Monterey Bay Aquarium Research Institute

 


Deep-sea chemistry
Day 7: It’s a gusher!
August 16, 2011

Location: Spinnaker Gas Vent site
Latitude: 48º 40.47 N
Longitude: 126º 50.46 W

Large pockets of methane gas in the seafloor can change the shape of the terrain. So when an otherwise flat expanse of seafloor is punctuated by many small mounds, like blisters on an overworked hand, there’s a good chance that they were created by the growing methane pressure from below. Careful surveys of two such mounds today helped to verify that theory.

The new tripod first used a few days ago to improve the use of the laser Raman probe was sent back to the seafloor. With the new handle that pilot Randy Prickett built onboard and the lessons learned from the first deployment, the tripod became an excellent tool for conducting surveys. This new contraption made it easy to conduct perfect, clean, controlled insertion of the probe into the seafloor, even if the mud was difficult to penetrate.

The pilots found it much easier to make a clean, straight insertion of the laser probe into the seafloor by using a sturdy tripod.

The methodical survey involved inserting the probe at incremental depths at sites just outside the mound, on the mound’s flanks, and at the top of the mound. The methane signal grew with depth in the sediment and as the sampling neared the top of the mound. The strongest signal was at a depth of 30 centimeters at the top of the mound. For the first time, a bit of the solid methane hydrate got into the delicate probe and froze it up so that no further measurements could be taken until the “frozen” methane could be removed.

The only way to clear the probe was to bring the tool up to about 450 meters until the water got warmer and the pressure decreased—conditions that would make the hydrate dissolve. But before leaving for the trip up, we stopped to collect a push core for collaborator Laura Lapham’s research. Some bubbles popped out when that sample was removed. So the logical next step, to see what was there, was to use a long metal rod to poke around. This unleashed an impressive methane gusher from the seafloor. The bubbles spewed out forcefully for some time.

This forceful gusher of gas bubbles flowed for at least a couple of hours after we poked around in the seafloor where a strong methane signal had been detected. The gas was trapped at shallow depth below the seafloor.
The bubble stream was so forceful it showed up clearly on the ship’s sonar. The red section rising up from the bottom of the image (representing the seafloor at a depth of 1,272 meters) is the acoustic signal bouncing off the methane gusher. Notice the thin red lines going up, across, and back down; these represent the remotely operated vehicle on its brief journey to 400 meters to clear the laser probe of hydrate. The gas plume dissolves well before reaching the surface.

The bubbles were still gushing when we returned two hours later after bringing the ROV up to about 400 meters depth to clear the probe of hydrate. As the ROV neared the site, a big crab ambled over, apparently thinking there’d be something good to eat.

This crab dipped its claws into the bottom of the gusher to get a snack and put something in its mouth. Soon we saw hydrate forming on its face and in its mouth. Apparently the crab realized this was not a good place for healthy food and started picking at its mouth to pull out the ice-like hydrate that had gotten stuck there.

Before returning to the surface, we did a favor for our colleagues back at the Monterey Bay Aquarium Research Institute and went to check on a whale’s remains. We took careful video of the site so that scientists Bob Vrijenhoek and Shannon Johnson could see how the animal community that lives off the dead whale has changed since it was last seen.

Above, a whale’s spinal column as it rests on the seafloor. This whale has been dead for several years and has created a source of food for a wide variety of animals. Below, the whale’s skull and jawbones, with an octopus, snails, rockfish, crabs, and a snail tower right on top of the skull.

— Nancy Barr



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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 the ROV'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.

 Crew

R/V Western Flyer

Ian Young
Master


 

George Gunther
First Mate


 

Matt Noyes
Chief Engineer


 

Andrew McKee
Second Mate


 

Lance Wardle
First Engineer


 

Olin Jordan
Oiler


 

Paul Tucker
Second Engineer


 

Vincent Nunes
Bosun


 

Dan Chamberlain
Electronics Officer


 

Patrick Mitts
Steward


 

ROV Doc Ricketts

Knute Brekke
Chief ROV Pilot


 

Mark Talkovic
Senior ROV Pilot


 

Randy Prickett
Senior ROV Pilot


 

Bryan Schaefer
ROV Pilot/Technician


 

Eric Martin
ROV Pilot/Technician


 

 Research Team

Peter Brewer
Chief 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 in situ laser Raman spectrometry instruments and lab based analytical techniques to study the composition of gases in gas hydrates and deep-sea vents. He has collaborated on the development of new instrumentation for the measurement of temperature and pH from ROVs and deep-sea observatories. 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.

Andreas Hofmann
Postdoctoral Fellow
MBARI

Andreas is a MBARI Postdoctoral Fellow in the Brewer lab. He obtained a PhD in marine biogeochemistry in the Netherlands after his biology undergraduate and bioinformatics graduate studies in Germany. Andreas' specialty is pelagic and benthic biogeochemical modeling with a focus on pH and proton cycling. At MBARI, Andreas is working amongst others on the characterization of marine hypoxic and suboxic zones, focusing on the explicit description of physical limitations to aerobic respiration. On this cruise, Andreas will be involved in obtaining and processing Raman spectra, as well as in various other tasks supporting the objectives of the group.

Nancy Barr
Web/Print Project Manager
MBARI

Nancy manages the editing, design, and production of the MBARI annual report and participates in a variety of editorial and communication projects. She also oversees the institute website. Nancy has been to sea with several MBARI research groups, helping them to carefully remove worms from whale bones, annotate video, sift seafloor sediment, and collect and process water samples. For this expedition she will be in charge of the daily reports that will be posted to this website and will assist with other science crew tasks.

Elizabeth Coward
Summer Intern
MBARI

Elizabeth is an MBARI summer intern in the Brewer lab. She is a senior at Haverford College, PA, where she is obtaining her undergraduate joint degree in biology and chemistry. Elizabeth's prior research has been principally concerned with the bioavailability and geochemical dynamics of oil in marine sediments. Her interest in oceanic fossil fuels and greenhouse gases has brought her to the Brewer lab, where she will be using laser Raman spectroscopy to investigate methane and carbon dioxide signatures, the dynamics of gas hydrates and ocean acidification.

Michael Riedel
Research Scientist
Natural Resources Canada - Geological Survey of Canada

Michael Riedel was part of an international team of scientists supported by the Integrated Ocean Drilling Program (IODP) which completed a unique research expedition in 2005 aimed at recovering samples of gas hydrate, an ice-like substance hidden beneath the seafloor off Canada's western coast. As IODP Expedition 311's co-chief scientist, Michael explored his interest in gas hydrate; he believes such deposits have played an important role in ancient global climate change.

Laura Lapham
Postdoctoral Researcher
National Energy Technology Lab, U.S. Department of Energy

Laura's research is concentrated on studying methane cycling at cold seeps, biogeochemcial cycling of methane and sulfer in deep sea sediments, development of deep sea instrumentation to collect novel samples, stable isotope geochemistry, modeling of biogeochemical processes and temporal variability of dissolved methane concentrations. The focus of her research has been mainly on gas hydrate environments, but she is also interested in other systems that relate to the carbon cycle. Her research seeks to understand how methane is distributed between different pools, e.g. dissolved or hydrate phases, and also to understand how local biogeochemical processes affect this methane, mostly through anaerobic methane oxidation.

Jon Furlong
University of Victoria

Jon is a graduate student at the University of Victoria studying with Michael Riedel. His bachelor's degree was completed in Earth Sciences from Memorial University in Newfoundland before he moved from one coast to the other. Jon's research focuses on neo-tectonic faulting offshore Vancouver Island and its links to gas hydrate formation and fluid migration.