It almost felt like going home. Two weeks through our cruise we were heading for land, but only to take on two pilots for our work at Folger Passage at the head of Barkley Sound. Larger ships are not allowed close to shore unless they have local navigators with sufficient experience on the bridge; therefore, a Zodiac was sent to Bamfield from the R/V Thomas G. Thompson to pick up the two pilots who were waiting and ready to jump in, not even the zodiac pick-up crew set foot on land. At least we were close enough to shore for cell phone coverage, a rare treat on these open ocean voyages.
Zodiac from R/V Thompson going to pick up pilots from Bamfield.
Our aim at Folger Passage was to conduct maintenance on the instrument platform at a site called Folger Deep. It has a staggering water depth just under 100 metres, so really, the name only makes sense when compared to our nearby site Folger Pinnacle at 30 metres depth. By the way, Folger Pinnacle is actually the only active NEPTUNE Canada site that we did not visit during this cruise. The three main research objectives at Folger Passage are to:
- identify factors controlling biological productivity both within the water column and at the seafloor
- evaluate the effects that marine processes have on fish and marine mammals, and
- provide learning opportunities for students, researchers and the public, many of whom will be working and studying at the nearby Bamfield Marine Sciences Centre.
We were ready to dive as soon as the zodiac and the pilots came aboard, but dinner time had also arrived, and so it was decided to delay the dive by 15 minutes. That verdict caused the longest line in the mess-hall that we've ever had!
Following dinner, everyone was keen to get down to the ocean floor. Once ROPOS submerged into the water it only took eight minutes to reach bottom (really quick compared to the three hour descent at NEPTUNE Canada's deepest node ODP1027 at 2660 metres). Unfortunately, Folger Passage waters are murky and it was really hard to see anything. Thus, ROPOS navigation relied heavily on its accurate positioning system and sonar scans. ROPOS sonar looks like a radar screen where you can see bright reflections of the instrument platform (IP). When you can finally see the IP on the visual, it is already close enough to grab with ROPOS' arms.
Maintenance of an IP happens on deck, so the IP was disconnected from the main cable, its bottom pressure recorder, and its hydrophone (usually sitting approximately 15 metres away from the platform). Then, ROPOS attached the instruments to itself and the IP, respectively, before it hopped on top of the IP to latch on and ascend.
Nine minutes later ROPOS was on the surface again. What came into our view was an IP that looked like it had seen much better days, as it was all completely covered in mud, algae and animals. Once the platform was secured on deck, some kind souls onboard started collecting crabs, fish and anemones to cast them back into their natural environment.
ROPOS swinging by with the dirty Folger Deep instrument platform.
Bold attempts with power hoses and brushes were made in order to get the IP nice and shiny again, and the improvement was considerable. Had you not seen the IP just before, though, you would think it could still do with a good bath. However, the important parts were good again, and the IP was refitted with a new CTD (Conductivity, Temperature, Depth (pressure) Sensor), ADCP (Acoustic Doppler Current Profiler), Hydrophone and Bottom Pressure Recorder.
Meanwhile, the ship cruised slowly along a survey line to measure water depths and currents with its own multi-beam sonar and ADCP. If it hadn't been the middle of the night, we could have seen some stunning sights of the coastline. At the end of this survey, the ship also performed a CTD cast with water sampling.
Towards sunrise, the IP looked quite respectable again. All instruments were checked to see if they successfully responded through a test cable when talked to, and final touches were applied to ensure that everything was ready for redeployment.
ROPOS lifting off with cleaned and overhauled IP to redeploy at Folger Deep.
Redeployment on the seafloor went smoothly, and after connecting the IP back to the main cable, our shore team confirmed that data were streaming in again. For calibration of the echo sounder, ROPOS hovered 40 metres above it at for awhile. After taking several mud and water samples in the murky waters, ROPOS returned to deck, and the two pilots were relieved of their duties, departing via another ride in the Zodiac. We used the opportunity of our journey back out to deep sea to conduct another survey with the ship's multi-beam echo sounder and ADCP at Barkley Canyon. Hopefully, we will set foot on land the next time we come so close to shore.