Cindy Byers : I know the MVP, and it is a fish! May 3, 2018

NOAA Teacher at Sea

Cindy Byers

Aboard NOAA Ship Fairweather

April 29 – May 13, 2018

 

Mission: Southeast Alaska Hydrographic Survey

Geographic Area of Cruise: Southeast Alaska

Date: May 3, 2018

Weather from the Bridge:                           

A view from the bridge

A view from the bridge

Latitude: 55°09.01 N

Longitude: 134°43.6 W

Sea Wave Height: 3 feet

Wind Speed: 6 knots

Wind Direction: 170°

 

Visibility: 10+ nautical miles

Air Temperature: 9.5°C  

Sky: Complete Cloud Cover

Science and Technology Log

NOAA Ship Fairweather uses a multibeam sonar to map the ocean floor. Sonar stands for SOund Navigation And Ranging.  This ship’s multibeam sonar sends sound (acoustic energy) to the seafloor in a fan shape, and then listens for the echos. The speed sound travels is vital to knowing the depth the sound has traveled to.  Sound travels about 1500 meters per second in seawater. This is much faster than in air where it travels at about 340 meters per second. Sound speed is an important consideration in ocean floor mapping.

 

What factors influence the strength of acoustic return? (sound back to the ship)

Spreading – As the sound energy gets farther from its source (the bottom of the ship) and after it hits its target, the sound wave gets weaker. This is why you can hear someone standing next to you better than somebody on the other side of a room.

Absorption – The energy of the wave heats up the molecules of water it goes through because of friction and loses energy. This is also the reason you can hear someone standing next to you better than somebody on the other side of a room.

Ambient Noise – . This refers to the fact that the fish, (towed behind the ship) the ship, and wave action are also producing sound sources of their own.  The sound “signal” needs to be extracted from this “noise”.

Target Strength – If the seafloor is muddy, some of the energy of the sound beam will be absorbed and less will be sent back to the ship.  If it is a rocky bottom, the sound energy scatters in different directions and a weaker signal returns.

How is the sound speed measured?

When you hear MVP in sports? MVP means Most Valuable Players, but on NOAA Ship Fairweather the MVP stands for Moving Vessel Profiler. The MVP consists of a small crane on the fantail (the back deck on the ship) that pulls what is called a FISH! The MVP has a computer controlled winch that can be used while the ship is moving.

MVP

This is the MVP that is on the ships fantail

The surveyors (marine technicians) call to the bridge to ask if they can, “take a cast.”  This means they will lower the “fish” to get readings and learn the speed of sound for the area. The bridge, which is where the boat is steered from, will respond that they may cast, only if it is safe.  Our last “cast” measured the water column down to 217 meters as we were travelling at 6 knots (about 7 miles per hour.)  The ship does not drop the “fish” while it is travelling at a high speed because that puts too much tension on the cable.

Bringing in the Fish

Bringing in the “fish”

 

The fish is the instrument that is pulled behind the ship, that collects data. The fish is actually a science instrument, much like the Hydrolab that we use at school.  It is a CTD, and is used to measure conductivity, temperature and pressure. This data allows the CTD to measure the speed of sound.

Grabbing the Fish

This picture show how the fish is grabbed from the water

 

Conductivity is a measurement of the ability of water to conduct an electrical current. The dissolved salts in the water are the conductors of the electricity. The salts, as you may remember, come from the breakdown of rocks and are carried by rivers to the ocean.  These “salts” are electrically charged ions, mostly in the form of sodium and chlorine. So, the conductivity measures the salinity (saltiness) of the ocean. This is very important, because the salinity affects the speed of sound. Since the sonar is sending sound to the bottom of the ocean, conductivity or salinity measurements are very important.

 

 

As sound travels through different densities (caused by the salinity) it causes refraction. You have seen refraction when you put a straw in a glass of water.  The straw appears to bend. So the salinity of the water needs to be measured using the conductivity instruments in order to account for different densities caused by the salinity levels.

The Fish Out of Water

Here is the fish out of water!

Temperature also affects the density of the water.  Colder water is more dense than warmer water. Remember when we studied how colder air is more dense than warmer air?

Since salinity and temperature change with depth, the CDT also measures depth. All three of these instruments together help determine the speed of sound through the water.  Since the sonar uses sound to map the ocean floor, measuring the speed of sound is vital for collecting good data.

The speed of sound generally increases with an increase of temperature, salinity or pressure.

 

 

 

CDT

These are two CDT’s (Conductivity, Density and Temperature) that can be used if the ship is not moving. They sure look like our Hydrolab!

 

Did you know?

Datum –  a noun meaning a piece of information, while data is plural.

Swath – a fan shaped area created by the sound beams

Transducer – where sound leaves from.

Receiver – where the sound comes back to.

Personal Log

One of the most exciting things about being at sea, is seeing animals.  On our first day out we were lucky to see a pod of orcas whales (killer whales.) Since then, someone on board reported the whales and got information back from NOAA Fisheries about whales they could identify from the pictures sent. We found out that whale A4,  named Sonora, and one of her four offspring A46, named Surf, were part of pod A5 which is a group that usually is in the water near British Columbia, but sometimes can be found in southeast Alaska, where we are right now. One male, named A66, was identified by the pictures. He was born in 1996! Look for more information about this pod here http://cetacousin.org/wild-database/orcas/northern-resident-orcas/ or http://orcinusorca.nl/

Orca

An Orca     Photo Credit Megan Shapiro

Two Orca Whales

Two Orca Whales Photo Credit Megan Shapiro

 

Orca

Orca whale near Ketchikan, Alaska           Photo Credit Megan Shapiro

 

Today we saw group of Dall’s porpoise.  They are very fast moving porpoise. They are found in the Northern Pacific Ocean in groups of 2-20 and can live 15-20 years. Individuals are about 7-8 feet long.

Dall's Porpoise

A Dall’s Porpoise, courtesy of NOAA

Information about Dall’s Porpoises:

“Dall’s Porpoise (Phocoenoides Dalli).” NOAA Fisheries, National Oceanic and Atmospheric Administration, 15 Jan. 2015, http://www.nmfs.noaa.gov/pr/species/mammals/porpoises/dalls-porpoise.html.

 

Rebecca Kimport, JUNE 29, 2010 part2

NOAA Teacher at Sea Rebecca Kimport
NOAA Ship Oscar Dyson
June 30, 2010 – July 19, 2010

Mission: Summer Pollock survey
Geograpical Area:Bering Sea, Alaska
Date: June 29,  2010

Time with Birds and Mammals

On our way out of Dutch Harbor and Captain’s Bay, I spent some time on the bow with Katie, Michele and birder Nate Jones. As I know very little about birds, I quizzed him on every flying specimen we encountered and used his binoculars to observe the birds up close. After a few sightings, I was able to identify the Fulmar by its unique wing movement (quick quick quick soar). We also saw tufted puffins and a black-footed albatross. There are two birders (Nate and Marty from US Fish and Wildlife Service) on this leg who are responsible for scanning the horizon and counting and identifying the seabirds they observe from the bridge.Here is bird observer Nate Jones scanning the horizon for seabirds:

Nate Jones observing

Nate Jones observing

We were distracted from our bird watching by a call of orcas. We hustled up to the “flying bridge” to join the marine mammal observers. There are three “mammals” (Paula, Yin and Ernesto from the National Marine Mammal Laboratory) on this leg and they are constantly scanning the horizon with their “big eyes” to observe and identify cetaceans. I was able to observe two separate groups of orcas and heard that porpoises were also spotted.Here is marine mammalian observer Ernesto Vazquez looking through the big eyes on the flying bridge:

Ernesto observing mammals

Ernesto observing mammals

Although I am technically on the fish shift, I hope to check in with the “birds” and “mammals” later in the cruise. After spotting birds and mammals, it’s time for the first installment of the “animals seen” list:Animals Seen in Dutch Harbor
Bald eagles
Ground Squirrel
Sea Urchin
Sea Stars
Sea Cucumber
Pigeon Guillemot
Oyster Catchers
Mussels
Chiton
Limpets
Hermit Crabs
Snails
(but no horses…)Animals Seen in Transit
Orcas
Fulmars
Black Footed Albatross
Tufted Puffin

UPDATE
As many of you know, I am a horrible speller. When I went to check the spelling for the birds I had seen, I spotted a Thick-billed Murre from the bridge. Okay, in reality, the observation and identification went more like this:

Me: “Hey that’s a bird”
Nate: “Yes, it was a Thick-billed Murre”

I am impressed by the seabird and marine mammal observers’ abilities to spot and identify birds and mammals from such far distances. Like any recall-related skill, I recognize that animal identification takes both an innate talent and years of practice. But the animal observers also need to have extreme patience to maintain a clear focus, a methodologically-sound routine and a sense of possibility (as the weather is not always in their favor). We’re lucky to have such talented scientists counting species in the Bering Sea.

As we say goodbye to land, we know the real adventure is about to begin

Goodbye Land

Goodbye Land

More soon!