BERKELEY, CA -- Two SOLO floats, the nation's first "robotic carbon observers" -- designed to descend to kilometer depths and collect information on the role of plankton and other living things in the ocean's carbon cycle -- were launched Tuesday morning, April 10, from the Coast Guard icebreaker Polar Star in the northern Pacific Ocean. Both have been transmitting regularly despite temporary interruption by storms at sea.
Todd Wood of the Department of Energy's Lawrence Berkeley National Laboratory carried the SOLOs to the Polar Star by helicopter from Dutch Harbor in the Aleutian Islands. At 3:00 a.m. Tuesday Wood deployed the floats at Ocean Station PAPA, 1,000 miles west of Vancouver Island, British Columbia, with the help of US Coast Guard personnel.
On Wednesday morning, April 11, they had resurfaced and began returning data by satellite link. Contact was interrupted by high waves during North Pacific storms later in the week, but no data was lost, and transmissions from both floats are now being received regularly.
SOLOs were invented by Russ Davis of the Scripps Institution of Oceanography in La Jolla, Calif., who dubbed them SOLO for "Sounding Oceanographic Lagrangian Observer." The floats measure temperature, salinity and mid-depth currents; those launched in April incorporate new carbon biomass sensors. From the surface they descend a thousand meters (a quarter of the way to the sea floor) and resurface at dawn and dusk each day.
Each time they surface the floats communicate their collected data, along with their positions, by two-way telemetry link to ORBCOMM satellites. For optimal data collection, a new bidirectional telemetry system allows land-based scientists to control the up and down motion of the floats anywhere in the remote ocean.
"This concept experiment will pave the way for a fully instrumented SOLO-carbon observer, able to measure all components of carbon in seawater," says Jim Bishop, director of the Ocean Biogeochemical Processes Group in Berkeley Lab's Earth Sciences Division. Bishop spearheaded the concept of robotic profiling carbon sensors and leads the collaboration that built and instrumented the floats and is collecting their data.
"We chose to deploy the floats at Ocean Station PAPA," he explains, "because our group has worked there extensively and because our colleagues at the Institute of Ocean Sciences in British Columbia regularly visit PAPA by ship. This way we can make sure we get consistent answers, in a place we understand."
A third of the carbon currently emitted by human activity -- roughly two billion metric tons each year -- is absorbed in the oceans, but the process is not well understood. The SOLO floats are vital, says Bishop, "because the plants that fix carbon in the ocean typically live and die in a single day. This makes it really hard and expensive to follow their variability using a ship. When the weather gets bad all work on a ship has to stop, yet biology goes on unobserved."
And the weather does get bad. The week before the carbon-observer SOLOs were launched, in the aftermath of the worst storm in the North Pacific in decades, the Polar Star was involved in the search for the fishing boat Arctic Rose that went down in the Bering Sea with the loss of all 15 aboard. "This tragedy," says Bishop, "underscores the difficulty and danger inherent in making observations at sea." SOLO floats are designed to operate in all weather conditions, however, and "they fly in the ocean as balloons fly in the air, for seasons at a time, tracking the daily rhythm of the plankton."
Partners in the SOLO-carbon venture include the Instrument Design Group at Scripps and WET Labs, Inc., of Philomath, Oregon, a private instrument firm. Support for the collaboration is provided by the National Oceanographic Partnership Program (NOPP), the Department of Energy, and the National Oceanic and Atmospheric Administration's Office of Global Programs. There are plans to launch two more SOLO-carbon observers in the North Atlantic later this year.