NDBC Technicians Attain Great Depth Cast with UnderwayCTD (USA)

Technicians from NOAA’s National Data Buoy Center (NDBC) working on the DART project (Deep-ocean Assessment and Reporting of Tsunamis) became the first UnderwayCTD users to attain a cast depth of over 2,000m with a record-shattering 2,041m cast during a mooring service cruise on the M/V Bluefin in July 2012.

Using the UnderwayCTD from a stationary vessel, a technique perfected by the NDBC technicians, represents the fastest way to gather true research-grade CTD data through the upper 2,000m of the water column. Astonishingly, this record cast took only 50 minutes from start to finish beating the same group’s 1,563m cast a year earlier. Made possible by some hardware upgrades, the record-breaking system on the Bluefin allows the NDBC group to gather high quality CTD profiles, even though the vessel is not equipped with a conventional deep water CTD winch.

NDBC technicians visit the DART tsunami warning moorings in the North Pacific Ocean annually to conduct routine maintenance. DART moorings are taut, with a scope of 0.97 and are very sensitive to snap loading so water depth must be known to highest degree of accuracy possible. An echo sounder is used to determine the exact water depth at each mooring location, but an accurate CTD-derived sound speed profile is also required. As the maintenance cruises are not conducted on oceanographic research vessels equipped with deep water CTD winches, the NDBC team needed a portable system that could be easily installed to gather the high quality and deep water CTD profiles they needed and the UnderwayCTD was selected as the best fit. A key requirement was the capability to cover most of the water depth with the CTD profile: 2,000m was specified as the maximum required profile depth. The NDBC’s UnderwayCTD was used first in 2011, and while deep profiles were achieved there was a requirement for a faster drop speed to approach the target 2,000m mark. Oceanscience engineers were able to implement an improved line loading regime for the UnderwayCTD’s unique probe tail spool, leading to a sustained CTD fall rate of over 3.5m/s for the first 1,100m of the descent. The NDBC technicians were among the first groups to test the new system, and the improvement was obvious. The 2012 mooring cruise saw the UnderwayCTD depth record broken four times in a row! Then, at DART Station 52405, positioned at 12° 52′ 53″ N, 132° 20′ 02″ E with no currents to drift the probe, NDBC technicians were able to send the CTD down to 2,041m. According to James Coleman of NOAA: “We were determined to capture the depth record. However, even we were surprised when we discovered that we had exceeded 2,000m!”

Although it is not possible to go much deeper, upcoming further development of the UnderwayCTD promises to make the profiling process even faster.

The Oceanscience Group, founded in 1998, is a world leader in design and manufacture of field data systems for hydrologists, hydrographers, and oceanographers. Products include tethered, remotely-controlled survey vessels and the revolutionary UnderwayCTDTM.

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Press Release, August 13, 2012