 |
|
Glacial advances
May 04, 2009The vast majority of the world's glaciers are retreating as the planet gets warmer. But a few, including glaciers south of the equator in South America and New Zealand, are inching forward.
A paper in this week's issue of the journal Science puts this enigma in perspective; for the last 7,000 years, New Zealand's largest glaciers have often moved out of step with glaciers in the Northern Hemisphere, pointing to strong regional variations in climate.
"This research should provide much more accurate reconstructions of glacial advances worldwide, allowing us in turn to make climate models more accurate," said Paul Filmer, program director in the National Science Foundation's (NSF) Division of Earth Sciences, which funded the research.
Conventional wisdom holds that during the era of human civilization, climate has been relatively stable. The new study is the latest to challenge this view, by showing that New Zealand's glaciers have gone through rapid periods of growth and decline during the current interglacial period known as the Holocene.
"New Zealand's mountain glaciers have fluctuated frequently over the last 7,000 years, and glacial advances have become slightly smaller through time," said Joerg Schaefer, lead author of the paper and a geochemist at Columbia University's Lamont-Doherty Earth Observatory.
"This pattern differs in important ways from the northern hemisphere glaciers. The door is open now towards a global map of Holocene [a geological time period that began about 11,700 years ago and continues to the present] glacier fluctuations and how climate variations during this period impacted human civilizations."
Glaciers are extremely sensitive to changes in temperature and snowfall, which makes them well suited for studying past climate. This archive has been largely untapped, however, because of the difficulty in assigning precise ages to glacier fluctuations.
One way to measure glacial fluxes is by studying the moraines, or rock deposits that glaciers often leave behind at their maximum points of advance.
However, until now the methods of dating such moraines, including radiocarbon dating of organic matter, could be off by hundreds of years.
By refining the analysis of a method called cosmogenic dating, Schaefer and colleagues were able for the first time to assign precise ages to young Holocene moraines.
They accomplished this by measuring minute levels of the chemical isotope beryllium 10 in the rocks, which is produced when cosmic rays strike rock surfaces, and builds up over time.
The researchers were thus able to pinpoint exactly when glaciers in New Zealand's Southern Alps began to recede, exposing the rocks to the cosmic rays.
From the results, they constructed a glacial timeline for the past 7,000 years and compared it against historic records from the Swiss Alps and other places north of the equator.
They found that within that timeframe, the glaciers around Mount Cook, New Zealand's highest peak, reached their largest extent about 6,500 years ago, when the Swiss Alps and Scandinavia were relatively warm.
That's about 6,000 years before northern glaciers hit their Holocene peak during the Little Ice Age, between 1300 and 1860 AD.
That finding was a surprise to some scientists who assumed that the northern cold phase happened globally. The record in New Zealand shows other disparities that point to regional climate variations in both hemispheres.
The new chemical and analytical protocols are expected to allow scientists to accurately date glacier fluctuations throughout the Holocene, rounding out the climate picture on the continents.
"With this measure we can go to almost any mountain range on earth and date the moraines in front of the glaciers and produce a similar chronology," said co-author George Denton, a glaciologist at the University of Maine and an adjunct scientist at Lamont-Doherty.
Overall, glaciers around the world have been declining since about 1860, with the exception of a brief advance in Switzerland in the 1980s, New Zealand in the late 1970s through today, and a few other places.
Changes in wind and sea surface temperatures are thought to be causing these regional fluctuations.
Currently in a wet phase, New Zealand is expected to swing back to a warmer, drier phase in the next few years, causing the glaciers to retreat once again.
National Science Foundation
Conventional wisdom holds that during the era of human civilization, climate has been relatively stable. The new study is the latest to challenge this view, by showing that New Zealand's glaciers have gone through rapid periods of growth and decline during the current interglacial period known as the Holocene.
"New Zealand's mountain glaciers have fluctuated frequently over the last 7,000 years, and glacial advances have become slightly smaller through time," said Joerg Schaefer, lead author of the paper and a geochemist at Columbia University's Lamont-Doherty Earth Observatory.
"This pattern differs in important ways from the northern hemisphere glaciers. The door is open now towards a global map of Holocene [a geological time period that began about 11,700 years ago and continues to the present] glacier fluctuations and how climate variations during this period impacted human civilizations."
Glaciers are extremely sensitive to changes in temperature and snowfall, which makes them well suited for studying past climate. This archive has been largely untapped, however, because of the difficulty in assigning precise ages to glacier fluctuations.
One way to measure glacial fluxes is by studying the moraines, or rock deposits that glaciers often leave behind at their maximum points of advance.
However, until now the methods of dating such moraines, including radiocarbon dating of organic matter, could be off by hundreds of years.
By refining the analysis of a method called cosmogenic dating, Schaefer and colleagues were able for the first time to assign precise ages to young Holocene moraines.
They accomplished this by measuring minute levels of the chemical isotope beryllium 10 in the rocks, which is produced when cosmic rays strike rock surfaces, and builds up over time.
The researchers were thus able to pinpoint exactly when glaciers in New Zealand's Southern Alps began to recede, exposing the rocks to the cosmic rays.
From the results, they constructed a glacial timeline for the past 7,000 years and compared it against historic records from the Swiss Alps and other places north of the equator.
They found that within that timeframe, the glaciers around Mount Cook, New Zealand's highest peak, reached their largest extent about 6,500 years ago, when the Swiss Alps and Scandinavia were relatively warm.
That's about 6,000 years before northern glaciers hit their Holocene peak during the Little Ice Age, between 1300 and 1860 AD.
That finding was a surprise to some scientists who assumed that the northern cold phase happened globally. The record in New Zealand shows other disparities that point to regional climate variations in both hemispheres.
The new chemical and analytical protocols are expected to allow scientists to accurately date glacier fluctuations throughout the Holocene, rounding out the climate picture on the continents.
"With this measure we can go to almost any mountain range on earth and date the moraines in front of the glaciers and produce a similar chronology," said co-author George Denton, a glaciologist at the University of Maine and an adjunct scientist at Lamont-Doherty.
Overall, glaciers around the world have been declining since about 1860, with the exception of a brief advance in Switzerland in the 1980s, New Zealand in the late 1970s through today, and a few other places.
Changes in wind and sea surface temperatures are thought to be causing these regional fluctuations.
Currently in a wet phase, New Zealand is expected to swing back to a warmer, drier phase in the next few years, causing the glaciers to retreat once again.
National Science Foundation
Glaciers Current Events and Glaciers News RSSAre the Alps growing or shrinking?
The Alps are growing just as quickly in height, as they are shrinking. This paradoxical result could be proven by a group of German and Swiss geoscientists.
Volcanoes played pivotal role in ancient ice age, mass extinction
Researchers here have discovered the pivotal role that volcanoes played in a deadly ice age 450 million years ago. Perhaps ironically, these volcanoes first caused global warming -- by releasing massive amounts of carbon dioxide into the atmosphere. When they stopped erupting, Earth's climate was thrown off balance, and the ice age began.
Arctic Sediments Show That 20th Century Warming Is Unlike Natural Variation
The possibility that climate change might simply be a natural variation like others that have occurred throughout geologic time is dimming, according to evidence in a Proceedings of the National Academy of Sciences paper published today.
Glacial melting may release pollutants in the environment
Those pristine-looking Alpine glaciers now melting as global warming sets in may explain the mysterious increase in persistent organic pollutants in sediment from certain lakes since the 1990s, despite decreased use of those compounds in pesticides, electric equipment, paints and other products.
Arctic lake sediments show warming, unique ecological changes in recent decades
An analysis of sediment cores indicates that biological and chemical changes occurring at a remote Arctic lake are unprecedented over the past 200,000 years and likely are the result of human-caused climate change, according to a new study led by the University of Colorado at Boulder.
NASA flies to Antarctica for largest airborne polar ice survey
NASA begins a series of flights Oct. 15 to study changes to Antarctica's sea ice, glaciers and ice sheets. The flights are part of Operation Ice Bridge, a six-year campaign that is the largest airborne survey ever made of ice at Earth's polar regions.
Peering under the ice of a collapsing polar coast
Starting this month, a giant NASA DC-8 aircraft loaded with geophysical instruments and scientists will buzz at low level over the coasts of West Antarctica, where ice sheets are collapsing at a pace far beyond what scientists expected a few years ago.
A Thermometer for the Earth
According to climate change experts, our planet has a fever - melting glaciers are just one stark sign of the radical changes we can expect.
North meets south? Glaciers move together in far-flung regions
Results of a new study add evidence that climate swings in the northern hemisphere over the past 12,000 years have been tightly linked to changes in the tropics.
Study predicts effect of global warming on spring flowers
An international study involving Monash University mathematician Dr Malcolm Clark has been used to demonstrate the impact of global warming and to predict the effect further warming will have on plant life.
More Glaciers Current Events and Glaciers News Articles
 |
Glaciers by Michael Hambrey (Author), Jürg Alean (Author) Glaciers are among the most beautiful natural wonders on Earth, but for most of us the least known and understood. This book describes how glaciers grow and decay, how they move, and how they influence human civilisation. Today covering a tenth of the Earth's surface, glacier ice has shaped the landscape over millions of years by scouring away rocks, transporting and depositing debris far from its source. Glacier meltwater drives turbines and irrigates deserts, yields mineral-rich soils, and has left us a wealth of valuable sand and gravel. However, glaciers also threaten human property and life. Our future is indirectly bound up with the fate of glaciers and their influence on global climate and sea level. A lively running text develops these themes and is supported by over 200 stunning... |
 |
Glaciers (True Books: Earth Science) by Larry Dane Brimner (Author) Ideal for today's young investigative reader, each A True Book includes lively sidebars, a glossary and index, plus a comprehensive "To Find Out More" section listing books, organizations, and Internet sites. A staple of library collections since the 1950s, the new A True Book series is the definitive nonfiction series for elementary school readers. |
 |
Icebergs and Glaciers by Seymour Simon (Author) The frozen rivers and sheets of ice known as glaciers can move as slowly as a few inches a year, yet they are a powerful force shaping the earth beneath and around them.Breathtaking photographs mark this dramatic introduction to a beautiful yet frozen world of mountaintops and polar regions. |
 |
Icebergs, Ice Caps, and Glaciers (Rookie Read-About Science) by Allan Fowler (Author) From friendly dolphins to giant pandas, from icebergs and glaciers to energy from the sun, from magnets to solids, liquids, and gases, Rookie Read-About Science is a natural addition to the primary-grade classroom with books that cover every part of the science curricula. Includes: animals, nature, scientific principles, the environment, weather, and much more! |
 |
GUESS Dexler Sublimation Crew Sweater, GLACIER GREY A921 (L) by GUESS Muted logo print on softly woven knit makes this sweater a stand out. Long sleeve crewneck shirt with logo detail on hip. 50% Cotton, 50% Polyester Machine wash cold Men > Tops > Sweaters & Sweatshirts |
 |
Glaciers: Alaska's Rivers of Ice Directed By: Jerry McFaul Also With: Bruce Molnia (Cinematographer), Jerry McFaul (Writer) They’re one of Earth’s greatest phenomenon – mountains of ice floating freely in our oceans. From the shattering roar of calving tidewater glaciers to the frigid world of the tiny ice worms, join the US Geological Survey as they explore the wonders of Glaciers: Alaska’s Rivers of Ice. Learn about the formations of Aretes and Fjords. As well as the difference between eskers and moraines. Explore the elaborate geometry of Ogives, Cirques, and Seracs, while discovering the dramatic dynamism of jokulhaups and the overall physics behind the intense blue beauty of glacier ice. |
 |
Glaciers and Glaciation (Hodder Arnold Publication) by Douglas I. Benn (Author), David J. A. Evans (Author) This major new text provides a synthesis of the nature, origin and behavior of glacier systems and the geological and geomorphological evidence for their former existence. It features a superb collection of color and black and white photographs, over 300 in all, together with over 450 line diagrams. Using case studies drawn from around the world, it is referenced throughout and concludes with a fully comprehensive bibliography. |
 |
Carbon Glacier by Laura Veirs On her Nonesuch debut Carbon Glacier, Laura Veirs re-imagines folk music in a bravely boundary-crossing way, employing the genre as a jumping-off point to create an intimate, affecting sound entirely her own. The Independent described it as "a benchmark by which future Americana releases will be judged." Uncut simply declared Carbon Glacier Veirs' "first masterpiece". |
 |
And The Sea Won The Battle The Glaciers (Primary Contributor) |
 |
Glacier Ice by Austin Post (Author), Edward R. Lachapelle (Author) The awesome beauty and majesty of glaciers, the world of ice which has shaped and reshaped large parts of the earth's surfaces, are presented here through more than 100 photographs and a closely integrated, informed text. Austin Post's series of aerial photographs of glaciers along the North Pacific Coast of North America and into the interior ranges of Alaska is supplemented with ground-based photographs from the Himalayas, Switzerland, Chile, and other parts of the world. The authors clearly explain the features illustrated. Their discussion of the effects of glaciers on the landscape, formation and mass balance, flow and fluctuations, moraines, ogives, and surface details is fascinating for the general reader as well as the expert. First published in 1971 and long out of print,... |
| © 2009 BrightSurf.com |