Environmental Engineering Reference
In-Depth Information
Positive Feedback From Sea Ice Loss
We have already touched on this topic when we looked at the amplification of climate
change in the Arctic, but now we will take a more detailed look. The Arctic is reaching a
situation where the melting trend is enabling more positive feedback mechanisms to interact
and support each other to accelerate ice loss even when atmospheric temperatures are not
setting record highs. We will look at three examples:
1. The 2007 ice loss record occurred in a year when winds, clouds and air temper-
atures were all favourable to promoting ice loss. However, although 2012 was
warmer than the climatic mean, it was markedly cooler than in 2007. It is prob-
able that the primary reason that the 2007 record was broken in 2012 was a
consequence of the ongoing trend for the spring to be dominated by thin, com-
paratively fragile first-year ice. This ice melts much more quickly in summer.
The increasing proportion of open water allows more solar energy to heat Arc-
tic surface ocean waters for a longer period of time. Increased evaporation
again leads to more water vapour being able to warm the Arctic atmosphere,
resulting in even less ice being able to survive the season.
2. Large areas of open water increase the fetch of wind-generated waves that can
then attack the now thinner and more fragile remaining seasonal ice. There-
fore, strong low-pressure systems, such as the ones that occurred in the central
Arctic in August 2007 and 2012, can accelerate the rate of sea ice loss. More
moisture in the atmosphere also has an impact on regional weather, but we will
get to that later.
3. Another positive feedback related to the expansion of open water is increasing
cloudiness resulting from evaporation. Clouds in winter mean more insulation
and less heat loss to the atmosphere. Nothing acts better than clouds to give us
a warm night and winter in the High Arctic is a very long night. Even in sum-
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