Ocean Methane and climate

[TC]

Part one.

As to not be off topic with several other threads regarding climate, I'll post this series of studies that deal with the phenomena of ocean gas being released along continental coast margins. For those of you interested in another aspect that comes into play with climate change, this is worth the read.


I'll start with a 2002 event that was witnessed first hand by scientists from UC Santa Barbara who observed and videotaped a massive blowout of methane from the ocean floor.

" It happened in an area of gas and oil seepage coming out of small volcanoes in the ocean floor of the Santa Barbara channel –– called Shane Seep –– near an area known as the Coal Oil Point seep field. The blowout sounded like a freight train, according to the divers.

Atmospheric methane is at least 20 times more potent than carbon dioxide and is the most abundant organic compound in the atmosphere, according to the studies authors, all from UC Santa Barbara.

"Other people have reported this type of methane blowout, but no one has ever checked the numbers until now," said Ira Leifer, lead author and an associate researcher with UCSB's Marine Science Institute. "Ours is the first set of numbers associated with a seep blowout." Leifer was in a research boat on the surface at the time of the blowouts.

Aside from underwater measurements, a nearby meteorological station measured the methane "cloud" that emerged as being approximately 5,000 cubic feet. The research team also had a small plane in place, flown by the California Department of Conservation, shooting video of the event from the air.

Virtually all the gas from the seeps escapes into the atmosphere, unlike the emission of small bubbles from the ocean floor, which partially, or mostly, dissolve in the ocean water. Transporting this methane to the atmosphere affects climate, according to the researchers. The methane blowout that the UCSB team witnessed reached the sea surface 60 feet above in just seven seconds. This was clear because the divers injected green food dye into the rising bubble plume.

Co-author Bruce Luyendyk, professor of marine geophysics and geological sciences, explained that, to understand the significance of this event (which occurred in 2002), the UCSB research team turned to a numerical, bubble-propagation model. With the model, they estimated methane loss to the ocean during the upward travel of the bubble plume.

The results showed that for this shallow seep, loss would have been approximately one percent. Virtually all the methane, 99 percent of it, was transported to the atmosphere from this shallow seep during the blowout. Next, the scientists used the model to estimate methane loss for a similar size blowout at much greater depth, 250 meters. Again, the model results showed that almost all the methane would be transported up to the atmosphere.

Over geologic time scales, global climate has cycled between warmer, interglacial periods and cooler, glacial periods. Many aspects of the forces underlying these dramatic changes remain unknown. Looking at past changes is highly relevant to understanding future climate changes, particularly given the large increase in atmospheric greenhouse gas concentrations in the atmosphere due to historically recent human activities such as burning fossil fuels.

One hypothesis, called the "Clathrate Gun" hypothesis, developed by James Kennett, professor of geological sciences at UCSB, proposes that past shifts from glacial to interglacial periods were caused by a massive decomposition of the marine methane hydrate deposits.

Methane hydrate is a form of water ice that contains a large amount of methane within its crystal structure, called a clathrate hydrate. According to Kennett's hypothesis, climatic destabilization would cause a sharp increase in atmospheric methane –– thereby initiating a feedback cycle of abrupt atmospheric warming. This process may threaten the current climate, according to the researchers. Warmer ocean temperatures from current global climate change is likely to release methane currently trapped in vast hydrate deposits on the continental shelves. However, consumption of methane by microbes in the deep sea prevents methane gas released from hydrates from reaching the ocean surface and affecting the atmosphere.

Bubbles provide a highly efficient mechanism for transporting methane and have been observed rising from many different hydrate deposits around the world. If these bubbles escape singly, most or all of their methane would dissolve into the deep-sea and never reach the atmosphere. If instead, they escape in a dense bubble plume, or in catastrophic blowout plumes, such as the one studied by UCSB researchers, then much of the methane could reach the atmosphere. Blowout seepage could explain how methane from hydrates could reach the atmosphere, abruptly triggering global warming.

Thus, these first-ever quantitative measurements of a seep blowout and the results from the numerical model demonstrate a mechanism by which methane released from hydrates can reach the atmosphere. Studies of seabed seep features suggest such events are common in the area of the Coal Oil Point seep field and very likely occur elsewhere.

The authors explain that these results show that an important piece of the global climate puzzle may be explained by understanding bubble-plume processes during blowout events. The next important step is to measure the frequency and magnitude of these events. The UCSB seep group is working toward this goal through the development of a long-term, seep observatory in active seep areas.

[TC]

Part. 2 The Thermal Maximum.

Around 55 million years ago took place one of the most rapid and extreme global warming events recorded in geologic history. Sea surface temperatures rose between 5 and 10 degrees C over a period of a few thousand years. This event, called 'Paleocene-Eocene Thermal Maximum' or the 'Initial Eocene Thermal Maximum' (PETM or IETM), unleashed climate shifts that endured tens of thousands of years.

What unleashed the PETM ? For years the majority accepted large volcanic eruptions being to blame, as they heaved millions of tons of carbon dioxide into the atmosphere over a short period of time.

But as of the last 20 years of study, another picture is becoming more the culprit than volcanism alone. And this is relative to the first post, as it seems to be an ongoing continuous event. Basically what took place is that lower ocean levels ( contained in glacier ice) caused an unprecedented release of ocean sediment contained methane. This input of isotopically light carbon into the ocean-atmosphere system is being considered the carbon injection that initiated pronounced global greenhouse warming and ocean acidification.

Subduction or down-welling of this warmer intermediate waters led to the unstable hydrates at deep water level and thermal dissociation of methane. A chain reaction if you will, as warmer water reached greater depths, this in turn released even more methane into the atmosphere, causing a thermal spike of over 10C at surface temperature.

My own opinion is something of a blend of both, with volcanism responsible for warming of atmospheric conditions in combination with lower sea level reactions of shallow water sediment methane release, and the chain reaction that led to the thermal maximum.

[TC]

Part 3. Holocene (the age of man)

There is a period called the Bølling-Allerød warming, ( 14,000 years ago) that just preceded the Holocene age where global sea level rose by 16 feet and temperatures in Greenland went up 27 degrees Fahrenheit during several hundred years, effectively melting the ice caps. As well as increased carbon dioxide, strengthening ocean currents, and a release of ocean-stored heat. ( NCAR study)

This study combined with pollen counts and trapped gas samples from ice core examination begins to reveal a picture of possible geological events that change climate on an abrupt scale, something that has been previously misunderstood as a trigger factor to runaway spikes.

With the onset of the Bolling-Allerod, Greenland warms at an alarming speed, largely due to reduced melt water that effect salinity counts, and Antarctica continues to warm as a result of large increases in greenhouse gas concentration. The methane and CO2 counts remained higher than today, ( roughly 40ppm) and were a direct result of a combination of both exposed wetlands and coast margin released methane.

[Prometheus]

Part 3. Holocene (the age of man)

There is a period called the Bølling-Allerød warming, ( 14,000 years ago) that just preceded the Holocene age where global sea level rose by 16 feet and temperatures in Greenland went up 27 degrees Fahrenheit during several hundred years, effectively melting the ice caps. As well as increased carbon dioxide, strengthening ocean currents, and a release of ocean-stored heat. ( NCAR study)

This study combined with pollen counts and trapped gas samples from ice core examination begins to reveal a picture of possible geological events that change climate on an abrupt scale, something that has been previously misunderstood as a trigger factor to runaway spikes.

With the onset of the Bolling-Allerod, Greenland warms at an alarming speed, largely due to reduced melt water that effect salinity counts, and Antarctica continues to warm as a result of large increases in greenhouse gas concentration. The methane and CO2 counts remained higher than today, ( roughly 40ppm) and were a direct result of a combination of both exposed wetlands and coast margin released methane.

Interesting read, shorty.

I appreciate this is accumalitive from a lot of reading(s), but a few refs on the bubble and Bølling-Allerød would be nice, when you have a few seconds. :-)

[Raptor Witness]

Nice work Short., you rule when it comes to interesting and well-thought articles.

[TC]

Interesting read, shorty.

I appreciate this is accumalitive from a lot of reading(s), but a few refs on the bubble and Bølling-Allerød would be nice, when you have a few seconds. :-)

The first is a bit academic, but a good read.

http://www.iceandclimate.nbi.ku.dk/p...eciale_IS.pdf/

I.K. Seierstad, S.J. Johnsen and B.M. Vinther

Short abstract. http://www.iceandclimate.nbi.ku.dk/p...s/Abstract238/

and this link is dealing with Bruce P. Luyendyk's study, one which we have been studing in class this last month.

http://www.bubbleology.com/Papers/SeepBoom.pdf

[Nasik]

For easy reference, here is the source to the narrative of the first post. I'm sure it was an inadvertent oversight that the article wasn't cited.

http://www.ocean.com/resource.asp?lo...abID=&SubTabID=

[TC]

For easy reference, here is the source to the narrative of the first post. I'm sure it was an inadvertent oversight that the article wasn't cited.

http://www.ocean.com/resource.asp?lo...abID=&SubTabID=

there is quotation marks at the beginning of the narrative... but ok maybe you missed that.

[TC]

Part 4. cyclic release of methane and ice ages.

There is a connection between our 100,000 year ice age cycles, and the subsequent 20,000 warming interludes with a cyclic release of trapped methane.

"O’Hara modeled methane releases.

What he found was that the methane releases happened relatively suddenly and then the methane persisted - which is weird because methane breaks down rather quickly in the atmosphere. This means that wherever the methane came from, it kept coming for a while, replenishing the methane that was being destroyed in the atmosphere.

That suggests there was a really big methane source. The biggest source that was available in those dry, icy times would be the frozen gas hydrates that exist throughout the world in the cold depths of the oceans.

The gas hydrates would have been vulnerable because the ice age sea level was close to 120 meters lower, which would expose shallower gas hydrates to lower pressures that that would make them unstable.


The oscillation between ice ages and interglacial periods is the dominant feature of Earth's climate for the last million years. But the computer models that predict significant global warming from carbon dioxide cannot reproduce these temperature changes. Something jump started these past periods, something massive and global.

My own opinion and the larger question, what shuts this process down to revert to a glacial period. Is the depletion of this gas the reason for an otherwise short interglacial period of 20.000 years, compared to the average 100,000 years of ice.

In short, ice age accumulated continental ice sheets creates the lower sea levels, which in turn starts the process of unstable hydrates, which in turn releases massive amounts of methane, which in turn creates the temperature spikes needed to melt the extended glacial periods.

[iulian28ti]

Soon farts will be considered evil....

[TC]

Soon farts will be considered evil....

There is some serious consideration given towards evil cowshit...lol