Crystal Ball of Ice

Crystal Ball of Ice Snow was flying last week on the Juneau Ice Field, and the last of the Jirps (members of the Juneau Ice Field Research Project) had flown or skied to warmer levels. They had completed one more season of probing Alaska's great ice mass, clocking its slow motions, and trying to use it as a vast crystal ball to predict the earth's future climate.

Organized in 1948, by the American Geographical Society, JIRP was led by Glaciologist Maynard Malcolm Miller (now 30), who decided that the Juneau Ice Field was an ideal subject for a long-range study of glaciers. It is comparatively accessible, only twelve miles from Juneau. Out of the huge field (700 sq. mi.) flow at least eleven glaciers, ten of which are slowly receding. The eleventh, which particularly intrigued the scientists, is the great Taku glacier, which has advanced more than 3 1/2 miles in the last 50 years.

Last summer the Jirps established their headquarters on a "nunatak," a rocky island in the Taku glacier. The scientists analyzed it for layers of summer pollen grains and proved that they could be used like the growth rings of a tree to measure the age of the ice. They explored the cold depths with drills and with shock waves from explosions. They took samples of wood from ancient trees left behind like exhumed corpses by the huge Mendenhall glacier, in the southeastern part of the field. When the ages of these trees have been measured by the carbon 14 method (see below), the glaciologists may know what the glacier was doing thousands of years ago.

JIRP is still a young project, which Glaciologist Miller thinks should be continued for at least 50 years. "Glaciers," says Miller, "write autobiographies, and we're just beginning to read them."

From what they have read so far, glaciologists suspect that since the last major ice age the earth's climate grew gradually warmer until about 5,000 B.C. Then the cold came again, and the glaciers reached a secondary peak about the time of Christ. Again the climate grew warm, allowing Scandinavians to live happily in Greenland. Then came another cold period and the Greenland Norse disappeared.

Miller hopes that continued study of the Juneau Ice Field will add more details to this chronology. It may also predict the future. At present the earth is enjoying a warm spell, with the northern regions more hospitable than they have been in 200 years. But no one yet knows whether the ice is gathering again to creep down out of the north.

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