Climate Change in the Arctic - The Changing Arctic Environment: The Arctic Messenger - page 254

The property of albedo is the ability of a surface to reflect the sun's energy back into
space without changing its wavelength. Snow and ice have a high albedo, resulting in a
high proportion of the incoming solar radiation being reflected back into space without be-
ing absorbed by (and warming) the surface. Water and terrain have a low albedo. Historic-
ally, much of the incoming Arctic solar radiation was reflected back into space and it was
not until late summer that the sun could significantly melt sufficient ice for areas of open
water and terrain to appear. As the climate has warmed, there has been a trend in which
open water and terrain have appeared earlier in the year. More solar radiation is now able to
reach and heat the low-albedo surface waters, which, together with warmer Arctic winter
temperatures, delays the production of new winter sea ice. This results in less ice being
formed before the next summer. Consequently, less and less first-year ice survives into its
second year and recruitment into the inventory of multiyear ice is diminished.
Once larger and larger portions of the Arctic Ocean lose the insulating protection of
summer sea ice, the warming seawater can evaporate more and more of that often over-
lookedGHGwatervapourintotheArcticatmosphere.MuchofthepresentlyobservedArc-
tic warming is caused by the positive feedback of this greenhouse effect due to increased
evaporation producing more moisture in the air. In an Arctic Ocean insulated by ice, there
is no such feedback. The bottom line is that much more water can evaporate from near
freezing water than can sublimate (go directly from ice to atmosphere) from ice.
Similar terrestrial feedback mechanisms are operating over longer periods (such as
decadal time scales) associated with plant growth. As permafrost layers are lost, the tundra
vegetation changes to larger shrubs, resulting in dark foliage that decreases Arctic albedo
even with moderate snowfall. This supports further positive climate warming.
Readers will have noticed that at least two of the mechanisms responsible for Arctic
climate change amplification are often linked and feed on one another in a cyclical manner.
A climate scientist would say they are coupled. This is an extremely important concept that
underpins a key finding of the SWIPA report: “There is evidence that two components of
the Arctic cryosphere - snow and ice - are interacting with the climate system to accelerate