Glacial Thermostat

Geologists have developed many theories to account for the ebb and flow of glaciers in Europe and North America. Some blame external causes, such as interstellar dust or changes in the earth's atmosphere. In Science, Professors (of geology) Maurice Ewing of Columbia University and William L. Bonn of Brooklyn College propound a theory of ice ages that requires no cause external to the earth and no change in the atmosphere.

The reason for the recurring Pleistocene ice ages, say Ewing and Donn, is that the earth's poles are where they are. The South Pole is in the middle of a continent, and the North Pole is in the middle of the small Arctic Ocean, which is almost entirely surrounded by land. This setup is like a slow-responding thermostat that keeps the earth alternating between glacial and interglacial periods.

Ice Cycle. Here is how the thermostat works, say Ewing and Donn:

At the present time (an interglacial period), the Arctic Ocean is mostly covered with ice. Very little water evaporates from it, and so the lands around it get little precipitation, and the glaciers in Greenland and northern Canada do not grow. But if the Arctic Ocean were ice-free because of more warm water flowing into it from the south, a great deal of snow would fall on the cold northern interiors of Eurasia and North America, and not all of it would melt in summer. Glaciers would grow and march southward toward New York and Paris.

The glaciers would not grow indefinitely. After a few ten thousands of years, they would lock up so much of the ocean's water that sea level all over the world would fall. Communication between the Arctic and North Atlantic oceans would be reduced, so that less warm water could flow northward over the "sill" between Norway and Greenland. Deprived of warmth, the Arctic Ocean would freeze over. The great continental glaciers, deprived of snowfall, would waste slowly away, restoring their water to the oceans. Then the level of the sea would rise. Warm Atlantic water would flow freely into the Arctic Ocean, melting its surface ice. Snow would increase on the northern land areas.The continental glaciers would start growing again, beginning another cycle.

Ewing and Donn believe that such cycles have already happened several times. They support their theory by citing cores of ocean-bottom mud that indicate warming of the Atlantic surface water about 11,000 years ago. This, they think, was when the last ice age lowered sea level so much that the Arctic Ocean, cut off from the Atlantic, froze over. The glaciers, then at maximum, began to retreat.

Unzoned Earth. During long geological ages before the Pleistocene, ice ages were unknown, and the earth had a fairly even climate all over. Drs. Ewing and Donn believe that this "unzoned" climate was possible because the earth's poles were then in large water areas. There was no nearby land for ice to accumulate on, and the water cooled by each winter season was soon dissipated by ocean currents. Far back, in the Permian age, there was another glacial period. Drs. Ewing and Donn suspect that the Permian poles moved to land areas and covered them with ice.

If the Ewing-Donn theory is correct, human civilization may be headed for trouble in a few thousand years. At present there is pretty good communication between the Atlantic and Arctic oceans. Warm water is flowing northward at a steadily increasing clip. When the Arctic Ocean melts, the glaciers, well fed with snow, will start creeping south. The human species will have to move out of its favorite real estate -or try to set the glacial thermostat for another interglacial cycle.

This file is automatically generated by a robot program, so reader's discretion is required.