Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New evidence shows Antarctica has warmed in last 150 years

06.09.2006
Despite recent indications that Antarctica cooled considerably during the 1990s, new research suggests that the world's iciest continent has been getting gradually warmer for the last 150 years, a trend not identifiable in the short meteorological records and masked at the end of the 20th century by large temperature variations.

Numerous ice cores collected from five areas allowed scientists to reconstruct a temperature record that shows average Antarctic temperatures have risen about two-tenths of a degree Celsius, or about one-third of a degree Fahrenheit, in 150 years. That might not sound like much, but the overall increase includes a recorded temperature decline of nearly 1 degree in the 1990s, said David Schneider, a University of Washington postdoctoral researcher in Earth and space sciences.

"Even if you account for the cooling in the '90s, we still see that two-tenths of a degree increase from the middle of the 1800s to the end of the 20th century," said Schneider, the lead author of a paper detailing the work published Aug. 30 in Geophysical Research Letters.

The main reason that Antarctica appears to have cooled during the 1990s is that a natural phenomenon called the Antarctic Oscillation, or Southern Annular Mode, was largely in its positive phase during that time. The Antarctic Oscillation is so named because atmospheric pressure in far southern latitudes randomly oscillates between positive and negative phases. During the positive phase, a vortex of wind is tightly focused on the polar region and prevents warmer air from mixing with the frigid polar air, which keeps Antarctica colder.

Typically the Antarctic Oscillation alternates between phases about every month. But in the 1990s the positive phase occurred much more often, Schneider said. Without the influence of the Antarctic Oscillation, he said, it is likely the Antarctic would show the same kind of warming as the rest of the Southern Hemisphere. Before 1975, Antarctica appears to have warmed at about the same rate as the rest of the hemisphere, about 0.25 degree C per century. But since 1975, while the Antarctic showed overall cooling, the Southern Hemisphere has warmed at a rate of about 1.4 degrees per century.

"The second half of the 20th century is marked by really large variability. The periods of cooling correspond with a very strong positive Antarctic Oscillation," Schneider said. "The caution is that we don't fully understand the feedbacks between overall climate warming and the Antarctic Oscillation. But having the 200-year record is what convinces us that there is a relationship between Southern Hemisphere temperature changes and Antarctic temperature changes."

He noted that other research has suggested that ozone depletion in the Southern Hemisphere is keeping the Antarctic Oscillation in its positive phase for longer periods.

Schneider began the work for his doctoral thesis and completed it as a post-doctoral researcher. Co-authors of the paper are Eric Steig, Schneider's thesis adviser, and Cecilia Bitz of the UW; Tas van Ommen of the Antarctic Climate and Ecosystems Cooperative Research Centre in Australia, Daniel Dixon and Paul Mayewski of the University of Maine and Julie Jones of the Institute for Coastal Research in Germany. The work was funded primarily by the National Science Foundation, with additional funding from the Scientific Committee on Antarctic Research and Australia's Cooperative Research Centre Program.

Reconstructing an annual temperature record for two centuries was complicated by the fact that Antarctica is the world's driest continent, so while annual snowfall for thousands of years is preserved in glacial ice there often isn't much snowfall in a given year. For this work, the scientists collected ice cores from five areas that typically receive at least 15 inches of snow per year, which provided more substance from each year for them to examine. They studied oxygen and hydrogen isotopes in the cores to develop the first reconstruction of Antarctic temperature records for the last 150 years.

"We have pretty good confidence that we're right, though some of the details might have to be refined," Schneider said.

Vince Stricherz | EurekAlert!
Further information:
http://www.washington.edu

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Gold shines through properties of nano biosensors

17.08.2017 | Physics and Astronomy

Greenland ice flow likely to speed up: New data assert glaciers move over sediment, which gets more slippery as it gets wetter

17.08.2017 | Earth Sciences

Mars 2020 mission to use smart methods to seek signs of past life

17.08.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>