Staci DeSchryver: Fair Winds and Following Seas, July 8, 2017

NOAA Teacher at Sea

Staci DeSchryver

Aboard NOAA Ship Oscar Elton Sette

July 6 – August 2, 2017

Mission:  HICEAS Cetacean Study

Geographic Area:  South of Oahu, heading toward the Big Island

Current Location:  20.20 N 156.37 W

Date:  July 8, 2017

Weather Data From the Bridge: 

 

Science and Technology Log

We have arrived!  Today members of the incoming crew on Oscar Elton Sette picked me up from Waikiki and we made our way over to Ford Island for training.  The HICEAS study is seven “legs” long, each lasting about a month with a one week break in between legs – ours is the first “leg” of the mission, and the training took place for all scientists and crew who would be traveling and conducting research through any of the four parts of the mission.  In August and September, two of the legs will run simultaneously, so the project is significant in size with respect to time, manpower, and data collection.  We had a very full house of various research teams, some of which will overlap among the various legs of the trip.  The full crew is a tight family, with hugs and greetings all around during breaks and meal times.  How nice to know that leaving for 28 days (some of them longer) doesn’t necessarily mean leaving your family.

PIFSC_20100926-S86_B-01784.JPG

Wanted:  pseudorca (Alias: False Killer Whales) For High Crimes of Adorableness and shyness from ships.  Photo Credit:  NOAA Fisheries/Corey Sheredy

During training, scientists reviewed procedural protocols to follow for different species sightings and learned the protocol changes for a few other species.  The primary target for this particular leg of the HICEAS is pseudorca, or False Killer Whale.  They are a socially interesting bunch – a little reminiscent of the hallways at Cherokee Trail High School.  Whereas most whale species travel as a “class” in one large group all together, pseudorca behave as though all day every day is passing period.  The entire group of pseudorca may travel together (similar to being in school all day), but they don’t all congregate together in the same location.  They are a rather “cliquey” bunch – with smaller groups milling about together on their own in different corners of the main group but all keeping at least somewhat in eyesight or earshot of the other groups.  Because of this, scientists must identify the group, and then each individual subgroup, making note of any groups that join up or split apart.  We haven’t spotted any pseudorca yet, but with some time, talent, and a little luck, we will soon!

In a broad sense, the search for cetaceans on a daily basis is executed a little something like this:  Three mammal observers take their positions at port (left), center, and starboard (right) on the “flying” bridge – or the topmost deck of the ship.  There is also a space reserved just right of center for the Seabird observers.  Each observer will rotate through these three positions for a total of a two-hour shift.  If, for example, an observer begins at the port side “Big Eye” station, they will scan the water in search of cetaceans for 40 minutes from that position, rotate to the center, and then finally to the starboard side.  Where does the starboard side observer go when he or she has completed the rotation?  There’s plenty to do onboard and to help with until the next two-hour rotation begins.  There are two seabird observers working alongside the mammal observing team, and they alternate in two-hour rotations, so only one bird observer is on the flying bridge at a time in an official capacity.  All visual observers work from sunrise to sunset.

Each position at the marine mammal observation area is responsible for visually sweeping the ocean’s surface during observations.  The two side observers are only responsible for scanning from 0 degrees (the bow of the ship) to 90 degrees to their direct left on the port side, or direct right on the starboard side.  They use a very imposing pair of binoculars called the “Big Eyes” to scan their respective areas.  These binoculars are impressive in size and abilities.  They can bring even the smallest birds far on the horizon into sharp focus.  The center observer does not have Big Eyes, but stands ready to take data if there is a sighting.  He or she can scan the area in general, but the big eyes offer much more detailed observation abilities at a much greater distance.  The center observer is also responsible for keeping time on the rotations, monitoring the weather, the sun’s position in the sky, and Beaufort sea state.

While the visual observers are on the flying bridge, two scientists work in the acoustics lab to listen for cetacean vocalizations.  The two groups work in parallel universes, but only the acousticians can cross dimensions.  In other words, if the visuals see cetaceans, they can tell the acoustics about what they are seeing, but if the acoustics scientists hear vocalizations, they will not tell the observers.    More often than not, the acousticians will hear clicks, whistles, and moans from the acoustics lab well before the visuals make a sighting, because the acoustics team has a large advantage over the visuals team.  The visuals team is restricted to what they can see at the surface, and the acoustics team can “see” many miles away and deeply into the water column, which significantly increases their volume of searchable space.

When the acousticians “see” or hear a vocalization, they plot the distance from the ship. They continue to listen for vocalizations and continue with the plots.  Eventually, they have enough data to narrow down the potential location of the cetacean to two spots. This process is not unlike earthquake triangulation, except the observers can narrow down the location to two spots, rather than just one.  There will be much more to come as to how this process works in future blogs, so stay tuned!  

Personal Log

At the end of training today, Dawn, one of the ornithologists (that’s a seabird “pro”) informed us of the third and far lesser-known Pearl Harbor Memorial, USS Utah.  Utah was the very first ship capsized by Japanese bombs on the early morning of December 7th, 1941.  Found on the opposite side of the island from USS Arizona, the Utah is only accessible by folks who have military clearance to get on the base, making the memorial incredibly secluded from exposure to the general public.  Utah took 64 lives with her when she sank, and a small monument now stands on the shore as a memento to the crew lost that fateful morning.  What makes Utah interesting is that she still stands partially above water, her mangled and rusted metal piercing through the water’s surface like the grasping hand of a drowning sailor.  There was a brief attempt by the military to right and raise her, but it proved futile, and they made the call to leave her remains be.  Her finest and final duty is to serve her watch over the men caught in her belly on the day she fell prey to the Axis forces.

Utah found herself in the wrong place at the wrong time on the morning of December 7. She was moored on a pier normally reserved for aircraft carriers, and her flat and shiny deck betrayed her identity to the incoming Japanese pilots.  Due to this mistaken identity, the Japanese attacked her on appearance, and she capsized almost instantly.  More interesting is that much like the beginning of a bad cop movie, she was nearing her retirement.  She was in port awaiting her execution date,  friendly-fire style, her technological abilities waning and falling out of favor compared to the newer commissioned ships.  Her final resting place was originally supposed to be somewhere in the Pacific as a victim of a practice bombing drill by the Air Force.  The Japanese pilots got to her first.  She wasn’t even at work that day.

Utah was built in 1909 and commissioned in 1911, the second of two Florida-class battleships built for service during World War I.  After a long stint in the service as a battleship, the Utah was re-appropriated as an auxillary ship for gunnery training and target practice for the allied forces.  On the day of the attack, the aircraft carriers that should have been in-port at the time were out to sea, and so Utah moored in one of the empty spaces intended to be held by the aircraft carriers.  In the confusion of the attack, it was determined that Utah was a carrier, and the Japanese navy opened fire.  The Chief Water Tender, Peter Tomich, served bravely as he assisted crew in their evacuations when the abandon ship call came over the ship’s systems.   While everyone was running off the ship, Tomich was running back onboard. He lost his life in that selfless move and is remembered as a hero of the day.

Today Utah sits idly close to shore alongside what used to be a dock.  Her neighbor is NOAA Ship Okeanos Explorer, and just a little further up the harbor, our ship, Oscar Elton Sette.  It was sobering honor to be so close to the memorial before we left port, and though USS Utah is one of the smaller memorials on Ford Island, I certainly will not forget her.

Species Report:

Number of cetaceans seen visually:  0 so far

Number/types of cetaceans “seen” acoustically:

*Blainsville’s Beaked Whale

*Sperm Whale

*Dolphins

Birds Seen:

Frigate Bird

Shearwaters

Red Footed Booby

Brown Footed Booby

Land Bird who shouldn’t have been out so far in the ocean (so possibly my spirit animal).  Let’s hope he eventually finds his way home.

Wes Struble: What in the World Is a CTD Cast? March 2, 2012

NOAA Teacher at Sea
Wes Struble
Aboard NOAA Ship Ronald H. Brown
February 15 – March 5, 2012

Mission: Western Boundary Time Series
Geographical Area: Sub-Tropical Atlantic, off the Coast of the Bahamas
Date: March 2, 2012

Weather Data from the Bridge

Position: 26 degrees 19 minutes North Latitude & 79 degrees 55 minutes West Longitude (8 miles west of Florida’s coast)
Windspeed: 14 knots
Wind Direction: South
Air Temperature: 25.4 deg C / 77.7 deg F
Water Temperature: 26.1 deg C / 79 deg F
Atm Pressure: 1014.7 mb
Water Depth: 242 m / 794 feet
Cloud Cover: none
Cloud Type: NA

Science/Technology Log:

There are four different ship’s stations that are involved in a CTD (Conductivity, Temperature, & Depth) operation: the bridge, the survey team, the winch operator, and the computer room. The bridge is responsible to keep the ship on position and stable over a predetermined latitude and longitude. The survey team is responsible for preparing the CTD platform for deployment and securing it back on deck at the completion of the cast. The winch operator controls the actual motion of the CTD platform by the use of a hoist.  The computer lab relays commands to the winch and survey team in reference to testing and sampling depths, and when to start and stop the ascent and descent of the platform. The CTD platform can carry many types of instruments depending upon the nature of the research being conducted. During this cruise our platform usually contained two each of a temperature gauge, conductivity gauge (from which you can obtain salinity), and oxygen gauge.  In addition there is one pressure gauge and a transmissometer (that measures the turbity of water which is an indicator of the phytoplankton), 23 Niskin water sampling bottles, and two Acoustic Doppler Range finders – one pointing toward the surface and one pointing at the sea floor.

The CTD (Conductivity, Temperature, & Depth) platform on the Ron Brown. The long grey cylinders are the water sampling Niskin bottles, the yellow and blue device at the bottom in the Acoustic Doppler Current Profiler (for measuring distance to the sea floor) for measuring the distance to the sea floor during descent phase of a cast, the grey cylinders are weights, and the green cylinder is the power supply.

A Niskin Bottle with my Nike shoe for scale

The CTD platform being lowered over the side for start of another cast.

The "downlooking" ADCP (Acoustic Doppler Current Profiler mounted on the CTD.

The "up-looking" ADCP (Acoustic Doppler Current Profiler) mounted on the CTD

The Niskin Bottle trigger release. This device is used to remotely close the Niskin bottles at depth

The bridge of the Ron Brown during a CTD cast

     A CTD cast begins when the ship arrives at prearranged coordinates of latitude and longitude. The bridge will announce that we are “on station”.

A photo of the Ron Brown off the coast of Grand Bahama Island

   The survey team acknowledges and then raises the CTD platform and places it is the water at the surface for a minute or two. Then after receiving a signal from the computer operator that all functions are operating within normal parameters the platform is lowered to 10 meters and held there for two minutes to allow the instruments to stabilize.

Here I am starting my midnight to 6 :00 am shift at the CTD computer control station in the computer lab of the NOAA Ship Ronald H Brown

The "brains" of the CTD. This device also contains the pressure sensor.

   After the two minute hold at 10 meters the entire platform is brought back to the surface and the log is started as the package is lowered. The descent begins at about 30 meters/minute and eventually reaches 60 meters/minute. Many of the deep water casts on this cruise were between 4000 m and 5500 meters (about 13000 ft and 18,000 ft) and take over an hour to reach the bottom. While the descent takes place all the instruments are recording data which is stored and plotted in real time at the computer monitor.   When the CTD platform is 10 meters from the bottom the descent is stopped and the first water sample is collected by sending a signal that closes the first Niskin bottle. At this point the CTD slowly begins its climb back to the surface (another hour or more) stopping at designated depths to collect water samples.After the last Niskin bottle is closed at the surface, the CTD platform is brought back on deck, the water samples are removed, and the entire platform is prepared for the next cast.

Here I am on the weather deck in my favorite chair on the ship. I enjoy relaxing here in the sun in the morning after a night shift at the CTD computer station.

Another beautiful western Atlantic pre-sunset. I enjoyed many of these during the cruise.

The early sun rising in the east off the stern of the Ron Brown brings another night of CTD's to an end.

Katie Turner, July 30, 2008

NOAA Teacher at Sea
Katie Turner
Onboard NOAA Ship Miller Freeman
July 10 – 31, 2008

Mission: Pollock Survey
Geographical Area: Eastern Bering Sea
Date: July 30, 2008

Screen shot 2013-11-03 at 10.15.47 AMWeather Data from the Bridge 
Visibility:  10 miles
Wind Direction:  050
Wind Speed:  7 knots
Sea Wave Height:  0-1 foot
Swell Wave Height:  2-3 feet
Seawater Temperature: 8.3 ˚C.
Present Weather Conditions: partly cloudy

Science and Technology Log 

This was the final day at sea for this cruise and we have just returned Dutch Harbor.  The cruise has been challenging for the scientists as they have had to scale back their study, and even eliminate some experiments.  Fifteen days of cruise time were lost while repairs were made to the ship. Conditions while working at sea are unpredictable and require acceptance, patience, and flexibility.

Ship's cruise path

Ship’s cruise path

The Buoy Experiment 

In addition to the side by side comparison study, a unique experiment was designed and performed during this cruise to investigate how walleye pollock (Theragra chalcogramma) behave in the absence versus presence of either vessel, to augment the comparison study.  Transducers were mounted on a buoy, which was deployed from OSCAR DYSON, and allowed to drift while collecting acoustic data on pollock schools with the ships at a distance.  As the buoy drifted along, MILLER FREEMAN and OSCAR DYSON alternately passed by the buoy on a “racetrack” 6 nautical miles (nm) long.  Each ship passed the buoy within 10 meters along the racetrack about every 30 minutes, and maintained a position opposite one another.

The racetrack pass experiment will provide information on how fish respond to the ship as it approaches and passes over them, and then as it moves away. The acoustic data collected by the transducers on the buoy was monitored aboard OSCAR DYSON during the operation, and was downloaded in entirety once the buoy was retrieved for analysis. We made a total of seven buoy passes, which took about 3 ••• hours.  This experiment was done at night when pollock schools migrate up from the bottom of the ocean into mid-water regions.  It was interesting to observe the navigation operations from the bridge as ships maneuvered around the racetrack in the dark. The computer screenshot below shows the track (in red) of the MILLER FREEMAN after our 6th pass of the buoy.  The short, blue vertical line at the end of the red track line at the top of the screen represents the ship. (Green lines are depth contours.) After completing the buoy experiment we picked up the transect from where we had left off and continued the side-byside study.

View of Unalaska

View of Unalaska

On the bridge bringing MILLER FREEMAN into Captain’s Bay, Executive Officer Natasha Davis (official owner of ship’s cat) and Ensign Otto Brown

On the bridge bringing MILLER FREEMAN into Captain’s Bay, Executive Officer Natasha Davis and Ensign Otto Brown

Another Setback 

Later that day the ship developed engine problems and it was necessary to shut down the main engine to investigate. Leaks in the cooling system involving two separate cylinders had developed. This same problem occurred recently with a different cylinder, and was one of the problems that originally delayed our cruise out of Dutch Harbor.  The engineers repaired the system and we were underway again within a few hours.  At this point we were nearly 450 nautical miles from Dutch Harbor, with limited resources for additional repairs.  In the best interest and safety of all aboard, the Commanding Officer decided to discontinue our north and westward direction along the cruise course and head the ship back to Dutch Harbor.

Ship's cat

Ship’s cat

Personal Log 

Our final day in the Bering Sea was mostly sunny.  Dall’s porpoise and whales were occasionally sighted off in the distance, and we watched ash clouds rise from Okmok volcano off our starboard side all afternoon as we closed in on Unalaska.  The wind seemed to be carrying the ash cloud to the southwest, and we hoped that it would not affect flights out of Dutch Harbor for those of us who are flying home.  We arrived in Unalaska before 10 pm, leaving just enough time to anchor and repeat the acoustic calibration. After the scientists and I leave the ship in the morning, she will head back to her home port of Seattle, where she will have a maintenance check before the next cruise. I have thoroughly enjoyed my stay on MILLER FREEMAN and owe many thanks to the officers and crew for their hospitality. It has been a pleasure to get to know everyone and I will have good memories of this cruise, despite the breakdowns and delays. I am especially grateful to the scientists on board, Patrick Ressler and Paul Walline, for sharing their work, helping me understand a little about acoustic surveys, and for their friendship during this experience.

Katie Turner, July 26, 2008

NOAA Teacher at Sea
Katie Turner
Onboard NOAA Ship Miller Freeman
July 10 – 31, 2008

Mission: Pollock Survey
Geographical Area: Eastern Bering Sea
Date: July 26, 2008

Rescue crew retrieves a dummy man overboard. It is a maritime custom to refer to the man overboard as “Oscar." This comes from an international regulation requiring the raising of the Oscar flag when a vessel is responding to a man overboard, warning other vessels to be on the lookout

Rescue crew retrieves a dummy man overboard. It is a maritime custom to refer to the man overboard as “Oscar.” This comes from an international regulation requiring the raising of the Oscar flag when a vessel is responding to a man overboard, warning other vessels to be on the lookout

Weather Data from the Bridge 
Visibility:  3 miles
Wind Direction:  050
Wind Speed:  8 knots
Sea Wave Height:  0-1 foot
Swell Wave Height:  2-3 feet
Seawater Temperature: 7.8˚ C.
Present Weather Conditions: cloudy

Science and Technology Log 

After leaving Captain’s Bay early Friday morning, the trip to the rendezvous point with OSCAR DYSON took nearly 20 hours. During that time we had our mandatory fire, abandon ship, and man overboard drills.  For our fire drill the Captain staged a mock fire, with smoke reported from the acoustics lab.  The fire fighting team had to respond, find the point of origin of the fire and figure out how to treat it. A debriefing was held afterward so that responders could discuss strategies and learn from the experience.

The rescue boat is brought back aboard the MILLER FREEMAN

The rescue boat is brought back aboard the MILLER FREEMAN

The abandon ship drill is regularly performed so all crew are ready to respond to a severe emergency by mustering at their assigned stations and getting into survival suits to be ready to board life rafts. It’s a good way for new crew members, such as me, to make sure they know where to go and what to bring. We made our rendezvous with OSCAR DYSON late Friday evening in the Bering Sea and immediately moved into position to run the first side by side transect. We are working on a comparison study to determine whether acoustic estimates of pollock (Theragra chalcogramma) abundance made by MILLER FREEMAN and OSCAR DYSON are comparable.  Pollock may have different behavioral responses to these vessels during surveys due to the differences in the amount of noise each vessel radiates into the sea from its propeller, engines, and other equipment.  These behaviors could affect the acoustic estimates of abundance.  OSCAR DYSON is taking over the task of acoustic pollock surveys in the Bering Sea and has been built under new specifications that require a lower level of radiated noise. MILLER FREEMAN has been doing the Bering Sea pollock surveys since 1977.  This study is important because it will ensure that future biomass estimates will be continuous with those done in the past. During this cruise the two ships will continuously collect acoustic backscatter data while traveling side by side along a transect line where pollock schools are known to occur. The distance between the two ships is maintained at 0.5 nautical miles (nm), while they travel at about 12 knots. Every 50 nm along the transect, the vessels switch sides.

OSCAR DYSON from the bridge of the MILLER FREEMAN in the Bering Sea

OSCAR DYSON from the bridge of the MILLER FREEMAN in the Bering Sea

For this to happen one vessel will slow down and cross behind the stern of the other vessel, then catch back up on the other side. The beginning and end of each transect section must be carefully coordinated between the scientific team in the acoustics lab The remainder of our time on this cruise will be spent working with the OSCAR DYSON to cover as much of the study area as possible before returning to the port of Dutch Harbor.  After the study is complete, the acoustic data collected by each vessel will be carefully compared to see if there is any consistent difference between them. At the same time officers on the bridge are in constant communication to coordinate navigation and maneuvering of the ships.

The figure above shows the final transect path of MILLER FREEMAN in the Bering Sea as straight lines in red. The parallel lines running nearly north and south were traversed from the east to the farthest westerly point. The zigzag red line across the parallel lines represents the path taken as we head back to the southwest on our return. Other colored lines on the map are depth contour lines.  Red lines indicate depths from -75 to -100 meters, yellow to -130 meters, green to -155 meters, and blue greater than  -160 meters.

Ship transect

Ship transect

Personal Log 

During these few days at sea the scientists onboard have taught me a lot about acoustic studies. It’s a complex science that requires both an understanding of the physical science of acoustics and the technology involved, but also the biology, behavior, and ecology of pollock.

One of the opportunities I have especially enjoyed has been watching and photographing the seabirds. They are an important part of this ecosystem and one that can be observed without acoustics. We have seen mostly northern fulmar (Fulmaris glacialis) and black-legged kittiwake (Rissa tridactyla), but also an occasional long-tailed jaeger (Stercorarius longicaudus), and flocks of thick-billed murre (Uria lomvia). Northern fulmar (Fulmaris glacialis) exhibit a lot of variation in color from very light, to light, and dark versions, with gradations in between. These different color morphs all mate indiscriminately. They are gull sized birds with moderately long wings, a short, stout, pale bill, and a short rounded tail. A key characteristic is their dark eye smudge.  They are common in the Bering Sea but also in the northeast Atlantic.

Northern fulmar, light morph

Northern fulmar, light morph

Northern fulmar, dark morph

Northern fulmar, dark morph

Fulmars are well known among commercial fisherman for scavenging waste thrown off fishing boats, which explains why they have been nearly constant companions to the MILLER FREEMAN on this cruise. Fulmars are members of the family Procellariiformes, also known as the “tube-nose” birds, along with albatrosses, petrels, and shearwaters. The term comes from the tubular nostril, a structure that looks like a tube on top of their beak.  Their beak, as you can see in the photo, is made up of many plates. This specialized nostril is an adaptation that enhances their sense of smell by increasing the surface area within to detect scent. They also have enlarged brain structures that help them process those scents. Learn more at the Cornell and U.S.G.S. websites.

Katie Turner, July 25, 2008

NOAA Teacher at Sea
Katie Turner
Onboard NOAA Ship Miller Freeman
July 10 – 31, 2008

Mission: Pollock Survey
Geographical Area: Eastern Bering Sea
Date: July 25, 2008

Bald eagles are abundant around the port in Dutch Harbor

Bald eagles are abundant around the port in Dutch Harbor

Weather Data from the Bridge 
Visibility: 10 nautical miles
Wind Direction: 075
Wind Speed: 13 knots
Sea Wave Height: 1-2 feet
Swell Wave Height: 3 feet
Seawater Temperature: 7.1˚C.
Present Weather Conditions: Cloudy, 9.3˚C, 94% humidity

Science and Technology Log 

After spending 3 weeks at the dock in Dutch Harbor, MILLER FREEMAN finally began the cruise with less than a week left to complete the study. We pulled away from the dock Thursday afternoon, 24 July, and sailed to nearby Captain’s Bay to calibrate the acoustic instruments.

A line diagram of MILLER FREEMAN showing the location of the centerboard below the hull

A line diagram of MILLER FREEMAN showing the location of the centerboard below the hull

Background 

Acoustics is the scientific study of sound: its generation, transmission, and reception.  Sound travels in waves at known rates, and the physical properties of the material the waves travel through affect the speed of sound.  These properties of sound waves enable their use in medical diagnosis, testing critical materials, finding oil-bearing rocks underground, and counting fish in the ocean. Sound travels through seawater of average salinity about 5 times faster than through air (~1,500 m/s, or about 15 football fields in one second).  Many animals that live in the ocean rely on sound more than vision for communication and survival. You are probably already familiar with echolocation and communication vocalizations in whales and porpoises.

Picture of the transducers in the centerboard, which is lowered when the ship is at sea. Lowering the transducer away from the hull reduces the noise interference of bubbles running along the hull while underway.

Picture of the transducers in the centerboard, which is lowered when the ship is at sea. Lowering the transducer away from the hull reduces the noise interference of bubbles running along the hull while underway.

The speed of sound in water increases as temperature and salinity increase.  It also increases with depth due to the increase in pressure.  Therefore, in order to know the speed of sound at a given location in the sea, you need to know the temperature, salinity, and depth. There are other factors that are important to consider as well.  As sound travels through seawater it loses energy because of spreading, scattering and absorption.  When sound waves strike bubbles, particles suspended in the water column, organisms, the seafloor, and even the surface, some of the energy bounces off or is scattered. When the sound energy is scattered at angles greater than 90 degrees it is referred to as backscatter.

Fish Assessment 

Scientists use acoustics to measure fish abundance in the ocean by emitting sound waves at specific frequencies and then measuring the amount of backscatter.  Different organisms and other objects will have a characteristic backscatter that is dependent on many biological factors as well as the physical properties of the medium. The most important biological factor is presence and the size of a swim bladder, but also the organism’s size, shape and orientation.  If scientists know the backscatter signature of the target species (which can be determined experimentally or by mathematical models), they can use sound to identify and measure certain fish populations in the ocean. Onboard the ship, sound waves are emitted from an instrument called a transducer, which is located in the centerboard of the ship. The transducer generates sounds directly beneath the ship into the water column below (pings).  When these sound waves are backscattered from the fish below back to the transducer, they are converted to an electrical signal that is sent to the scientist’s computer.  There, a profile can be created that represents the fish in a graphical image.

Chief Scientist, Patrick Ressler, attaches calibration spheres to the line that will be lowered beneath the ship.

Chief Scientist, Patrick Ressler, attaches calibration spheres to the line that will be lowered beneath the ship.

Before making any actual measurements during this study, it is necessary to calibrate the acoustic instruments on board the ship. Calibrations of instruments and other measuring devices are done by using a known standard to compare the output of the instrument. So for example, if I wanted to calibrate a stick as a measuring device, first I would compare its length to a known standard such as a ruler. We anchored in Captain’s bay, on both bow and stern to keep the ship from moving much, and spheres with known acoustic properties were suspended beneath the ship at a known distance below the transducers. Acoustic data were then collected on backscatter from the spheres. Knowing the distance to the spheres, their acoustic qualities (how they will backscatter the sound), and the physical qualities of the medium (seawater temperature and salinity) allowed the scientists to standardize their equipment.   While acoustic calibrations were performed by the scientists, the survey technicians collected seawater temperature and salinity. The way these properties are measured is standard practice on research vessels.  An instrument package called a “CTD” measures conductivity (which is converted to salinity), temperature, and depth.  Sensors for each of these make up the package, and are mounted on a metal frame called a rosette. The rosette is lowered into the water column by a crane, and the data collected is transmitted via a cable to a computer on board. Once the calibration and CTD measurements were completed, we pulled anchor and headed northwest into the Bering Sea to meet up with NOAA Ship OSCAR DYSON.  We expect to reach our rendezvous point by late Friday to begin our study.

Survey Technician Tayler Wilkins monitors the CTD data transmission while communicating with the crane operator as the rosette is lowered through the water column. The computer automatically produces a profile of temperature and salinity with depth.

Survey Technician Tayler Wilkins monitors the CTD data transmission while communicating with the crane operator as the rosette is lowered through the water column. The computer automatically produces a profile of temperature and salinity with depth.

Personal Log 

The long stay in Dutch Harbor made the departure that much more exciting.  I am looking forward to what little time is left.  The crew of MILLER FREEMAN have all made me feel welcome, and have been helpful in answering my questions and educating me on shipboard operations.

New Terms 

acoustics, calibration, backscatter, centerboard, transducer, CTD rosette

Learn more here