Wednesday, 10 March 2010

Paper of the Week

Natalia Shakhova, Igor Semiletov, and collaborators (of University of Alaska’s International Arctic Research Centre and Russian Academy of Sciences in Vladivostok) published a paper last week in Science, titled Extensive Methane Venting to the Atmosphere from Sediments of the East Siberian Arctic Shelf’. They declared that the methane-rich, shallow East Siberian Arctic Shelf (ESAS), with a seafloor area of more than 772,200 square miles (three times the area of the Siberian wetlands, which are considered to be a chief source of atmospheric methane), is venting methane (the greenhouse gas) into the air and might trigger abrupt global warming.

After collecting over 5000 samples of seawater, the scientists measured the levels of dissolved methane at varying depths. High methane concentrations were observed in more than 80% of deep water and more than 50% of surface water samples, with most having concentrations more than eight times the normal amount in the Arctic Ocean. Analysing the air directly above the water surface and at higher elevations confirmed their findings. The team calculated that the region is releasing about 7 teragrams per annum (1 teragram is approximately 1.1 million tonnes), which is equal to the amount of methane emitted from the oceans (about 2% of the overall methane emissions to the atmosphere). As a result, more than 100 hotspots were located where methane is leaking from the sub-sea permafrost, which is believed to generally act as a lid to contain the methane reservoir.

When the earth becomes warm, warmer seawater enters the area. If and when the permafrost thaws, the stored frozen methane is released in two ways: Firstly, the stored organic material (ESAS, being shallow and averaging around 50 meters in depth, would have been submerged or terrestrial over the millennia) decomposes and gradually releases methane. Secondly, methane gas or methane hydrates could be released. Although methane usually oxidises into carbon dioxide before reaching the surface of deeper waters, it escapes to the atmosphere in the shallow ESAS.

The current average methane concentrations in the Arctic is around 1.85 ppm (which is the highest in 40,000 years), with much higher concentrations in ESAS- very alarming when considering that the
Earth’s geological record indicates that atmospheric methane concentrations are between 0.3 to 0.4 ppm (during cold periods) and 0.6 to 0.7 ppm (during warm periods). As pointed out by Martin Heimann in his perspective in Climate Change: How Stable Is the Methane Cycle? (in the same edition of Science), more warming in the Arctic, implies more destablisation of the permafrost, which implies more release of methane and the creation of ‘a positive feedback loop that amplifies global warming’.

Despite the current controversies in the field and the increased scepticisim about the effects of climate change, these findings might have heavy implications. A caveat is the vagueness over whether this is a new phenomenon or whether it is a constant natural phenomenon. What are the precise factors behind this? Will there be further larger release of methane? Will global warming accelerate this release? What would happen in such a scenario? Would it result in a rapid and devastating climate change, as predicted?

Additional reference:


David said...

That is an enormous amount of methane, I hope it is being monitored closely! Imagine the devastating local effects of a sudden release of so much methane, even before the global atmosphere is affected.
Lowering the tone slightly, It is calculated that each cow in Brazil produces about 250g of methane per day. There are an awful lot of cows and this works out (I think!) at about 14 teragrams per year!

Sarah Stephen said...

An exceptionally valid point!
Brazil apparently has 187087000 cattle, which implies 17.19 teragrams, which is over twice the ESAS contribution!

Re: ESAS, I reckon the gravity lies in whether these emissions have been ongoing or whether it has been effected by the recent changes, and whether there is a likelihood of more release, in larger amounts.


By using this blog, you signify your agreement to this disclaimer. Do not use this website if you do not agree to this disclaimer.

This blog is published by Sarah Stephen and Ruth Stephen, and reflects the personal views of the contributors, in their individual capacities as a concerned citizen of this planet. The term 'Ecoratorio', as well as every graphic, opinion, comment, and statement expressed in this blog are the exclusive property of the blog publishers and contributors (© 2009 - present), unless explicitly stated otherwise, and should not be disseminated without the written consent of the author(s). The views expressed in this blog are not necessarily representative of the views of any school, college, University, company, organisation, city, town, state, country, or church where the author(s) have studied, worked, worshipped, or lived, and is not sponsored or endorsed by them.

This blog and its contents does not receive any sponsorship, financial or otherwise, neither is it aimed at generating any money.

The matter on this blog has been prepared for informational purposes only, and the reader(s) should not solely rely upon this information for any purpose nor should he/she assume that this information applies to his/her specific situation. Furthermore, the matter on this blog may or may not reflect the current and future trends/developments, may or may not be general or specific, accordingly, information on this blog is not promised, or guaranteed, to be correct or complete. The publishers and author(s) explicitly disclaims all liability in respect to actions taken, or not taken, based on any, or all, the contents of this blog. Thus, the reader(s) is/are reading the posts and arriving at conclusions about the information, or about the author(s), or otherwise, at his/her own risk.

This blog may contain weblinks, which are provided solely for the reader(s) convenience. Such weblinks to another blog or website does not imply any relationship, affiliation, endorsement, responsibility, or approval of the linked resources or their contents (over which we have no control). Accessing these links will be at the reader(s)’s own risk.

The publishers and author(s) are not responsible for translation and interpretation of content. Occasionally, the blog might contain subjects which may be considered offensive from certain individuals’ points-of-view, and the author(s) refuses to accept any liability for any psychological, physical, and emotional reactions, short-term or long-term, which the posts might generate in the reader(s). However, each post in this blog is the individual opinion of the author(s) and is not intended to malign any city/town/village, state, country, continent, faith, religion, practice, ethnic group, club, organisation, company, or individual. Neither are the publishers and author(s) responsible for any statements bound to government, religious, or other laws from the reader(s)’s country of origin.

The publishers and author(s) reserves the right to update, edit, delete or otherwise remove, the posts or any comments, the latter of which might be deemed offensive or spam. The publishers and author(s) cannot warrant that the use of this blog will be uninterrupted or error-free, or that defects on this site will be corrected. The publishers and author(s) also reserves the right to publish in print media, in whole or part, any of the posts which might be an edited version. If the reader(s) has a problem with any post, the publishers and author(s) expects them to contact them, explaining the reasons for their discomfort. However, if the reader(s) choose to communicate with the publishers and author(s) by email, the reader(s) must note that since the security of unencrypted email is uncertain, sending sensitive or confidential emails holds the risks of such uncertainty and possible lack of confidentiality.

The publishers and author(s) reserve the right to change this Disclaimer, from time to time, in their sole and absolute discretion. If the reader(s) using this website after the institution of such changes, he/she is signifying their agreement to these changes. The publishers and author(s) also reserve the right to discontinue any aspect of this website at any time.