Map Of Oceans

NASA ocean-watch satellite ready for June launch

WASHINGTON — The US space agency said Tuesday it is preparing to launch a satellite to observe levels of salt on the surface of the world's oceans and how changes in salinity may be linked to future climate.

The June 9 launch of Aquarius/SAC-D comes three months after NASA lost Glory, a 424-million-dollar Earth-observing satellite that failed to separate properly from its rocket launcher and plunged into the ocean.

The orbiting science instrument will aim to map the entire open ocean every seven days from its position 408 miles (657 kilometers) above Earth, producing monthly estimates that show how salt levels change over time and location.

"There are vast tracts of the ocean where salinity has never been collected, ever," said Eric Lindstrom, Aquarius program scientist at NASA, describing the high level of precision expected from the mission.

"We are going to be sampling the whole planet in one week," he told reporters.

While a European satellite was launched in 2009 to measure soil moisture and ocean salinity, the Aquarius/SAC-D is a global collaboration -- with partner Argentina as well as France, Brazil, Canada and Italy -- that will add to scientists' knowledge of the oceans in novel ways.

"Aquarius will map global variations in salinity in unprecedented detail, leading to new discoveries that will improve our ability to predict future climate," said principal investigator Gary Lagerloef of the Earth & Space Research in Seattle, Washington.

Scientists from the European Space Agency who launched the Soil Moisture and Ocean Salinity (SMOS) mission have been working in parallel and sometimes in partnership with NASA and Argentina's space agency, Comision Nacional de Actividades Espaciales (CONAE) as the two separate missions took shape, he said.

SMOS is a dual-purpose mission whose main focus is soil moisture, while Aquarius is aimed primarily at measuring ocean salinity, which plays a key role in exchanges of water and heat in the atmosphere.

"It has been a strong cooperative effort," said Lagerloef. "Once we have both of these missions in orbit, we will compare results, we will intercalibrate them," he told reporters.

"We will do a lot of things cooperatively to provide the best information about ocean surface salinity to the scientific community that we possibly can."

The satellite observatory is also to carry seven additional instruments to "collect environmental data for a wide range of applications, including studies of natural hazards, air quality, land processes and epidemiology," NASA said.

Nature News Blog: Sea turtles use magnetic maps to navigate oceans

Loggerhead turtles can do from birth what humans struggled to master for centuries – tell longitudinal, or east-west, direction to navigate thousands of miles of ocean with no visual landmarks. They do so using magnetic cues, according to a study by researchers from the University of North Carolina - Chapel Hill published in the journal Current Biology .

The turtles set off on a grand migration around the Atlantic immediately after they hatch and enter the sea. They swim from Florida to the circular currents swirling around the Sargasso Sea, called the North Atlantic subtropical gyre. They stay in the gyre and slowly migrate around the Atlantic, before returning home.

Such travels need the ability to tell both east-west and north-south direction. It is well known that many animals can tell latitudes, or north-south direction, using cues from the Earth’s magnetic field. But a few, such as the loggerhead turtle, also seem to be capable of deciphering east-west direction using a magnetic map. Before this paper, no one has actually shown this is true.

Telling east-west direction is quite a feat because while the Earth’s magnetic field varies predictably with latitude, less information is available about the field with longitude.

To see whether the turtles somehow use magnetic information to decipher east-west direction, researchers recreated ocean-like conditions. They placed hatchlings inside a circular, water filled arena. The space was surrounded by coils to generate a magnetic field. The turtles were tethered to a tracking device that monitored their swimming direction.

When the turtles were exposed to a field like that which exists on the southwest side of the Atlantic, near Puerto Rico, the animals swam northeast, which would take them back toward North America and their normal migration route.

When they were exposed to fields as exist on the northeast side of the Atlantic, near the Cape Verde Islands, they swam southwest. This would again take them to the North American coast. Since the hatchlings had never been in the ocean, the ability to recognize east-west direction seems to be inherent. “Turtles exploit at least two different geomagnetic features that vary in different directions across the Atlantic,” states the report.

How they do so remains a mystery. The scientists postulate that they are able to tell longitude by keeping track of the inclination angle at which the magnetic fields intersect the earth surface, and intensity of the field. These change with longitude and latitude and form a “magnetic signature.

Oceans

Oceans, The Threats to Our Seas and What You Can Do to Turn the Tide

Atlas of continental displacement, 200 million years to the present

Oceans, A Scientific History of Oceans and Marine Life

Encyclopedia of Marine Science