 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. 
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. —Ed Peltzer 
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
|
Track the ship
Equipment
 R/V Western FlyerThe R/V Western Flyer is a small water-plane area twin hull (SWATH) oceanographic research vessel measuring 35.6 meters long and 16.2 meters wide. It was designed and constructed for MBARI to serve as the support vessel for ROV operations. Her missions include the Monterey Bay as well as extended cruises to Hawaii, Gulf of California and the Pacific Northwest.
ROV Doc Ricketts is MBARI's next generation ROV. The system breaks new ground in providing an integrated unmanned submersible research platform, with many powerful features providing efficient, reliable and precise sampling and data collection in a wide range of missions.
By bouncing a specially tuned laser beam off of almost any object or substance—solid, liquid, or gas—a laser Raman spectrometer can provide information about that object's chemical composition and molecular structure.
A push-core looks like a clear plastic tube with a rubber handle on one end. Just as its name implies, the push core is pushed down into loose sediment using ROV Tiburon's manipulator arm. As the sediment fills up the core, water exits out the top through one-way valves. When the core is pulled up again, these valves close, which (most of the time) keeps the sediment from sliding out of the core tube. When we bring these cores back to the surface, we typically look for living animals and organic material in the sediments.
Vibracoring is a common technique used to obtain samples from water-saturated sediment. These corers work by attaching a motor that induces high frequency vibrations in the core liner that in turn liquefies the sediment directly around the core cutter, enabling it to pass through the sediment with little resistance.
Carbon dioxide is a liquid at the temperatures and pressures on the seafloor where hydrates are known to occur. Because of this, one cannot simply take down a tank of gas and expect to be able to release it at depth. Instead, the CO2 piston accumulator is used to deliver precise volumes of liquid CO,2 to experiments on the seafloor. The valves are operated hydraulically by remote control and hydraulic pressure is used to expel the liquid CO2 and deliver it to the experiments.
MBARI's heat-flow probe is mounted on the side of the ROV Doc Ricketts inside the vertical stainless steel box. This both protects the delicate probe and provide the track so that the probe can be inserted into the sediment along a totally straight path. The probe contains five high precision platinum sensors which are used to measure the vertical temperature gradient in the sediments. This gradient along with some knowledge of the heat capacity of the sediment allows scientists to calculate the rate of heat loss from the sediments into the ocean. Research Team
Peter has taken part in more than 30 deep-sea cruises, and has served as chief scientist on major expeditions and on more than 90 ROV dives with MBARI ships and vehicles. His research interests include the ocean geochemistry of the greenhouse gases. He has devised novel techniques both for measurement and for extracting the oceanic signatures of global change. At MBARI his current interests include the geochemistry of gas hydrates, and the evolution of the oceanic fossil fuel CO2 signal. He has developed novel techniques for deep ocean laser Raman spectroscopy, and for testing the principles and impacts of deep ocean CO2 injection.
Ed is an ocean chemist who has been with MBARI since 1997. He has been involved in developing instrumentation and analytical techniques to study the composition of gases in gas hydrates and deep-sea vents. He has also collaborated on the development of new instrumentation for the measurement of temperature and pH from an ROV. As the group's project manager, Ed is also responsible for expedition planning and logistics.
Peter has worked as a research technician for a variety of scientists at MBARI. Most recently he has supported the research efforts of Dr. Peter Brewer and his interests in the ocean chemistry of greenhouse gases such as methane and carbon dioxide. Peter assists with the design, testing and deployment of the ocean going science hardware and works closely with the marine operations group to integrate new equipment to work with MBARI's ROV's.
Xin Zhang is a Ph.D. student from the Ocean University of China and is now studying at MBARI with Peter Brewer and Bill Kirkwood. He has been involved in the development of a Deep-Sea Raman Probe for the measurement of sediment pore water geochemistry. In this expedition, he will focus on obtaining the in situ pore water Raman spectra and the collection of pore water samples for subsequent shipboard analyses by ion and gas chromatography.
Keith is currently an associate engineer with ConocoPhillips focused on natural gas hydrates. Keith received his PhD in Chemical Engineering from the Colorado School of Mines in 2007. This was followed by a two-year postdoctoral fellowship at the Monterey Bay Aquarium Research Institute with Dr. Peter Brewer. His research interests include the use of carbon dioxide to replace methane in natural hydrates.
John has been a staff member at the NRC since 1974, first with the Division of Chemistry, then with the Steacie Institute for Molecular Sciences upon its establishment in 1991. His research focuses on the chemical applications of solid state nuclear magnetic resonance (NMR) spectroscopy, the development of multi-technique approaches to the characterization of materials, supramolecular chemistry, porous materials, clathrates, gas hydrates, and other guest-host materials. He has nearly 500 publications and six patents and is often an invited speaker at special events. |
