Monterey Bay Aquarium Research Institute
2009 Pacific Northwest Expedition


Leg 1 Logbook - Laser Raman Spectroscopy
Day 6 – Somewhere there is a place for us...
July 12, 2009

0800 hours - Southern Summit of Hydrate Ridge 50 nautical miles west of the Oregon coast
Latitude 44 degrees 34.2 minutes N
Longitude 125 degrees 8.9 mimutes W

Today’s dive objectives were to explore the seafloor in search of a methane hydrate deposit and to practice filling the glass hydrate chambers in preparation for our gas substitution experiment. We began by looking at sites we explored in 2000 and 2004. Unfortunately, these sites were heavily excavated then and show no signs of methane hydrates today. After some hard digging we did manage to find a spot with a few small pieces of gas hydrate. Thanks to the dexterity of the ROV pilots, using both ROV manipulators at the same time, we were able to dig the hydrate loose and capture it in a collecting funnel. With a magnificent display of skill, the hydrate was transferred to our glass chambers. While we did not collect enough hydrate for our experiment, we did manage to learn the critical techniques. Tomorrow we will return and hopefully find a place sufficiently rich in hydrates that we can fill our chambers for the experiment.

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While exploring the seafloor at the Southern Summit of Hydrate Ridge, we found an MBARI marker we planted in July of 2000 to mark the site of a gas vent where large chunks of methane hydrate had been found. I guess we got them all as there was no methane hydrate at this site.

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In 2004, we began using a more whimsical temporary site marker: a plastic pink flamingo affectionately named “Pinkie.” This marker was placed near the site of a very active gas vent. In the five years since then either the source of this natural gas reservoir has run out or the vent chimney has become clogged as we did not observe any gas venting at this site during either of our dives here.

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Using both manipulator arms simultaneously, the ROV pilots were able to scrape loose some small hydrate chunks and then capture them as they floated free of the sediment cloud.

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Methane gas hydrate is slightly less dense than seawater so the few pieces we collected floated to the top of the glass chamber. Unfortunately, we will need a lot more than this for our experiment. Finding a rich site of gas hydrate tomorrow will be a real exploratory challenge.

After lunch, we continued with another round of pore-water measurements using the laser Raman spectrometer pore-water probe. This work was quite successful. Working continuously throughout the afternoon, many pore-water profiles were obtained, to the delight of the science team and ROV pilots. We saw pore-water sulfate decrease to below the detection limit while both methane and hydrogen sulfide increased in a classic demonstration of anoxic pore-water chemistry.

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After a somewhat disappointing and frustrating morning, the science team returned after lunch to collect a highly successful series of pore-water profiles. ROV pilots Bryan Schaefer and Eric Nelson assist Xin Zhang and Peter Brewer with the collection of the pore-water profiles. A real-time Raman spectrum of the pore-water chemistry can be seen in the right-hand screen in the uppermost row of monitors.

—Ed Peltzer

 

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Leg 1
 Equipment

R/V Western Flyer

The 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

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.

Laser Raman spectrometer DORISS2

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.


Push cores

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.

Vibracores

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.


CO2 accumulator

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.


Heat-flow probe

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 Brewer
Senior Scientist, MBARI

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 Peltzer
Senior Research Specialist, MBARI

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 Walz
Senior Research Technician, MBARI

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
Graduate Student, Ocean University of China & Visiting Investigator, MBARI

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 Hester
Conoco Phillips

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 Ripmeester
Principal Research Officer, Materials Structure and Function Group
National Research Council Canada

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.