NOAA Teacher at Sea
Onboard NOAA Ship Gordon Gunter
May 15 – June 5, 2015
Mission: Right Whale Survey
Geographical area of cruise: Northeast Atlantic Ocean
Date: June 4, 2015
Weather Data from the Bridge:
Air Pressure: 1025.1 mb
Air Temperature: 13.3 degrees C
Relative Humidity: 64%
Wind Speed: 13 knots
Wind Direction: 63 degrees
Science and Technology Log:
The sounds marine mammals make are often used to study them. Dolphins make clicks and whistles whereas humpback whales mostly sing. North Atlantic right whales also make sounds with their signature sound being described as an up-call, a rising whoop that lasts for about a second. Sei whales, on the other hand make a down-call, a sinking whoop. Right whales also make a variety of other sounds including: 1) eerie moans, 2) shrill screams which often occur when gathered in groups, and 3) a gunshot sound that sounds like a very loud pop and is thought to be an aggressive call towards males. These sounds are not easily heard, but can be observed on a sound spectrogram. A sound spectrogram is a graph of frequency (the number of cycles in a second, given as hertz) on the vertical axis and time on the horizontal axis. Right whale up-calls range in the low hertz levels of 100-300 hertz, while dolphins are much higher in pitch. The darker the call on the spectrogram, the louder the call is. To listen to a variety of right whale calls go to the Right Whale Listening Network for examples.
Right whale up-call on a spectrogram posted on the Northeast Fisheries Protected Species Branch website. Go to link to actually hear the call of a right whale and several other whale species.
Close up of a right whale up-call on a spectrogram. Image from the Right Whale Listening Network.
Whale acoustics can be recorded by a variety of methods. On this cruise we are using two methods: sonobuoys deployed from the ship and autonomous acoustic technology (aka “gliders”). Let’s talk about sonobuoys first. The sonobuoys used on this cruise were first designed for the military but have found a second use in scientific research. They are housed in an aluminum tube about a meter in length and 10 centimeters in diameter. When the tube hits salt water it starts a chain reaction starting with deployment of the bright orange float. The sonobouy, with hydrophones, then bobs freely in the ocean and sends radio signals to an antenna high on the ship’s mast. The signal is then captured by a computer and a spectrogram of the sound is displayed and recorded. The sonobuoy has about an eight hour life span and a five mile range.
There are some limits to sonobuoys, namely the five mile (or more depending on model and antenna location) range. Doctors Baumgartner and Fratantoni at the Woods Hole Oceanographic Institution (WHOI) have developed a means of retrieving real-time detection of whale acoustics from autonomous acoustic gliders. The particular glider used in the Great South Channel is a Slocum glider. It looks a bit like a torpedo. It is programmed to follow a specific track and come to the surface every two hours to send data. The two researchers also developed a computer program that detects, classifies and reports interesting marine mammal calls otherwise the amount of data coming in would be completely overwhelming. The Slocum glider also measures fluorescence and other oceanographic conditions, similar to the CTD.
View of the Slocum glider underwater. Photo from NE Fisheries, Protected Species Branch (Dave Fratantoni, WHOI).
How the slocum glider travels and sends data. (Autonomous Real-time Marine Mammal Detections, WHOI)
For more information on acoustics check out the following links:
- NOAA Northeast Fisheries Science Center, Protected Species Branch
- Passive Acoustic Research, NOAA Northeast Fisheries Science Center, Protected Species Branch
- Discovery of Sounds in the Sea (DOSITS), University of Rhode Island
- Right Whale Listening Network, The Cornell Lab of Ornithology
- Slocum Glider, Woods Hole Oceanographic Institution
- Autonomous Systems Lab, Woods Hole Oceanographic Institution
- Autonomous Real-time Marine Mammal Detections – The Great South Channel, Gulf of Maine – Spring 2015, Woods Hole Oceanographic Institution
Today is the last full day on the ship and it is bittersweet. I have had a wonderful time and will be sad to go (but also glad to get home). I have learned so much about whales and the ocean. I have met some absolutely wonderful people, both scientists and crew. I am very grateful to all for incorporating me into their family. I would love to do this again next year.
Even though we did not see the as many of the right whales that we wanted to, we did see several species including: humpbacks, sei whales, fin whales, minke whales, and Pete saw a sperm whale. Yesterday (June 4th) we were deploying plankton nets encircled by a few dozen feeding humpback whales. It was a spectacular show.
And I will end with a sunset photograph.