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Arctic

Posts Tagged ‘Arctic’

If you need another reason to act – think Arctic sea-ice

Arctic sea-ice minimum 2007

Everybody knows that the sea-ice in the Arctic is melting. Now a new study shows just how severly this melting is proceeding.

2007 was the year where Arctic sea-ice gave us a scary example for what we have found true since then: that the IPCC report was not just describing true changes in our climatic system, but that these changes are often faster than some of the worst case scenarios of the climate models. The extent of the Arctic sea-ice had shrunk so much, that for the first time in human memory the Northwest passage was navigable (see Fig. 1).

If melting continues like that, then – so scientists fear – the summer Arctic sea-ice could be completely gone within 20 to 30 years; the tipping point for a complete melting of Arctic sea-ice in the summer even might have been crossed already (Lenton 2009).

Whereas we have been well informed about the extent of the Arctic sea ice, it was not clear by how much the Arctic had decreased in ice-thickness over the years. Here you might be in for a surprise if you are new to the topic of Arctic sea ice. Most people estimate its thickness between several 100 or several 1000 m. These estimates probably stem from images of Greenland, where the ice is indeed 2000 to 3000 m thick. However, the Arctic sea-ice is frozen ocean water, and it is extremely thin. On average, it used to be about 3 m thin (see Figure 2).

Figure 2. ICESat measurements of the distribution of winter sea ice thickness over the Arctic Ocean between 2004 and 2008, along with the corresponding trends in overall, multi-year and first-year winter ice thickness. Credit: Ron Kwok, NASA/JPL

As figure 2 indicates, nowadays sea-ice is on average less than 2.5 m thick. That is likely less than the distance between the floor and the ceiling of your apartment. Not only that, but the extent of thin first year ice is increasing to the cost of thicker multi-year ice (see Fig. 3).

Figure 3. ICESat measurements of winter multi-year ice cover in the Arctic Ocean between 2004 and 2008, along with the corresponding downward trend in overall winter sea ice volume, and switch in dominant ice type from multi-year ice to first-year ice. Credit: Ron Kwok, NASA/JPL

This increase in first year ice is happening as more and more multi-year ice is melting. In the winter, new (first -year) ice is forming, which of course is thinner than ice that has been forming over several years. The problem is that thinner ice is melting faster than thicker ice. So we are in a typical positive feedback loop: the more ice is melting, the thinner will be the remaining ice, the fastter that ice is melting…

You might wonder why all this is worrisome. Quite a few people think that it is a great thing that the Arctic sea-ice will be melting, because we can then have shorter shipping routes, and we can have access to unexploited oil reserves. Indeed, this will bring amazing riches to a few people – over the short-term.

However, over the long-term the melting of the Arctic could be disastrous, as it triggers a positive feedback loop that could greatly warm our planet. And here is why:

The Arctic sea-ice functions as a huge fridge to our earth, because the sun’s rays are being reflected from the ice to 80-90%. However, when the sun’s rays hit water, their energy is absorbed by about 80%, and the water heats up. The more ice is melting, the more water is forming, the more heat is absorbed; thus, more ice is melting, so that there is even more water surface which absorbs more heat…if this positive feedback loop causes the permafrost to melt faster, then another feedback loop will be added to the mix as greenhouse gases are released from the permafrost.

We need to avoid such positive feedback loops if we want to avoid creating an earth that will not represent the earth as we know it today. And we can only avoid those feedback loops if we act quickly and courageously to create an energy future that is void of any fossil fuels.

Maiken Winter

Source: NASA

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If you need another reason to act – think permafrost

Fig. 1. Thawing permafrost. Image credit – Edward A.G.Schuur, University of Florida

Permafrost is a subject in the climate change debate I have tried to not think about too much. It is just too scary to think about the vast amounts of carbon stored in frozen soils, ready to be released if global temperatures keep rising. But it seems to be [mehr...]

But why is the decomposition of organic material so worrisome? Decomposition means that an object is falling into its parts. And a large part of the decomposing organic material stems from plants. To really understand what is happening in the Arctic we therefore need to shortly take a look at photosynthesis (Fig. 2):

Plants take up water and carbon dioxide, add a bit of sunlight and nutrients, and assemble all this during the absolutely amazing process of photosynthesis into a completely new structure: sugar, with the “waste product” of oxygen.

Fig. 2. Photosynthesis and decomposition. Picture from Wikipedia

In reverse, during decomposition sugar molecules and oxygen react with enzymes that decompose sugar to water and CO2; or, under unaerobic circumstances (i.e., without oxygen, such as in soils underneath lakes), the sugar molecules decompose into other molecules, including methane (CH4). Both CO2 and methane are very potent greenhouse gases. The thawing of permafrost thus releases vast amounts of greenhouse gases.

Fig. 3. Measured (1995-2003) and calculated (1930-1995) averaged over the year soil temperatures in Fairbanks, Alaska area

But is permafrost thawing already? You bet it does. Indeed, in some areas permafrost has warmed by up to 3ºC within the last decades (Fig. 3). In some areas, temperatures of the permafrost are getting dangerously close to above freezing. In fact, in some areas, soil temperature has already passed the thawing point (see references at NOAA) .

Just how much organic material is stored in the permafrost has so far been “hugely under-estimated.” A new report indicates that the amount of carbon stored in permafrost around the North-Pole might bee twice as high as previously thought (CSIRO).

Executive Director of the Global Carbon Project at CSIRO, Dr Pep Canadell, mentioned that

“Projections show that almost all near-surface permafrost will disappear by the end of this century exposing large carbon stores to decomposition and release of greenhouse gases.”

According to these new estimates, a thawing of about 10% of the Arctic soil would release about 80 ppm CO2. Global temperature would then increase on abverage by about o.7ºC.

Considering

that we are already above the CO2 concentration that is considered relatively safe for the future of human civilization (350 ppm CO2)
that in June 2009 we reached 390 ppm CO2
that a global increase in temperature above 2ºC will likely cause the passing of irreversible tipping points, and
that we are already almost committed to a global increase in temperature to 2ºC,

this estimate is extremely worrisom – to say the least.

Even though it is important to clearly understand what will happen if we do not act in time, let’s not worry too much about what could happen in case of inaction. Instead, let’s focus on what we need to work towards:

We need a carbon free energy future which is exclusively supported by truly renewable energies like the sun, wind, water, and geothermy within the coming decades. Such a “Great Transformation” will only be possible with vast energy savings through energy efficiency and through a change in our behavior, wasting much less energy than we do now. We must not be satisfied with half measures. Without effective fast action, all our efforts will likely be to no prevail.

Maiken Winter

More information:

http://www.csiro.au/news/Permafrost-climate-change-threat.html

http://www.reuters.com/article/africaCrisis/idUSSP458218

http://www.arctic.noaa.gov/essay_romanovsky.html

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