Sunday, 21 December 2014

Tweet of the week - Losing ice

This week NASA tweeted this:

The picture shows the change in sea ice (left) and in absorbed solar radiation (right) since the year 2000. As expected, areas with greater absorbed radiation show the greatest decrease in sea ice. This also means the albedo will be lower in the areas with less ice, causing even more heating in those areas. We've seen the ice albedo feedback before, in the Snowball Earth and the Ordovician mass extinction, but working the other way around: cooling promotes the ice to expand, so the albedo rises, reflecting more sunlight, which leads to more cooling. Now we are seeing the opposite: warming in the Arctic means there is more sea ice melting, lowering the albedo (exposing the dark sea), which absorbs more heat and there is more warming. 

Overland and Wang (2013) looked into different studies and methods regarding sea ice loss and found that the Arctic could be nearly ice free (less than 1 million km2) in summer by the first half of this century. One of these studies, by "trendsetters", found that if the current sea ice loss trend continues, this could happen as soon as 2020. Models predict a later date, around 2040 at the earliest. 

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