Geoscience Reference
In-Depth Information
off Cape Farewell and southeastern Greenland (>40 percent) and in the Bering Sea
(>30 percent).
At locations dominated by anticyclonic conditions and strong, persistent surface-
based temperature inversions, winds are light. This is also true in sheltered valleys
and coastal fiords. For example, in January 1958, the mean wind speed was 4.7 m
s
−1
at Alert, 5.1 m s
−1
at Eureka, but only 1.3 m s
−1
inland at Lake Hazen (Jackson,
1959b
). At stations in the Canadian Arctic, mean wind speeds are typically less than
in the Russian Arctic owing to the lower frequency of cyclone activity and calms are
frequent. Nevertheless, when gales do occur, they may last several days and extreme
wind speeds exceeding 45 m s
−1
(hurricane strength) can occur on the east coast of
Baffin Island. Katabatic winds over Greenland are discussed in
Chapter 8
.
2.3.9
Blowing Snow
Despite the general predominance of light winds, blowing snow is a frequent phe-
nomenon during the Arctic winter months. Winds greater than 5 m s
−1
will begin
to lift loose snow off the ground causing drifting snow and when it is raised to
1.8 m or more it is designated as blowing snow. This requires suspension of snow
particles, which typically occurs with wind speeds greater than 15 m s
−1
. It plays
an important, yet still poorly quantified, role in sublimation of the snow cover (a
direct change from solid to vapor phase), as snow grains in transport are more sub-
ject to this process. In the Barren Grounds of Canada, frequencies of blowing snow
reach 15 percent or more in winter, but they may be twice as high on the Greenland
ice cap.
Focus Questions and Exercises
1)
Figure 2.24
shows spatial patterns of average Arctic surface air temperature
for January, April, July, and October. Imagine a world in which all ocean areas
poleward of 70
o
N were replaced by land (i.e., there is no longer an Arctic
Ocean). Draw a new set of temperature maps for January, April, July, and
October corresponding to this imaginary world and describe how and why
they differ from those in
Figure 2.24
.
2) Why is annual average temperature and precipitation much lower at the South
Pole than at the North Pole?
3) The Arctic is an ideal location for the development of large depth hoar crys-
tals as the base of the snowpack. Explain why this is so.
