Washington — Scandinavia has risen more than a half-mile in the past 20,000 years, rebounding from the weight of mountains of ice that depressed the land's surface. Satellite measurements show the land is rising at almost half an inch a year.
During the last ice age, ice sheets almost two miles thick covered Sweden, Norway, Finland, Denmark and the Gulf of Bothnia, pressing down with a weight of about 6.6 million pounds per square yard, researchers say.
"There is not one place in Scandinavia that was not covered with ice," said Jerry Mitrovica of the University of Toronto. "The land was pressed down about a kilometer (five-eighths of a mile), and when the ice melted, the land started going up in a process that continues even today."
Mitrovica is co-author of a study appearing today in the journal Science.
Scientists have long known that Scandinavia, Canada and other places buried under frozen mountains during the last ice age have been rebounding. Until now, however, researchers were not sure how fast the land was rising.
Mitrovica and his co-authors used data from 33 sensors placed strategically around Scandinavia to pick up signals from the Global Positioning Satellite system. Combining this data, corrected for atmospheric distortion, enabled them to measure the land movement to a scale of about one millimeter, a fraction of an inch, per year.
They found that, on average, the land under the ancient ice burden is rising annually by about 9 mm. An inch is about 25 mm.
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