ANTARCTIC ATMOSPHERIC CIRCULATION 
side of the Palmer Peninsula, along the Adélie Land 
Coast, and near McMurdo Sound, and must influence 
weather processes there. 
Actually, there are two frontal zones in the subant- 
aretic oceans: the antarctic front, encircling the con- 
tinent at least in segments, and the southern polar 
front, trending diagonally southeastward across each 
ocean and interrupted over the continents [41, 70, 
133]. Palmer [18] identified 
.. three major frontal systems in the Southern Hemisphere 
(1) that which runs from a point a little south of Tahiti 
southeastward along the southern boundary of the quasi- 
stationary subtrgpical anticyclone of the South Pacific, (2) 
that which crosses South Africa somewhere between 30 and 
40°S latitude and extends southeastward on the poleward 
side of the South Indian anticyclone, and (3) that which lies 
in the vicinity of the mouth of the Plata River and stretches 
across the South Atlantic Ocean and far to the south of 
South Africa. 
While the southeastern ends of these polar-front seg- 
ments enter subantarctic waters and may even reach 
the continent, they are less directly connected with 
Antarctica’s circulation than the antarctic front, about 
which far less is known, especially in winter. For the 
area south of Cape Horn, Serra and Ratisbonna [42] 
postulated that 
The Antarctic front follows a SW-NE direction. It passes 
from the Pacific to the Atlantic, extending from the pressure 
trough of the Belgica [Bellingshausen] Sea around through 
the low of the Weddell Sea. It is most intense in winter when 
the gradient is particularly steep and the circulation most 
active because of the deepening of the depressions over the 
Antarctic seas. 
This last assumption was not accepted by Coyle 
[27]. Allowing for wintertime semipermanent lows in 
the Weddell and Ross Seas, he said: 
We get a very sinuous picture of the Antarctic front during 
the winter months and here we meet one of the strange 
Southern Hemisphere facts, namely, that contrary to ex- 
pectation there seems to be a lesser easterly stream behind 
the front in the wintertime than there is in the summertime. 
It is during the summertime that the Weddell and Ross Sea 
lows disappear, thus theoretically allowmg the Antarctic 
front to straighten out and recede poleward as the summer- 
time weakening of the Antarctic anticyclone becomes effec- 
tive. ... 
We therefore come to a picture of the Southern Hemisphere 
wintertime westerly band (30° to 60° south) being composed 
of two parts, an equatorward warm westerly stream between 
30° and 45° south and a cool band of transitional Antarctic 
air, seen as a west to southwest stream between 45° and 60° 
south. The Southern Hemisphere “Polar” front then would 
seem to be this boundary between the ... currents... . 
It seems that the cold southwest streams which invade the 
{South American] continent are breaks through the Antarctic 
front of cold air drawn up about the westward side of the 
cyclones, and these streams, with continental transport equa- 
torward, become deflected to south and southeast streams to 
form the migratory anticyclones which then move up over 
Argentina and Brazil. It is only when this cool transitional 
923 
Antarctic air moves north of latitude 45° that it becomes 
well defined and the ‘Polar’ front becomes well developed as 
it moves against the tropical continental masses.... It is 
difficult to say just when the leading edge of a cold mass 
ceases to be the Antarctic front and becomes the Polar front. 
On their January and July maps, which extend only 
to 70°S, Haurwitz and Austin [133] showed an antarctic 
front northwest of the Palmer Peninsula in July, north- 
east of the Weddell Sea in January. 
No continuous antarctic front, but only segments of 
it, were found by those in the best position to observe 
it, the aerologists [2] of Operation Highjump; on their 
mean surface pressure chart, ‘““The mean position of the 
zone of convergence between the polar easterlies and 
maritime westerlies, [which] represents the antarctic 
front, is not accurate because the methods of summariz- 
ing and presentation of data obscure the minute details 
of the pressure trough.’ In summer, semipermanent 
segments of the antarctic front were found along the 
pack-ice edge in the Bellingshausen Sea and south of 
Australia, extending west from 170°E along 65°S. 
Each section was either warm or cold, depending on 
the relative strengths of the warm moist air to the 
north and the cold dry air to the south. The segment 
south of Australia was normally 50 to 150 miles north 
of the ice pack, sometimes 500 miles north, and oc- 
casionally pushed onto the contmental plateau itself 
by extremely strong northerly circulation. Strong out- 
bursts from the anticyclone along 145°H, which was 
bounded by this front, at times drove it eastward to 
trend southeastward across the Ross Sea. As a cold 
front, it had a line of snow showers, a wind shift of as 
much as 90°, and a temperature drop of 2 to 3F, oc- 
casionally 5 to 7F. As a warm front, it had a well-defined 
cloud shield, but without cirriform clouds, and snow 
showers ahead of the snow shield. 
As long as the anticyclone located along 120°W during 
the 1947 summer was strong, its cold air mass did not 
“meet a barrier or front that would separate it from the 
warmer air mass to the north,” but when it was re- 
established after an intense low had penetrated the 
southeastern Ross Sea, a weak cold front formed near 
65°S. 
The following summer another group of aerologists 
found [4] ‘the antarctic front . . . observed on numerous 
occasions .. . to be very similar to the Equatorial front 
...a zone of convergence of two air masses with similar 
properties. The slope of the front varies according to 
which air mass is the colder.” 
Air Masses. The Highjump aerologists operating 
south of Australia assumed that the cold dry polar 
continental (cP) air of the high antarctic plateau was 
transformed by slight humidifying of the lower layers 
and subsidence aloft into continental antarctic (cA) 
air of the coastal area and solid pack ice, then into 
maritime antarctic (mA) air by rapid humidification as 
it passed over open pack ice or open water for 50 to 100 
miles, after which it became fresh polar maritime (mP) 
air, with “the antarctic front the northern boundary 
of this cA or mA air mass.” 
