Little Ice Age

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Aurora borealis

August 11-12, 2000, over Mount Baker

Blue-green streaks over a snow peak

Photographer Wade B. Clark, Jr., © 2000. 35mm Canon F1 set on a tripod, 28mm wide angle f1.8 lens, Fuji NHG II 800 speed color print film, and about a 20-second exposure via cable release.

Viewed from Baker Lake east of Bellingham, Washington. Left of the Big Dipper is the constellation Boötes (The Herdsman) and at extreme left is part of the constellation Corona Borealis (Northern Crown).

Owen's Dictionary stated that ". . . the aurora borealis is a very common phaenomenon in countries near the pole; but there are not many upon record, as having appeared in England before that of March 1715." Since that time, however, they have been and still continue very frequent. Apparently no one had noticed that the auroras, like so many other natural phenomena, appeared in cycles. When the Owen's was published our sun was just entering a cycle of activity that warmed earth up from the "Little Ice Age." As described by geologist Robert Bergantino,

The term "Little Ice Age" applies to a period of cooler and wetter weather in parts of the northern hemisphere. The date of onset depends largely on location. The Norse colonies on Greenland had already succumbed to increasing cold by the early 1300s, but glacial studies in the Rockies and Pacific Northwest suggest that glacial increase did not begin there until the early 1400s, and then the increase was quite slow.

The "cold maximum" occurred in the mid-1700s (picture George Washington crossing the Delaware River amid ice floes—now non-existent—or hauling his cannons across the ice of rivers that haven't frozen over since). Many glaciers in the Northwest, however, did not reach their maximum extent in the early 1800s. The main cold period had ended in most places by the mid-1800s, but temperature graphs show a slight increase in some areas until the early 1900s, then the temperature dropped again, only to begin rising again after the 1940s.1

In terms of sunspot activity, the Little Ice Age era is called the "Maunder Minimum," for the twentieth-century British astronomer who discovered it. Written records and carbon-142 both show that minimal sunspot eras occurred in the seventh and fifteenth centuries A.D., while the first century B.C. ("Roman Maximum") was a time of frequent sunspots, as was the 12th century A.D. ("Medieval Maximum"). Carbon-14 testing also indicates that the sunspot cycle may have lasted about ten years in the past, shorter than today's eleven-year cycle.3

Other than sunspot activity, some scientists believe, the sun undergoes much longer cycles of overall activity that cause slow heating and cooling in earth's climate. The earth .s magnetic fields also experience long-term alterations, with their uneven circles expanding, contracting, and changing shape.4

1. Robert Bergantino to Joseph Mussulman, October 2, 1998.

2. Carbon-14, radioactive carbon, is present in all living things, and is replenished while they live. After death, carbon-14 decays at a fixed rate. By testing the amount of carbon-14 in organic matter, the date of the item's death can be determined. Sunspot activity also affects how much carbon-14 is present in earth's atmosphere at a given time, so testing ancient tree rings, for example, can trace increases and decreases in auroras' frequency.

3. T.Neil Davis, "Historical Auroras," at Alaska Science Forum, Jan. 7, 1981. An earlier study of sunspot activity between 1750 and 1950 has suggested that the peak of one of the sun's eleven-year cycles occurred at about the time Clark reported his sightings. Sir Fred Hoyle, Astronomy (New York: Doubleday, 1962), p. 216.

4. Davis, "Historical Auroras."