The global Argo array features more than 3,000 autonomous floats gathering and transmitting data around the world.
The U.S. component of Argo is supported primarily by the National Oceanic and Atmospheric Administration through
the National Oceanographic Partnership Program.
The unit has a 10-day cycle, diving to 1,000 meters and
drifting with the current for nine days, then dropping
to 2,000 meters and ascending while taking data on
temperature and salinity on the way back up.
At the surface, the unit’s antenna transmits its position along with the data collected during its journey
from 2,000 meters to the surface. The data is sent to
NOAA satellites, and then on to data-collection centers.
While drifting at the 1,000-meter level, the float may
travel as little as a kilometer a day, 30 kilometers in a
strong current. In places like the circumpolar Southern
Ocean current, 200 kilometers is not unheard of.
It is safer to drift submerged.
“All the bad things that can happen to the Argo float
happen on the surface — hit by a boat, picked up by a
fisherman, sensors get fouled — so the less time spent
on top of the ocean the better,” Roemmich said.
Spray gliders are autonomous underwater vehicles
that, like floats, take vertical profiles of data, giving scientists a clearer understanding of the temperature,
salinity and turbidity of specific areas of the oceans.
But they also can be programmed to steer to waypoints
and redirected to make course changes as needed.
Each Spray Glider is 2 meters ( 6. 5 feet) in length,
and has a wingspan of 1. 2 meters ( 3. 9 feet), according
to Dan Rudnick, a professor of oceanography at
The gliders have no external moving parts or motors.
Instead, they move on a preprogrammed course vertically
and horizontally in the water by pumping mineral oil
between two bladders, one internal and the other external
to the hull. The movement of the oil and the subsequent
shrinking of the external bladder decreases the glider’s
volume. This action changes the volume of the glider,
making it denser or lighter than the surrounding water.
Power for onboard electronics and communications
comes from lithium batteries. Data is sent to the
National Oceanic and Atmospheric Administration’s
National Data Buoy Center at Stennis Space Center in
Bay St. Louis, Miss.
The gliders are deployed from shore or a research
ship using a Zodiac boat. A mission may last three to
“We send them out for months at a time. They are
not expendable. We bring them back, turn them
around and send them back out. Every time we take
one out we put another one in,” Rudnick said.
The gliders have been used in the Pacific from
Monterey Bay on the U.S. West Coast to the Solomons
Sea and Palauan Islands, and in the Gulf of Mexico to
look for oil in the water during the Deepwater Horizon
spill last year.
Gliders can be used to provide persistent surveillance,
according to Edison Hudson, director of business