Global warming yields “glacial earthquakes,” future sea level rise
March 23, 2006
Special to World Science
In new studies, scientists report that global warming may cause sea levels to rise dramatically in a century—and is now producing a
newfound and growing phenomenon, “glacial earthquakes.”
Three studies published in the March 24 issue of the research journal Science warn of the events.
Two studies found that the Earth may be warm enough by 2100 for widespread melting of the Greenland Ice Sheet and partial collapse
of the Antarctic Ice Sheet.
In one paper, Jonathan Overbeck at the University of Arizona in Tucson, Ariz., and colleagues wrote that based on reconstructions of
past climates, conditions could be ripe to raise sea level by several meters (yards) by this century’s end.
Most scientists believe the melting is due to global warming, a gradual increase in the Earth’s temperature caused by the burning of
fossil fuels.
In a third study, seismologists reported an unexpected offshoot of global warming: “glacial earthquakes,” in which Manhattan-sized
glaciers lurch unexpectedly. Glaciers are normally slow-moving masses of ice.
The lurches yield temblors up to magnitude 5.1 on the moment-magnitude scale, which is similar to the Richter scale, the researchers
said. Glacial earthquakes in Greenland, they added, are most common in July and August, and have more than doubled in number
since 2002.
The researchers, at Harvard University in Cambridge, Mass. and Columbia University in New York, first described glacial
earthquakes in 2003, but without reporting on their seasonality or changing frequency.
“People often think of glaciers as inert and slow-moving, but in fact they can also move rather quickly,” said Harvard’s Göran
Ekström, one of the researchers. “Some of Greenland’s glaciers, as large as Manhattan and as tall as the Empire State Building, can
move 10 meters (11 yards) in less than a minute, a jolt that is sufficient to generate moderate seismic waves.”
As glaciers and the snow on them gradually melt, water seeps downward. When enough water accumulates at a glacier’s base, it can
serve as a lubricant, causing giant blocks of ice to lurch down valleys known as “outlet glaciers,” the team explained. These funnel
Greenland’s glacial runoff toward the surrounding sea.
“Our results suggest that these major outlet glaciers can respond to changes in climate conditions much more quickly than we had
thought,” said Meredith Nettles, a postdoctoral researcher at Columbia and member of the research team.
“Greenland’s glaciers deliver large quantities of fresh water to the oceans, so the implications for climate change are serious.”
Greenland is not a hotbed of traditional seismic activity associated with the grinding of the Earth’s tectonic plates, the traditional
source of earthquakes, the scientists noted. But seismometers worldwide detected 182 earthquakes there between January 1993 and
October 2005, they added.
They examined the 136 best-documented of these events, ranging in magnitude from 4.6 to 5.1. All temblors were found to have
originated at major valleys draining the Greenland Ice Sheet, they said, implicating glacial activity.
While glacial earthquakes appear most common in Greenland, the scientists reported finding evidence of them also in Alaska and at
the edges of Antarctica.
Global warming may bring tsunami and quakes: scientists
By Richard Meares
LONDON | Thu Sep 17, 2009 2:37am IST
(Reuters) - Quakes, volcanic eruptions, giant landslides and tsunamis may become more frequent as global warming changes the
earth's crust, scientists said on Wednesday.
Climate-linked geological changes may also trigger "methane burps," the release of a potent greenhouse gas, currently stored in solid
form under melting permafrost and the seabed, in quantities greater than all the carbon dioxide (CO2) in our air today.
"Climate change doesn't just affect the atmosphere and the oceans but the earth's crust as well. The whole earth is an interactive
system," Professor Bill McGuire of University College London told Reuters, at the first major conference of scientists researching the
changing climate's effects on geological hazards.
"In the political community people are almost completely unaware of any geological aspects to climate change."
The vulcanologists, seismologists, glaciologists, climatologists and landslide experts at the meeting have looked to the past to try to
predict future changes, particularly to climate upheaval at the end of the last ice age, some 12,000 years ago.
"When the ice is lost, the earth's crust bounces back up again and that triggers earthquakes, which trigger submarine landslides, which
cause tsunamis," said McGuire, who organized the three-day conference.
David Pyle of Oxford University said small changes in the mass of the earth's surface seems to affect volcanic activity in general, not
just in places where ice receded after a cold spell. Weather patterns also seem to affect volcanic activity - not just the other way round,
he told the conference.
LONDON'S ASIAN SUNSET
Behind him was a slide of a dazzlingly bright orange painting, "London sunset after Krakatau, 1883" - referring to a huge Asian
volcanic eruption whose effects were seen and felt around the world.
Volcanoes can spew vast amounts of ash, sulphur, carbon dioxide and water into the upper atmosphere, reflecting sunlight and
sometimes cooling the earth for a couple of years. But too many eruptions, too close together, may have the opposite effect and
quicken global warming, said U.S. vulcanologist Peter Ward.
"Prior to man, the most abrupt climate change was initiated by volcanoes, but now man has taken over. Understanding why and how
volcanoes did it will help man figure out what to do," he said.
Speakers were careful to point out that many findings still amounted only to hypotheses, but said evidence appeared to be mounting
that the world could be in for shocks on a vast scale.
Tony Song of NASA's Jet Propulsion Laboratory in California warned of the vast power of recently discovered "glacial earthquakes" - in which glacial ice mass crashes downwards like an enormous landslide.
In the West Antarctic, ice piled more than one mile above sea level is being undermined in places by water seeping in underneath.
"Our experiments show that glacial earthquakes can generate far more powerful tsunamis than undersea earthquakes with similar
magnitude," said Song.
"Several high-latitude regions, such as Chile, New Zealand and Canadian Newfoundland are particularly at risk."
He said ice sheets appeared to be disintegrating much more rapidly than thought and said glacial earthquake tsunamis were "lowprobability but high-risk."
McGuire said the possible geological hazards were alarming enough, but just one small part of a scary picture if man-made CO2
emissions were not stabilized within around the next five years.
"Added to all the rest of the mayhem and chaos, these things would just be the icing on the cake," he said. "Things would be so bad
that the odd tsunami or eruption won't make much difference."
Questions:
1.
What are glacial earthquakes? Why do they happen and how large can they get on the Richter scale?
2.
How can global warming, which causes ice to melt, create a higher frequency of glacial quakes (describe the process
mentioned in the first article)?
3.
How many glacial quakes have been detected in Greenland within the past 25 years? Why are we worried so much about
Greenland’s seismic activity?
4.
Where else have glacial quakes been detected, other than Greenland?
5.
What is a “methane burp” and why is it potentially dangerous?
6.
What is released from a volcano? What can happen if there are too many volcanic eruptions around the same time?
7.
Before man, what was the source of the biggest abupt climate changes on Earth? Explain, using your knowledge, why this
would occur.
8.
Why, reading the second article, are we concerned about the increased frequency of glacial earthquakes? Who is at risk?
9.
What do scientists perceive could eventually happen if we do not stop releasing so many greenhouse gasses?