2007 when the previous record was set?Julienne:This summer the weather was not particularly warm or conducive to ice loss, yet 2012 shattered the 2007 minimum. This tells me that the ice was likely very thin and vulnerable to melting out even under more normal weather conditions. As the Arctic loses more of its store of old, thick ice, it is being replaced with thinner first year ice, which is more prone to melting out each summer. While natural climate variability makes it difficult to predict if a new record low will be set again next summer, it is becoming increasingly clear that the Arctic is in a new climate state with more seasonal ice loss each summer.Nick: In 2007 the weather conditions were right for the ice to shrink. Last year there were no unusual weather conditions, but the ice came close to beating the 2007 minimum. We are now seeing ice that is ‘pre-conditioned’ to dip lower than the previous year’s extent. This means that the ice pack is in such a weakened state, composed of mostly young thin ice, that it cannot recover by re-thickening enough over the winter to survive the summer melt season. The long-term trend is accelerated sea ice retreat, resulting in ice-free summers in our lifetimes.
What are the different functions of ice thickness (volume), and ice extent (surface area)?
Julienne: Ice extent is important for reflecting the sun’s rays and keeping the atmosphere cool. But if we lose ice volume, the ice becomes very thin and melts more easily. The decrease in thickness is why we are losing so much surface area of the ice. Read more: http://www.greenpeace.org/international/en/news/features/Arctic-melting-the-science-behind-the-ice/