Melting Permafrost - should I be worried?

Just before getting started, I found the video I really wanted to share with you guys before, but ended up using a replacement. It's from the fantastic series 'Earth: The Power of the Planet', presented by the brilliant Prof Iain Stewart, a Geologist at the University of Plymouth. He's like Geology's answer to Brian Cox! If you missed the series, I'd encourage you to have a catch-up. Interestingly, this video also features the same Dr Walter as the previous video..

Although it's the easiest and most spectacular way of showing the processes which are happening, it's not the lakes that are causing the most concern. Phrases like 'ticking time bomb' and 'unstoppable warming' are used
frequently when talking about melting permafrost, and I hope I'll explain why the potential impacts of melting permafrost are definitely cause for concern.

Firstly, what's happening? Well, the frozen soils in the high Arctic prevent organic matter from being decomposed, so they contain huge stores of carbon. Some estimate that the Arctic contains as much carbon as the whole of the atmosphere, although, of course, estimates vary considerably. As the permafrost in the soil melts with rising average temperatures, these stores begin to decompose, a process which releases Methane, a greenhouse gas much more 'powerful' than Carbon Dioxide, as well as CO2 itself. These emissions are also affected by changing drainage conditions melting soil causes. It's these processes in areas which have historically produced little methane and been sinks for CO2, that have the potential to contribute significantly to warming. Such warming would likely cause more melt, causing a 'run-away' reaction which would be very difficult to stop.

'Drunk' trees which cannot remain firmly rooted, and topple over due to changing soil conditions  http://www.sciencepoles.org/uploads/pictgalleries_images/current_state_permafrost_009.jpg    

Oeschel et al (1993) calculated that in the 1980s the Alaskan Tundra let out a huge pulse of CO2 due to warming of the soils in the Arctic tundra, a release which was greater than that absorbed by the region through photosynthesis. They also suggested that soil drainage conditions and hydrology was also a factor, with warm and dry soils releasing very high levels of CO2. Modelling predictions are also alarming. Lawrence and Slater (2005) used a global climate model to forecast changes in permafrost extent (crucially, not depth, which may be an as important factor) until 2100. Under high emissions, the extent of permafrost reduced from 10.5 million square Km to only 1 million square Km by 2100, a significant change! The model has been criticised for it's simplicity, but it does highlight the potential for serious changes during this century.

Things might not all be so simple, however. Some have suggested that ground cover changes may help to buffer permafrost melting. A thickener and drier layer of moss would likely insulate more effectively against further warming. Also, uptake of carbon by vegetation is likely to reduce the impacts significantly, but further warming would still cause a net increase in GHG emissions from the region.

Arctic moss species may help to insulate the frozen ground from rising temperatures.

For example, Oeschel et al (2000) followed up the 1993 paper with recent data, and found that the rate of release during the 1980s had declined during the 1990s, with some areas returning to near 'normal' levels. Although the causes of this are unknown, the authors propose carbon uptake by vegetation which exhibits lagged growth once sufficient Nitrogen is available as well as a shift to more productive plants, such as deciduous shrubs. They therefore propose that warming temperatures would cause a 'pulse' of CO2 as seen in the 1980s followed by a period where increased vegetation growth and changing plant communities reduce carbon releases to the atmosphere.

For this reason, it's less likely that melting permafrost will suddenly release methane and carbon dioxide, and cause runaway warming. That being said, the pattern shown in the Alaskan Arctic is a response to fairly limited warming and frost melt. If warming were to accelerate, as is likely, slow response of these vegetation buffers may mean strong positive green house gas feedbacks start up. Data, though, is lacking, and modelling is difficult, meaning it's only really possible to suggest future trends.

Should we be worried though? Probably! The potential for worldwide consequences if warming accelerates and strong feedback mechanisms start up are huge. That being said, reports which state the carbon stored in the Arctic, and the warming which would occur if it is all released into the atmosphere are likely sensationalist. I hope this topic will stimulate some discussion; do you think the potential for runaway warming is cause for concern? Leave a comment below.

Coming Soon: SCPs, POPs and PCBs!