Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Southern glaciers grow out of step with North

04.05.2009
New dating technique points to differences over 7,000 years

The vast majority of the world’s glaciers are retreating as the planet gets warmer. But a few, including ones south of the equator, in South America and New Zealand, are inching forward.

A new study in 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.

Conventional wisdom holds that climate during the era of human civilization has been relatively stable, but 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 lead author Joerg Schaefer, 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 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 his colleagues were able for the first time to assign precise ages to young Holocene moraines. They did 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 the glaciers around Mount Cook, New Zealand's highest peak, reached their largest extent in the past 7,000 years 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, including glacial peaks during classic northern warm intervals such as the Medieval Warm Period and the Roman Age Optimum.

The new chemical and analytical protocols developed in Schaefer's cosmogenic dating lab is 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 coauthor George Denton, a glaciologist who is a senior professor 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.

"The application of this technique should allow for much more accurate reconstructions of glacial advances worldwide," says Paul Filmer, program director for the National Science Foundation (NSF)'s Division of Earth Sciences, which helped fund the study. "This would provide more constraints to allow us to make our climate models more accurate."

The study also received funding from the Comer Science and Education Foundation and the New Zealand Foundation for Research, Science and Technology.

The other researchers involved in the study were: Michael Kaplan and Roseanne Schwartz, also of Lamont-Doherty; Aaron Putnam, University of Maine; Robert Finkel, University of California, Berkeley; David Barrell, GNS Science, New Zealand; Bjorn Anderson, University of Oslo; Andrew Mackintosh, Victoria University of Wellington, New Zealand; Trevor Chinn, Alpine and Polar Processes Consultancy, New Zealand; Christian Schluchter, University of Bern, Switzerland.

Copies of the paper, "High-Frequency Holocene Glacier Fluctuations in New Zealand Differ from the Northern Signature," are available from the authors or from Science: 202-326-6440 or scipak@aaas.org.

Scientist contacts:

Joerg Schaefer, schaefer@ldeo.columbia.edu, Ph: 845-365-8756
George Denton, gdenton@maine.edu, Ph: 207-581-2193
Robert Finkel, rfinkel@berkeley.edu, Cell: 510-520-1738
More information: Kim Martineau, Science Writer, Lamont-Doherty Earth Observatory, kmartine@ei.columbia.edu, Ph: 845-365-8708, Cell: 518-221-6890

The Earth Institute at Columbia University mobilizes the sciences, education and public policy to achieve a sustainable earth. Through interdisciplinary research among more than 500 scientists in diverse fields, the Institute is adding to the knowledge necessary for addressing the challenges of the 21st century and beyond. With over two dozen associated degree curricula and a vibrant fellowship program, the Earth Institute is educating new leaders to become professionals and scholars in the growing field of sustainable development. We work alongside governments, businesses, nonprofit organizations and individuals to devise innovative strategies to protect the future of our planet.

Lamont-Doherty Earth Observatory, a member of The Earth Institute at Columbia University, is one of the world's leading research centers seeking fundamental knowledge about the origin, evolution and future of the natural world. More than 300 research scientists study the planet from its deepest interior to the outer reaches of its atmosphere, on every continent and in every ocean. From global climate change to earthquakes, volcanoes, nonrenewable resources, environmental hazards and beyond, Observatory scientists provide a rational basis for the difficult choices facing humankind in the planet's stewardship.

Kim Martineau | EurekAlert!
Further information:
http://www.ei.columbia.edu

More articles from Earth Sciences:

nachricht Massive impact crater from a kilometer-wide iron meteorite discovered in Greenland
15.11.2018 | Faculty of Science - University of Copenhagen

nachricht The unintended consequences of dams and reservoirs
14.11.2018 | Uppsala University

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: UNH scientists help provide first-ever views of elusive energy explosion

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

Purdue cancer identity technology makes it easier to find a tumor's 'address'

16.11.2018 | Health and Medicine

Good preparation is half the digestion

16.11.2018 | Life Sciences

Microscope measures muscle weakness

16.11.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>