Sep 5, 2009

Cable Lays at Cascadia Basin

Cable laying is an important task at all of our locations – after all, we're building a cabled seafloor observatory. But it was especially important and challenging at our Cascadia Basin location, where we sought to install three 12.5km cables radiating out from the instrument platform to form an equilateral triangle with bottom pressure recorders at each corner. Such an array will be invaluable to researchers studying tsunamis in this region.

To accomplish these cable lays we used ROCLS, ROPOS's Remotely Operated Cable Laying System. ROCLS consists of a rugged aluminum frame that holds detachable cable drums. Individual cables are carefully spooled onto drums. Then, when it is time to deploy, they are fitted onto ROCLS. ROPOS is then attached to ROCLS and the two deployed piggy-back, like tandem parachutists.

Since the spool is heavy, it is lowered to the seafloor by the ship's winch. ROPOS is deployed, finds ROCLS on the seafloor and detaches the cable end from the spool for connection to its designated node or platform. Then ROPOS locks onto ROCLS and dispenses cable via a hydraulic motor connected to a chain drive that turns the spool while ROPOS flies over the cable lay route.

ROCLS

Cables spooled onto ROCLS drums aboard the R/V Thompson, 7 September 2009.

Photograph of the plume edge in summer (photo credit: Kevin Bartlett).

ROCLS on the seafloor at ODP 1027, fully loaded with a 12.5km extension cable. Here, ROPOS is unfastening the cable end to connect it to our instrument platform.

ROPOS crew member Keith Tamburri and a R/V Thompson crew member prepare a fully-loaded ROCLS spool for deployment, 2 September 2009.

The 12.5km spools deployed at Cascadia Basin (ODP 1027) were very full and very heavy. Consequently, the ROPOS crew encountered many challenges dealing with them. One of the cables became snarled during deployment, and could not be laid. The spool had to be recovered from the seafloor and the cable now awaits repairs.

Later, a difficult happenstance resulted in ROPOS breaking an arm. After laying 12.5km of cable, ROCLS was set down on the seabed to remove the end connector and attach the bottom pressure recorder. But ROCLS sank too deeply into the soft sediment. ROPOS normally rotates the drum by hand during removal, but this time it would hardly budge. ROPOS operators tried again and again, using the ROPOS arms as levers to inch the drum upward. Finally, a bolt in the right arm snapped, rendering it nearly useless. But the ROPOS crew persevered and eventually managed to complete the installation.

ROPOS Breaks an Arm

The ROPOS team continued using Yang arm even after it broke. Here, the broken claw is lifting the dust cover for the bottom pressure recorder connector, 5 September 2009.

ROCLS sank deeply into the soft sediment on the abyssal plain during deployment of our ODP 1027 bottom pressure recorders. While attempting to rotate the drum by hand, a bolt on the Yang (right) arm snapped, leaving ROPOS with only one functional arm.

ROPOS crew member Dan Cormany worked to repair the broken Yang arm after the dive was completed, 5 September 2009.

 

Passing through the Water Column

At over 2.6km, Cascadia Basin is our deepest location. This means we spent a lot of time passing through the water column, observing various creatures along the way. Here are photos of some of them. If you can tell us more about any of these organisms, please post a comment below!

Creatures of the Deep

This red jellyfish was captured simultaneously by two different cameras on ROPOS. The left half is from the HD video camera; the right half is from the 3-chip CCD still camera. Observation taken at 1395m, 4 September 2009.

Close-up view of the unusual organism we observed at 1933m during a cable deployment dive at ODP 1027.

This deep sea organism, observed at 1933m depth, seems to resemble flowering Scotch Broom. If you can tell us more about it, please submit a comment below!

A red jellyfish observed at 1395m.

This beautiful jellyfish was observed at a depth of 1220m. We welcome your comments as to the type or other details you may be able to contribute.

 

Deployment and Recovery

Whenever ROPOS is deployed, "lemons" are involved. After ROPOS is lowered into the water, lemon-shaped floats are snapped onto the ROPOS umbilical cable to prevent it from snarling the sub during a dive. Of course, during recovery, each "lemon" must be unsnapped and stowed before ROPOS can be lifted onto deck.

Lemons

After ROPOS enters the sea, R/V Thompson crew members snap lemon-shaped floats onto the ROPOS umbilical cable to prevent it from snarling the sub during underwater operations. When ROPOS returns to the surface, R/V Thompson crew members also help remove the "lemons" from the ROPOS umbilical cable.

 

Not all recoveries are equal, though. High seas and gusty winds made an adventure out of our final recovery at ODP 1027.

Stormy Seas

ROPOS crew member Steve Buckley operates the crane during recovery of the sub with ROCLS attached. The task was complicated by high waves and strong winds, 5 September 2009.

Stormy Skies

Storm clouds loomed on the horizon as we recovered ROPOS and prepared to flee ODP 1027 ahead of a developing storm at sea.

expedition | cables | cascadia basin | ODP 1027 | ROPOS | ROCLS | spool | stormy
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