Geoscience Reference
In-Depth Information
side) the Beaufort and Chukchi seas. This pattern is linked to positive anomalies
in air and sea surface temperature and negative anomalies in end-of-summer sea
ice extent (Serreze, Barrett, and Stroeve,
2012
). However, the extent to which the
increased Arctic water vapor is acting as a feedback remains to be determined.
5.11.5
Integration of Feedbacks
Although there is a great deal of uncertainty, the best estimate is that, apart from the
aerosol-dehydration feedback proposed by J-P. Blanchet and E. Girard (
1995
), all of
the individual climate feedbacks in the Arctic are positive. This, of course, ignores
the obvious negative feedback associated with the Stefan-Boltzman relationship
(that as surface temperature rises, radiative cooling increases to the fourth power of
the temperature). One must also be aware that in the real world, positive feedback
mechanisms may promote negative (compensating) feedbacks. For example, if the
ice-albedo and cloud feedbacks were to promote large warming in the Arctic, there
ought to be a corresponding change in poleward heat transports by the atmospheric
circulation. Other possibilities include unforeseen negative cloud feedbacks or neg-
ative feedbacks between the sea ice and ocean (Curry et al.,
1996
). In many ways,
our understanding of climate feedbacks in the Arctic is still in its infancy.
Focus Questions and Exercises
1) It has been argued that cloud cover is the single most important driver of
spatial and temporal variations in the Arctic surface radiation budget. Do you
agree or disagree and why?
2) Imagine that you have been measuring all components of the surface energy
balance (radiative and non-radiative terms) in units of watts per square meter
over an area of sea ice close to the North Pole during early April. The air
temperature is −25
o
C. Suddenly, right where you are measuring these energy
balance terms, a large lead opens up in the ice cover. Describe how the com-
ponents of the energy balance will change. Consider the situation 15 minutes,
6 hours, 24 hours, and 48 hours after the lead first opens (hint - if it's really
cold, the lead will freeze over fairly quickly). It might help as part of your
description to make a table of reasonable values of the energy fluxes at the
three times.
3) The amount (thickness) of first-year ice that grows at two different locations
on the Arctic Ocean over the period of October through March can be quite
different, even if the average air temperature at the two locations is very simi-
lar. How can this be?
