Frank Hubacz: ADCP Deployment, May 2, 2013

NOAA Teacher at Sea
Frank Hubacz
Aboard NOAA ship Oscar Dyson
April 29 – May 10, 2013

 

Mission: Pacific Marine Environmental Laboratory Mooring Deployment and Recovery
Geographical Area of Cruise: Gulf of Alaska and the Bering Sea
Date: May 2, 2013

Weather Data from the Bridge:

Partly sunny, WindsN 5-10 knots
Air Temperature 1.3C

Relative Humidity 60%

Barometer 1008.2 mb

Surface Water Temperature 2.8C

Surface Water Salinity 31.37 PSU

Science and Technology Log

As I described previously, one of the instruments being deployed on this cruise is an Acoustic Doppler Current Profiler (ADCP), which measures speed and direction of ocean currents across an entire water column using the principle of Doppler shift (effect).  The Doppler Effect is best illustrated when you stop and listen to the whistle of an oncoming train.  When the train is traveling towards you, the whistle’s pitch is higher. When it is moving away from you, the pitch is lower. The change in pitch is proportional to the speed of the train.  The diagrams below illustrates the effect.

Doppler Effect
Doppler Effect
Another view of the Doppler Effect
Another view of the Doppler Effect

The ADCP exploits the Doppler Effect by emitting a sequence of high frequency pulses of sound (“pings”) that scatter off of moving particles in the water. Depending on whether the particles are moving toward or away from the sound source, the frequency of the return signal bounced back to the ADCP is either higher or lower. Since the particles move at the same speed as the water that carries them, the frequency shift is proportional to the speed of the water, or current.

The ADCP has 4 acoustic transducers that emit and receive acoustical pulses from 4 different directions. Current direction is computed by using trigonometric relations to convert the return signal from the 4 transducers to ‘earth’ coordinates (north-south, east-west and up-down. (http://oceanexplorer.noaa.gov/technology/tools/acoust_doppler/acoust_doppler.html).  The most common frequencies used on these units are 600 KHz, 300 KHz, and 75 KHz.  The lower the frequency the greater the distance that the wave can propagate through the ocean waters.

Determining current flow helps scientist to understand how nutrients and other chemical species are transported throughout the ocean.

Typical 4 beam ADCP sensor head. The red circles denote the 4 transducer faces.
Typical 4 beam ADCP sensor head. The red circles denote the 4 transducer faces.

Prior to sailing, ADCP mooring locations are selected by various research scientists from within NOAA.  Next, engineers develop a construction plan to secure the unit onto the ocean floor.  Once designed, the hardware needed to construct the mooring is sent to the ship that will be sailing in the selected mooring locations.  Prior to arriving at the designated location it is the responsibility of the science team to construct the mooring setup following the engineering diagram shipped with each ADCP unit. ADCP moorings can be constructed to hold a wide variety of measuring instruments depending upon the ocean parameters under study by the research scientist.

ADCP Construction Diagram
ADCP Construction Diagram

The moorings are built on the ship’s deck starting with an anchor.  The anchor weight is determined based upon known current strength in the area where the mooring will be located.  Anchors are simply scrap iron railroad train car wheels which bury themselves into the sediment and eventually rust away after use.  The first mooring unit that we assembled had an anchor composed of two train wheels with a total weight of 1,600lbs.  Although this mooring was built from the anchor up this is not always the case.  When setting very deep moorings the build is in the reverse order.

Selecting the anchor
Selecting the anchor
Anchor on the back deck
Anchor on the back deck below the gantry

Next, an acoustic release mechanism is attached to the anchor by way of heavy chains.  This mechanism allows for recovery of the ADCP unit as well as the release mechanism itself when it is time to recover the ADCP.  The units that we are deploying will remain submerged and collect data for approximately 6 months.

Acostic Release Mechanism
Acoustic Release Mechanism
Bill attaching the acoustic release mechanism
Bill attaching the acoustic release mechanism

Finally, an orange closed-cell foam and stainless steel frame containing the actual instrumentation is connected to the assembly and then craned over the back deck.  The stainless steel frame has a block of zinc attached to it which acts as a sacrificial anode.  Sacrificial anodes are highly active metals (such as zinc) that are used to prevent a less active metal surface from rusting or corroding away.  In fact, our ship has many such anodes located on its hull. Once the entire unit is in position, a pin connected to a long chord is pulled from a release mechanism and the unit is dropped to the ocean floor.  Date, time, and location for each unit are then recorded. 

Hoisting ADCP
Hoisting ADCP
ADCP unit assembly
ADCP unit assembly
Assembling mooring unit
Assembling mooring unit
Ready for launch
Ready for launch

To recover the unit, an acoustic signal (9-12 Khz) is sent to the ship from the sunken mooring unit to aid in its location.  Once located, a signal is used to activate a remote sensor which powers the release mechanism to open.  The float unit then rises to the surface bringing all of its attached instruments along with it.  The stored data within the units are then secured and eventually sent along to the research scientist requesting that specific mooring location for ocean current analysis.

Recovering a mooring with a rope lasso
Recovering a mooring with a rope lasso

Personal Log

On my first day of “work” I was able to watch the science teams deploy three different ADCP moorings as well as conduct several CTD runs.  I will discuss CTD’s in more detail in future blogs.  I was impressed by the camaraderie among all of the science team members regardless of the institution that they represented as well as with members of the deck crew.  They all work as a very cohesive and efficient group and certainly understand the importance of teamwork!

Adjusting to my new work schedule is a bit of a challenge. After my work day ended today at 1200 hours, I fell asleep around 1500 hours for about 4 hours.  After trying to fall back asleep again, but to no avail, I decided to have a “midnight” snack at 2000 hours (8pm).  I finally fell asleep for about 2 more hours before showering for my next shift.  I think I now have more empathy for students who come to my 8am chemistry class and occasionally “nap”!

A wide selection of food is always available in the ship’s galley. I have discovered that I am not the only one taking advantage of this “benefit”!  I will definitely need to reestablish an exercise routine when I return home.  We are currently heading for Unimak Pass which is a wide strait between the Bering Sea and the North Pacific Ocean southwest of Unimak Island in the Aleutian Islands of Alaska.

Did you know that since the island chain crosses longitude 180°, the Aleutian Islands contain both the westernmost and easternmost points in the United States. (172° E and 163° W)!

180 longitude

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.

Diane Stanitski: Day 16, August 26, 2002

NOAA Teacher at Sea

Diane Stanitski

Aboard NOAA Ship Ka’imimoana

August 16-30, 2002

Day 16: Sunday, August 26, 2002

Today we are at the equator!!! (0° latitude, 140° west longitude)

The FOO (Field Operations Officer)’s quote of the day: 

“The greatest thing in the world is to know how to be self-sufficient.”
– Michael de Montaigne

Weather Log:
Here are our observations at 1400 today:
Latitude: 0°02’N
Longitude: 139°56’W
Visibility: 12 nautical miles (nm)
Wind direction: 140°
Wind speed: 9 kts
Sea wave height: 3-4′
Swell wave height: 5-7′
Sea water temperature: 27.1°C
Sea level pressure: 1010.3 mb
Cloud cover: 4/8, Cumulus, Altocumulus

Hurricane Fausto is currently located at 21.3°N, 132.7°W and continues to diminish in strength. It has sustained winds of 60 kt, gusting to 75 kt. and is moving toward 300° (WNW) at 15 kt. Its central pressure has risen to 987 mb.

Greeting:

First of all, I’d like to say WELCOME to my classes at Shippensburg University. Today is the first day of classes there and I want to acknowledge those people who are helping to cover my classes and are also assisting with the link between me and my students this week and next. Those who have helped tremendously include Drs. Niel Brasher, George Pomeroy, William Rense, Christopher Woltemade, and Holly Smith. Thank you!

I have already received email messages from many of you in my classes. Remember, part of your assignment for this first week is to email me at least 3 times asking me questions about the ship’s operations, science on board, or anything else that you feel would be of interest to you. Please read all of my logs, check out my photos, watch the previous videos, and follow the path that the ship takes across the Pacific Ocean. We’ll be referring to all of the information shared on the web throughout the semester. Welcome to the Pacific Ocean – glad you could join me!

Science and Technology Log:

I awoke and immediately starting preparing for our second general broadcast of the trip. Seven guests were scheduled to be interviewed during this broadcast. They did an excellent job. Unfortunately, Dave Zimmerman was immersed in the operations of the morning Acoustic Doppler Current Profiler (ADCP) retrieval and deployment, and so couldn’t join us for a short interview. I’ll try to catch him again when things aren’t quite as hectic. Overall, the show went well and I’ll spend the rest of the day preparing for the next three broadcasts with my students in Introduction to the Atmosphere, Meteorology, and the Atmospheric Environment at Shippensburg University. I’m anxious to meet everyone in the classroom from the ship to share some of the things that I’ve been learning on board the Ka’imimoana. Please check out all of the videos on this web site to see who I’ve interviewed in the past. The ship’s scientific equipment and research, and my interactions with scientists using them, will definitely add to what I teach in the classroom, which should make for a more interesting and valuable experience for all of you.

Here are some interesting facts about the ADCP. It is a subsurface mooring, which means that it is anchored to the bottom of the ocean but remains nearly 300 meters below the surface of the water, and it measures current velocity profiles. It is a large round floating orange sphere (see photo logs) that measures the velocity of ocean currents in approximately the upper 250 meters of the ocean using the Doppler effect. Today, after triggering the acoustic release separating the anchor from the old ADCP that was being replaced, the instrument emerged at the surface of the water, was spotted, and then dragged through the water to the ship where it was hoisted up with one of the ship’s cranes onto the fantail. The thousands of meters of line were then reeled in and later deployed again with a replacement ADCP attached. The instrument uses the Doppler effect meaning that there is a change in the observed sound pitch that results from relative motion of an object, in this case water. If something is coming toward you, the wave frequency appears to be higher and if something is going away from you, the frequency of waves appears to be lower. The example that is always used is that of a moving train. The train’s whistle has a higher pitch when the train approaches and a lower pitch when it moves away from you. The change in pitch is directly proportional to how fast the train is moving. If you measure the pitch and how much it changes, you can calculate the speed of the train.

ADCPs use the Doppler effect by transmitting sound at a fixed frequency and listening to echoes returning from waves and sound scatterers in the water, such as small particles or plankton reflecting the sound back to the ADCP. Scatterers float in the water and on average they move at the same horizontal velocity as the water. When these scatterers move toward the ADCP, the sound heard by the organisms is Doppler-shifted to a higher frequency. The ADCP uses four beams to obtain velocity in many dimensions. Overall, it’s an amazing instrument.

The equatorial buoy was retrieved tonight and a new one will be deployed tomorrow. That buoy will be dedicated to the Grace B. Luhrs Elementary School and Shippensburg University. It will be signed by the Captain, Chief Scientist, and me, and will be located at 0°, 140°W for the next year. Shippensburg’s name will be on the Pacific for at least 365 days!

Personal Log:

Most of my afternoon and evening was spent answering emails and preparing lesson plans. I am looking forward to tomorrow’s activities but have many miles to go before I sleep. Keep in touch!

Question of the day: 

At what heights in the atmosphere are altostratus or altocumulus clouds found?

One of my Meteorology students, Steve Osmanski, provided the correct answer to my previous question of the day, “what are crepuscular rays?” His answer is: “They are the classic ‘sunburst’ effect caused when sunlight is blocked by a cloud and appears to be “streaming in rays” around the shadow. They are visible from scattering of sunlight by dust or water droplets, and appear to diverge as a trick of perspective.” Excellent, Steve! I look forward to having you in class!

Until tomorrow…
Diane

Dana Tomlinson: Day 12, March 12, 2002

NOAA Teacher at Sea

Dana Tomlinson

Aboard NOAA Ship Ka’imimoana

March 1 – 27, 2002

Date: Tuesday, March 12, 2002
Lat: .5°S
Long: 110°W
Seas: 2-4 ft.
Visibility: unrestricted
Weather: partly to mostly cloudy
Sea Surface Temp: 77-82°F
Winds: N/NE 5 knots
Air Temp: 88-76°F

As it turns out, the ADCP (Acoustic Doppler Current Profiler) was rigged up to deploy when I went outside this morning. The scientists had determined a new method of having it enter the water so there would be even less likelihood of anything going wrong. And they did a great job, because it was a very easy deployment. Mission accomplished – there’s an ADCP successfully collecting data on the equatorial currents at 110°W for the next year.

There was even more excitement to come for me, however. I had the privilege of being the first Teacher at Sea to ever have a buoy dedicated to her school. At 1130 today, Cdr. Tisch, Chief Scientist McPhaden and I each signed a large NOAA sticker on which we had written “Emory Elementary School, San Diego CA.” The gentlemen placed it on the plastic covering of the instrumentation and when it was deployed at the equator 110°W, that sticker actually kept its face to us until we could no longer read it. What’s truly amazing is that very buoy was the very first buoy that NOAA ever deployed in 1979. Our school is very honored.

The deployment of the Emory buoy took quite a while today because of the many fairings that the crew had to put on the wire line that goes down 250m below the buoy. Tomorrow is also a busy day on board. We are doing several CTD casts (Conductivity, Temperature and Depth), and we will be going by the buoy at 2°S to check on it, but we’re not recovering it.

Question of the Day: 

What is a fairing and what does it do?

Answers of the Days: 

Due to the weekend, there are several questions to catch up on. Here we go:

From Friday: No one answered this one correctly, so I’m going to give it to you. GMT is Greenwich Mean Time. It is 7 hours ahead of us here in Mountain Time and it is where all time is based because it is the 0 degree line of longitude. In nautical letters, zero is Zulu, hence, Zulu time. So, if it’s 9pm here in Mountain time, in GMT it is 4am.

From Saturday: Ditto on no answer for this one (come on you guys!!).
TAO stands for Tropical Atmosphere Ocean.

From Sunday: Karen R. in San Diego knows that MBARI stands for Monterey Bay Aquarium Research Institute. And Vanessa P.(again!) in San Diego knows that pelagic means of the open ocean. And Brian R. in San Diego knows that chlorophyll is the green matter found in certain cells of plants, algae and some bacteria and it’s important because it changes light energy into chemical energy.

Til tomorrow,
🙂 Dana

Dana Tomlinson: Day 11, March 11, 2002

NOAA Teacher at Sea

Dana Tomlinson

Aboard NOAA Ship Ka’imimoana

March 1 – 27, 2002

Date: Monday, March 11, 2002
Lat: 
Long: 110°W
Seas: 2-5 ft.
Visibility: unrestricted
Weather: cloudy, rain possible
Sea Surface Temp: 77-82°F
Winds: N/NE 5 knots
Air Temp: 88-77°F

What an interesting day, all the way around. Weather-wise, we awoke to clear skies, with clouds on the horizon and we could tell it was going to be hot. By 9am, I could feel the backs of my legs burning with my back to the sun. I went in for lunch and came out and it was totally clouded over and a few minutes later, it was raining! Not drizzling – raining. Welcome to the equatorial Pacific!!

Yes, we made it to the Equator! My days as a Pollywog are numbered. Shellback is coming soon. Today, there were several important events going on onboard. Most importantly to me was our first live webcast. This was an exclusive to my school only and fortunately, was a technical success! It was actually a pretty perfect broadcast, a great way to start. All of the schools that have contacted either the NOAA offices or myself have received word about future live webfeeds. Once again, if there are any teachers out there who would like a live feed right into your classroom or any computer at the school that has an internet connection and RealPlayer (a free download), just let me know asap and we’ll get you the info you need.

The other important events on board today were another buoy recovery (more barnacles!!), a ADCP recovery/deployment and a deep CTD cast (to 3600 meters). The buoy was recovered, but it was 30 miles from where it should have been due to the strong currents at the equator. We will deploy the new one tomorrow morning. It will be a very special buoy – the first one ever dedicated to a school. It will have a sticker on it signed by the Commander, the Chief Scientist and me, dedicated to Emory Elementary! Neat, huh?!

The ADCP is an Acoustic Doppler Current Profiler that’s been in the water for the last year. This is a big, round orange device (a little bit bigger that a weather balloon) with instrumentation on it that records the currents. There are 4 of them across the equator resting at different depths. It is anchored so that it rests 250 feet below the surface and periodically sends sonar waves up to the surface that bounce off of the surface and the plankton above and somehow that helps to record the currents. The information is stored in the device until it is recovered and then the data is learned. Like the buoys, it has an acoustic release device on it that releases it from the anchor when remotely told to do so and it floats to the surface.

The recovery went perfectly. We had a bit of trouble with the deployment, however. Hey, sometimes, things happen and this was one of them. Just as the crew was carefully loading it into the water, a wire snapped and the ADCP fell into the water untethered. It had to be rounded up just like the old one and brought back up on deck. Presently, it’s still sitting there as the scientists decide whether or not to deploy it tomorrow or to wait. Stay tuned.

Question of the Day: 

Above I mentioned being a Pollywog and being a Shellback. What do I mean?

Answer of the Day: 

Once again, since the logs weren’t posted over the weekend, let me give the GMT/Zulu question one more day. 🙂

Til tomorrow,
🙂 Dana