Climate Change in the Arctic - The Changing Arctic Environment: The Arctic Messenger - page 282

Canada, it is projected that the top 2-3 metres will thaw more than 16-20% of the perma-
frost zone by 2100, at which time widespread permafrost degradation is also anticipated
throughout Alaska. What I find really sobering is to remember that (as we saw a little earli-
er in the paragraphs on sea level change) world GHG emissions may be following a path
that is close to the highest RCP given in IPCC AR5 (RCP8.5). Add this to polar ampli-
fication and it means there is cause to be concerned that we may well see higher Arctic
temperatures than anticipated in AR5 in this century. This would lead to a faster thaw of
Arctic permafrost.
There is understandably a great deal of concern about the practical implications of
a thawing tundra. Some of the potential impacts to infrastructure are easy to understand.
For example, the easiest way to transport heavy loads on Arctic land is to do so in winter,
when ice roads can support the weight. The season when this is possible is declining sig-
nificantly. Existing infrastructure, such as buildings and airports - even if designed for late
twentieth-century Arctic conditions - is in danger of being destabilized. Degraded perma-
frostleaveslandformsmuchmoresusceptibletomarineandfreshwatererosion.Otherwor-
ries are much more difficult to assess. Some of the latter are related to new observations
and estimates on the amount of carbon frozen in certain Arctic soils, which suggest that the
total Arctic carbon pool could be 1,400 to 1,850 Gt. This is more than is presently in the
global atmosphere. About 1,024 Gt may be stored in the top 0-3 metres. The obvious ques-
tion is whether thawing of these layers will move the Arctic tundra from being a carbon
sink to a carbon source for the global carbon cycle. At this stage, there is no clear answer.
There are two other observations related to the same possible positive feedback issue.
High nitrous oxide (N 2 O) emissions have been detected from permafrost regions in Russia
and in north-eastern Greenland. It is not known how ubiquitous such emissions may be in
the Arctic. N 2 O is a powerful GHG with a GWP 300 times that of CO 2 and it has a resid-
ence time in the atmosphere of 114 years. It occurs naturally as part of the nitrogen cycle
but is also produced by human activities, such as agricultural fertilizer manufacture and use
and automobile exhaust.