Tag: teacher at sea

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Denise Harrington: Post Processing — Final Days, May 2, 2014

NOAA Teacher at Sea
Denise Harrington
Aboard NOAA Ship Rainier
April 20 – May 3, 2014

Geographical Area of Cruise: North Kodiak Island

Date: May 2, 2014, 23:18

Location: 57o  43.041’ N  127o 152.32.388’ W

Weather from the Bridge: 13.09o C (dry bulb), Wind 1 knots @ 95o, clear, 0′ swell, balmy “crazy nice weather”  say Able Seaman Jeff Mays

Our current location and weather can also be seen at NOAA Shiptracker: http://shiptracker.noaa.gov/Home/Map

Science and Technology Log

Today’s blog is all about post processing, or “cleaning up” the data and being on night shift.  It is a balmy, sliver moon night at port here, in Kodiak.  We have come a long way in the last two weeks, during which survey crews have been working hard to finalize a Cold Bay report from last season before they devote themselves entirely to North Kodiak Island. I am in the plot room with Lieutenant Junior Grade Dan Smith who is on Bridge Duty from midnight until 4 a.m. with Anthony Wright, Able Seaman.

Able Seaman Anthony Wright consults with Ensign Steven Wall about conditions on the bridge and other things.
Able Seaman Anthony Wright consults with Ensign Steven Wall about conditions on the bridge and reports “all conditions normal.”

People work around the clock on Rainier whether it be bridge watch, processing data, or in the engine room.  One thing that makes the night shift a little easier is that there is no shortage of daylight hours in Alaska: within two months, there will be less than an hour of complete darkness at night.

After watching Commander Brennan guide us north, and seeing all the work it entails, it is a great sight to see him enjoy a 10 p.m. sunset.
After watching Commander Brennan guide us north, with all the work it entails, it is a great sight to see him enjoy a 10 p.m. sunset with his wife (by phone).

In previous blogs, I described how the team plans a survey, collects and processes data.  In this blog, I will explain what we do with the data once it has been processed in the field. Tonight, Lieutenant Dan Smith is reviewing data collected in Sheet 5, of the Cold Bay region on the South Alaskan Peninsula.  In September, 2013, the team surveyed this large, shallow and therefore difficult to survey area.  The weather also made surveying difficult.  Despite the challenges, the team finished collecting data for Sheet 5 and are now processing all the data they collected.

Cold Bay Sheet Map
Cold Bay Sheet Map.  Recall the shallow areas are shaded light blue, and as you can see much of the north end of Sheet 5 is blue.

While I find editing to be one of the most challenging steps in the writing process, it is also the most rewarding.  Through the editing process, particularly if you have a team, work becomes polished, reliable and usable.  The Rainier crew reviews their work for accuracy as a team and while Sheet 5 belongs to Brandy Geiger, every crew member has played a part in making the Sheet 5 Final Report a reality, almost.  On the left screen, Lieutenant Smith is looking at one line of data.  Each color represents a boat, and each dot represents the data from one boat, and each dot represents a depth measurement  computed by the sonar. The right screen shows which areas of the map he has already reviewed in green and the areas he still needs to review in magenta.

Dan looks for noise after midnight.
Lieutenant Smith looks for noise after midnight.

While the plot room is calm today in Kodiak, there have been times when work conditions are challenging, at best.

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The crew continues on, despite the weather, so long as work conditions are safe.

Several days ago, Lieutenant Smith taught me the difference between a sonar ping that truly measured depth, and other dots that were not true representations of the ocean floor.  Once you get an eye for it, you kill the noise quickly.  In addition, when Lieutenant Smith finds a notable rise in the ocean floor he will “designate as a sounding.”  Soundings are those black numbers on a nautical chart that tell you how deep the water is.

This line shows three colors, meaning three boats sent pings down to the ocean floor in this area.
This line shows three colors, meaning three boats sent pings down to the ocean floor in this area.

If the line has dots that rise up in a natural way, the computer program recognizes that these pings didn’t go as far down as the others and makes a rise in the ocean floor indicated with the blue line.  It is the hydrographer’s job to review the computer processed data.  One of the differences between a map and a nautical chart is the high level of precision and review to ensure that a nautical chart is accurate.

This nautical chart went through many layers of analysis, processing and review before becoming published as a nautical chart that can be used as a legal document.
This nautical chart of Cold Bay went through many layers of analysis, processing and review before becoming published as a nautical chart that can be used as a legal document. It may be updated after Brandy Geiger and NOAA’s hydrography work in the area is completed.
This is a topographical map of the same area, Cold Bay, that provides some information about landmarks but not necessarily the same legal standing or authority.
This is a topographical map of the same area, Cold Bay, that provides some information about landmarks but not necessarily the same legal standing or authority.

NOAA has several interesting online resources with more information about the differences between charts and maps: http://oceanservice.noaa.gov/facts/chart_map.html .

Now let’s kill some noise on this calm May evening.

In this image of a shipwreck on the ocean floor most sonar pings reached the ocean floor or the shipwreck and bounced soundings back to the survey boat.  Look carefully, however, and you see white dots, representing pings that did not make it down to the ocean floor.  Many things can cause these false soundings.  In this case, I predict that the pings bounced back off of a school of fish.  Here, the surveyor kills the “noise” or white pings by circling them with the mouse on his computer. It wouldn’t be natural for the ocean floor or other feature to float unconnected to the ocean floor, and thus, we know those dots are “noise” and not measurements of the ocean floor.

Lieutenant Smith estimates that at least half of his survey time is spent in the plot room planning or processing data.  The window of time the team has in the field to collect data is limited by weather and other conditions, so they must work fast.  Afterward, they spend long, but rewarding hours analyzing the data they have collected to ensure its accuracy and to provide synthesized information to put into a nautical chart that is easy to use and dependable. Lieutenant Smith believes that in many scientific careers, as much time or more time is spent planning, processing and analyzing data than is spent collecting data.

 

Personal Log

As we post process our data, I too, begin post processing this amazing adventure.  I am hesitant to leave: I have learned so much in these two short weeks, I want to stay and keep learning.  But at NOAA we all have many duties, and my collateral, wait–my primary duty is to my students and so, I must return to the classroom.  I will leave many fond memories and a camera, floating somewhere in Driver Bay, behind me.  I will take with me all that I have learned about the complexity of the ocean planet we live on and share my thirst to know more back to the classroom where we can continue our work. I will miss the places I’ve seen and the people I met but look forward to the road or channel of discovery that awaits me and my students.

I am also taking with me a NOAA flag, full of memories from the North Kodiak Island crew and my new friends.
I am also taking with me a NOAA souvenir flag, full of memories from the North Kodiak Island crew — my new friends.

Did You Know? The Sunflower Sea Star is the largest and fastest moving sea star travelling up to one meter per minute.

Here we taking a quick break during a tide gauge set up to look at sea stars and anemones.
Here we taking a quick break during a tide gauge set up to look at sea stars and anemones.

Below are a few photo favorites of my time at sea.

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Kimberly Gogan: The Sounds of the Sea: Marine Acoustics: April 20, 2014

NOAA Teacher at Sea
Kim Gogan
Aboard NOAA Ship Gordon Gunter
 April 7 – May 1, 2014

Mission: AMAPPS & Turtle Abundance Survey, Ecosystem Monitoring
Geographical area of cruise:  North Atlantic Ocean
Date: Sunday, April 20th – Easter Sunday!

Weather Data from the Bridge
Air Temp: 6.2 Degrees Celsius
Wind Speed: 33.5 Knots
Water Temp: 10.1 Degrees Celsius
Water Depth: 2005.4 Meters ( deep!)

Genevieve letting me listen to the sounds of a Pilot Whale and explaining how the acoustics technology works.
Genevieve letting me listen to the sounds of a Pilot Whale and explaining how the acoustics technology works.

Science and Technology Log

As I explained in an earlier blog, all the scientist on the ship are here because of the Atlantic Marine Assessment Program for Protected Species, or AMAPPS for short. A multi-year project that has a large number of scientists from a variety of organizations whose main goal is “to document the relationship between the distribution and abundance of cetaceans, sea turtles and sea birds with the study area relative to their physical and biological environment.” So far I have shared with you some of the Oceanography and Marine Mammal Observing. Today I am going introduce you to our Marine Mammal Passive Acoustics team and some of their cool acoustic science. The two acoustic missions of the team are putting out 10 bottom mounted recorders called MARUs or Marine Autonomous Recording Units  and towing  behind the ship multiple underwater microphones called a Hydrophone Array to listen to the animals that are as much as 5 miles  away from the ship. The two different recording devices target two different main groups of whales. The MARU records low frequency sounds from a group of whales called Mysticetes or baleen whales: for example, Right Whales, and Humpback Whales. Once the the MARU has been programmed and deployed, it will stay out on the bottom of the ocean collecting sounds continuously for up to six months before the scientist will go retrieve the unit and get the data back.  The towed Hydrophone Array is recording higher frequency sounds made by Odontocetes or toothed whales like dolphins and sperm whales. The acoustic team listens to recordings and compares them with the visual teams sighting, with a goal of getting additional information about what kind and how many of the species are close to ship. Even though the acoustic team works while the visual team is working during the day, as long as there is deep enough water, they can also use their equipment in poor weather and at night.

Here are Chris and Genevieve preparing to deploy the MARU.
Here are Chris and Genevieve preparing to deploy the MARU.

Science Spot Light: The two Acoustic team members we have on the Gordon Gunter are Genevieve Davis and Chris Tremblay. Genevieve works at Northeast Fisheries Science Center (NEFSC)  doing Passive Acoustic research focusing on Baleen Whales. She has worked there 2 and a half years after spending  10 weeks as a NOAA Hollings Intern. Genevieve graduated from Binghamton University in New York. She is planning on starting her masters project looking at the North Atlantic Right Whale migration paths.  I have been been very lucky to have Genevieve as my roommate here on the ship and have gotten to know her very well. Chris is a freelance Marine Biologist. Chris recently helped develop the Listen for Whales Website and the Right Whale Listening Network. He also worked for Cornell University for 7 years focusing on Marine Bioacoustics. Chris is also the station manger at Mount Desert Rock Marine Research Station run by the College of the Atlantic in Maine. He actually lives on a sail boat he keeps in Belfast, Maine. Chris also intends of attending graduate school looking at Fin Whale behavior and acoustic activity.

Personal Log

So while most adults were worrying about their taxes on April 15th, I was having fun decorating and deploying Drifter Buoys. Before I left for my trip Jerry Prezioso had sent me an email letting me know that two Drifter Buoys would be available for me to send out to sea during my time on the ship.  Drifter buoys allow scientists to collect observations on earth’s various ocean currents while also collecting data on sea surface temperature, atmospheric pressure, as well as winds and salinity. The scientists use this to help them with short term climate predictions, as well as climate research and monitoring. He explained that traditionally when teachers deploy the buoys, they will decorate them with items they bring from home and that we would be able to track where they go and the data they collect for 400 days! The day before I left, I had my students and my daughter’s class decorate a box of sticky labels for me to stick all over the two Drifter Buoys. I spent the morning of the 15th making a mess on the lab floor peeling and sticking all of the decorations onto each of the buoys. Around mid-day we were at our most south eastern point, which would be the best place to send the buoys out to sea.  Jerry and I worked together to throw the buoys off the side of the ship, as close together as we could get them. A few days later we heard from some folks at NOAA that the buoys were turned on and floating in the direction we wanted them too.

If you would like to track the buoys I deployed, visit the site below and follow the preceding directions.

<http://www.aoml.noaa.gov/phod/trinanes/xbt.html> for near real time GTS data.

From the site, select “GTS buoys” in the pull-down menu at the top left. Enter the WMO number (please see below) into the “Call Sign” box at the top right. Then, select your desired latitude and longitude values, or use the map below to zoom into the area of interest. You can also select the dates of interest and determine whether you’d like graphics (map) or data at the bottom right. Once you’ve entered these fields, hit the “GO!” button at the bottom. Shortly thereafter, either a map of drifter tracks or data will appear.
ID            WMO#
123286    44558
123287    44559
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Suzanne Acord: Cetaceans Are Among Us! March 26, 2014

NOAA Teacher at Sea
Suzanne Acord
Aboard NOAA Ship Oscar Elton Sette
March 17 – 28, 2014

Mission: Kona Area Integrated Ecosystems Assessment Project
Geographical area of cruise: Hawaiian Islands
Date: March 26, 2014

Weather Data from the Bridge at 13:00
Wind: 6 knots
Visibility: 10+ nautical miles
Weather: Hazy
Depth in fathoms: 2,473
Depth in feet: 14,838
Temperature: 26.0˚ Celsius

Science and Technology Log

Cetaceans Are Among Us!

We use these cameras to take close up shots of the marine mammals.
Commanding Officer, Koes (right), and scientist, Gadea, during MMO on the flying bridge.

Our Marine Mammal Observation (MMO) crew was in for a treat today. Just after lunch, we spot a pod of sperm whales. We spotted them off the port side, off the starboard side, and eventually off the bow of the Sette. We frequently see Humpback whales in Hawaii, but sperm whales often evade us. Sperm whales can dive down to extreme depths and they feed on squid. These same squid feed on the micronekton that we are observing during the cruise. Sperm whales are the largest of the toothed whales. Their enormous size is obvious when they slap the ocean with their giant tails. Another unique characteristic of the sperm whale is their blow hole, which sits to the left rather than on top of the head. This feature allows our MMO team to easily identify them.

Our MMO lead, Ali Bayless, determines that we should take the small boat out for a closer examination of the pod. Within minutes, the small boat and three scientists are in the water following the pod. We think that a calf (baby) is accompanying two of the adult whales. Throughout the next few hours, our small boat is in constant contact with our flying bridge, bridge, and acoustics team to determine the location of the whales. We keep a safe distance from all of the whales, but especially the calf. While on the small boat, MMO scientists also identify spotted and spinner dolphins. We are essentially surrounded by cetaceans. The small boat is just one of the many tools we use to determine what inhabits the ocean. We also use an EK60 sonar, our Remotely Operated Vehicle, our hydrophone, and sonar buoys.

Notice the location of the blow hole on the sperm whale. Photo credit: Ali Bayless
Sperm whale sighting during MMO operations. Photo credit: Eric Mooney
Two adult sperm whales and a calf. Photo credit: Erin Mooney
This sperm whale is about to dive deep to feed. Photo credit: Gadea Perez-Andujar

Our acoustics lead, Adrienne Copeland, is especially excited about our sperm whale sightings. Adrienne is a graduate student in zoology at the University of Hawaii. She earned her Bachelor’s of Science in biology with a minor in math and a certificate in mathematical biology from Washington State University. She has served on the Sette four times and is currently serving her third stint as acoustics lead. This is a testament to her expertise and the respect she has earned within the field.

Adrienne Copeland monitors our acoustics station during our 2014 IEA cruise.
Adrienne Copeland monitors our acoustics station during our 2014 IEA cruise.

Adrienne Copeland studies the foraging behavior of deep diving odontocetes (toothed whales). She shares that some deep diving odontocetes have been known to dive more than 1000 meters. Short finned pilot whales have been observed diving 600-800 meters during the day. During night dives we know they forage at shallower depths on squid and fish. How do we know how deep these mammals dive? Tags placed on these mammals send depth data to scientists. How do we know what marine mammals eat? Scientists are able to examine the stomach contents of mammals who are stranded. Interestingly, scientists know that sperm whales feed on histioteuthis (a type of squid) in the Gulf of Mexico. A 2014 IEA trawl operation brought in one of these squid, which the sperm whales may be targeting for food.

Notice the distinct blue and gray lines toward the top of the screen. These are the think layers of micronekton that migrated up at sunset. The number at the top of the screen expresses the depth to the sea floor.
Notice the distinct blue and gray lines toward the top of the screen. These are the thick layers of micronekton that migrated up at sunset. The number at the top of the screen expresses the depth to the sea floor.

Examine the acoustics screen to the left. Can you identify the gray and blue lines toward the top of the screen? These scattering layers of micronekton ascend and descend depending on the sun. Adrienne is interested in learning how these scattering layers change during whale foraging. Our EK60, Remotely Operated Vehicle, and highly prescribed trawling all allow us to gain a better understanding of the contents of the scattering layers. A greater understanding of whale and micronekton behavior has the potential to lead to more effective conservation practices. All marine mammals are currently protected under the Marine Mammal Protection Act. Sperm Whales are protected under the Endangered Species Act.

Interesting fact from Adrienne: Historical scientists could indeed see the scattering layers on their sonar, but they thought the layers were the ocean floor. Now we know they represent the layers of micronekton, but old habits die hard, so the science community sometimes refers to them as false bottoms.

Live Feed at 543 Meters! 

The ROV prior to deployment.
The ROV prior to deployment.

Our Remotely Operated Vehicle (ROV) deployment is a success! We deploy the ROV thanks to an effective team of crew members, scientists, and NOAA Corps officers working together. ROV deployment takes place on the port side of the ship. We take our ROV down to approximately 543 meters. We are able to survey with the ROV for a solid five hours. A plethora of team members stop by the eLab to “ooh” and “ahh” over the live feed from the ROV. Excitingly, the ROV is deployed prior to the vertical migration of the micronekton and during the early stages of the ascent. The timing is impeccable because our acoustics team is very curious to know which animals contribute to the thick blue and gray lines on our acoustics screens during the migration. In the ROV live feed, the micronekton are certainly visible. However, because the animals are so small, they almost look like snow falling in front of the ROV camera. Periodically, we can identify squid, larger fish, and jellies.

ROV deployment requires teamwork. These are our winch operators.
Two scientists connect the umbilical and the winch line to ensure our ROV is stable.
Scientist, Eric Mooney, operates our ROV during its deployment using the live feed and the joy stick.

Did you Know? 

Kevin Lewand of the Monterey Bay Aquarium constructs a hyperbaric chamber for marine life on board the Sette.
Kevin Lewand of the Monterey Bay Aquarium constructs a hyperbaric chamber for marine life.

Mini hyperbaric chambers can be used to save fish who are brought to the surface from deep depths. These chambers are often used to assist humans who scuba dive at depths too deep for humans or who do not effectively depressurize when returning to the surface after SCUBA diving. The pressure of the deep water can be life threatening for humans. Too much pressure or too little pressure in the water can be life threatening for marine life, too. Marine life collector, Kevin Lewand, constructed a marine life hyperbaric chamber aboard the Sette. He learned this skill from his mentor. Be sure to say Aloha to him when you visit the Monterey Bay Aquarium in Monterey, California.

 

 

 

 

Personal Log

Daily Life Aboard the Sette

Our chief scientist, Dr. Don Kobayashi, examines a specimen after a trawl.
Examining a cookie cutter shark in the wet lab.
Night watch on the Sette.

There is never a dull moment on the ship. Tonight we have ROV operations, squid jigging, acoustics monitoring, and a CTD deployment. We of course can’t forget the fact that our bridge officers are constantly ensuring we are en route to our next location. Tonight’s science operations will most likely end around 05:00 (tomorrow). Crew members work 24/7 and are usually willing to share their expertise or a good story. If they are busy completing a task, they always offer to chat at another time. I find that the more I learn about the Sette, the more I yearn to know. The end of the cruise is just two days away. I am surprised by how quickly my time aboard the ship has passed. I look forward to sharing my new knowledge and amazing experiences with my students and colleagues. I have a strong feeling that my students will want to ask as many questions as I have asked the Sette crew. Aloha and mahalo to the Sette.

 

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Liz Harrington: Introductory Blog, July 25, 2013

NOAA Teacher At Sea
Liz Harrington
Soon to be aboard  NOAA ship Oregon II (NOAA Ship Tracker)
At Sea August 10 – 25, 2013

Mission: Shark/Red Snapper Bottom Longline
Geographical Area of Cruise: Western Atlantic Ocean and Gulf of Mexico
Date: July 25, 2013

Weather: current conditions from Morrisville-Stowe State Airport
Sunny
Lat. 44.53°  Lon.- 72.61°
Temp.  64°F (18° C)
Humidity 54%
Wind speed   3 mph
Barometer  30.16 in (1021.3mb)
Visibility  10.00 mi

Personal Log:

Mt. Mansfield
Mt. Mansfield

Greetings from Vermont, the Green Mountain State.  My name is Liz Harrington and I live in Cambridge, VT.  Cambridge is a small town at the foot of Mount Mansfield, our state’s tallest mountain with a peak of 4395 feet (1340 meters).  Ok, the Green Mountains aren’t as big as the Rockies, but they provide us with recreational opportunities, wildlife habitat and scenic beauty. We love them.   I am a science teacher at Essex High School in Essex Junction, VT.   Currently I am teaching Earth Science and Forensics.  I also help teach a Belize Field Study class.

Essex High School
Essex High School

My teaching career has worked out perfectly for me.  After graduating from UConn with an Animal Science degree, I married and raised four wonderful children.  As they grew, I returned to school to earn my teacher certification in secondary science education.  When my youngest went to kindergarten, I began teaching part time at Essex High School. I had the best of both worlds.  It was during these first few years of teaching that I heard about NOAA’s Teacher at Sea (TAS) program.  I immediately knew I wanted to be involved in the program, but it required being a full time teacher.  A few years ago my teaching became full time.  I applied to TAS, was accepted and will be aboard the NOAA ship Oregon II this summer.  I’m thrilled!

I have always had a close connection with the ocean as I grew up on the shore of southeastern Connecticut.  I spent many hours swimming off the docks or climbing out onto the rocks to crab.  I also did lots of fishing and boating, but I took the ocean for granted.  I didn’t realize how much I would miss it when I moved away.  I am fortunate that my parents still live at the shore and my children have had the opportunity to create their own ocean experiences.  And it is always an amazing sight to see their Vermont friends encounter the sounds, smells, textures and activities of the ocean for the first time!

CT shore
Recent visit to the Connecticut shore.
Belize
Belize class trip

The Belize Field Study class has a culminating ten day trip to Belize.  The first four days are spent exploring the coral reefs and learning more about issues concerning the reef.  Some of the students snorkel and some of them scuba dive, but either way they are able to explore the underwater world.  Here, again, I am able to bring students to the ocean and I love to see their excitement, interest and concern.  The ocean’s fate will soon be in their generation’s hands and these personal connections make a difference.

Belize sunset
Belize sunset

Science and Technology Log:

The Oregon II is a NOAA ship which supports the programs of the National Marine Fisheries Service (NMFS).  The ship conducts studies at various times of the year on organisms such as ground fish, sharks, plankton, reef fish and marine mammals.  I will be joining a Shark/Red Snapper Bottom Longline Survey.  We will be sailing from Mayport, Florida and spending two weeks in the Gulf of Mexico.  The trip will end in the home port of Pascagoula, Mississippi. I am honored at having been chosen as a Teacher at Sea.  I can’t wait to be working with the scientists and crew aboard the Oregon II and participating in real scientific research.  I’m also looking forward to sharing my experiences with my students and bringing new topics into the classroom.  Through this trip I’m hoping they can make connections to the ocean as well.  I’ll be sharing my adventures a few times a week with this blog.  I hope you will follow along.

Oregon II
NOAA ship Oregon II

 

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Avery Marvin: Beaming With Excitement – Sound Waves and the Sea Floor, July 19, 2013

NOAA Teacher at Sea
Avery Marvin
Aboard NOAA Ship Rainier (Ship Tracker)
July 8-25, 2013 

Mission: Hydrographic Survey
Geographical Area of Cruise: Shumagin Islands, Alaska
Date: July 19, 2013

Current Location: 54° 49.684 N, 159° 46.604 W

Weather Data from the Bridge: Foggy and overcast, wind 21 knots, air temperature: 11.5° C

Science and Technology Log:

As the fog horn sounds every two minutes and we sail solitary through the ocean, we are now in full swing surveying the Shumagin Islands, between and around Nagai, Bird, and Chernabura Islands. Unlike the old-time surveyors who used lead lines (lead weight attached to a long string), we are using a multibeam sonar system, which enables us to gather a large quantity of very accurate data in a more efficient and timely fashion.

3D sea floor
Processed sonar data showing 3D image of the sea floor.

Sonar, (SOund Navigation And Ranging) uses the principle of sound wave reflection to detect objects in the water. Just as our eyes see the reflection of visible light off of the objects around us to create a visual image, when a sound wave hits something, it reflects off that “thing” and returns to its starting point (the receiver). We can measure the time it takes for a pulse to travel from the Sonar device below the boat to the ocean floor and then back to the receiver on the boat. Using a simple distance=speed * time equation, we can get the water depth at the spot where each beam is reflected.

The skiff that we use for the shoreline activities discussed in the last post has a single-beam sonar system that directs a pulse straight down beneath the hull to get a rough depth estimate. However, for our hydrographic work on the ship and launches, we use a multibeam system that sends 512 sound pulses simultaneously towards the sea floor over a 120° angle. When many sound waves or “beams” are emitted at the same time (called a pulse) in a fan like pattern (called a swath), the reflected information creates a “sound picture” of the objects or surface within that swath range. The actual width of this swath varies with the depth, but with 512 beams per pulse, and sending out between 5-30 pulses every second, we acquire a lot of data. If you piece together many swaths worth of data you get a continuous topographical or physical map of the ocean floor, and thus the depth of the water. For more information about the specific sonar system used aboard the Rainier and its launches, check out the ship page or the NOAA page about their hydrography work.

Multibeam
Graphic showing an example of the multibeam swath below a launch. Notice how the swath gets wider as the depth increases.
Multibeam data
Cross section of sea floor data showing dot or “ping” for each multibeam measurement. Notice how many individual measurements are represented in this one section.
Swath data
Cross section of sea floor data. Each color represents data from one swath. Notice the overlap between swaths as well as the width for each one.
3D floor image
Processed sonar data showing 3D image of the sea floor.

In order to understand the complexities of sonar, it is important to understand the properties of sound. Sound is a pressure wave that travels when molecules collide with each other. We know that sound can travel in air, because we experience this every day when we talk to each other, but it can also travel in liquids and solids (which whales rely on to communicate). As a general rule, sound travels much faster in liquids and solids than in air because the molecules in liquids and solids are closer together and therefore collide more often, passing on the vibration at a faster rate. (The average speed of sound in air is about 343 meters every second, whereas the approximate speed of sound in water we have been measuring is around 1475 meters every second). Within a non-uniform liquid, like saltwater, the speed of sound varies depending on the various properties of the saltwater at the survey site. These properties include water temperature, dissolved impurities (i.e. salts, measured by salinity), and pressure. An increase in any of these properties leads to an increase in the speed of sound, and since we’re using the equation distance = speed * time equation, it is crucial to consistently measure them when seeking depth measurements.

CTD Data
Data from CTD showing temperature vs. sound speed from one data set. Notice how the temperature and sound speed seem correlated.

To measure these properties, a device called a CTD (Conductivity-Temperature-Depth) is used. Conductivity in this acronym refers to the free flowing ions in salt water (Na and Cl, for example), which are conductive and the concentration of these ions determines the salinity of the water. The CTD measures these three properties (Conductivity, Temperature and Depth) so the speed of sound in the water can be calculated at every point in the water column

To use the CTD, lovely humans like Avery and I will drop it into the water (it is attached to a winch system) at the area where we are surveying and as it travels to the sea floor, it takes a profile of the three saltwater properties mentioned before. Back in the computer lab, software takes this profile data and calculates the sound velocity or speed of sound through the water in that region.  As a crosscheck, we compare our profile data and sound velocity figures obtained at the site to historical measured limits for each property. If our measurements fall significantly outside of these historical values, we might try casting again or switch to a different CTD. However, because we are surveying in such a remote area, in some cases, data outside historical limits is acceptable.

CTD graphs
Graph of our sound speed vs. depth data showing comparison to historical data.

Given that we are trying to determine the water depth to within centimeters, variations in the sound speed profile can cause substantial enough errors that we try to take a “cast” or CTD reading in each small area that we are gathering data. The software the survey team uses is able to correct automatically for the sound velocity variations by using the data from the CTD. This means that the depth profile created by the sonar systems is adjusted based on the actual sound velocities (from the CTD data) rather than the surface sound speed. We are also able to account for speed changes that would cause refraction, or a bending of the beam as it travels, which would otherwise provide inaccurate data about the location of the sea floor.

Avery lowers the CTD into the water for a "cast". The CTD needs to sit in the water for a few minutes to acclimate before being lowered for a profile.
Avery lowers the CTD into the water for a “cast”. The CTD needs to sit in the water for a few minutes to acclimate before being lowered for a profile.
Avery successfully hauls in the CTD out of the water.
Avery successfully hauls in the CTD out of the water.

Personal Log:

You can’t go to Alaska without fishing its waters, rich with a variety of delectable fish species.  So I decided to get my Alaskan recreation fishing license and try my hand at it on the fantail (stern) of the Rainier, while we were anchored in Bird Island cove. Carl VerPlanck, an experienced fisherman with arms like Arnold Schwarzenegger, had coached me on the best jigging techniques for catching a halibut and with my eyes (and mind) on the prize I followed his instructions diligently.  It paid off as I landed several fish my first night on the fantail, with one halibut being a true keeper. John Kidd, NOAA Corps. Officer, gaffed my meaty fish over the steep rail of the Rainier and hauled it aboard.  He was impressed with my catch (and hidden fishing talent), stating “This is the biggest fish caught so far this season.” Woohoo! Most impressive was the amount of meat the fish yielded (4 large filets) which I proudly donated to the kitchen and John. (Three big filets to the kitchen and one filet to John for his camaraderie, the use of his high-tech rod set-up and filleting skills). The following night, we all ate delicious baked Pacific Halibut filets, coated in a creamy Caesar glaze, prepared by chef-extraordinaire, Kathy. It’s pretty cool that I got to feed the ship!!

Avery's meaty catch, a Pacific Halibut.
Avery’s meaty catch, a Pacific Halibut.
John Kidd (NOAA Officer) filleting my halibut
John Kidd (NOAA Corps. Officer) filleting my halibut
Look at all that meat!
Look at all that meat!
4 large fillets from the halibut
4 large fillets from the halibut

This was my first time catching a halibut and after close examination (and dissection) of this large, rather bizarre looking flatfish I became very intrigued and had several questions: How and why do the eyes migrate to one side?  How do you tell the age of a halibut? What does the word “halibut” mean?

Like any good scientist, I proceeded to find the answers to these questions, and in doing so, learned many more interesting tidbits about Halibut. (The other species of halibut is the Atlantic Halibut which is very similar to the Pacific Halibut and is named as such for the ocean it occupies.)

So lets start with the name “halibut.” It’s origin is Latin (hali=haly=holy, but=butt=flat fish) and literally translates to “holy flat fish” because it was popular on Catholic holy days. Now what’s with the eye migration and why are both eyes on the same side? Well to understand this question thoroughly we must look at the conditions under which the halibut is born. Female halibut are sexually mature at age 12, spawning from November to March in deep water (300-1500 feet). Depending on their size, females release several thousand to several million eggs which are fertilized externally by the males. After the eggs are fertilized by the males, they become buoyant and start to float up the water column, hatching into free floating larva at about 16 days.  As the larva mature, they continue to rise to the surface. At this larval stage they are upright, like any other “regular” fish, with one eye on each side of their head. This eye placement makes sense, considering they are in the open ocean with water on all sides of them.  When at or near the surface, the larvae drift towards shore by ocean currents. As they get closer to shore and at about 1 inch in length, they undergo a very unique metamorphosis in which the left eye moves over the snout to the right side of the head. At the same time their left side fades in color eventually becoming white and their right side becomes a mottled olive-brown color. By 6 months, they are ready to settle to the bottom in near shore areas, hiding under the silt and sand, with just eyes exposed. Their mottled side will be face up, blending into their surrounds and their white side will face down, creating a “countershading” coloration, which helps keep them hidden from predators.

From halibut larvae to adult halibut. Notice the migration of the left eye to the right side and the pigmentation at the last stage.
Halibut development: from halibut larvae to adult halibut. Notice the migration of the left eye to the right side and the pigmentation at the last stage.

The Pacific Halibut I caught was by no means a monster or “barn door” as the huge ones are called. But it also was not a “chicken”, slang for a small halibut. Female halibut can reach lengths of 8 feet and a weight of 500+ pounds. Males rarely exceed 100 pounds.  Halibut are generally not picky eaters and will pretty much eat anything that lives in the ocean.  Carl joked that a halibut would even eat an old shoe dangling from a fishing pole.

I was surprised to learn that halibut can live as long as 55 years.  Scientists can accurately age a halibut by counting the rings in their ear bone or “otolith”, similar to dating a tree using its annual growth rings. So next time you catch a halibut and plan on keeping it, try to find the ear bone, grab a microscope and age the fish. If that fails, don’t forget to cut the cheeks out of the halibut (along with the 4 regular meaty fillets), for I am told that is the best part to eat. 🙂

Halibut otolith or ear bone that can be used to age the fish by counting the rings under a microscope
Halibut otolith or ear bone that can be used to age the fish by counting the rings on the otolith (under a microscope).

Fun factoid: Sonar works a lot like the echo sounding of a bat, and its development was partially prompted by the Titanic disaster.