XXVI Congreso Internacional de Americanistas

- 335 ­
!ween winter and suml11er temperatures be ing I3.5° F., it has been shc¡v,n
that once the theoretical non-glacial winter temperature at the pole falls
below 25.5° F. the summer temperZltures \ViII not be sufficient to disperse
th e ice-cap. The theoretical non-glacial temperature at the po le must
rise above 39° F. before the permanent glacial conditions can be broken
The theoretica l non-glacia l January temperature now stands a round 25 F.
and the July temperature a round 38.5° F . Thus, glacial conditions obtain,
This accounts for the present frigid poles. During non-glacial conditions
the poiar ice-cap would not existo
Of the thirteen planetary wind be.lts now prevailing, four - two al
each pole- seem to be dependent upon the 10 1V polar temperatures
induced by the ice-caps and the present glacial conditions. During nonglacial
times the high pressure areas that now exist at the pol es woulll
be replac ed by low pressures. Across the middle latitude vvou ld be a
broad zone of steady poleward blowing winds that would have a westerly
component resulting from rotational deflection. The sub-tropica l
high pressure belt, the Trade Winds, and the tropical low pressure belt
\\fould still exist and would be somewhat expanded. The continental
and oceanic high and low pressure systems would be considerably mo­
Jified. The cyclonic circulation which now brings moisture to the middle
latitudes, would be considerably weakened and would be confinecl mainly
to the circumpolar region. 'vVith a change frOl11 non-g la cial to glac i:t ;
con cliti oll s. just the re ver~e wOllld take place. The cycloni c circulation
would l110ve into the middle latitudes with an increase in storm intensity
ancl frequency. The wind systems would move proportionately equa torwarel
and '\\'oulcl be intensified. The 'wind systems in both cases 'wo uld
be folJ owed by the c1 imatic regions which are dependent upon them.
Even the temperature cu rves from the equator to the pol e have definite
characteristics pertaining to glacial or non-g lacial conditions.
Through the study of varved clays, the close of th e last glacial perion
ha s, been set at about 6,500 B. C. By that time conditions had reac hecl
a temperature le vel similar to the present. H owever, this does not mean
that there have been no signi ficant f1u ctuations during the post-glacial
peri od -that is to say 6,500 B. C. to the prcsent. The view that climate
has shown li ttle or no va ri ations during post-glac ial times is no longer
tenable. The Fini-Glacial epi sode of Scandinavia or D aun Stadium of
the Alps, which co rresponds to the Lake Border Glacial epi so cl e of
North America, is now even considered to have occu rred during the
post-glacial eporh - between 1.000 B. C. and 500 A. D. During this time
the general mean temperature seems to have been depressed as much as
three or fou r clegrees F ahrenheit below that of today. Preceding thi s
col d stage was a period from about 6,500 B. C. to I,CXX:> B. C. when the
general mean temperature stood decidedly aboye the present. During ih
maximum between 3,000 B. C. to 1,3°0 B .c. the temperatures must have