Monterey Bay Aquarium Research Institute
2009 Pacific Northwest Expedition


Leg 1 Logbook - Laser Raman Spectroscopy
Day 15 – Our last dive…
July 21, 2009

0900 hours – On-station at the Southern Summit of Hydrate Ridge, 50 nautical miles west of the coast of Oregon.
Latitude 44 degrees 34.2 minutes N
Longitude 125 degrees 8.9 minutes W

We have two tasks remaining for today’s dive: first, we need to complete the gas hydrate decomposition experiment and, second, we need to release the elevator from the seafloor for recovery. As you may recall, on day 7 we set up the experiment by placing gas hydrate inside a glass chamber and then filling the chamber with nitrogen gas. The nitrogen reduces the chemical activity of the methane in the system causing the gas hydrate to decompose. The questions we are asking by performing this experiment are how fast does this happen and how far will the decomposition proceed: will all of the hydrate we left behind be gone?

Arriving on the seafloor, we find the elevator in good shape and waiting for our return. Close inspection of the glass chamber reveals that all of the gas hydrate has decomposed leaving behind an enlarged gas volume. Next, we carefully pick up the chamber with one manipulator while inserting the laser Raman spectrometer pore-water probe inside. First we measure the composition of the liquid phase, and then we measure the composition of the gas phase. While we see some methane dissolved in the seawater, the major amount is in the gas phase. A curious and high climbing crab looks on. When the measurements are complete, we release the gas and stow the glass chambers in a box on the ROV for recovery. After, releasing the float and recovery line, we pull the line dropping the anchor and the elevator floats away to the surface. We quickly recover the ROV so that when the elevator floats to the surface the ship will be able to steam over and recover it.

link to larger image
Upon arriving on the seafloor, we find the elevator sitting pretty much just as we left it with our hydrate decomposition experiment sitting on the shelf on the side.

link to larger image
Close inspection of the glass chamber reveals that all of the gas hydrate that we left behind has decomposed. The bulk of the methane has mixed with the nitrogen gas and a small fraction is dissolved in the seawater.

link to larger image
With an amazing display of dexterity, two ROV pilots work together to lift the glass chamber high and insert the laser Raman spectrometer pore-water probe inside in order to sample the gas dissolved in the liquid layer. We find a small amount of methane dissolved in the water.

link to larger image
Here, the pilots have carefully placed the insertion probe all the way into the glass chamber so that we can sample the gas phase. We find the nitrogen greatly enriched with methane. Our prediction that all of the hydrate would decomposed under these conditions was tested and verified.

link to larger image
A crab has climbed to the top of the elevator and looks down precariously at our work. Is he in for a big surprise…

link to larger image
After retrieving the glass chambers from the elevator and stowing them for recovery on the ROV, the pilots send the elevator to the surface by pulling on the anchor release line. As soon as the anchor drops, the elevator floats away. Now it is a race to the sea surface as the ship cannot go chasing after the elevator until the ROV has been safely recovered and is aboard the Western Flyer.

Once the elevator arrives at the sea surface, Paul Tucker grapples for the recovery line and the crew quickly haul the elevator aboard. When all the gear is secured, we steam for Newport, Oregon. Our cruise leg is nearly complete and all of our objectives were successfully met. All that remains is packing up the gear and cleaning out the lab.

link to larger image
Once at the sea surface, the elevator floats free and begins to drift with the wind and current. As soon as the R/V Western Flyer pulls along-side, crewman Paul Tucker grapples for the recovery line so that it can be attached to the crane and the elevator hauled aboard.

link to larger image
Once the elevator is onboard the R/V Western Flyer, Peter Walz and Paul Tucker make it secure while Lance Wardle keeps watch over their operation. Crewman Kevin Pinegar then radios the bridge to give them the word that all is secure and we can begin our transit to Newport, Oregon.

Tomorrow will be our last daily log posting. In it we will reveal the identity of the mystery fish.

—Ed Peltzer

 

Previous log Next log

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.