes seemingly endless minutes or hours, days or weeks, maybe even months or years of simply walking the path, step after step after step, watching the slow passing of tree after tree after tree.
Those less thrilling hours rarely are described in the grand adventure stories, but in those countless footfalls lie many of the greatest parts of exploration, for it is only in those moments that the explorer has time to ponder.
Smooth water and thick fog are common conditions in the navigable waterways of Southeast Alaska, underscoring the importance of good nautical charts.
In 1905 a very bright young man in his mid-twenties worked for a few years as a clerk in the patent office in Bern, Switzerland. Although the post gave him access to interesting new inventions and processes being developed in electronics, thermodynamics, mechanics, and communications, his job often required him to grind through the daily routine of receiving, reviewing, and filing thousands upon thousands of technical and administrative documents, tasks which his brilliant mind could achieve without much effort. Not too exciting, perhaps. But it is only in that easy comfort of performing the same routine behaviors minute after minute that the young clerk found the quiet sanctuary to evaluate and synthesize a miasma of strange ideas and eventually synthesize them into five papers about matter, time, energy, space, and motion that would revolutionize the field of physics.
Indeed, not every person is Albert Einstein, but all explorers sometimes find themselves in that “cruise control” mode, where the body knows the routine mechanics to perform, and so the mind can invest in a different sort of exploration. Inward.
Small cruise ships can navigate deep into scenic waterways, like Bay of Pillars along Chatham Strait.Teacher At Sea Rob Ulmer uses the winch aboard launch vessel RA-6 to cast the CTD device, which gathers data about conductivity, temperature, and depth of the water in the column from the surface to the sea floor.
A gardener mowing back and forth across the lawn, a painter applying the brush line after overlapping line to cover the wall, and a swimmer pulling stroke after stroke to swim his half-mile of warm-up laps all gain skill with their craft over hours or miles or practice, and so their minds can be freed to wander a bit, perhaps contemplating more deeply the patterns in the passing clouds, maybe solving a puzzle that has been teasing at the edge of consciousness, or maybe considering how a hedge of heather might look if planted in a certain area of the landscape. Or – just as meaningfully – maybe the explorer in those moments revisits something far more personal or spiritual or metaphysical, some conundrum or quandary or dilemma, whether recent or from long ago, in a way that is available only because of the serenity of the repetition. Sometimes such musings simply aren’t accessible when the mind is occupied with more accelerated or more cumbersome activity.
This winch mechanism can lower the CTD device (the tube to the left) through many fathoms of water.AB Jeff Mays casting the “fish” with the MVP
And as the explorer’s mastery of basic skills evolves from novice toward more expert levels, his place on the learning curve changes, as well. The learning curve where the novice stands is steep, as every bit of investment offers the possibility of relatively fast and tremendous growth, while the marginal returns for the wise and skilled explorer of the craft come subtly from patient observation and insight. For the rookie woodworker, for example, every spin of the lathe is an iteration of powerful change to be controlled and investigated and marveled at, but the more advanced craftsman who has milled thousands of dowels in his journey toward expertise in his craft has room during the lathe-work to possibly discover some small nuance about cutting bevels or reading grains that would be lost even if offered to the rookie in his excited novitiate mindset.
AB Tony Nielsen operates the Moving Vessel Profile (MVP) to cast and recover the “fish” as Rainier conducts a multi-beam survey of the sea floor in Chatham Strait.
The “fish” in the water
Some of my own moments of greatest inspiration have arrived when my friend Rien and I have been wordlessly walking the autumnally brisk trails of the North Georgia mountains. No longer burdened with the previously-taxing questions of how to deal with unstable rocks at my feet or what gait to use on a certain downhill slope, in those miles of simply continuing to walk forward my cleared mind has unfolded complete verses of poetry, bits of insight about soccer or macroeconomics or how to differently arrange the gear in my backpack, even exact phrasings for whole lessons or assessments to be used in my classroom. Those thoughts simply couldn’t have reached such clarity in the exciting exhaustion of the first morning’s climb up Amicalola Falls.
Survey/Launch team meeting on the fantail
Yesterday morning, after Field Operations Officer Mike Gonsalves finished the usual pre-launch meeting on the fantail and dismissed the crews to their boats (with my shift remaining aboard the ship to learn some data processing skills), I began one of my most common activities aboard Rainier, taking photographs of the scene. Pictures of the FOO and the Chief Boatswain coordinating launch activities, pictures of the rest of the crew at work, pictures of the ship herself, pictures of the waters and land features surrounding the ship… all very routine.
This is the view forward across the bow of NOAA Ship Rainier as a launch vessel departs to survey the sea floor of Chatham Strait.Isn’t it difficult to notsee the fog above the rock island now that you’re looking for it?
But then it happened. I noticed in the distance beyond the bow of the ship a slight something. Something different than usual. A small hemispherical island – a rock, really – extending ten feet or so above the waterline, protruding through the fog that hovered ethereally a few feet above the water in every direction. But it was the fog that caught my eye. The fog didn’t just surround the rock; it blanketed the rock at not quite exactly the same elevation that it otherwise maintained above the nearby sheet of flat, still water. And in the quiet comfort of my rote and repeated clicking of the shutter, I had an epiphany, a sudden symphonic upwelling of clarity about pressure and temperature and fluid dynamics and light that simply could not have happened if my thoughts had been cluttered with hasty necessities of rapid activity.
FOO Mike Gonsalves and HAST Curran discuss survey data in the plot room.
Like most insights, I’m not sure if or when that particular bit of understanding will ever matter again in my future, but at the moment it was pure and good in its value to the core of my inner explorer: I saw something that I had not seen before.
Some very exciting information during multi-beam surveying aboard the launch vessel surprises TAS Rob Ulmer and HAST Curran.A whole day of surveying aboard the launch vessel can become a long venture in close quarters!
So where does this soliloquy about walking the long and quiet path fit with my experiences aboard NOAA Ship Rainier? For the past several days and for the next several coming days, two or three small, crewed launch vessels per day (and often the ship herself) are painting overlapping swaths of sonar across the sea floor in Chatham Strait. Back, forth, back, forth….
Imagine mowing an enormous lawn miles long at a slow walking pace with a lawnmower that needs constant adjustment and calibration every time you pass a tree or shrub, all the while keeping data about the thickness of the grass, the color of the soil beneath, the amount of dew on the blades, and the exact rotational velocity of the motor. And this lawn is not just enormous by usual standards, either. It’s miles long, miles wide. Rain, snow, wind, uneven ground, you just keep mowing. And when you get finished for the day, not only do you know that you have dozens of days left before you finish mowing this lawn as it continues over the horizon, but you also discover as you look back out with your special viewing machinery at home that there are a few spots that you missed on the first pass and must clean up tomorrow before you can move forward, maybe because the mower blade malfunctioned, or maybe because the ground underneath was slightly tilted as you passed above it. But you keep mowing, both because you want the job done, but also because you love the work and take great pride in your work product.
The boys finally reach a resolution in their debate about survey data.
Replace it with painting a giant wall, and the analogy to multi-beam sea floor hydrographic surveying still is nearly perfect.
Oh, and don’t forget that you have a partner at home who will spend hours analyzing every bag of grass clippings, sorting and organizing and then weaving every single blade of grass into a beautiful and varied quilt of fabric that she makes from the piece that you bring her after painstakingly separating out random bugs and sticks leaves from trees and shrubs that look like grass but aren’t…. Whew! This partner (following the analogy) is a member of the post-launch evening processing crew, by the way, who begins work as soon as the launch vessels return and doesn’t finish until hundreds of lines of data have been uploaded, converted into other numerical and graphical forms, and then “cleaned” for initial post-survey analysis aboard ship before being more thoroughly analyzed for months or years at NOAA shore-side labs and offices before ultimately evolving into published nautical charts or other useful end-products.
Launch vessel RA-4 “paints” the huge floor of Chatham Strait one slow swath at a time.Aboard launch vessel RA-6, we passed this fishing boat several times while surveying a “polygon” of Chatham Strait.
Day after day, mile after mile, the NOAA survey teams explore the seas, quietly walking their own trail so that other explorers can more safely navigate their treks, as well. And every once in an inspired while, the hydrographer can be heard uttering a gleeful, “Aha!” about some insight discovered along the way.
Keep walking, my friends, even when the trail is long. Sometimes it is there that you will do your best exploring.
Another pass of the same fishing boat. A long day for both crews, perhaps, but at least the magnificent scenery leaves plenty of room for pondering.
Geographical area of cruise: Southeast Alaska, including Chatham Strait and Behm Canal, with a Gulf of Alaska transit westward to Kodiak
Log date: June 19, 2013
Weather conditions: 10.93⁰C, less than 0.5 km visibility in thick fog, 95.42% relative humidity, 1013.38 mb of atmospheric pressure, light variable winds (speed of less than 3 knots with a heading between 24⁰ and 35⁰)
Explorer’s Log: Survey, sample, and tide parties
Scientists are explorers, wandering the wilderness of wonder and curiosity their with eyes and minds wide open to events, ideas, and explanations that no other humans may have previously experienced. And by definition, explorers — including scientists — also are builders, as they construct novel paths of adventure along their journeys, built always upon the strong foundations of their own reliable cognitions and skill sets.
Ensign Rosemary Abbitt making a level sighting measurement
Starting from their own observations of the world around them, prior knowledge, and context, scientists inject creativity and insight to develop hypotheses about how and why things happen. Testing those ideas involves developing a plan and then gathering relevant data (pieces of information) so that they can move down the path of whittling away explanations that aren’t empirically supported by the data and adding to the collective body of knowledge, so that they and others might better fathom the likely explanations that are behind the phenomena in question.
NOAA Ship Rainier lowers launch vessel RA-5 for a survey excursion.
Because progress along the scientific path of discovery and explanation ultimately depends on the data, those data must be both accurate and precise. Often these terms are confused in regular conversation, but each word has its own definition.
A view from the skiff of the shoreline where the benchmarks and tide gauge staff already are installed.
Accuracy is a description of the degree of closeness or proximity of measurements of a quantity to the actual value of that quantity. A soccer player who shoots on goal several times and has most of his shots reach the inside of the net is an accurate shooter. Likewise, a set of measurements of the density of a large volume of seawater is more accurate if the sample data all are near the actual density of that seawater; a measurement that is 0.4% higher than the actual density of the water is just as accurate as another measurement of the same water that is 0.4% below the actual density value.
Before making more detailed data collections, Hydrographic Assistant Survey Technician (HAST) Curran first conducts a visual inspection of the previously-installed tide staff upon arriving at the shore.
Precision (also called reproducibility or repeatability), on the other hand, is the degree to which repeated measurements under unchanged conditions show the same results. If every shot attempted by the soccer player strikes the left goalpost four feet above the ground, those shots aren’t necessarily accurate – assuming that the player wants to score goals – but they are very precise. So, similarly, a set of measurements of seawater density that repeatedly is 5.3% above the actual density of the water is precise (though not particularly accurate).
HAST Curran collects data near the tide staff during the closing level run in Behm Canal.
The NOAA teams that conduct hydrographic surveys, collect seafloor samples, and gather data about tide conditions must be both accurate and precise because the culmination of their work collecting data in the field is the production of nautical charts and tide reports that will be used around the world for commerce, recreation, travel, fisheries management, environmental conservation, and countless other purposes.
Crew of the survey/sample team in the cabin of the launch vessel (and the Coxswain piloting the boat)
Hydrographic surveys of some sort have been conducted for centuries. Ancient Egyptian hieroglyphs show men aboard boats using ropes or poles to fathom the depths of the water. In 1807, President Thomas Jefferson signed a mandate establishing the Survey of the Coast. Since that time, government-based agencies (now NOAA’s Office of Coast Survey) have employed various systems of surveying depths, dangers, and seabed descriptions along the 95,000 miles of navigable U.S. coastlines, which regularly change due to attrition, deposition, glaciation, tectonic shifts, and other outside forces.
Hydrographic Senior Survey Technician Barry Jackson and Physical Scientist Kurt Brown analyze historic and new data from multi-beam sonar aboard the launch vessel.
For most of that history, data were collected through a systematic dropping of weighted lines (called “lead lines”) from boats moving back and forth across navigable channels at points along an imaginary grid, with calibration from at least two shore points to assure location of the boat. Beyond the geometry, algebra, and other mathematics of measurement and triangulation, the work was painstakingly slow, as ropes had to be lowered, hauled, and measured at every point, and the men ashore often traveled alongside the boat by foot across difficult and dangerous terrain. However, the charts made by those early surveys were rather accurate for most purposes.
Starboard of launch vessel RA-4
The biggest problem with the early charts, though, was that no measurements were made between the grid points, and the seafloor is not always a smooth surface. Uncharted rocks, reefs, or rises on the seabed could be disastrous if ships passed above them.
HSST Barry Jackson pulls a line hand over hand to retrieve a scooped sea floor sample from a depth of more than 45 meters in Behm Canal.… and then analyzes what the scoop captured: mud and gravel in this case.
Starting in the 1990s, single-beam sonar became the primary mechanism for NOAA’s surveys. Still looking straight down, single-beam sonar on large ships and on their small “launch vessels” (for areas that couldn’t be accessed safely by larger craft) provided a much more complete mapping of the seafloor than the ropes used previously. Sonar systems constantly (many times per second) ping while traveling back and forth across and along a channel, using the speed and angle of reflection of the emitted sound waves to locate and measure the depth of bottom features.
Data about sea floor samples first are recorded by hand on a chart aboard the launch vessel before being uploaded to NOAA computers later.
Sound waves travel at different speeds through different materials, based on the temperature, density, and elasticity of each medium. Therefore, NOAA also deploys CTD devices through columns of surveyed waterways to measure electrical conductivity (which indicates salinity because of ionization of salts dissolved in the water, thus affecting solution density), temperature (which usually is colder at greater depths, but not necessarily, especially considering runoff from glaciers, etc.), and depth (which generally has a positive-variation relationship with water pressure, meaning more pressure – and thus, greater density – as depth below the surface increases).
This CTD device measures conductivity, temperature, and depth in the water. All three affect the speed of the sound waves in water, and the speed of sound is a necessary bit of data when using sonar (which tracks reflected pings of sound) to determine the distance to the sea floor.
The most modern technology employed by NOAA in its hydrographic surveys uses multi-beam sonar to give even more complete coverage of the seafloor by sending sound waves straight downward and fanned outward in both directions as the boat travels slowly forward. Even though sonar beams sent at angles don’t reflect as much or as directly as those sent straight downward, uneven surfaces on the seabed do reflect some wave energy, thus reducing the occurrence of “holidays” (small areas not well-defined on charts, perhaps named after unpainted bits of canvas in portraits because the painter seemed to have “taken a holiday” from painting there).
FOO Mike Gonsalves and HAST Allix Slagle acquire hydrographic data with the ship’s Kongsberg EM-710 multi-beam sonar.Aboard the small launch vessel, everyone works. This is Teacher At Sea Rob Ulmer hauling in a sea floor sample in Behm Canal.
But that’s not all. To help sailors make decisions about navigation and anchoring – and often giving fishermen and marine biologists useful information about ecology under the waterline – NOAA also performs systematic samples of the types of materials on the sea floor at representative points in the waterways where it conducts surveys. Dropping heavy metallic scoop devices on lines* dozens of meters long through waters at various locations and then hauling them back aboard by winch or hand-over-hand to inspect the mud, sand, silt, gravel, rocks, shells, plants, or animals can be physically demanding labor but is necessary for the gathering of empirical data.
* A note about terminology from XO Holly Jablonski: Aboard the ship, lines have a job. Think of a “rope” as an unemployed line.
Additionally, Earth’s moon and sun (along with several underground factors) affect the horizontal and vertical movement of water on Earth’s surface, especially due to their gravitational pulls as Earth spins on its axis and orbits the sun and as the moon orbits Earth. Therefore, information about tides is extremely important to understanding the geography of nautical navigation, as the points below the waterline are identified on charts relative to the mean low water mark (so sailors know the least amount of clearance they might have beneath their vessels), and points above the waterline are identified relative to the mean high water mark (including notation of whether those object sometimes are fully submerged).
Can you see the evidence of tidal changes along the shoreline of Behm Canal? Color differences form strata along the rocks, and lowest leaves of the trees give further evidence of the highest reach of the water.Ensign Damian Manda manually levels the sighting rod upon the “turtle” using a carpenter’s bubble-leveling device.
To gather accurate and precise data about tidal influences on local waters, NOAA sends tides-leveling shore parties and dive teams into difficult conditions – commonly climbing up, down, and across rock faces, traversing dense vegetation, and encountering local wildlife (including grizzly bears here in Alaska!) – to drill benchmarks into near-shore foundation rocks, install (and later remove) tidal gauges that measure changing water heights and pressures, and use sophisticated mathematics and mechanics to verify the levels of those devices.
Ensign Rosemary Abbitt and HST Brandy Geiger ponder the placement of equipment before the next level measurement.
Needless to say, this description is significantly less detailed than the impressively intricate work performed at every level by NOAA’s hydrographic scientists, and in the end, all of the collected data described in the paragraphs above – and more, like the velocity of the sonar-deploying vessel – must be analyzed, discussed, and interpreted by teams of scientists with broad and deep skills before the final nautical charts are published for use by the public.
A leveling rod is balanced on the highest point of a “turtle,” positioned carefully to be seen from multiple points.
As you choose where and how to proceed in your own journeys, remember that you can be more confident about your decision-making by using information that is both accurate and precise. And keep exploring, my friends.
This is the view from the benchmark atop a rocky outcropping (under an 80-foot evergreen) along Behm Canal while righting a measurement rod with the tide gauge leveling party.
Did You Know?
NOAA Ship Rainier in Behm Canal with launch vessels underway
Every ship in the NOAA fleet also is a voluntary mobile weather station, and so are many other seagoing vessels around the world. For many years ships have been required to report their locations and identities on a regular basis to agencies like the U.S. Coast Guard and local or regional harbormasters. Those periodic reports were (and still are) vital for local traffic control on the waters and for helping to provide quick response to emergency situations on vessels at sea.
The view aft through Behm Canal from the launch vessel
Eventually, someone insightful realized that having the ships also provide weather reports from their positions along with those identity-and-location reports would make a much richer and broader network of timely data for the National Weather Service, which is another branch of the National Oceanic and Atmospheric Administration. As NWS adds the weather data from those many boats to the data gathered at land-based NWS stations and from voluntary land-based reporters of conditions, their models and forecasts become stronger.
(For more info about being a volunteer weather observer or volunteering with NOAA in some other capacity related to oceans, fisheries, or research, please visit www.volunteer.noaa.gov.)
Especially because weather conditions are the results of interactions among local phenomena, regional climate, and the global systems, building more accurate and precise forecast models depends on information from everywhere, but the result is that everyone benefits from the better forecasts, too.
Southeast Alaska is area with frequent tectonic activity, including uplift and earthquakes. Here a scar among the trees on the mountainside shows evidence of tectonic shifts, which also creates a ready path for meltwater to move downhill from the snowy mountaintop to the seawater below, taking trees and soil with it.NOAA Ship Rainier waits offshore, ready to receive the skiff returning with the tide/level shore party.
NOAA Teacher at Sea Yaara Crane Aboard NOAA Ship Thomas Jefferson June 22, 2013 – July 3, 2013
Mission: Hydrographic Survey Geographical area of cruise: Mid-Atlantic Date: Saturday, June 22, 2013
Latitude: 38.81°N Longitude: 75.10°W
Weather Data from Bridge:
Wind Speed: 10.27 knots
Surface Water Temperature: 20.59°C
Air Temperature: 20.60°C
Relative Humidity: 79.00%
Barometric Pressure: 1023.18mb
Science and Technology Log
My first view of the NOAA ship Thomas Jefferson.
This morning I came aboard the Thomas Jefferson via small boat transfer from the pilot station dock in Lewes, Delaware. Since coming on board, I have been welcomed by so many people, toured the ship, had a safety training, cautiously drove the small boat around the Delaware Bay, and tried to learn some background about hydrographic surveys. That is quite a lot of new things to process in only 5 hours!
The major purpose of hydrography is to create a thorough imaging of the ocean floor, particularly to warn mariners of any obstructions or shallows. There is evidence that nautical charts showing depth have been in use since as early as the sixth century BCE, and can easily be created through the use of a lead weight and a string. These days, NOAA ships have much more high tech ways of surveying the ocean floor. The Thomas Jefferson spends most of its time at sea charting waterways and coastlines to ensure safe travels for both private and commercial mariners to be able to navigate safely. Priorities in a nautical charting mission are based on factors including: waterway usage rates, stakeholder requests, rates of change to the sea floor (both natural and anthropogenic), and age of the chart’s source. For example, a waterway to a port used by oil tankers would be very important to survey because the result of a tanker running headlong into an obstruction would be disastrous. After Hurricane Sandy hit the East Coast in October 2012, the Thomas Jefferson was assigned to survey the sea floor of New York City’s harbor in case of any new obstructions that might have been blown in undetected. No other ship was allowed to sail through the harbor until the Coast Guard received the new charts. So far this summer, the Thomas Jefferson has already spent countless hours surveying the area around Long Island Sound and the Delaware Bay.
To have a better grasp of the major scientific research that occurs on a hydrographic research vessel, I spent a portion of the afternoon speaking with Ensign Andrew Clos. Ensign Clos mentioned that the two most important tools for data collection are the side scan sonar (SSS) and the multi-beam echo sounder (MBES). These two tools work through the use of sound waves to collect both 2D and 3D data. The SSS and the MBES send sound waves which are reflected back to the ship and transformed into images analyzed by the scientists on board. The side scan sonar is towed by the ship in very carefully spaced horizontal lines to gather the initial data about the existence of any objects in the water. An acoustic image is created and analyzed for anything out of the ordinary, in which case the MBES is launched for further investigation. The MBES is hull-mounted to the ship and survey launches, and lets out sound waves in a 128° cone which much more accurately determines the depth and position of the object. The MBES can collect millions of data points in a day, which is converted into three-dimensional images.
This SSS image is of the wreck of the Herbert D. Maxwell. The white area to the upper right is called a shadow because the sonar cannot pass into that area. (Photo courtesy of NOAA)This MBES image shows a fuller picture of the wreck of the Herbert D. Maxwell. (Photo courtesy of NOAA)
The scientists aboard spend many hours sifting through the data, and correcting the data for differences in depth based on tidal flows and water data. Sound waves travel through water at approximately 1500 meters/second (m/s), much faster than the 340 m/s in air. However, differences in salinity and temperature can impact the accuracy of measurements. All of the branches of NOAA must work together to piece together the puzzle of the ocean floor.
Personal Log
Hanging out at the beach the day before getting aboard the TJ.
This has been quite a busy week for me, which has culminated in this spectacular adventure. Monday was our last day of final exams, and today I feel like that was a lifetime ago! I spent most of yesterday morning driving to Delaware, and was rewarded with spending the afternoon relaxing on Rehoboth Beach. As it turns out, relaxing is on the table for tomorrow, too. The TJ is waiting on a repair to the MBES, and will need to stay anchored close to port for at least one more day. Commander Krepp has allowed some of the members of the crew to arrange for a day out paddling and kayaking around the beach. Still, there is work to be done and safety to consider aboard a NOAA vessel, so even that excursion has to be carefully managed into two shifts.
Weather-wise, it has been a beautiful weekend. There is a slight breeze, but not enough to make waves worth mentioning. The TJ is also anchored just behind a breakwater which helps to keep waves at bay. All of this adds up to a very calm shipboard experience, with barely any feeling of rocking or swaying while aboard the ship. I have rarely suffered from motion sickness and hope to continue my good record throughout this cruise. No seasickness means I can make my way over to the ice cream bar for a little afternoon snack…
Did You Know?
Fossil remains of horseshoe crabs have been found spanning approximately the last 450 million years. They are called living fossils because they are some of the rare species that have survived extinction with little genetic diversity.
The horseshoe crab is a living fossil found on Delaware’s shores.
