SCUBA Travel News

Researchers from the Woods Hole Oceanographic Institution (WHOI) and Webb Research Corporation (Falmouth, Mass.) have successfully flown the first environmentally powered robotic vehicle through the ocean. The new robotic “glider” harvests heat energy from the ocean to propel itself across thousands of kilometers of water.

Unlike motorized, propeller-driven vehicles, gliders propel themselves through the ocean by changing their buoyancy to dive and surface. Wings generate lift, while a vertical tail fin and rudder allow the vehicles to be steered horizontally.

Gliding underwater vehicles trace a saw-tooth profile through the ocean’s layers, surfacing periodically to fix their positions via the Global Positioning System and to communicate via Iridium satellite to a shore lab.

“Gliders can be put to work on tasks that humans wouldn’t want to do or cannot do because of time and cost concerns,” said Fratantoni, an associate scientist in the WHOI Department of Physical Oceanography. “They can work around the clock in all weather conditions.”

The vehicles can carry a variety of sensors to collect measurements such as temperature, salinity, and biological productivity. Gliders also operate quietly, which makes them ideal for acoustic studies.

Though the thermal glider is not the first autonomous underwater vehicle to traverse great distances or stay at sea for long periods, it is the first to do so with green energy. Most gliders rely on battery-powered motors and mechanical pumps to move ballast water or oil from inside the vehicle’s pressure hull to outside. The idea is to increase or decrease the displacement (volume) of the glider without changing its mass.

The new thermal glider draws its energy for propulsion from the differences in temperature—thermal stratification—between warm surface waters and colder, deeper layers of the ocean. The heat content of the ocean warms wax-filled tubes inside the engine. The expansion of the warming wax converts heat to mechanical energy, which is stored and used to push oil from a bladder inside the vehicle’s hull to one outside, changing its buoyancy. Cooling of the wax at depth completes the cycle.

“We are tapping a virtually unlimited energy source for propulsion,” said Fratantoni. The computers, radio transmitters, and other electronics on the glider are powered by alkaline batteries, which are, for now, the principal limit on the length of operation.

The engineering trial for the thermal glider is the first step in a broader plan by Fratantoni and colleagues to launch a fleet of gliders for studies of the waters in the subtropical gyre of the North Atlantic, a key region for assessing the ocean’s response to climate change.
-
What do you think of this news item? Start a discussion.
Bookmark with: del.icio.us | Digg | Newsvine | NowPublic | Reddit
|   Slashdot It! | Facebook | StumbleUpon

--
Subscribe to SCUBA News (ISSN 1476-8011) for more free news, articles, diving reports and marine life descriptions - http://www.scubatravel.co.uk/news.html

Corruption in global fisheries is compounding the devastating effects of overfishing – and the problem could get worse, according to The World Conservation Union (IUCN).

Corruption in fisheries is increasing against a backdrop of declining fish stocks and increased consumer demand. It taints all aspects of the fishing industry, from the scientific evidence that quotas are based on, to the mislabelling of fish.

“The large-scale occurrence of corruption adds insult to injury,” said Head of IUCN’s Global Marine Programme Carl Gustaf Lundin. “The world’s global fish stocks are already severely depleted by overfishing and this is just making the situation worse.”

Fisheries corruption undermines the ability of scientists to know how many fish are removed from the oceans, causing inaccurate stock assessments. Fisheries managers are therefore far more likely to approve total allowable catches that are higher than those that would be based on sound scientific advice.

“Scientists’ evidence is not being taken into consideration when it comes to management decisions on fisheries and quotas,” said Deputy Head of IUCN’s Global Marine Programme Andrew Hurd. “Fisheries managers should be held accountable when ignoring scientific advice.”

Source: IUCN

What do you think of this news item? Start a discussion.
Bookmark with: del.icio.us | Digg | Newsvine | NowPublic | Reddit
|   Slashdot It! | Facebook | StumbleUpon

--
Subscribe to SCUBA News (ISSN 1476-8011) for more free news, articles, diving reports and marine life descriptions - http://www.scubatravel.co.uk/news.html

Win a dive guide to Safaga, on Egypt's Red Sea coast. To enter just tell us how many dives sites are included in the Safaga pack (visit http://www.travellingdiver.com/ to find out) and e-mail your answer, together with your name and address, to news@scubatravel.co.uk before 29 February 2008.

Designed for the recreational holiday diver, the guide integrates detailed site-by-site information and maps with loose-leaf logbook pages. The pages fit into a standard 3-hole diving binder and let you research, plan and record your dives in one place.

You can purchase the Safaga guide from http://www.travellingdiver.com/ or Amazon at http://www.amazon.co.uk/exec/obidos/asin/0955640229/nws-21. Or wait and see if you win our competition!


What do you think of this news item? Start a discussion.
Bookmark with: del.icio.us | Digg | Newsvine | NowPublic | Reddit
|   Slashdot It! | Facebook | StumbleUpon

--
Subscribe to SCUBA News (ISSN 1476-8011) for more free news, articles, diving reports and marine life descriptions - http://www.scubatravel.co.uk/news.html

Labels: competition, Red Sea

A new system lets SCUBA divers perform many measurements underwater with a precision similar to that possible in a laboratory.

Microsensors are powerful tools for environmental studies. These are miniature electronic devices that detect information about a specific variable such as temperature or pH. However, their use has often been restricted to laboratory applications due to the lack of adequate equipment for their deployment in the field. A new report details a diver-operated motorised device with microsensors for underwater work to a depth of 25 m.

The new device can accommodate pH, oxygen and hydrogen sulphide measurements. The system can be pre-programmed to autonomous operation or interactively operated by divers. Internal batteries supply power for up to 24 hours of measurements, storing up to 64 million data samples.

Three studies are discussed in the report. In the first the oxygen distribution in a sand ripple was 3-D-mapped. The second looked at sediment build-up on hard corals and the third oxygen dynamics in sedimentation.

Journal Reference: Environ Sci Technol, September 1, 2007; 41(17): 6210-5.
-
What do you think of this news item? Start a discussion.
Bookmark with: del.icio.us | Digg | Newsvine | NowPublic | Reddit
|   Slashdot It! | Facebook | StumbleUpon

--
Subscribe to SCUBA News (ISSN 1476-8011) for more free news, articles, diving reports and marine life descriptions - http://www.scubatravel.co.uk/news.html

Labels: research