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Their article, which appeared last week in the peer-reviewed journal Nature Geoscience, states that the Arctic Ocean is releasing methane at a rate more than twice what scientific models had previously anticipated.
Shakhova, the lead author of the most recent report, said the methane release rate likely is even greater than their paper describes.
"We decided to be as conservative as possible," Shakhova said. "We're actually talking the top of the iceberg."
The submerged East Siberian Arctic Shelf contains much of the same stored carbon as the dry-land tundra just to its south but it also contains at least 17 teragrams of methane, the study states. A teragram is equal to 1 million tons.
The UAF researchers also concluded the Arctic methane release creates a positive feedback loop. As temperatures increase, more methane is released, and as more methane is released, temperatures increase.
I posted this in one of Rezlooper threads to give a idea of how much methane
From 2003 to 2008, an international research team led by University of Alaska-Fairbanks scientists Natalia Shakhova and Igor Semiletov surveyed the waters of the East Siberian Arctic Shelf, which covers more than 772,200 square miles (two million square kilometers) of seafloor in the Arctic Ocean.
"This discovery reveals a large but overlooked source of methane gas escaping from permafrost underwater, rather than on land," the study said.
"More widespread emissions could have dramatic effects on global warming in the future."
Here is the contribution from Semiletov and Shakhova:
We would first note that we have never stated that the reason for the currently observed methane emissions were due to recent climate change. In fact, we explained in detail the mechanism of subsea permafrost destabilization as a result of inundation with seawater thousands of years ago. We have been working in this scientific field and this region for a decade. We understand its complexity more than anyone. And like most scientists in our field, we have to deal with slowly improving understanding of ongoing processes that often incorporates different points of views expressed by different groups of researchers.
We found that the temperatures of the sediments were from 1.2 to 0.6 degrees below zero, Celsius, yet they were completely thawed.
There have been observations of bubbles emanating from the sea floor in the Arctic (Shakhova, 2010; Shakhova et al., 2005) and off Norway. The Norwegian bubble plume coincides with the edge of the hydrate stability zone, where a bit of warming could push the surface sediments from stable to unstable. A model of the hydrates (Reagan, 2009) produces a bubble plume similar to what’s observed, in response to the observed rate of ocean water warming over the past 30 years, but with this warming rate extrapolated further back in time over the past 100 years.
The response time of their model is several centuries, so pre-loading the early warming like they did makes it difficult to even guess how much of the response they model could be attributed to human-induced climate change, even if we knew how much of the last 30 years of ocean warming in that location came from human activity.
Ruppel et al. 2011
Catastrophic, widespread dissociation of methane gas hydrates will not be triggered by continued climate warming at contemporary rates (0.2ºC per decade; IPCC 2007) over timescales of a few hundred years. Most of Earth's gas hydrates occur at low saturations and in sediments at such great depths below the seafloor or onshore permafrost that they will barely be affected by warming over even 103 yr. Even when CH4 is liberated from gas hydrates, oxidative and physical processes may greatly reduce the amount that reaches the atmosphere as CH4.
The CO2 produced by oxidation of CH4 released from dissociating gas hydrates will likely have a greater impact on the Earth system (e.g., on ocean chemistry and atmospheric CO2 concentrations; Archer et al. 2009) than will the CH4 that remains after passing through various sinks.
Could there be a methane runaway feedback?.
The “runaway greenhouse effect” that planetary scientists and climatologists usually call by that name involves water vapor. A runaway greenhouse effect involving methane release (such as invoked here) is conceptually possible, but to get a spike of methane concentration in the air it would have to released more quickly than the 10-year lifetime of methane in the atmosphere.
It wouldn’t be a methane runaway greenhouse effect, it would be more akin to any other carbon release as CO2 to the atmosphere. This sounds like semantics, but it puts the methane system into the context of the CO2 system, where it belongs and where we can scale it.
So maybe by the end of the century in some reasonable scenario, perhaps 2000 Gton C could be released by human activity under some sort of business-as-usual scenario, and another 1000 Gton C could come from soil and methane hydrate release, as a worst case. We set up a model of the methane runaway greenhouse effect scenario, in which the methane hydrate inventory in the ocean responds to changing ocean temperature on some time scale, and the temperature responds to greenhouse gas concentrations in the air with another time scale (of about a millennium) (Archer and Buffett, 2005). If the hydrates released too much carbon, say two carbons from hydrates for every one carbon from fossil fuels, on a time scale that was too fast (say 1000 years instead of 10,000 years), the system could run away in the CO2 greenhouse mode described above. It wouldn’t matter too much if the carbon reached the atmosphere as methane or if it just oxidized to CO2 in the ocean and then partially degassed into the atmosphere a few centuries later.
The fact that the ice core records do not seem full of methane spikes due to high-latitude sources makes it seem like the real world is not as sensitive as we were able to set the model up to be. This is where my guess about a worst-case 1000 Gton from hydrates after 2000 Gton C from fossil fuels in the last paragraph comes from.
The melting of the subsea permafrost in the Arctic Ocean can't be blamed on modern humans—it's been slowly warming down there for thousands of years—it's just recently however, reached the point where it melts in the summer just enough to allow the methane in it to seep out and bubble up into the sea column above.
The researchers note that their measurements contradict predictions by others that a massive "pulse" of methane will very soon add as much as 50 billion tonnes of methane to the atmosphere, causing a dramatic spike in global air temperatures. Instead, they suggest, it appears more likely that the methane will continue to bubble up slowly, contributing to greenhouse gases much as is happening currently—though they do caution that its possible global warming could cause more or bigger storms in the Arctic Ocean, releasing methane on a bigger scale.
Read more at: phys.org...
If world leaders had any brains, they would be taking constructive action.
As in constructing harvesting equipment to harvest these methane deposits, before they get released into the atmosphere. We could solve our planets energy problems in a far more effective way. Japan is already working on this