Methane in the Arctic Circle

In conditions without oxygen, such as at the bottom of […]

Post Author:

Chris Machens

Date Posted:

August 6, 2013

In conditions without oxygen, such as at the bottom of a lake or the sea, decomposition turns organic matter into methane, rather than carbon dioxide. Large increases in methane emissions would be a grave concern, because methane is 25 times more effective at warming the planet than carbon dioxide (over a 100 year time scale). Lakes, ponds and mires in the Arctic can release methane and carbon dioxide at high rates if conditions are right. Decreasing ice cover over lakes is known to increase methane production. Large releases of methane from permafrost areas were first recorded in autumn 2007 in northeast Greenland, and thaw lakes in Siberia are known as hotspots for methane production.

Future rates of methane production from Arctic wetlands and thawing permafrost are difficult to predict because it is not clear whether more wetland and lakes will be formed due to the thawing of ice-rich permafrost, or fewer, because of summer drying. Large quantities of methane are stored in sub-sea permafrost layers as methane hydrates. In the last three years, high levels of methane have been discovered emerging from below the bed of the Laptev Sea, pluming upwards to 1800 m high in the atmosphere. This methane has been stored since the end of the last ice age when sea level started to rise.

It has been calculated that a release of just 1% of the methane estimated to be present in permafrost below the seabed of the East Siberian shelf would have a warming effect equivalent to doubling the amount of carbon dioxide in the atmosphere. Source Arctic Climate Issues 2011: Changes in Arctic Snow, Water, Ice and Permafrost (Page 97)

When freshwater flows into the Arctic Ocean from rivers and melting land ice, it does not mix well with the salty sea water, but sits near the surface and insulates the sea ice from warmer Pacific and Atlantic water beneath. All the main sources of freshwater entering the Arctic Ocean are increasing: river discharge, rainfall and melt water from land ice. Calculations estimate that an extra 7700 km3 of freshwater – equivalent to one metre of water over the entire land surface of Australia – has been added to the Arctic Ocean in recent years. It is not known what will happen to this freshwater (see section 6.2). However, largescale ocean currents, such as the Atlantic thermohaline circulation that brings warm water to northwest Europe, are sensitive to freshwater flows from the Arctic, and can affect climate and rainfall patterns on a continental scale. Source Arctic Climate Issues 2011: Changes in Arctic Snow, Water, Ice and Permafrost (page 82)

Source page 27 Arctic Climate Issues 2011: Changes in Arctic Snow, Water, Ice and Permafrost

New York Times “Warming Arctic Permafrost fuels Climate Change worries

A troubling trend has emerged recently: Wildfires are increasing across much of the north, and early research suggests that extensive burning could lead to a more rapid thaw of permafrost.

“If, in a warmer world, bacteria decompose organic soil matter faster, releasing carbon dioxide,” Dr. Ciais wrote, “this will set up a positive feedback loop, speeding up global warming.”

Dr. Walter Anthony’s seminal discovery was that methane rose from lake bottoms not as diffuse leaks, as many scientists had long assumed, but in a handful of scattered, vigorous plumes, some of them capable of putting out many quarts of gas per day. In certain lakes they accounted for most of the emerging methane, but previous research had not taken them into consideration. That meant big upward revisions were probably needed in estimates of the amount of methane lakes might emit as permafrost thawed.

When organic material comes out of the deep freeze, it is consumed by bacteria. If the material is well-aerated, bacteria that breathe oxygen will perform the breakdown, and the carbon will enter the air as carbon dioxide, the primary greenhouse gas. But in areas where oxygen is limited, like the bottom of a lake or wetland, a group of bacteria called methanogens will break down the organic material, and the carbon will emerge as methane.

Historically, tundra, a landscape of lichens, mosses and delicate plants, was too damp to burn. But the climate in the area is warming and drying, and fires in both the tundra and forest regions of Alaska are increasing.

The Anaktuvuk River fire burned about 400 square miles of tundra, and work on lake sediments showed that no fire of that scale had occurred in the region in at least 5,000 years.

Undersea methane hydrate deposit is the shallowest yet found (Dec 2012)

The trapped gas deposit is located in an area of small conical hills on the ocean floor just 290 metres below sea level. Before the discovery, the shallowest known marine gas-hydrate deposits were found in the Gulf of Mexico and in the vicinity of the Svalbard Islands at depths of around 400 m

The Arctic is thought to be undergoing some of the most dramatic effects of climate change anywhere in the world. And this particular deposit is just within what scientists call the ‘methane hydrate stability zone’, the range of pressure and temperature at which gas hydrates are stable. In this region, the stability zone begins at a depth of about 270 m, above which sea temperatures are too warm to ensure the methane remains locked in its water-molecule cage. Source

A Thesis in Geosciences by Xiaoli Liu | 2006

Hydrate coexists with liquid water in regions of low gas flux. In this type of hydrate system, although a temperature increase can release a large amount of gas from hydrate, the dissociated gas will move upward and refreeze as hydrate at shallower depths. Thus the dissociation process does not directly affect the methane emission to the 101 ocean. The dissociated free gas can escape to the ocean only when the surface warming is so high that no hydrate can remain stable at the seafloor. (2) Massive release of methane from gas hydrate depends on its proximity to the three-phase boundary. Where methane flux is high, there is a three-phase zone from the base of the hydrate stability zone to the seafloor. The three-phase zone increases the amount of hydrates located at the three-phase boundary; thus it can rapidly respond to environmental changes. Hydrate dissociation within the three-phase zone is regulated by changes in salinity required for three-phase equilibrium with temperature. The dissociated free gas can be released to the ocean via the three phase zone, even though hydrates do not completely dissociate during a small warming event. We estimate that a 4°C increase in seafloor temperature can release 70% of methane stored in the hydrate system that is initially at three-phase equilibrium, providing a mechanism for rapid methane release

Locked greenhouse gas in Arctic sea may be ‘climate canary’ Undersea methane hydrate deposit is the shallowest yet found
Zoë Corbyn | 07 December 2012

The trapped gas deposit is located in an area of small conical hills on the ocean floor just 290 metres below sea level. Before the discovery, the shallowest known marine gas-hydrate deposits were found in the Gulf of Mexico and in the vicinity of the Svalbard Islands at depths of around 400 m, says Charles Paull, a senior scientist at the Monterey Bay Aquarium Research Institute in Moss Landing, California, who presented the work on Thursday at the annual meeting of the American Geophysical Union in San Francisco, California

An accurate model to predict the thermodynamic stability of methane hydrate and methane solubility in marine environments
Rui Sun, Zhenhao Duan | 2006

Comparison of the prediction of this model with experimental data indicates that this model can predict the three-phase equilibrium condition of methane hydrate in seawater and in porous media with high accuracy. Salts dissolved in seawater and the capillary force arising from small pores increase the pressure needed for H–L–V equilibrium for a given temperature. Although there exist only a few experimental data demonstrating the accuracy of the prediction of this model for H–L equilibrium, we believe that this model can reliably predict methane solubility and cage occupancy at H–L equilibrium, since accurate thermodynamic methods are used in this model. The prediction of this model shows that: (1) dissolved salts and the capillary force decrease the P–T range for methane hydrate stability; (2) in H–L two-phase region, increasing the salt concentration will decrease the solubility of methane needed to form methane hydrate. The methane solubility will decrease about 10% in 35‰ of seawater; (3) the capillary force increases methane solubility in liquid at H–L equilibrium; (4) within methane hydrate stable zone, CH4 solubility in liquid increases with depth

Submarine pingoes: Indicators of shallow gas hydrates in a pockmark at Nyegga, Norwegian Sea

The discovery of up to 1 m high sediment mounds, here called ‘hydrate pingoes,’ on the mid-Norwegian margin adds to the diversity of seabed seep-related features. We have previously documented anomalous ridges of methane-derived authigenic carbonates, together with a distinct fauna. We interpret the mounds as submarine pingoes, formed as a result of gas hydrate sub-surface build-up at specific focused fluid flow locations. The process is dynamic in the sense that the pingoes grow and collapse over time due to probable cycles of freezing and thawing of hydrates in the shallow sub-surface. Although there seems to be a close relationship to the adjacent carbonate ridges, it is still unknown which processes link the two phenomena (carbonate production and pingo formation). We suggest that the pingoes manifest a close interplay between seawater, dissolved gases migrating up from depth, gas hydrate formation and release of melt-water (dissociation fluids). This is also in agreement with geochemical results obtained from shallow cores showing the presence of abundant hydrocarbon gases in the sediments. Our findings imply that pingoes can be used as seep localizers, and probably also manifest the whereabouts of shallow gas hydrates. The pingoes emphasise the dynamic nature of pockmarks, and provide information that should be taken into account for engineering purposes. However, much more fieldwork is needed at locations such as G11 before the true mechanisms of complex pockmarks and pingoes are understood


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About the Author: Chris Machens

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Covering the climate for Climate State since 2011. Peter Sinclair noted in 2017, "Climate State has been doing an absolutely amazing job of providing a useful historical archive of important experts warning on climate issues through past decades."

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