Methane, Faults and Sea Ice

Shield breaking down

Until now, Arctic sea ice has been acting as a shield, in a number of ways, including:

• preventing sunlight from warming up water underneath the sea ice 
• facilitating currents that currently cool the bottom of the sea
• preventing much methane from entering the atmosphere; as discussed in an earlier post, the sea ice collects and holds the methane in places close enough to the surface for the methane to be consumed through photochemical and biochemical oxidation. 

However, as the sea ice declines, this shield is breaking down. As a result:

• more sunlight is reaching the water, contributing to warming of water in the Arctic Ocean
• sea ice decline comes with the danger of weakened currents that cool the seabed
• more methane is able to penetrate the cracks and openings in the ever-thinner ice. 

Warm Water traveling along Gulf Stream

At the same time, global warming is causing more extreme weather events to occur, such as the record warmth observed in July 2013 in part of the northeastern Atlantic Ocean off the coast of North America. As discussed in a recent post, this warm water has meanwhile traveled along the Gulf Stream and reached the Arctic Ocean.

Methane venting from Seabed

As a result, warmer water is now destabilizing sediments under the seabed that hold huge amounts of methane in the form of free gas and hydrates. Methane is now venting from the seabed of the Arctic Ocean, driven by sea ice decline and "by Gulf Stream heating, earthquakes and deep pyroclastic eruptions", as Malcolm Light explains in a recent comment and as described in an earlier post.

The image below shows the result: Massive amounts of methane venting from the seabed, penetrating the sea ice, and entering the atmosphere over the Arctic Ocean. 

Methane, Faults and Sea Ice

The animation below illustrates links between: 

• The fault line that crosses the Arctic Ocean and forms the boundery between two tectonic plates (i.e. the North American Plate and the Eurasian Plate)
• Arctic sea ice, which until now has acted as a shield
• The prominence of high methane readings over the Arctic Ocean 

High Methane Levels over Laptev Sea

A major fault line crosses the Arctic Ocean, forming the boundery between two tectonic plates, the North American Plate and the Eurasian Plate. These plates slowly diverge, creating seismic tension along the fault line.

From where the Mid-Atlantic ridge enters the Arctic Ocean, it is called the Gakkel Ridge. The fault continues as the Laptev Sea Rift, on to a transitional deformation zone in the Chersky Range in Siberia, then the Ulakhan Fault between the North American Plate and the Okhotsk Plate, and then continues as the Aleutian Trench to the end of the Queen Charlotte Fault system.

Above map shows the location of some of the main points of interest, i.e. the Laptev Sea Rift and the Gakkel Ridge, where high methane readings have been recorded recently, as shown in the image below. Indicated in yellow are all methane readings of 1950 ppb and over, for a period of just over one day, October 19 - 20, 2013.  

To pointpoint more closely where methane is venting along the Laptev Sea Rift, the image below gives readings for October 20, 2013, pm, at just three altitudes (607 - 650 mb). 

This is a very dangerous situation, since high levels of methane have been recorded over the Arctic Ocean for more than a month now. Furthermore, large amounts of methane have vented in the Laptev Sea area in previous years. Added below is an edited part of a previous post, Unfolding Climate Catastrophe. 

In September 2005, extremely high concentrations of methane (over 8000 ppb, see image on the right) were measured in the atmospheric layer above the sea surface of the East Siberian Shelf, along with anomalously high concentrations of dissolved methane in the water column (up to 560 nM, or 12000% of super saturation).

The authors conclude: "Since the area of geological disjunctives (fault zones, tectonically and seismically active areas) within the Siberian Arctic shelf composes not less than 1-2% of the total area and area of open taliks (area of melt through permafrost), acting as a pathway for methane escape within the Siberian Arctic shelf reaches up to 5-10% of the total area, we consider release of up to 50 Gt of predicted amount of hydrate storage as highly possible for abrupt release at any time".

In 2007, concentrations of dissolved methane in the water column reached a level of over 5141 nM at a location in the Laptev Sea. For more background, see the previous post, Unfolding Climate Catastrophe. 

Satellite measurements show methane readings of up to 2411 ppb on October 20, 2013. Sadly, no current data are available from measurements in the Laptev Sea, neither methane levels in the water, nor atmospheric methane levels just above sea level. Perhaps in time, some data will become available from expeditions.