Ch+4

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Click here to download a pdf version of the slide show, with three slides per page and lines for notes.

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Convection Currents

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Another day, another cause for worry in the Arctic

Melting ice plays a more dominant role in Arctic warming than previously thought. This has been the take away message from a study analysing 30 years of satellite data in the region. The researchers, based at the University of California in San Diego, discovered that the Arctic albedo levels dropped from 52% in 1979 to 48% in 2011; nearly twice a s much as predicted in climate models.

Let’s take a step back: Just what is albedo anyway?

The albedo of a surface describes its ability to reflect sunlight (energy). It is measured on a scale between 0 and 1 and commonly can refer to the "whiteness" of a surface, with 0 meaning black and 1 meaning white. A value of 0 means the surface is a "perfect absorber" that absorbs all incoming energy. A value of 1 means the surface is a "perfect reflector" that reflects all incoming energy.

Now, let’s think of albedo in relation to the Arctic environment. The Arctic, as we know, is full of ice and much of this ice is coated in snow. In terms of albedo, the ice has an albedo of around 0.5 (it reflects 50% of the energy it receives). If this ice is covered in snow, then its albedo increases to 0.9 (it reflects 90% of the energy it receives). It is this snow covered ice that keeps the Arctic cool, by reflecting incoming solar radiation back into space. If this ice melts what is left is open water, which has an albedo of 0.06 approx; reflecting only 6% the solar radiation.

The balance between sea ice and open water meant that in the latter half of the 20th century that total albedo of the Arctic region was 52%. The 21st century saw this decrease to 48% as result of an on-going increase in carbon dioxide levels. 4% may not sound like a lot, but this decrease in albedo is equivalent to roughly 25% of the average warming currently happening.

What we appear to be seeing is that the amplified feedback of Arctic Sea ice on warming is larger than we thought and this needs to be reflected in models.

-Jean

For more information: @http://www.ibtimes.co.uk/climate-change-arctic-sea-ice-melting-twice-fast-models-predict-1436926