On 11-12 September, we laid a new extension cable from Folger node up into very shallow water on Folger Pinnacle, where an instrument platform will be installed by divers later this year. Poor visibility and strong swell made this installation particularly challenging.
The node is positioned in the main channel connecting Barkley Sound to Port Alberni Inlet. Water is quite turbid at the seafloor in this channel. We could barely make out the node from a distance of 2m, so ROPOS was sent down with a small video camera attached to one arm, which made it easier to see the connector ports in the murky water.
Murky Waters |
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ROPOS crew had a tough time finding and releasing the cable end connectors from the ROCLS cable drum, 12 September 2009.
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Even from 1m distance, the trawl-resistant frame was difficult to make out.
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This was the view when ROPOS reached the seafloor near our Folger Passage node, 12 September 2009.
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When we moved from the channel up onto the rocky terrain of Folger Pinnacle, strong surge became our enemy. ROPOS seemed powerless to hold position as the waves caused the sub to surge, sway and heave erratically. We had to maintain a safe distance and were unable to set ROPOS down to gather high-resolution images of proposed instrument platform site.
Rocky Terrain |
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This spectacular anemone was observed growing on rock at 41m.
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Close-up view of hard rock community observed at 30m 12 September 2009.
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White anemones colonize a boulder at 43m, 12 September 2009.
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Fish are numerous in the vicinity of Folger Pinnacle, which is a rock fish conservancy. This school was observed at 30m, 12 September 2009.
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Shell hash at the base of a rock outcrop at 30m depth.
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Rock fish swimming at 45m over rocky terrain in the mid-ground between the node and Folger Pinnacle, 12 September 2009.
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After laying the cable, the next task was to stabilize it. We prepared burlap bags filled with sand, planning to pin the cable down with them.
The sand bags were loaded onto the ROPOS tool tray, and ROPOS ferried the tool tray to the seafloor. However, when it reached the rocky bottom, a sudden swell drove ROPOS downward, smashing the tool tray onto the rocks. It snapped. With the heavy surge, it was too dangerous to reach many of the sand bags or attempt to recover the broken tool tray. The dive was aborted and we were forced to leave them on the seafloor.
Our chief scientist is now arranging for a crew of divers to swim to the cable and re-stabilize it before the winter storm season begins.
Sand Bag Travails |
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Some sandbags were placed to stabilize the cable before conditions became too dangerous to continue.
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A chimera visits the broken ROPOS tool tray resting on the rocky seafloor at 43m, 12 September 2009.
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Sand bags rest in the ROPOS tool tray prior to deployment, 12 September 2009.
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Folger Pinnacle Platform Location
We were able, however, to decide on a future location for Folger Pinnacle instrument platform. A relatively flat rock, 22m below the surface is the likely site. This fall, if all goes right, a custom platform will be fabricated and installed there.
Proposed Folger Pinnacle Instruments
- high-resolution video camera with lights
- current meter
- acoustic Doppler current profiler (1200 kHz)
- acoustic current profiler (2 MHz)
- ecosounder
- fluorometer
- 3-D high-resolution camera array
Learn more about research planned for this location.
Glimpses of Folger Pinnacle |
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Prospective site for the Folger Pinnacle platform.
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The shallow rocks of Folger Pinnacle provide habitat for a profusion of benthic organisms.
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Flourishing community of organisms living atop Folger Pinnacle, 12 September 2009.
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September 14-15 we installed and connected a second broadband seismometer to the NEPTUNE Canada network. The first was installed at Barkley Canyon on 8 September. The second was installed at ODP 1027, not far from the ODP 1026B CORK and our instrument platform there.
About the Seismometers
Pacific Geosciences Centre technician Bob Meldrum prepared and oversaw the installation of this delicate instrument. The cast titanium case, designed by Monterey Bay Aquarium Research Institute, holds both a seismometer and a strong motion accelerometer. The seismometer is equally sensitive to movements in three dimensions at periods from 6 minutes all the way down to 1/50th of a second.
In fact, it's so sensitive it can detect subtle tilts in the ground from earth tides caused by the moon's gravitational pull!
While the seismometer is tuned to small movements, such as waves produced by an earthquake on the other side of the earth, it cannot be used to measure intense shaking, such as might be caused by a nearby earthquake. That's where the strong motion accelerometer comes in. This device picks up where the seismometer leaves off, coping with accelerations up to 2G.
Preparations |
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Pacific Geosciences Centre instrument technician Bob Meldrum prepares a broadband seismometer for deployment to ODP 1027, 13 September 2009.
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A peek at the ODP 1027 broadband seismometer within its cast titanium sphere, 12 September 2009. The NEPTUNE Canada broadband seismometers (model CMG-1T) are manufactured by Güralp Systems Limited.
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Dalhousie University oceanographer Doug Schillinger and NEPTUNE Canada instrument manager Reece Hasanen admire the ODP broadband seismometer prior to deployment, 12 September 2009.
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NEPTUNE Canada contractor Jason Williams and Pacific Geosciences Centre instrument technician Bob Meldrum prepare seismometer-related instrument package for deployment to ODP 1027, 13 September 2009.
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(Click images to view slideshow.)
Deployment
The original plan called for the ODP 1027 seismometer to be deployed along with a small frame to hold a battery, differential pressure gauge and an acoustic Doppler current meter. The battery could supply the seismometer for up to a month's time in the event a large power failure (such as might result from a large earthquake) knocks out the NEPTUNE Canada network.
But even best-laid plans do not always work out. When we deployed the instrument frame and tested it through the network, a ground fault was detected. The seismometer itself tested perfectly, so we were able to leave it in position, connected to the ODP 1027 instrument platform by a 70m cable. But the battery and additional instruments could not be deployed, so we recovered them.
The actual process of installation was the same as before. ROPOS pushed a wide-diameter section of heavy plastic pipe (the "caisson") down into the seafloor sediment, then vacuumed the interior out with its zip pump. We poured a shallow layer of glass beads into the base of the caisson and placed the seismometer inside. Finally, we buried the seismometer completely in glass beads.
Seismometer Deployment |
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ROPOS spills bags of tiny glass beads over the seismometer within its installation caisson, 15 September 2009.
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Placement of the ODP 1027 broadband seismometer within its caisson, 15 September 2009.
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ODP 1027 seismometer, now buried in glass beads, 15 September 2009.
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ROPOS carries the ODP 1027 seismometer to its deployment site, 15 September 2009.
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ROPOS gingerly places the seismometer into the caisson, 15 September 2009.
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Seismometer and caisson after it was vacuumed out by the ROPOS zip pump, 25 September 2009.
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(Click images to view slideshow.)
Animal Encounters
Sea creatures are ever-present during our installation operations, and today was no exception. While descending through the water column, we passed through a dense school of tiny fish. Squid lurked on the perimeter, feeding on the fish. Then, when we reached bottom and began the seismometer installation, several rattail fish came to supervise.
Small Fry and Rattails |
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Rattail fish observed at 2660m, 14 September 2009.
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This rattail fish was very interested in our seismometer installation work at ODP 1027 (2660m). The fish hung around for much of the time we worked, watching, smelling, and even trying to eat bits of nylon rope. 14 September 2009.
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During the descent for installation, ROPOS passed through a dense school of small fish swimming downward between 350-650m. Local time was between 5:30-6:00 AM, 14 September 2009.
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(Click images to view slideshow.)