February 28, 2012 Slocum Gliders
My plan for today was foiled by the weather. I’ve been extremely fortunate in that I’ve been able to get out on the zodiacs to help with fieldwork every day since my arrival. Today I was planning to accompany scientists from Rutgers University to help them with their sampling, but the high winds we’re experiencing make it unsafe to travel by zodiac. The researchers from Rutgers use Autonomous Underwater Vehicles (AUVs) to collect data for the Antarctic Long Term Ecological Research (LTER) program.
The scientists deploy wireless Slocum gliders off Anvers Island to collect data about phytoplankton abundance near Palmer Station. Gliders are valuable tools because they allow real-time data collection. The gliders fly near a submarine canyon responsible for nutrient-rich water that results from upwelling. The nutrient-rich water is responsible for causing phytoplankton blooms, which provide food for krill. Krill are eaten by penguins and some seals, which are the apex predators in this ecosystem. Collecting data about the upwelling from the submarine canyon allows scientists to test various food web interaction hypotheses as well as providing information about how those interactions are being impacted by changing climate.
I spent some time in the lab today with Travis Miles and Katie Brennan, two of the people from Rutgers working on the glider project. Travis is a physicist getting a PhD from Rutgers and Katie is a research assistant. Here's Travis explaining some data collected by the gliders:
The way the gliders work is fascinating! Here are the answers to some frequently asked questions:
How does an underwater glider fly?
Unlike submarines, the gliders do not use a propeller to move through the water. The gliders are too small to carry enough battery power to operate a propeller for long, so instead they move by changing their buoyancy. To do this they change their density so they alternate between being more dense or less dense than the surrounding ocean water. Changes in buoyancy cause the glider to rise and sink in the ocean. The glider changes its density by moving a small piston forward and back to increase and decrease its volume. The density of an object is its mass divided by its volume; because the mass of the glider is constant, the volume is changed to alter its density. Small changes in volume are all that are needed to change the density of the glider so that it will rise or sink. As the glider moves up and down, its wings provide forward motion.
Why are they called Slocum gliders?
The gliders are named after Joshua Slocum, the first man to sail around the world on his own. He wrote a book in the year 1900 about his adventures called “Sailing Along Around the World.” The gliders are designed to travel the oceans alone, like Captain Slocum.
How deep do the gliders go?
The gliders fly between 5 meters and 100 meters (15 to 300 feet) below the surface of the ocean. Check out this short video to get an idea of what it's like for a glider to fly underwater.
How big are the gliders?
The gliders weigh about 60.6 kilograms (134 pounds). Batteries comprise almost 40% of the glider’s weight. They are about 8 feet long and can be easily launched and recovered from a small boat.
How are the gliders controlled?
Each day, pilots look at maps via Google Earth to determine where the ocean currents are most favorable for the glider. Pilots choose the best path for maximizing the glider’s speed and save the coordinates in a file for transmission to the glider. When the glider calls home, it uploads the data collected and checks its instructions from the pilots. It continues diving and rising until a timer goes off at which time it calls home again for new instructions from the pilots.
If weather permits, I’ll try again to go sampling with this group of scientists on Thursday, so I’ll tell you more about it then! This afternoon I’m going to Skype with Mrs. Morse’s class at Tuckahoe Elementary School in Arlington, VA and I’m really looking forward to it.