Mystery at the 'End of the World'

In July of this year, a large crater was spotted puncturing the Siberian landscape. Theories regarding its formation immediately appeared, ranging from suggestions of a metorite impact, to gas explosions, and even alien invasion.

So, I present you with a mystery: what caused this hole?

The 30 metre wide crater on the Yamal Peninsula, Siberia.
Source: www.siberiantimes.com

The crater is located on the Yamal Peninsula in Siberia ('Yamal' meaning 'end of the world' in the Nenet language), and is 30 metres wide (Moskvitch, 2014). While investigations are still ongoing (for example, exploration into the interior of the crater has only recently taken place, made easier by the frozen ground), scientists have found an explanation for the structure (The Siberian Times, 2014). Sorry, I haven't kept you in suspense for long.

Analysis has shown that air at the bottom of the crater has a methane concentration of 9.6%, compared to the usual 0.000179%, providing a large clue as to its origins (Moskvitch, 2014). When permafrost (soil, rock or sediment that remains frozen for at least two years) thaws, methane is released. It is thought that the methane released here was trapped underground by a layer of ice, leading to a build up of pressure, and subsequent explosion (Moskvitch, 2014). This is worrying, especially given the close proximity of the site to the Bovanenkovskoye gas field (Moskvitch, 2014).

While the enigma of the crater in itself attracted a lot of attention, the implications of this story for the rest of the Arctic are also deserving of some study.  

Map to show Arctic permafrost distribution. Darker shading represents areas with
a greater percentage of permanently frozen ground. Source: www.nsidc.org

During the summers of 2012 and 2013, the Yamal Peninsula experienced unusually high temperatures (~5°C above average (Moskvitch, 2014)). While some believe this to be the cause of the permafrost thaw in the region, others attribute the large amount of methane released to long-term global warming (Moskvitch, 2014). Indeed, it has been suggested that permafrost temperatures rose by as much as 6°C over the course of the 20th Century (NSIDC, 2014). As shown by the map above, permafrost covers a significant area of ground in the Arctic region (to be more specific, ~22.79 million square kilometres), making this a large-scale issue (NSIDC, 2014). 

Coastal erosion during a ("not...particularly strong" - NSIDC) storm
in Shishmaref, Alaska, 2003. A combination of sea ice decline and
permafrost melt have led to this erosion.These photos were taken only
two hours apart; the barrel can be used for reference.
Source: www.nsidc.org; Tony Weyiouanna, Sr.

As discussed by Rowland et al. (2011), it can be difficult to model the response of the Arctic ecosystem to permafrost thawing, owing to the complexity of the potential feedback mechanisms involved. For example, loss of permafrost can lead to drying of the substrate surface, increasing fire risk (Rowland et al., 2011). A fire would in turn alter the albedo of the land surface, leading to more permafrost warming and thawing (Rowland et al., 2011). However, some likely consequences of permafrost degradation have been suggested. Permafrost contains both ground ice and massive ice (basically just large blocks of ground ice). When massive ice melts, voids are left in the ground, making it unstable. This can lead to erosion and the creation of thermokarst (an irregular land surface formed through subsidence), causing problems for Arctic communities (Rowland et al., 2011). Increased sediment from erosion of river channels could have implications for Arctic fisheries, and permafrost melting also alters soil permeability, changing surface water flow (Rowland et al., 2011). This list is not exclusive, but gives an indication of the sorts of issues that may arise as a result of permafrost melt.

Of course, although I want to focus on the Arctic specifically today, it would be impossible to finish without mentioning the potential global impact of melting permafrost. What was the cause of the explosion that created the Siberian crater? Methane. According to Anthony et al. (2012), "the Arctic geologic methane reservoir is large", "with a carbon store of over 1200Pg". This figure is particularly striking when compared to the 5Pg store of the atmospheric methane reservoir (Anthony et al., 2012). When permafrost melts, methane can be released via physical or biological processes: through the release of methane clathrate, or decay of organic matter, respectively. It is thought that microbial processes will be of fundamental importance in the transfer of carbon to the atmosphere (Schuur et al., 2008), but further research is needed before they can be fully understood (see Graham et al., 2012). It has been estimated that thawing permafrost may release as much as 100Pg of carbon into the atmosphere by the end of the century (Schuur et al., 2008). Methane is a more potent greenhouse gas than carbon dioxide, and its release would lead to positive feedback cycles as increased warming caused more permafrost to melt. As such, media coverage on this topic seems to be increasing, with the situation often being referred to as a 'time bomb'...