Leg 1 Logbook - Laser Raman Spectroscopy
Day 8 – Hump Day
July 14, 2009
0800 hours - Underway to Barkley Canyon at 10 knots
Traditionally, the middle day of a cruise is known as “Hump Day". For us, this takes on a different meaning today as we arrive on station at Barkley Canyon and begin our search for a special series of humps: the several large hydrate mounds that are known to occur here at Barkley Canyon.
We arrived on-station around noon, just a mile or so from the R/V Atlantis from WHOI. They are just completing a series of ROV ROPOS dives helping the Canadians install instruments on their undersea observatory which is part of the NEPTUNE cabled observatory system. In addition to the Atlantis, the Danish cable-laying ship, Lodbrog, works a few kilometers away deploying new cables for the observatory. Obviously, this is a popular site.
1200 hours - Barkley Canyon, west of Vancouver Island, Canada.
Latitude 48 degrees 18.6 minutes N
Longitude 126 degrees 3.9 minutes W
Randy Prickett and Eric Nelson ready the ROV for launch.
We begin our dive shortly after lunch today. The objective is to find the hydrate mounds that were first found by the Canadian ROV ROPOS and were visited by us in 2006. The mounds were mapped in 2006 using MBARI's mapping AUV and are marked with several passive markers, so we are planning on using our sonar navigation system to find them. Unfortunately, after just a few minutes searching, it was obvious that the sonar tracking is not working as well as it did in the past. Without precise positioning we begin searching back and forth. We know that the ROV can’t be too far off the dive targets as the tether is only so long, but when the target is only a couple of meters across it can be a very big ocean.
After 30 very frustrating minutes of random wandering on the seafloor we come across the elevator weights left on the seafloor the last time we were here. Now we know where we are relative to the hydrate mounds and can begin searching for the hydrate mounds by dead reckoning.
We find our first hydrate mound but there are no markers here. It is not the one we want, but a new one. Its position is marked on our map and then we go on. Another hour of searching goes by, then we come across a hydrate mound with markers. It is Double Mound (below). Not the one we want, but close. Now we can begin mound hopping: navigating from one mound to the next by dead reckoning. It works. We find Cliff Hanger, the site where we collected several hydrate samples last time. In the three years since we were here last it has become heavily eroded. We proceed north towards Hyberg mound taking a tour of the several hydrate mounds along the way. Our navigation skills have improved and we find the mound and an old friend pretty much where we expect it.
The rest of the dive is devoted to taking a few preliminary pore-water spectra and scouting out sites for tomorrow. The ROV arrives on deck at 7 p.m. just in time for a late sunset.
This is Double Mound. The white material visible on the side is a bacteria mat that overlies the massive hydrate mound. The yellow polypro “monkey’s fist” is a marker left by the ROV ROPOS.
Close-up of the face of Cliff Hanger. The yellow material is hydrate stained with a very light petroleum oil. The grey material is once again bacteria mat and it is all covered with the green-brown sediment typical of the area. When we visited this site in 2006, a thick layer of white hydrate was exposed below the yellow hydrate. It is all eroded away leaving behind the large cavities.
Hyberg mound with our old friend Pinkie in the foreground. We placed this marker during our dives in 2006. Who would ever think that a plastic pink flamingo would make such a useful oceanographic tool!
ROV Doc Ricketts returns to the moonpool at the end of dive #46. If you look closely you can see sediment on the tray at the front of the toolsled. This sediment was impregnated with a light petroleum oil that just reeked of aromatic hydrocarbons. It took several minutes of vigorous washing (and some hand-to-bucket work) to clean the ROV.
Not quite sunset through broken clouds. Photo by Peter Walz