Geoscience Reference
In-Depth Information
The climate, he continued, is abnormal on both sides of the North Atlantic. To the
west, for example in Labrador, the -18 C(0F) January isotherm passes a little
to the north of the 50th parallel. To the east, the same isotherm reaches Spitz-
bergen (Svalbard) in March and April just to the south of latitude 80 N. In the
North Pacific, on the other hand, where little interchange of heated and chilled
water can take place through the shallow and restricted opening of the Bering
Strait and where the direction of the prevalent winds is of a different character,
there is less variation between the average temperature of the coasts of North
America and of Asia in similar latitudes, either in winter or summer. Harmer
continued the story:
It may be instructive, therefore, to compare the present conditions, geographical and
meteorological, of the basins of the North Atlantic and the North Pacific. Geographically,
these regions closely resemble each other, except in one respect. Both are similarly open to
the south, but the latter is (practically) closed to the north. Communication exists, how-
ever, between the North Atlantic and the Polar Sea not only through the Icelandic Channel,
but also by means of the Davis Strait and fiords of the Arctic Archipelago. At present the
latter are blocked by the ice pack, but at a certain stage of the glacial epoch they may have
exerted an important influence on the climate of North America.
It seems clear that the closing of the gap between Greenland and Europe would
effect a change in the winter temperatures of northwestern Europe by terminating
the geographical conditions to which its normally mild climate is due. Such an
exclusion of the warm waters of the North Atlantic, as described by Wallace,
would result in an extraordinary accumulation of snow and ice on the mountains of
Scandinavia and Britain:
In the region with which we are most immediately interested it is easy to see how a
comparatively slight alteration of land and sea, such as has undoubtedly occurred, would
produce an enormous effect on climate. Let us suppose, for instance, that the British Isles
again became continental, and that this continental land extended across the Färoe Islands
and Iceland to Greenland. The whole of the warm waters of the Atlantic, with the Gulf
Stream, would then be shut out from Northern Europe, and the result would almost
certainly be that snow would accumulate on the high mountains of Scandinavia till they
became glaciated to as great extent as Greenland, and the cold thus produced would react
on our own country and cover the Grampians with perpetual snow (Wallace 1880).
However, Harmer believed that the diversion of the storm tracks and the conse-
quent alteration in the direction of the prevailing winds would have been an even
more important factor in such a situation. The northward track of Atlantic
depressions, as well as that of the North Atlantic Drift, would be barred by the
existence of an Icelandic bridge, the former would be turned towards the southeast,
as those are now in the north Pacific.
As he mentioned, the displacement of the mean winter low pressure area of the
North Atlantic to the south of the supposed barrier would certainly produce
changes of far-reaching importance in the atmospheric circulation as well as that of
the ocean waters (Fig.
4.5
):
