The World Wide Fund for Nature (WWF) has just published a new report on climate change in the Arctic — Arctic Climate Feedbacks: Global Implications [PDF], and it’s a fascinating read. Over the last two years I’ve blogged regularly on the changes being seen in the Arctic — sea ice reductions, melting of the Greenland ice sheet, the danger of increased carbon release from permafrost and sea floor methane hydrates, and the possible impacts on northern hemisphere weather patterns and climate. WWF’s report — written by some of the leading names in the field (including Serreze, Stroeve, Cazenave, Rignot, Canadell, and for the methane hydrate chapter Shakhova and Semiletov) — pulls together all those strands to paint a picture of a region undergoing rapid change. The authors provide a fully-referenced review of our current understanding of the processes at work as the pole warms, with chapters covering atmospheric circulation feedbacks, ocean circulation changes, ice sheets and sea level, marine and land carbon cycle feedbacks, and sea floor methane hydrates. It’s compelling stuff, and well worth reading in full, but for this post I want to focus on the excellent overview of methane hydrate feedbacks provided by Natalia Shakhova and Igor Semiletov.
The methane hydrate chapter is the last in the report, but includes some of the more sobering information. It starts with an excellent primer on what methane hydrates are (methane molecules trapped in a lattice of ice crystals) and how they’re formed. The deposits on the floors of the shallow seas north of Siberia are particularly vulnerable — “extreme sensitivity to warming” is how the authors put it, and there’s an awful lot of methane up there:
…the arctic continental shelf […] is estimated to contain 2,500 gigatonnes of carbon in the form of methane hydrates, which is more than 3 times greater than the amount of carbon currently stored in the atmosphere and more than 600 times greater than the current atmospheric content of methane. Release to the atmosphere of only 0.5 per cent of the methane stored within arctic shelf hydrates could cause abrupt climate change.
The key to the stability of the hydrate deposits is the state of the permafrost “cap” that overlies them. This permafrost is much warmer than land-based permafrost because the ocean temperature is around freezing, whereas annual air temperatures over land in the region average around -17ºC. As ocean temperatures are rising (there have been “pulses” of warm water entering the Arctic Ocean over the last decade), the cap is becoming vulnerable. Just how vulnerable was news to me:
…recent observational data obtained in the East Siberian Arctic Shelf showed that extensive methane release from the seafloor is occurring at depths ranging from 6 to 70 metres, emerging as huge clouds of bubbles rising through the water column. This bubbling release of gas is called ebullition. […] In the East Siberian Arctic Shelf, which constitutes about 30 per cent of the entire Arctic shelf area, more than 50 per cent of the area studied is currently releasing methane to the atmosphere.
Methane released from deep sea deposits (such as the plumes off Spitsbergen discovered last year) dissolves in the sea water as it rises and is oxidised, but in shallower seas the gas reaches the atmosphere as bubbles. Over the ESS, atmospheric methane concentrations of up to 4 times normal levels have been measured in the last few years, and current methane release from Arctic hydrates could be as high as 10 to 50 million tonnes of methane per year. The situation in the ocean?
Multi-year observational data obtained in the East Siberian Arctic Shelf suggest that, contrary to modelling results, more than 80 per cent of bottom water and 50 per cent of surface water in the study area is supersaturated with methane by a factor of 10 to 1,000 relative to the background level of 3.5 nanomoles. That means that very likely more than 5 to 10 per cent of the East Siberian Arctic Shelf area is already affected by sub-sea permafrost destabilisation.
And what happens if a lot of methane is released?
Recent studies have examined two possible cases of how surface air temperature could respond to release of only 2 per cent (50 gigatonnes) of the total amount of methane preserved in arctic continental shelf hydrate deposits if this amount is released in either of two ways: slowly over 50 to 100 years, or quickly over approximately 5 to 10 years. When methane is released quickly over the brief 5 to 10 year time period, the maximum temperature increase is higher by about a factor of three compared to the “slow†case. This greater temperature response is more likely to produce irreversible consequences.
Take that information, and feed it back into Chapter One of the report, where there’s a good discussion of how sea ice reductions spread winter warming onto the continents around the Arctic Ocean, and the potential for further positive feedback from permafrost becomes all too obvious. Carbon cycle feedbacks on that sort of scale have the potential to make any mitigation efforts we might undertake completely irrelevant. And that’s not good news.
Gareth I’m in two minds about that link to the Byrds. One of my favourite bands. “The change is now” while not one of their most well known, is perhaps, one of their most poignant. Its just the association with a favourite song and such a fearsome probability.
You have my sympathies, but I never let them stand in the way of a good song title for a post… It is a nice track though: I like the “sound” – that 60s gentle psychedelia, sitar/guitar twang and great harmonies…
Yes I completely understand – A very good title for the post!
How about “One hundred years from now”? Which of course would be 2070 or there abouts. 🙂
This is probably the best illustration of the folly of the current denialist meme that “we are just rebounding from the LIA”.
The denialists like to assert that the MWP was just as warm as today, and that the recent warming has only just got the planet back to “normal” MWP conditions.
However, if the MWP really was as warm as today, then there should have been outgassing from methane hydrates during that period as well. As this study shows, this additional methane release is a positive feedback. Had the MWP been warm enough to trigger methane outgassing, there is no way that temperatures could actually have dropped enough to bring about the LIA.
The only logical conclusion is that today’s temperatures are considerably warmer than the MWP (which, oddly enough, is exactly what the temperature proxies tell us).
Or that negative feedbacks exist…..
(Your assertion that if the MWP was warmer than today it would have caused methane emissions and hence a run away greenhouse is based on the assumption that greenhouse gases are the main driver of climate and hence would not work on a ‘denialist’ like myself)
(Also – the alarmist ‘meme’ is that the MWP was regional. Do you have any papers that show proxy records in Siberia suggest todays temperatures are warmest. I found this one:
http://18a.akadem.ru/Articles/02/naurzbaev_en_2.pdf
Figure 6 shows temperatures were warmer during the Roman Warm Period – however it uses tree rings as a proxy and I remember our discussion on why at high temperatures tree rings are not ideal….
Perhaps you make a good point: the theory of run away greenhouse effect (positive feedback dominance) is not backed by history…..)
R2D2 – that MWP was regional event is well established. For starters look at Antarctic ice core. Excellent time resolution into MWP period, best temperature proxy possible. And yes, you see LIA, MWP type periods – just not at the same time!
(Though I have seen denialist web sites gloss over that by assuming that readers dont know the actual dates for MWP from NH records). The next question you would ask – do you see free-ocean plankton in sediment core in the artic where the summer melt is now letting this happen?
And to repeat a comment – MWP, proxies, and uncertainities discussed ad nauseum in IPCC chapter 6, and there you will find the papers you are looking for.
As to greenhouse gas driving warming – you can certainly argue sensitivity because of some undiscovered negative feedback, but are you seriously suggesting that you dont believe greenhouse gases will affect global temperature??
Sorry, yes I agree the MWP was regional, as is the current warming.
Really?! We kind of have a global temperature network plus measurements from space. Climate trend is global warming on these not regional! More importantly it has the spatial trend predicted by AGW models.
http://www.geo.arizona.edu/geo4xx/geos478/Resources/Dlugokencky09.CH4.pdf
R2D2. Lets clarify here. By “regional” I mean that warming is isolated, cold in other parts and so little impact on a global average temperature. Even with global warming, some parts will be colder some considerably warmer. Given that there is more CO2 and CH4 in NH, it would hardly be surprising if NH warms faster than SH – that is the model prediction.
Now to the methane. No one expects that there will be methane
erupting everywhere. Hydrates are stable only within a narrow pressure/temperature range. When temperature crosses that stable point, then methane is emitted. Where this is happening is in the arctic. Raising the deep ocean temperature to the point where say all the hydrates on the NZ shelf outgas is an Armageddon scenario which fortunately doesnt seem likely (though my work does have people working in this area – its an active research area because hydrates are potentially a menace but also a possible resource. As a caution, it wasnt that long ago, that my colleagues were discussing whether methane from hydrates could make it to the surface without oxidizing (as CO2 the carbon is a lot safer than as CH4. Clearly it can so the risk assessment has gone up.)
Byrd link is dead … choice of 2 http://www.youtube.com/results?search_query=%E2%80%9CThe+change+is+now%E2%80%9D+Byrds&search_type=&aq=f
“the MWP was regional, as is the current warming.”
Give it a break! You have NO evidence for this assertion.
If you mean that some regions will warm more quickly than others, then yes, you would be right. But I doubt that is what you are saying – which is to completely overlook all the evidence.
R2D2, you should let Ian know…..
http://briefingroom.typepad.com/the_briefing_room/2009/11/is-hot-topic-wrong-about-this-too.html