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New Study — Risk of Significant Methane Release From East Siberian Arctic Shelf Still Growing

Large plumes of methane bubbling up from the Arctic Ocean sea-bed, saturating the water column, venting into the air, adding significantly more heat forcing to an already dangerous, fossil fuel-based, accumulation of greenhouse gasses in the Earth’s atmosphere. It’s a nightmare scenario. One in which human-forced warming, already at 1 C above 1880s levels, is further amplified through the feedback release of ancient carbon stored over the past 8 million years of Northern Hemisphere glaciation. And a recent study by the now famous Semiletov and Shakhova team provides still more reason for appropriate concern that such an event may be in the works.

ESAS methane release organic carbon store

(Shakhova and Semiletov’s new study produces an increasingly clear picture of a destabilizing organic carbon store beneath thawing permafrost in the East Siberian Arctic Shelf region. The above images show organic carbon concentration [left frame] and rate of release of methane in grams per square meter per day over observed regions. Image source: The Royal Society.)

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By now, many of us are familiar with the controversy over the potential risks of significant-to-catastrophic methane release due to human-forced warming of the ArcticAn increasing number of observational specialists are pointing toward a risk that rapid human warming will set off the release of still more carbon in the Arctic. For some, this release is expected to be gradual. Others believe there’s enough risk of a rapid release to warrant an equally rapid emergency response.

But regardless of where you stand on the issue, new research coming to light from some of the Arctic’s top observational scientists more clearly describes what appears to be an increasingly dangerous situation.

Disintegrating Permafrost Cap in ESAS

At issue is the fact that, at the end of the last ice age, a great store of permafrost carbon was submerged as the Arctic Ocean rose. A low lying region containing about 500 billion tons of carbon as methane became inundated by the shallow sea that is the East Siberian Arctic Shelf (ESAS). The waters of this sea remained cold — below the freezing point of non-salt water in its lower reaches for most of the year. But, in some places, warmth invaded, and it is thought that small portions of the permafrost cap deteriorated.

In the near shore zones and in geologically active zones, methane conduits called taliks developed. And from these expanding taliks an increasing amount of methane bubbled to the surface.

Submerged Thermokarst Lake

(Ivashkina Lagoon was once a thermokarst lake. It has since been flooded by the Laptev Sea. For much of the time of inundation, the fresh water lake surface remained frozen. It is now thawing and releasing its organic carbon store as methane. Image source: The Royal Society.)

However, for the most part, the permafrost cap over the methane stores remained in tact — waiting to be rejuvenated by a new ice age. That is, until human industry belched billions of tons of carbon into the atmosphere, removing the possibility of a new ice age and forcing the world ocean and connecting Arctic Ocean to begin to warm in excess of peak Holocene temperatures. This warming, twice as fast in the Arctic as in the rest of the world, added still more heat pressure to the permafrost cap locking methane within the ESAS sea floor.

Now, more and more permafrost beneath the shallow ESAS waters is starting to thaw. And this, much more rapid than normal thaw is resulting in an increasing risk that methane stores beneath the permafrost cap will destabilize.

Shallow Waters, Geothermal Hot Spots, Taliks

Recent observational records by Dr. Natalia Shakhova and Dr. Igor Semiletov have found what they hypothesize to be an expanding array of methane vents in the East Siberian Arctic Shelf sea bed. According to their recent research, the vents appear to be growing more robust — bubbling up greater volumes of methane from a more vigorous and inter-connected network of channel beneath the thawing sea floor.

Atmospheric Methane September 6 2015

(Ever since 2005, atmospheric methane levels have again been on the rise. Much of this increase may be due to human emissions. However, an overburden of atmospheric methane and carbon dioxide in the Arctic zone hints that destabilizing carbon stores may also be adding substantial volumes of greenhouse gasses to the world’s airs. Image source: NOAA OSPO.)

Currently, according to Shakhova and Semiletov, methane emissions are most vigorous in the near-shore region of the ESAS and in the offshore slope region. Shakhova and Semiletov believe that near shore emissions are increasingly active due to rapid warming occurring there. Not only are the regional waters impacted by a rapidly warming Siberian land mass. They also see the flux of hotter waters from rivers issuing from the continent. As a result, the near shore region is most vulnerable to permafrost thaw and destabilization. In the slope zone, however, geological features are more active. These features provide a natural heat for the formation of taliks. And though most of this region was once frozen to the point that even geological activity did not result in methane venting, the now warming permafrost cap is generating weaker regions that natural geological heat can exploit to greater and greater degrees.

Sea Ice Melt, Storms, Heighten Methane Emissions

Ever since the mid 2000s Shakhova and Semiletov have observed what appears to be a generally heightened methane emission coming from the ESAS. Estimates for total release rates have doubled and then doubled again. By 2013, the scientists were estimating that 17 million tons of methane was venting from the ESAS sea surface each year.

The increased rate of methane release is not only due to permafrost thaw on the sea floor. It is also due to an increase in large polynyas in the ESAS during winter time as well as an overall increase in the area of open water that can be impacted by storms. An ice locked ESAS keeps more of its methane in the water column and gives the methane a longer period to be absorbed by the water or consumed by microbes. But as the ice recedes, more of the methane is able to break the surface and reach the airs above. In addition, ice free seas are more susceptible to the action of storms. Storms increase wave heights, increase the rate of breaking waves, and reduces ocean surface stratification. As a result methane moves more rapidly through the upper level water column and encounters a larger surface area from which to transfer from water to air.

An ice free ESAS is not only warmer, generating more destabilization forcing to the permafrost cap which locks in methane, it is also more and more devoid of the surface ice cap which acts as a secondary barrier to methane to air transfer.

Shakhova, Semiletov Recommend Adding ESAS Methane Release to Global Climate Models

Shakhova and Semiletov’s findings continue to compel them to issue warnings over the prospect of continuing increases in methane emissions from the ESAS and nearby seas. They conclude:

The observed range in CH4 emissions associated with different degrees of subsea permafrost disintegration implies substantial and potent emission enhancement in the ESAS as the process of subsea permafrost thawing progresses with time. While it is still unclear how quickly CH4 flux rates will change, the current process of Arctic warming and associated sea ice loss will accelerate this process. The potential for the release of substantial amounts of CH4 from the ESAS region has important implications not only for atmospheric CH4 concentrations but also, given CH4‘s potency as a greenhouse gas, for the global climate. Because the ESAS contains the largest and arguably most vulnerable stores of subsea CH4, inclusion of the ESAS source in global climate models should be considered a high priority.

Links:

The East Siberian Arctic Shelf: Further Assessment of Permafrost Related Fluxes and the Role of Sea Ice

Double the Rate of Methane Release From the Arctic Sea Floor

NOAA OSPO

Concern Over Arctic Methane Release

Threat of Permafrost Destabilization is ‘Real and Imminent’

 

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High Velocity Human Warming Coaxes Arctic Methane Monster’s Rapid Rise From Fens

Fens. A word that brings with it the mystic imagery of witch lights, Beowulfian countrysides, trolls, swamp gas, dragons. A sight of crumbling towers overlooking black waters. Now, it’s a word we can add to our already long list of amplifying Arctic feedbacks to human-caused warming. For the rapid formation of Arctic fens over the past decade has now been linked in a recent scientific study, at least in part, to a return to atmospheric methane increases since 2007.

Ribbed Fen

(A Ribbed Fen in Arctic Canada. Image source: The Government of Canada.)

The Role of Methane in Past Climate Change

Over the past 800,000 years, ice core records show atmospheric methane levels fluctuating between about 800 parts per billion during warm interglacial periods and about 400 parts per billion during the cold ice age periods. These fluctuations, in addition to atmospheric CO2 flux between 180 and 280 parts per million value were due to Earth Systems feedbacks driven by periods of increased solar heat forcing in the northern hemisphere polar region and back-swings due to periods of reduced solar heat forcing.

Apparently, added solar forcing at the poles during periodic changes in Earth’s orbit (called Milankovitch Cycles) resulted in a flood of greenhouse gasses from previously frozen lands and seas. This new flood amplified the small heat forcing applied by orbital changes to eventually break Earth out of cold ice age periods and push it back into warm interglacials.

Compared to current human warming, the pace of change at the time was slow, driving 4-6 degrees Celsius of global atmospheric heating over periods of around 8 to 20 thousand years. A small added amount of solar heat gradually leached out a significant volume of heat trapping gasses which, over the course of many centuries, undid the great grip of ice on our world.

Ice core record of Greenhouse Gas Flux

(Ice core record of greenhouse gas flux over the last 650,000 years. Methane flux is shown in the blue line that is second from the bottom. It is worth noting that current atmospheric methane values according to measures from the Mauna Loa Observatory are now in excess of 1840 parts per billion value. Temperature change is indicated in the lowest portion of the graph in the form of proxy measurements of atmospheric deuterium which provide a good correlation with surface temperature values. The gray shaded areas indicate the last 5 interglacial periods. Temperature year 0 is 1950. GHG year zero is 2006 in this graph. Image source: IPCC.)

By comparison, under business as usual human fossil fuel emissions combined with amplifying feedbacks from the Earth climate system (such as those seen in the fens now forming over thawing Arctic tundra), total warming could spike to an extraordinarily damaging level between 5 and 9 degrees Celsius just by the end of this century.

Methane — Comparatively Small Volume = Powerful Feedback

A combination of observation of past climates and tracking the ongoing alterations to our own world driven by human greenhouse gas emissions has given us an ever-clearer picture of how past climates might have changed. As Earth warmed, tundra thawed and ice sheets retreated releasing both CO2 and methane as ancient organic carbon stores, trapped in ice for thousands to millions of years, were partly liberated from the ice. In addition, warming seas likely liberated a portion of the sea bed methane store even as warming brought on a generally more active carbon cycle from the wider biosphere.

Overall, the added heat feedback from the increases in atmospheric methane to due these processes was about 50% that of the overall CO2 feedback, even though the volume of methane was about 200 times less. This disproportionately large share of heat forcing by volume is due to the fact that methane is about 80 times more efficient at trapping heat than CO2 over the course of 20 years.

A Problem of High Velocity Thaw

In the foreground of this comparatively rosy picture of gradual climate change driven by small changes in solar heat forcing setting off relatively more powerful amplifying greenhouse gas feedbacks, we run into a number of rather difficult problems.

The first is that the rate at which humans are adding greenhouse gasses to the atmosphere as an initial heat forcing is unprecedented in the geological record. Even the great tar basalts of the end Permian Extinction were no equal to the rate at which humans are now adding heat trapping gasses to the atmosphere. In just a short time, from 1880 to now, we’ve increased atmospheric CO2 by 120 parts per million to around 400 ppm and atmospheric methane by more than 1100 parts per billion to around 1840 parts per billion. The result is an atmospheric heat forcing not seen in at least the past 3 million years and possibly as far back as 10 million years (due to the radical increase in methane and other non CO2 heat trapping gasses).

This extraordinary pace of heat trapping gas increase has led to a very rapid pace of global atmospheric temperature increase of about .15 degrees Celsius per decade or about 30 times that of the end of the last ice age. As atmospheric heat increases are amplified at the poles and, in particular in the northern polar region, the areas with the greatest stores of previously frozen carbon are the ones seeing the fastest pace of warming. Siberia, for example, is warming at the rate of .4 C per decade. Overall, the Arctic has warmed by about 3 degrees Celsius since 1880 or nearly 4 times the pace of overall global warming.

arctic temperature increase since 1880 NASA

(Pace of Arctic warming since 1880 in degrees Fahrenheit based on reports from 137 Arctic observation stations over the period. Image source: Tamino. Data source: NOAA’s Global Historical Climatology Network.)

The result is that, over the past two decades, the Arctic has been warming at the pace of about .6 C (1 F)every ten years. And what we are seeing in conjunction with very rapid warming is an extraordinary high-velocity thaw. A thaw that is rapidly liberating stored organic carbon locked in tundra at a rate that may well have no rational geological corollary.

The Arctic Methane Monster and a Multiplication of Fens

So it is in this rather stark set of contexts that a study released in early May examining 71 wetlands around the globe found rapidly melting permafrost was resulting in the formation of an immense number of fens along the permafrost thaw boundary zone. Tundra melt in lowlands became both sources and traps for water. Such traps gained added water as atmospheric temperature increases held greater levels of humidity resulting in increased heavy rainfall events such as thunderstorms. These newly thawed and flooded fens, the study found, were emitting unexpectedly high volumes of methane gas.

From the methane standpoint, fens are a problem due to the fact that they are constantly wet. Whereas bogs may be wet, then dry, fens remain wet year-round. And since bacteria that break down the recently thawed organic carbon stores into methane thrive in a constantly wet environment the fens were found to be veritable methane factories. A powerful amplifying feedback loop that threatens to liberate a substantial portion of the approximately 1,500 gigatons of carbon stored in now melting tundra as the powerful heat trapper that is methane.

Mauna Loa Methane 1985 to 2014

(Mauna Loa methane levels 1985 to 2014. A return to rising atmospheric levels post 2007 is, in part, attributed to rapid tundra thaw and the formation of methane producing fens. Other significant new methane sources likely include sea bed methane from Arctic stores and rising human methane emissions due to expanding coal use and hydraulic fracturing. Image source: NOAA ESRL.)

By comparison, drier environments would result in the release of stored carbon as CO2, which would still provide a strong heat feedback, but no-where near as powerful as the rapid environmental forcing from a substantial methane release.

Lead study author Merritt Turetsky noted:

“Methane emissions are one example of a positive feedback between ecosystems and the climate system. The permafrost carbon feedback is one of the important and likely consequences of climate change, and it is certain to trigger additional warming. Even if we ceased all human emissions, permafrost would continue to thaw and release carbon into the atmosphere. Instead of reducing emissions, we currently are on track with the most dire scenario considered by the IPCC. There is no way to capture emissions from thawing permafrost as this carbon is released from soils across large regions of land in very remote spaces.”

 

Links:

A Synthesis of Methane Emissions From 71 Wetlands

Arctic Methane Emissions Certain to Trigger Warming

The Government of Canada

IPCC

NOAA’s Global Historical Climatology Network

More Cold Cherries

NOAA ESRL

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