Geoscience Reference
In-Depth Information
Figure 4.12.
Mean zonal winds (m s
−1
) (top panels) and meridional temperature gradient
(K (100 km)
−1
) (bottom panels) from the equator to the pole at 140
o
E for January and
June. Positive values are shaded (from Serreze et al.,
2001
, by permission of AMS).
In eastern North America, the high-latitude summer frontal zone is not well
expressed. At 80°W (not shown), both the winter and summer cross sections show
a single jet. There is no evidence of a pronounced summer baroclinic zone along
the Arctic coast. This follows in that the Canadian Arctic Archipelago is a hetero-
geneous landscape with a combination of land and ice-covered channels, acting
to inhibit amplification of the baroclinicity such as seen along the Eurasian coast
where the land/ocean boundary is well defined.
As first noted by Bryson (
1966
), the extent of Arctic air in summer, as repre-
sented by the median location of the Arctic front, also corresponds well with the
northern limit of boreal forest. Barry (
1967
) confirmed this relationship for Canada
west of Hudson Bay, but noted the existence of a broad forest-tundra ecotone over
Labrador-Ungava. Krebs and Barry (
1970
) also demonstrated the close spatial asso-
ciation of the median location of the Arctic front over northern Eurasia in summer
and the forest-tundra boundary. J. Larsen (
1974
) examined these ideas further for
Canada. However, Hare (
1968
) pointed out that the relationships need not repre-
sent cause and effect - both the climatic and biotic patterns may be a consequence
of atmospheric circulation conditions determined by radiative controls. This view