Tuesday, September 25, 2012

Expedition to study methane gas bubbling out of the Arctic seafloor

The black rectangle on this map shows the general region
where Paull and his collaborators have been studying
methane releases in the Beaufort Sea. The smaller red
rectangle indicates the edge of the continental shelf and
continental slope where they will conduct research during t
heir current expedition. These areas are shown in greater
detail in the maps below. Base image: Google Maps

Chasing gas bubbles in the Beaufort Sea

In the remote, ice-shrouded Beaufort Sea, methane (the main component of natural gas) has been bubbling out of the seafloor for thousands of years. MBARI geologist Charlie Paull and his colleagues at the Geological Survey of Canada are trying to figure out where this gas is coming from, how fast it is bubbling out of the sediments, and how it affects the shape and stability of the seafloor. Although Paull has been studying this phenomenon for a decade, his research has taken on new urgency in recent years, as the area is being eyed for oil and gas exploration.

In late September 2012, Paull and his fellow researchers will spend two weeks in the Beaufort Sea on board the Canadian Coast Guard ship Sir Wilfred Laurier, collecting seafloor sediment, mapping the seafloor using sonar, installing an instrument that will "listen" for undersea gas releases, and using a brand new undersea robot to observe seafloor features and collect gas samples.

This will be Paull's third Beaufort Sea expedition. As in previous expeditions, he will be working closely with Scott Dallimore of Natural Resources Canada's Geological Survey of Canada and Humfrey Melling of Fisheries and Oceans Canada's Institute of Ocean Sciences.

Paull's work in the Arctic started in 2003, with an investigation into the enigmatic underwater hills called "pingo-like features" (PLFs) that rise out of the continental shelf of the Beaufort Sea. (Pingos are isolated conical hills found on land in some parts of the Arctic and subarctic.)

Over time, the focus of the team's research has moved farther offshore, into deeper water. Their second expedition in 2010 looked at diffuse gas venting along the seaward edge of the continental shelf. The 2012 expedition will focus on three large gas-venting structures on the continental slope, at depths of 290 to 790 meters (950 to 2,600 feet).

This idealized cross section of the continental shelf and
continental slope in the Beaufort Sea shows zones in the
seafloor where permafrost and methane hydrate are
likely to exist, as well as hypothetical locations of methane
seeps on the seafloor. Ocean depths not shown to scale.
Image: © 2012 MBARI

Frozen gas—a relict of previous ice ages

The Beaufort Sea, north of Canada's Yukon and Northwest Territories, is a hostile environment by any definition of the term. It is covered with ice for much of the year. Historically, only from mid-July to October has a narrow strip of open water appeared within about 50 to 100 kilometers (30 to 60 miles) of the coast. Even at this time of year, winds often howl at 40 knots and temperatures can drop well below freezing at night. Researchers must allow extra time for contingencies such dodging pack ice and having to shovel snow off the deck of the research vessel.

Average annual air temperatures along the coast of the Beaufort Sea are well below freezing. Thus deeper soils remain permanently frozen throughout the year, forming what is called permafrost. Around the Beaufort Sea, permafrost extends more than 600 meters (about 2,000 feet) below the ground.

Permafrost also exists in the sediments underlying the continental shelf of Beaufort Sea. This permafrost is a relict of the last ice age, when sea level was as much as 120 meters lower than today. At that time, areas that are now covered with seawater were exposed to the frigid Arctic air.

As sea-level rose over the last 10,000 years, it flooded the continental shelf with seawater. Although the water in the Beaufort Sea is cold—about minus 1.5 degrees Centigrade—it is still much warmer than the air, which averages minus 15 degrees C. Thus, as the ocean rose, it is gradually warmed up the permafrost beneath the continental shelf, causing it to melt.

Quite a bit of methane, the main component of "natural gas," is trapped within the permafrost. As the permafrost melts, it releases this methane, which may seep up through the sediments and into the overlying ocean water.

The deeper sediments of the Beaufort Sea also contain abundant layers of methane hydrate—an ice-like mixture of water and natural gas. As the seafloor has warmed, these hydrates have also begun to decompose, releasing additional methane gas into the surrounding sediment.

These maps show the area to be studied during the
current expedition. The lower map shows the continental
shelf and continental slope of the Beaufort Sea. The
upper image shows detailed seafloor bathymetry of a
portion of the continental slope that will be studied
during the current cruise, as well as the three seafloor
mounds that the researchers will explore using their
new ROV. Lower image modified from Google Maps.
Upper image: Natural Resources Canada.

A tantalizing glimpse

A 2010 expedition by Paull and his colleagues provided a tantalizing glimpse of how much methane is present on the continental shelf of the Beaufort Sea. Using a remotely operated vehicle (ROV) with video camera to explore the shelf edge, they found white mats of methane-loving bacteria almost everywhere. They also videotaped what turned out to be methane bubbles emerging from many of these mats. Based on these observations, as well as the contents of sediment cores collected by the Geological Survey of Canada, the researchers concluded that the shelf edge is an area of "widespread diffuse venting" and that "methane permeates the shelf edge sediments in this region."

During 2010, the research team also conducted ROV dives on a shallow underwater mound called Kopanoar PLF. At the top of this mound they discovered "vigorous and continuous gas venting" that released clouds of bubbles and sediment into the water. In one ROV dive, the researchers saw something no one had ever seen before—a plume of gas bubbles that moved rapidly along the sea floor, apparently following a crack in the sediment that was in the process of being forced open by the pressure of the gas coming up from below.

The researchers also studied several deeper PLFs during the 2010 expedition. They dropped core tubes into the tops of these mounds. When the cores were lifted back onto the ship, the sediments inside fizzed and bubbled for up to an hour. The sediment was chock full of methane hydrates. Paull said, "We knew that there was a lot of gas venting going on down there, and now we have good reasons to believe that methane hydrates are present within the surface sediments. But our ROV couldn't dive deep enough, so we weren't able to go down and see what these areas actually looked like." That's one reason the team is heading back to the Arctic in 2012.

MBARI researchers tested this new mini-ROV
in the institute's test tank before sending it out
to face the challenges of the Arctic Ocean.
Image: Todd Walsh © 2012 MBARI

Heading back for more

For the 2012 expedition, the team will continue its strategy of following the topography to study areas of gas venting in the Beaufort Sea. They plan to focus on three circular, flat-topped mounds on the continental slope. The researchers believe that these pingo-like features form at the tops of "chimneys" or conduits where methane is seeping up from sediments hundreds of meters below the seafloor.

During his previous cruises, Paull used a small ROV that could dive only about 120 meters below the surface. However, the mounds on the continental slope are in about 300 to 800 meters of water. So MBARI engineers Dale Graves and Alana Sherman designed and built an entirely new ROV just for this expedition. The new ROV is small, portable, agile, relatively inexpensive, and can dive to 1,000 meters. It can also be launched and operated by just two people (for the 2012 expedition, those two people will be Graves and Sherman).

Amazingly, the new mini-ROV went from initial design to final field tests in only 15 months. But the vehicle's simple yet elegant design reflects Graves' decades of experience designing ROVs and underwater control systems. "It was a fun project for me," Graves said. "A dream come true. We designed it from scratch with a budget of just $75,000, not including labor. We mostly reused parts from MBARI's older ROVs, and built the rest in house. MBARI's electrical and mechanical technicians and machinists worked on it in between their other projects."

In addition to a state-of-the-art high-definition video camera, the ROV carries a special system for collecting methane gas bubbles. This is not as easy as it sounds, because the methane gas has a tendency to turn back into solid methane hydrate, which blocks the flow of any additional methane gas into the system. The new ROV's gas collection system includes a built-in heater to melt the hydrates and keep the gas flowing.

In addition to collecting samples of gas, the ROV will be used to look for communities of tubeworms or clams that typically grow around seafloor methane seeps. Paull said, "Nobody has ever found a living chemosynthetic biological community in the Arctic proper. But I think we have a good chance of finding them at the tops of these structures."

Dale Graves tests the control system for MBARI's new
mini-ROV in the lab before the Arctic expedition.
The entire system fits in just three small shipping cartons.
Image: Todd Walsh © 2012 MBARI

Addressing the big questions

Although the researchers have begun to understand where the gas in the Beaufort Sea is coming from, many other questions remain. One of the big questions the researchers are trying to answer is whether the three gas chimney structures on the continental slope are related to the gas venting systems in shallower water, on the continental shelf. As Paull put it, "Are they independent gas-venting structures that just happen to be together, or are they all part of the same system?"

Another important question is how all this methane gas affects the stability of the seafloor. When methane hydrates warm up and release methane gas, the gas takes up much more space than the solid hydrate, putting pressure on the surrounding sediments. Similarly, the decomposition of either methane hydrate or permafrost can reduce the mechanical strength of the surrounding sediment. Either process could make the seafloor more susceptible to submarine landslides.

Undersea landslides are common along the continental slope of the Beaufort Sea, but researchers do not yet know when or how they form. However, decomposing methane hydrates are believed to have triggered major landslides in other deep-sea areas. Such landslides could potentially destabilize oil platforms, pipelines, or other equipment on the seafloor, and have the potential to generate tsunamis.

If there is time during the 2012 cruise, the researchers hope to perform ROV dives on one or more underwater-landslides. In Fall 2013, when the team returns to the Beaufort Sea for a fourth time, these features will become the primary focus. During that expedition, the team also hopes to use one of MBARI's autonomous underwater vehicles (AUVs) to make very detailed maps of the shelf edge, the underwater landslides, and areas where methane is bubbling out of the seafloor.

Oil and gas companies have known for decades that deep oil and natural gas deposits exist in the sediments below the continental slope of the Beaufort Sea. With the warming of the Arctic and the retreat of sea ice, these hydrocarbons have become more accessible. However, it remains to be seen whether they can be extracted safely, economically, and without excessive environmental damage. Thus, the team's research will not only provide new insights into previously unknown geological processes, but will also provide important information for decision-makers involved in oil and gas permitting.

For more information on this article, please contact MBARI.

Related links:

Charlie Paull's web site describing first-hand observations of methane bubbling out of seafloor during the Arctic 2010 expedition (includes video clips).
Article describing the origin of seafloor mounds in the Beaufort Sea.
Article on Paull's initial research regarding pingos and pingo-like-features on the seafloor.
Charlie Paull's web site
Web site of the Geological Survey of Canada

Source: Monterey Bay Aquarium Research Institute news release

Monday, September 24, 2012

Changes to Polar Vortex affect mile-deep ocean circulation patterns

Sept. 23, 2012 – A University of Utah study suggests something amazing: Periodic changes in winds 15 to 30 miles high in the stratosphere influence the seas by striking a vulnerable “Achilles heel” in the North Atlantic and changing mile-deep ocean circulation patterns, which in turn affect Earth’s climate.

“We found evidence that what happens in the stratosphere matters for the ocean circulation and therefore for climate,” says Thomas Reichler, senior author of the study published online Sunday, Sept. 23 in the journal Nature Geoscience.

Simplified artist’s conception showing how changes in polar vortex winds high in the stratosphere can influence the North Atlantic to cause changes in the global conveyor belt of ocean circulation. Credit: Thomas Reichler, University of Utah.

Scientists already knew that events in the stratosphere, 6 miles to 30 miles above Earth, affect what happens below in the troposphere, the part of the atmosphere from Earth’s surface up to 6 miles or about 32,800 feet. Weather occurs in the troposphere.

Researchers also knew that global circulation patterns in the oceans – patterns caused mostly by variations in water temperature and saltiness – affect global climate.

“It is not new that the stratosphere impacts the troposphere,” says Reichler, an associate professor of atmospheric sciences at the University of Utah. “It also is not new that the troposphere impacts the ocean. But now we actually demonstrated an entire link between the stratosphere, the troposphere and the ocean.”

Funded by the University of Utah, Reichler conducted the study with University of Utah atmospheric sciences doctoral student Junsu Kim, and with atmospheric scientist Elisa Manzini and oceanographer Jürgen Kröger, both with the Max Planck Institute for Meteorology in Hamburg, Germany.

Stratospheric Winds and Sea Circulation Show Similar Rhythms

Reichler and colleagues used weather observations and 4,000 years worth of supercomputer simulations of weather to show a surprising association between decade-scale, periodic changes in stratospheric wind patterns known as the polar vortex, and similar rhythmic changes in deep-sea circulation patterns. The changes are:

– “Stratospheric sudden warming” events occur when temperatures rise and 80-mph “polar vortex” winds encircling the Artic suddenly weaken or even change direction. These winds extend from 15 miles elevation in the stratosphere up beyond the top of the stratosphere at 30 miles. The changes last for up to 60 days, allowing time for their effects to propagate down through the atmosphere to the ocean.

– Changes in the speed of the Atlantic circulation pattern – known as Atlantic Meridional Overturning Circulation – that influences the world’s oceans because it acts like a conveyor belt moving water around the planet.

Sometimes, both events happen several years in a row in one decade, and then none occur in the next decade. So incorporating this decade-scale effect of the stratosphere on the sea into supercomputer climate simulations or “models” is important in forecasting decade-to-decade climate changes that are distinct from global warming, Reichler says.

“If we as humans modify the stratosphere, it may – through the chain of events we demonstrate in this study – also impact the ocean circulation,” he says. “Good examples of how we modify the stratosphere are the ozone hole and also fossil-fuel burning that adds carbon dioxide to the stratosphere. These changes to the stratosphere can alter the ocean, and any change to the ocean is extremely important to global climate.”

A Vulnerable Soft Spot in the North Atlantic

“The North Atlantic is particularly important for global ocean circulation, and therefore for climate worldwide,” Reichler says. “In a region south of Greenland, which is called the downwelling region, water can get cold and salty enough – and thus dense enough – so the water starts sinking.”

It is Earth’s most important region of seawater downwelling, he adds. That sinking of cold, salty water “drives the three-dimensional oceanic conveyor belt circulation. What happens in the Atlantic also affects the other oceans.”

Reichler continues: “This area where downwelling occurs is quite susceptible to cooling or warming from the troposphere. If the water is close to becoming heavy enough to sink, then even small additional amounts of heating or cooling from the atmosphere may be imported to the ocean and either trigger downwelling events or delay them.”

Because of that sensitivity, Reichler calls the sea south of Greenland “the Achilles heel of the North Atlantic.”

From Stratosphere to the Sea

In winter, the stratospheric Arctic polar vortex whirls counterclockwise around the North Pole, with the strongest, 80-mph winds at about 60 degrees north latitude. They are stronger than jet stream winds, which are less than 70 mph in the troposphere below. But every two years on average, the stratospheric air suddenly is disrupted and the vortex gets warmer and weaker, and sometimes even shifts direction to clockwise.

“These are catastrophic rearrangements of circulation in the stratosphere,” and the weaker or reversed polar vortex persists up to two months, Reichler says. “Breakdown of the polar vortex can affect circulation in the troposphere all the way down to the surface.”

Reichler’s study ventured into new territory by asking if changes in stratospheric polar vortex winds impart heat or cold to the sea, and how that affects the sea.

It already was known that that these stratospheric wind changes affect the North Atlantic Oscillation – a pattern of low atmospheric pressure centered over Greenland and high pressure over the Azores to the south. The pattern can reverse or oscillate.

Because the oscillating pressure patterns are located above the ocean downwelling area near Greenland, the question is whether that pattern affects the downwelling and, in turn, the global oceanic circulation conveyor belt.

The study’s computer simulations show a decadal on-off pattern of correlated changes in the polar vortex, atmospheric pressure oscillations over the North Atlantic and changes in sea circulation more than one mile beneath the waves. Observations are consistent with the pattern revealed in computer simulations.

Observations and Simulations of the Stratosphere-to-Sea Link

In the 1980s and 2000s, a series of stratospheric sudden warming events weakened polar vortex winds. During the 1990s, the polar vortex remained strong.

Reichler and colleagues used published worldwide ocean observations from a dozen research groups to reconstruct behavior of the conveyor belt ocean circulation during the same 30-year period.

“The weakening and strengthening of the stratospheric circulation seems to correspond with changes in ocean circulation in the North Atlantic,” Reichler says.

To reduce uncertainties about the observations, the researchers used computers to simulate 4,000 years worth of atmosphere and ocean circulation.

“The computer model showed that when we have a series of these polar vortex changes, the ocean circulation is susceptible to those stratospheric events,” Reichler says.

To further verify the findings, the researchers combined 18 atmosphere and ocean models into one big simulation, and “we see very similar outcomes.”

The study suggests there is “a significant stratospheric impact on the ocean,” the researchers write. “Recurring stratospheric vortex events create long-lived perturbations at the ocean surface, which penetrate into the deeper ocean and trigger multidecadal variability in its circulation. This leads to the remarkable fact that signals that emanate from the stratosphere cross the entire atmosphere-ocean system.”

References:

Stratosphere Targets Deep Sea to Shape Climate - North Atlantic 'Achilles Heel' lets Upper Atmosphere Affect the Abyss - University of Utah News Center.
http://unews.utah.edu/news_releases/stratosphere-targets-deep-sea-to-shape-climate/

A stratospheric connection to Atlantic climate variability

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo1586.html

Sunday, September 23, 2012

Methane fields in the Laptev Sea

Below is part of a recent interview published by Voice of Russia - click here for the full report. Editorial note: We anxiously await further findings from the research team as to what the source is of these releases, when the methane was formed and by how much these releases are likely to increase over the years.

Methane emission in the Arctic – a possible key to the global warming

Tags: natural resources, Arctic, Society, World, Russia, Opinion & Analysis

Maria Dunayeva

18.09.2012, 16:52

Russian scientists have discovered more than 200 sources of methane emissions in the Arctic, particularly in the north of the Laptev Sea. Two of the methane fields exceed 1 kilometer in diameter, said Igor Semiletov, expedition head aboard the Viktor Buinitsky research vessel. Methane emissions in the Arctic have been observed before and are explained by bacterial activity. Head of the ecology department at Moscow State University, Dmitry Zamolodchikov, spoke about the possible consequences in an exclusive interview with the Voice of Russia.

How would you comment on this discovery by Russian scientists?

Different examples of methane emissions in Arctic coastal regions and in the tundra systems have been observed over the last 20 or 30 years. There is really nothing surprising about this. Because, first of all, we are talking about frozen substances and cold conditions in the coastal area, in addition to the water pressure, all of which make perfect conditions for so called gas hydrates. That is a bond between methane and water, which looks like snow, and is fairly unstable. Gas hydrates can quite easily break and can cause, correspondingly, methane emissions. Methane emerges as a result of bacteria activity in an environment with little oxygen which decomposes organic substances. The tundra has a humid climate, meaning it has the perfect conditions for the methane-producing bacteria. In that sense tundra is the source of methane and these bacteria are active in this region. In other words the Arctic has many mechanisms for production of natural methane. There are many mechanisms that conserve methane, for example gas hydrates. Many of those mechanisms are broken at higher temperatures. Therefore, in some cases, mass emissions of methane can be observed.

Source: Voice of Russia.

Saturday, September 22, 2012

Professor Peter Wadhams calls for action

In the Youtube video below, Professor Peter Wadhams, Professor of Ocean Physics and Head of the Polar Ocean Physics Group of the University of Cambridge and one of the world's top sea-ice experts, joins The Big Picture, a show with Thom Hartmann filmed live and broadcast from the RT America studios in Washington DC.

Professor Wadhams warns that the Arctic sea ice looks set to be completely melted in just a few years. Professor Wadhams adds that action is needed that includes not only emissions cuts, but also geoengineering methods.

It was a Skype connection, so the sound quality was not optimal, but Peter Carter has improved this in the version below. Anyway, the message is important enough to be watched closely and to be further shared and discussed.

The diagram below illustrates this further.