What could be mistaken for a surfboard missing its surfer is now the latest tool to help scientists take measurements for critical science missions at Pacific Marine Environmental Laboratory (PMEL).
"Wave gliders are quickly becoming the future of ocean research. They require no expensive research ships and can be deployed off the back of a small fishing vessel and run along pre-determined or custom courses. A single pilot with an internet connection can fly up to 10 at one time, depending on the mission," said Christian Meinig, Director of Engineering at PMEL.
Manufactured by Liquid Robotics, the wave gliders, classified as Unmanned Maritime Vehicles (UMV), are one of the latest technological advances in the field of autonomous vehicles. Each wave glider is made up of a 7-foot long surfboard-like float that is tethered to 23-foot-cord attached to a submerged glider that controls speed and direction.
The wave glider immediately converts wave motion into thrust, pulling the float along a programmed or piloted path, while solar panels replenish the batteries for sensors and communications. Data are transmitted to shore via satellite and pilots can control the wave gliders from any device with an Internet connection.
Measuring an Ocean of Carbon
PMEL's carbon group began using wave gliders in August 2011 to measure carbon dioxide (CO2) changes during a recent West Coast ocean acidification cruise.
Engineers at PMEL designed and integrated custom instruments on two wave gliders including a MAPCO2, a system that measures CO2 in the surface seawater and marine boundary air layer, to accurately determine how much CO2 is entering or leaving the ocean surface. The gliders also measure conductivity and temperature as well as pH, the acidity of the ocean, and are the most heavily instrumented wave gliders deployed so far.
The carbon wave gliders were deployed near Westport, Wash., and sampled side-by-side for two weeks as they traveled an east-west line. After a successful first phase, they split off with one traveling south to measure surface ocean carbon concentrations off the Washington and central Oregon coasts while the other surveyed the northern Washington coastline and circled offshore buoys with similar instruments, for quality control checks.
The wave gliders traveled more than 2000 nautical miles during their 60-day mission, collecting more than 10,000 measurements. Performing the same work with a ship would take over 60 days at sea and the crew of a large research vessel to perform, whereas the gliders can be piloted by a single individual from shore.
"The carbon wave gliders provided us the unique opportunity to sample in areas where CO2 data is sparse and where conditions often change from location to location," said Christopher Sabine, Ph.D., an oceanographer at PMEL.
Using a combination of shipboard and buoy measurements, scientists in the carbon group hope to paint a more accurate picture of how CO2 enters and exits the ocean along the U.S. West Coast, home to a multi-million dollar oyster industry that can be negatively affected by changing ocean carbon conditions.
Taking the Temperature of the Arctic
Traveling further north, PMEL, in collaboration with the University of Washington, deployed two additional wave gliders to make critical temperature measurements in the Beaufort Sea. Temperature sensors were embedded within the glider tether at six different locations to take measurements near the surface down to 22 feet and relayed the data back to PMEL in near real-time.
"Collecting temperature measurements anywhere in the Arctic is difficult. By recording the yearly upper ocean temperature during the newly sea ice-free season during late summer as in 2011, we can provide a baseline for additional heat storage with the potential to modify future climate," said James Overland, Ph.D., an oceanographer with PMEL and the NOAA Arctic program.
NOAA's Arctic program tracks the changes in the Arctic where the past decade has shown record summer sea ice loss and warming of the atmosphere. Data are often hard to come by, usually requiring sophisticated satellite images or large icebreakers to collect. The wave gliders allow annual and economical study of the area.
Gliding into the Future
PMEL has big plans for their wave gliders. The carbon wave gliders will be deployed off the coast of Hawaii this winter to collect data at the Hawaii Ocean Time-Series (HOT) site where measurements have been made since 1988. The Arctic wave gliders will be outfitted with even more sensors and will make the trip to Arctic in the summer of 2012 when the ice has receded.
"These inaugural expeditions of the wave gliders proved to be a huge success, saving valuable resources and gathering a unique data set. By adding these gliders to our research tool kit we will be able to affordably collect measurements wherever the science may take us," said Meinig.