by Brooks Hays
Washington (UPI) Oct 24, 2017
New research suggests volcanic eruptions can trigger periods of rapid ice sheet melting.
Researchers surveyed evidence of melting among ice cores and meltwater deposits, and compared their findings to a timeline of ancient volcanic eruptions between 12,000 to 13,000 years ago. Their analysis revealed a connection between the two phenomena.
"Over a time span of 1,000 years, we found that volcanic eruptions generally correspond with enhanced ice sheet melting within a year or so," Francesco Muschitiello, a postdoctoral researcher at Columbia University's Lamont-Doherty Earth Observatory, said in a news release.
The volcanoes of note weren't situated next-door, but thousands of miles from the ice sheet, a reminder of the unexpected global impacts of volcanic activity.
The new research -- detailed this week in the journal Nature Communications -- suggests ash ejected into the atmosphere by erupting volcanoes can be deposited thousands of miles away. When it's deposited on ice sheets, the dark particles cause the ice to absorb more thermal energy and accelerate melting.
Ancient glacial varves, layers of sediment deposited by glacial meltwater, helped scientists document periods of accelerated melting at the end of the last ice age. Like a hearty tree rings reveal periods of intense growth, thicker varve layers indicate increased periods of melting. Researchers matched varve layers with ice core layers, which can reveal ancient atmospheric conditions.
The data helped scientists build a computer model to better predict how much melting a single volcanic eruption could cause. As expected, simulations proved a volcano's impact on melting is dependent on a variety of factors, including the snowpack, weather patterns, ice thickness and more.
"Change any one of these and you would get different amounts of melt," said James Lea, a glaciologist at the University of Liverpool.
In the worst case scenario, researchers predicted a volcanic eruption in the northern latitudes could removed between 20 centimeters to one meter of ice, or several inches to a few feet.
Until recently, volcanic eruptions were mostly linked with broad cooling effects on the planet's climate, as thick layers of ash can partially block out the sun for months or years. Particulate matter also encourages cloud formation, further shadowing Earth's surface.
But a number of studies suggests a more complicated story -- a combination of warming and cooling mechanisms.
Some scientists have even suggested melting encouraged by volcanic eruptions could trigger even more eruptions, a positive feedback loop. As glaciers and ice sheets melt, pressure is relieved from the planet's crust, allowing magma to rise to the surface.
Seattle WA (SPX) Oct 23, 2017
Until recently, glaciers in the United States have been measured in two ways: placing stakes in the snow, as federal scientists have done each year since 1957 at South Cascade Glacier in Washington state; or tracking glacier area using photographs from airplanes and satellites. We now have a third, much more powerful tool. While he was a doctoral student in University of Washington's Depar ... read more
Beyond the Ice Age
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