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.
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.
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.
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.
- high-resolution video camera with lights
- current meter
- acoustic Doppler current profiler (1200 kHz)
- acoustic current profiler (2 MHz)
- 3-D high-resolution camera array