GLOBAL DISTRIBUTION OF TRITIUM
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1959
1960
196]
1963
1964
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Fig, 10—Comparative rates of tritium decline after cessation of tests
in 1959 and 1963.
and a few stations in New Zealand and Australia (NZ). Shorter records
for South Pacific island locations (LJ) are also available.
The information clearly shows that the tritium pulse in the south-
ern hemisphere in 1962 to 1963 remained far below that in the northern
hemisphere. The mean tritium level for precipitation in the southern
hemisphere appears to be about 15 T.U., somewhat higher on the continents and somewhat lower on the ocean islands.
The northern hemisphere is remarkable for the general conformity
of the tritium peaks at widely separated sites. The same degree of
uniformity is not found in the southern-hemisphere sites. Malan, South
Africa, shows two peaks (S), both in the southern summers of 1961-
1962 and 1962-1963. The peak in 1962—1963 is very certain, inasmuch
as it is reproduced at four stations: Gough Island, Malan, Pretoria,
and Windhoek (S). Tritium peaks at Kaitoke, New Zealand (NZ), in 1961
and 1962 are less distinct, but the 1963 peak is very pronounced. The
Kaitoke peaks appear to be two to three months in advance of the South
African peaks, appearing in the southern spring rather than in the
summer. Similar time displacement is observed with the Sr fallout
peaks between Pretoria and Wellington, New Zealand. Explanation of the