(Woods Hole Oceanographic Institution, 28 June 2013) Our understanding of the ocean and its variability relies on the tools ocean scientists deploy to collect data. One tool routinely used is the eXpendable BathyThermograph (XBT) probe, which is usually deployed manually at sea. One probe is launched approximately every hour for 36 hours. Oceanographic data has been collected this way for several decades. However, an advanced robotic auto-launcher system has now been developed to make the process more efficient.
Hundreds of XBT probes are manufactured each year and all of them are built to be deployed by hand, so working within the constraints of the probes’ existing design was a challenge for the developers.
Over the past five years the Autonomous eXpendable Instrument System (AXIS) has been developed, a white box about the size of a mini-fridge containing a carousel loaded with up to a dozen XBT probes. AXIS can be programmed to release a probe at a specific time or location.
The AXIS unit is attached to a rail off the deck of a ship. At a programmed time or location, AXIS will drop a probe out of the bottom of the box into the ocean that sends data back to scientists in the lab via satellite. The system is completely self-contained and self-powered. It has its own communications system, so does not require any wires, cables or computers on the ship.
The first AXIS prototype was tested at sea over the past 12 months aboard the M/V Oleander (see image), a container ship owned and operated by Bermuda Container Lines and part of the NOAA Ship of Opportunity Programme run out of the Northeast Fisheries Science Center’s Laboratory in Narragansett, Rhode Island. The M/V Oleander makes weekly journeys between New Jersey and Bermuda, crossing the Gulf Stream on each trip.
Because the Gulf Stream plays a major role in the global redistribution of heat from low to high latitudes and is a crucial component of the earth’s climate system, NOAA has deployed oceanographic probes and towed a continuous plankton recorder on the M/V Oleander on a monthly basis since the mid-1970s.
The development and deployment of AXIS has allowed enhanced ocean observations of the Gulf Stream and its variability while substantially reducing the workload at sea.
The developers envision AXIS units as part of a global observing network using vessels that operate under the auspices of the World Meteorological Organization’s Volunteer Observing Ship (VOS) programme. AXIS streamlines data collection, facilitates novel and interactive observational approaches, and reduces both the operational cost and logistical complexity of probe deployment from research and commercial vessels.
The development of AXIS was made possible by awards from WHOI’s Cecil H. and Ida M. Green Technology Innovation Program and the National Science Foundation to Associate Scientist Dave Fratantoni and Principal Engineer Keith von der Heydt. The mechanical and electrical components of AXIS were designed and built by WHOI engineers Terry Hammar and Jeff O’Brien.
With NSF support a second AXIS unit was recently constructed for deployment aboard the M/V Norröna, a Smyril Line ferry operating between Denmark, the Faroe Islands, and Iceland. This route provides an opportunity to regularly monitor the upper limb of the Atlantic overturning circulation, a key component of the climate system. Installation and operation of AXIS aboard Norröna is in support of the NSF-funded Norröna Project led by scientists Tom Rossby at the University of Rhode Island and Charlie Flagg at SUNY-Stony Brook.
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