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Exploring Carolina Canyons by the Numbers

September 8, 2017
Sunset at sea.

Sunset at sea.

  • 25,000 gallons of water used.
  • 2 ship safety drills, which required putting on immersion suits both times.
  • 7 Sentry dives.
  • 22 CTD stations.
  • 4.7 TB of data collected by Sentry.
  • 400 freshly baked chocolate chip cookies consumed.
  • 1 live audio presentation piped into the SECU Daily Planet Theater at the Museum.
  • 105.5 hours of time underwater for Sentry.
  • 200 bottles and bags of mud collected.
  • 14,000 gallons of fuel consumed.
  • 139.5 km traveled by Sentry.
  • 69,691 photos taken by Sentry and reviewed by the Chief Scientist.
  • 4 photo-worthy sunsets.
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Life in the Mud

September 7, 2017

When you think of canyons on land, you picture deep, steep sides with a river at the bottom. Rockslides and mudslides bring debris crashing down, and evidence of them can be seen strewn across the canyon floor. But what happens in deepwater canyons? What evidence can we find of what is raining down from above?

Launching the CTD.

Launching the CTD.

During this mission we are using a Conductivity, Temperature, and Depth (CTD) instrument to sample the water column. Attached to that is a monocore, which plunges into the mud and brings back a 2-inch-diameter core sample. These two tools are helping us gain an understanding of how nutrients and minerals cycle in the canyons by sampling “what is raining down from above.”

The CTD consists of both sensors to collect water chemistry data and Niskin bottles, which sample water at specific depths. We use charts to determine the best locations for sampling based on depth and the geography of the canyon. The sampling sites cover a variety of areas in the canyon – some near the mouth of the canyon, others in its deepest recesses. Using a winch, we lower the CTD and monocore over the side, letting the apparatus sink until the monocore hits bottom. As the CTD returns to the surface, we stop at the predetermined depths and fire the Niskin bottles. The bottles seal tightly, allowing no additional water in. The number of samples you take is dependent upon the number of bottles your CTD can hold. We usually took eight water samples, and always sampled at the bottom and surface.

Rob filtering water from the CTD.

Rob filtering water from the CTD.

Once the CTD is back on deck, the water from each Niskin bottle is collected in clean containers. This water is run through a 0.7-micron glass fiber filter, concentrating the particulate matter. The filters are kept frozen until they are brought back to the lab. Once back on shore, the researchers scrape off the material captured on the filters, and analyze it for organic content. Comparing what we find at the top to what is found near the seafloor helps us understand what “food” is making its way down into the canyons. The surface of the ocean is highly productive, with phytoplankton converting the sun’s energy into fuel useful for animals. Examining these filters tells us the quantity, and chemical signature, of the food that is available at the top. We can then compare it to the quantity and chemical signature of what we collect close to the bottom.

The core sample of mud.

The core sample of mud.

The monocore also returns to the deck, bringing a cylindrical core sample of the bottom. While the sample depends upon the make-up of the seafloor (for example, we do not get a sample if the bottom is rocky), we usually bring up a tube of mud that is about 10 centimeters high. Precise slices are taken from the core and preserved for future examination. Formalin is added to some samples in order to preserve the animals that might be present, such as small worms and tiny crustaceans. Most of these animals are found in the top two centimeters. Other samples are used to look at the physical and chemical make-up of the mud, such as particle size (is it more sand or more silt?) and the percentage of organic matter.

Amanda is ready to preserve samples.

Amanda is ready to preserve specimens.

While these tiny animals that live in the deep dark ocean might not appear to be relevant to our life on land, they perform important functions, helping cycle nutrients and sequestering carbon. They are part of the food chain and are eaten by many things including bottom-dwelling fish and crabs that sift through the mud hunting for these prey.

Some of the jars of preserved mud.

Some of the jars of preserved mud.

Full Fathom Five

September 6, 2017

Full fathom five thy father lies;

Of his bones are coral made;

— From Ariel’s Song by William Shakespeare

The Tempest, Act I, Scene II

Todd and Robert working with the Multibeam.

Todd and Robert working with the Multibeam.

When you look at a nautical chart, you see the depths of the area scattered about. There are also contour lines indicating the general slope of the seafloor. So why then, you might ask, are we spending some of our time mapping?

An example of a nautical chart.

An example of a nautical chart.

We are mapping because there are only limited areas with detailed maps of the seafloor. Every chart lists the dates when the surveys were conducted to gather the printed information. You’ll see specific areas, such as places important for commerce, that have been updated between 1990 and 2013. However, if you look at larger, more remote areas, you’ll find that most of that information is pre-1900. So not only is the data old, it was made using less sophisticated technology. Additionally, these old maps are not very detailed. Imagine if your road map only gave you the interstates and you wanted to explore a little town off the beaten path?

Multi-beam mapping allows us to generate much more detailed maps of the seafloor. Mapping still relies on sonar, but the signal is split into several beams. As the information bounces back, it is compared to the other pieces of information to keep everything within the same parameters. If all the beams except one read the depth as 1000 meters, and the outlier reads ten meters, then the ten meter reading will be averaged out automatically at that point. The ship is able to send out these beams to a width about three times the depth of the sea beneath it. If we are in 100 meters of water the ship can map a track about 300 meters wide. Generally, to map an area, we run back and forth, following lines drawn over the area of interest. On board this is sometimes affectionately called “mowing the lawn” because the motion of the ship is much like that of a lawnmower.

An example of mapping the track, or 'mowing the lawn.'

An example of mapping the track – “mowing the lawn.”

On this mission the beams come off of the ship in a V-shape, and the information gathered by the center beam is more accurate and detailed than the beams on the sides. When the sounding files return, a computer program makes corrections to account for a wide variety of variables, including water temperature, the speed of the ship as it moves along, sound velocity, tidal effect and where we are in the world. When all of these parameters are checked we have a 95% confidence in the accuracy of our depth.

We have access to some extremely accurate maps, but there are places where information is missing. We are attempting to help fill in some of the missing data by targeting specific locations that are near our study sites.

Todd Walsh is the Hydrographic Senior Survey Technician on the NOAA Ship Pisces. With help from Robert Figueroa-Downing, Todd is leading our mapping activities. Todd says that being a hydrographer is a great way to travel all over the world. He has worked from within the Arctic Circle to Midway Atoll, and has enjoyed mapping new places, including newly discovered wreck sites. While he says it is good to have a math and science background, having excellent computer skills is really key to this career.

In Ariel’s song, Shakespeare references “full fathom five,” meaning Ariel’s father is lying in 30 feet of water (1 fathom=6 feet). The desire to know what lies beneath the waves, and how deep it lies, has been a question for hundreds of years. Today’s work is helping answer that question.

Adding Pieces to the Puzzle

September 4, 2017
Launch of AUV Sentry in the evening. Photo credit: Liz Baird.

Launch of AUV Sentry in the evening. Photo credit: Liz Baird.

The Autonomous Undersea Vehicle (AUV) Sentry is a marvelous tool for exploring the ocean. It is pre-programmed to follow a designated path along the seafloor. The members of the Sentry crew watch her every move, and make adjustments to keep her on target. While down, Sentry is taking high definition images, running side scan sonar and recording a variety of environmental variables such as depth, salinity, temperature, and dissolved oxygen. Every image is geo-referenced, so we know where the photo was taken and can match it to the corresponding data. Sentry is set up to take one image every three seconds, which results in thousands of images from every twelve-hour deployment.

Dr. Martha Nizinski reviewing photos. Photo credit: Liz Baird.

Dr. Martha Nizinski reviewing photos. Photo credit: Liz Baird.

Chief Scientist Dr. Martha Nizinski is interested in learning more about the deepwater canyons off the coast of North Carolina. She is focused on looking for deepwater corals. There is a great deal of interest in deepwater corals, and we are still gathering some fundamental information such as where they are located, how abundant they are, where are they distributed, and how diverse they are. Our study sites were chosen based upon historic evidence, bathymetry, and habitat suitability models. By using Sentry, we can take pictures of the seafloor, looking for coral over a large geographic area in a short period of time.

Sea Urchins on the seafloor.

Sea Urchins on the seafloor.

Brittle Stars on the seafloor. The two red lasers are 10 centimeters apart so that the researchers can estimate the sizes of objects in the image.

Brittle Stars on the seafloor. The two red lasers are 10 centimeters apart so that the researchers can estimate the sizes of objects in the image.

When Sentry returns to the deck of the ship, Dr. Nizinski begins reviewing the low resolution images. While Sentry does have an altimeter to keep it at the correct height off the seafloor, not every image is focused on an animal or geologic feature. This morning’s set of photos contained more than 10,000 images! These photo reviews help us determine whether to continue working at the same site or to move on to a new location.

The area around Cape Hatteras is very interesting because of the numerous canyons incising the continental shelf. Additionally, the Gulf Stream and the colder waters coming down from New England intersect in this region. Using the AUV Sentry is really the first step in studying the North Carolina canyons. We can take information from this mission, and refine our study locations and sampling tools to complete a more detailed exploration of a smaller geographic area.

Having explored more than 30 canyons, Dr. Nizinski knows that knowledge from a variety of the canyons is key. We must assess what each has to offer if we are to wisely manage our marine resources. This research mission is adding another piece to the puzzle of understanding our deepwater canyons.

Pilot Whales Off the Bow!

September 2, 2017
Pilot Whales - note the rainbow from the blow! Photo credit: Liz Baird.

Pilot Whales – note the rainbow from the blow! Photo credit: Liz Baird.

It is not unusual to have dolphins riding the bow wave off the front of a ship, but yesterday we were treated to a visit from a special member of the dolphin family – Pilot Whales! With their dark black or gray backs and large rounded heads, they are easy to distinguish from their slender streamlined relatives. One look over the bow and we were mesmerized. Having seen Pilot Whales at a distance previously, it was amazing to have them close to the ship.

There are two species of Pilot Whales that occur in the waters off North Carolina – Long-finned Pilot Whales and Short-finned Pilot Whales. All the references we checked said it was nearly impossible to tell them apart while at sea. However, Short-finned Pilot Whales have a lighter gray patch just behind their fins. We did not see that marking, so are assuming that our visitors are the Long-finned Pilot Whales, which are found from North Carolina to Nova Scotia.

Pilot whale mother and calf. Photo credit: Liz Baird.

Mother and calf. Photo credit: Liz Baird.

We were enthralled watching a baby Pilot Whale with its mother. It stuck close to her side, and surfaced when she did. Young Pilot Whales nurse for up to three years, and develop a strong bond with their mothers. In fact, all of the offspring remain with their mother’s pod. They are highly social, living in groups of 10 to 30. They live a long time, with an average lifespan of 45 years for males and 60 years for females.

blow hole

Pilot whale next to the bow – you can really see the blow hole. Photo credit: Liz Baird.

As the whales approached the bow they looked “really big.” Although we could not agree upon their size, we decided they were over 12 feet long. Male Pilot Whales can reach sizes up to 20 feet in length and weigh up to three tons; females can reach sizes up to 16 feet in length and weigh 1.5 tons. Members of the dolphin family, Pilot Whales are one of the largest species, second only to orcas. And like orcas, they have fewer teeth than other dolphins. Pilot whales and orcas have between 40 and 56 teeth, while most dolphins have between 80 and 100 teeth. Perhaps the difference in tooth number is related to differences in their diets. Pilot whales eat primarily squid, while most dolphins feed on fish.

Row

Swimming off in a row. Photo credit: Liz Baird.

The whales appeared to be simply “hanging out.” We watched as they swam from one side of the ship to the other, sometimes diving under the waves and rolling over (we could see the lighter counter shading on their bellies).  We could hear them blow from their single blow hole, and occasionally caught sight of a slightly curved fluke (or tail) as they dove. Pilot Whales belong to the genus Globicephala, which comes from the Latin “Globus” meaning “round ball or globe” and “Kephale”, which means head, in recognition of their large melon-like heads.

We don’t know what attracted them to us. We had a CTD (a type of sampling gear) in the water and wondered if that sound made them curious. Or perhaps they simply wanted to play in our shadow on the sea. After about ten minutes, they swam away from us, lined up in row, leaving us wanting to learn more about these cetaceans.

Navigating without landmarks

September 1, 2017
Launching the Sentry. Photo credit: Martha Nizinski.

Launching the Sentry. Photo credit: Martha Nizinski.

Heading home you pass the familiar landmarks – the gas station, the big old oak tree, the school. You know where you are and know how long it might take to reach your destination. You can call if you are delayed and you can grab a paper map if you need to take a side road. And sometimes you can tap into a GPS to help navigate. “Turn right in 1000 feet,” or “In 5.4 miles take exit 95” can get you home.

Imagine if you didn’t have any of that. No landmarks, no paper map, no GPS, not even roads. How would you figure out where you are? How would you call home to let someone know you were going to be late?

That is the challenge facing the AUV Sentry from Woods Hole Oceanographic Institution. How to determine its location and aid its communicate with the ship for its recovery. It must “know” where it is relative to the ship in order to provide accurate information for the scientists, and must be able to communicate with the NOAA Ship Pisces in order to be recovered after the dive.

The Sentry crew takes care of this by running a “calibration.” Essentially a calibration is a four to twelve-hour test that allows them to align the communication with the AUV. Much like the way we have to align the eight projectors in the Daily Planet Theater at the Museum so that the visitor sees one image, we have to determine the best alignment for our equipment to allow Sentry to focus on one spot on the ship in the sea.

The NOAA Ship Pisces communicates with Sentry through sound waves that are transmitted underwater. The altitude of the GPS, the location of the transceiver, and the gyroscope (GYRO) all change with each pitch and roll of the ship. We have enough background information to make some predictions about the impact of these motions, but we need more accurate data for our work.

Pattern the ship needs to run for the calibration.

Pattern the ship needs to run for the calibration.

The calibration involves putting a reference acoustic transponder overboard with a steel weight attached so that it sinks to the seafloor. The ship drives in a specific pattern (see photo), collecting data about the GPS, GYRO, transceivers and other equipment used in navigation.

Spotting the transponder. Photo credit: Martha Nizinski.

Spotting the transponder. Photo credit: Martha Nizinski.

Bringing the transponder on board. Photo credit Martha Nizinski.

Bringing the transponder on board. Photo credit Martha Nizinski.

After completing this test run, a signal is sent to drop the steel weight, which allows the transponder to return to the surface. Then the crew uses CASIUS software to run the calculations necessary to fix all the errors that occur with the movement of the ship, and provide Sentry with accurate data for the science and the recovery. Without the CASIUS software these calculations could take many days.

We ran our calibration last night, and completed it in five hours, allowing us to launch Sentry right before sunset. Sentry worked all night, collecting data for precise mapping and taking photographs of an unnamed, unexplored canyon in the waters offshore of Oregon Inlet.

What is this?

August 30, 2017

IMG_4036

Good news! It appears we will be able to shove off later this afternoon. While we cannot wait to get some work done, we took advantage of being in port and ran to buy some macarons at lunchtime.