Geoscience Reference
In-Depth Information
2
Physical Characteristics and Basic
Climatic Features
Overview
The Arctic climate system is characterized by its low thermal energy
state and intimate couplings between the atmosphere, the ocean, and the
land. This makes the Arctic a challenging and fascinating region to study.
But given the complex nature of the Arctic climate system, where does
one start in describing it? The necessary basic foundation is provided in
the present chapter through an overview of some of the basic physical
characteristics of the Arctic.
The most formal definition of the Arctic is the region north of the
Arctic Circle (66.5°N). When defined in this way, its most fundamental
characteristic is continuous summer daylight and its absence during the
polar night, the duration of each depending on latitude.
Figure 2.1
shows
the changes in day length with latitude and time of year. For the extreme
case of the North pole, the sun is above the horizon for six months
between the spring and autumn equinoxes and below the horizon for the
remaining six months. In more common usage, the Arctic does not have
strict geographical boundaries. Arctic conditions (e.g., extreme winter
cold or the presence of permafrost) may be found well south of the Arctic
Circle. The terms Arctic and North Polar Region are sometimes used
interchangeably.
The geography of the North Polar Region is in striking contrast to
its southern counterpart. The Arctic Ocean occupies most of the area
north of latitude 70°N. Apart from the sector between 20°E and 20°W,
it is almost entirely surrounded by the landmasses of Eurasia and North
America. Throughout the year, much of the Arctic Ocean is covered by
23
