Analysis of an ice core taken by the National Science Foundation- (NSF) funded West Antarctic Ice Sheet (WAIS) Divide drilling project reveals that warming in Antarctica began about 22,000 years ago, a few thousand years earlier than suggested by previous records.
Brian Bencivengo, of the National Ice Core Laboratory, holds a segment of the WAIS ice core.
This timing shows that West Antarctica did not "wait for a cue" from the Northern Hemisphere to start warming, as scientists had previously supposed.
For more than a century scientists have known that Earth's ice ages are caused by the wobbling of the planet's orbit, which changes its orientation to the sun and affects the amount of sunlight reaching higher latitudes.
The Northern Hemisphere's last ice age ended about 20,000 years ago, and most evidence had indicated that the ice age in the Southern Hemisphere ended about 2,000 years later, suggesting that the South was responding to warming in the North.
But research published online Aug. 14 in the journal Nature shows that Antarctic warming began at least two, and perhaps four, millennia earlier than previously thought.
Most previous evidence for Antarctic climate change had come from ice cores drilled in East Antarctica, the highest and coldest part of the continent. However, a U.S.-led research team studying the West Antarctic core found that warming there was well underway 20,000 years ago.
WAIS Divide is a large-scale and multi-year glaciology project supported by the U.S. Antarctic Program (USAP), which NSF manages. Through USAP, NSF coordinates all U.S. science on the southernmost continent and aboard vessels in the Southern Ocean and provides the necessary logistics to make the science possible.
The WAIS Divide site is in an area where there is little horizontal flow of the ice, so the data are known to be from a location that remained consistent over long periods.
The WAIS Divide ice core is more than two miles deep and covers a period stretching back 68,000 years, though so far data have been analyzed only from layers going back 30,000 years. Near the surface, one meter of snow is equal to a year of accumulation, but at greater depths the annual layers are compressed to centimeters of ice.
"Sometimes we think of Antarctica as this passive continent waiting for other things to act on it. But here it is showing changes before it 'knows' what the North is doing," said T.J. Fudge, a University of Washington doctoral student in Earth and Space Sciences and lead corresponding author of the Nature paper. Fudge's 41 co-authors are other members of the WAIS project.
Fudge identified the annual layers by running two electrodes along the ice core to measure higher electrical conductivity associated with each summer season. Evidence of greater warming turned up in layers associated with 18,000 to 22,000 years ago, the beginning of the last deglaciation.
"This deglaciation is the last big climate change that we're able to go back and investigate," he said. "It teaches us about how our climate system works."West Antarctica is separated from East Antarctica by a major mountain range. East Antarctica has a substantially higher elevation and tends to be much colder, though there is recent evidence that it too is warming.
"It's not surprising that West Antarctica is showing something different from East Antarctica on long time scales, but we didn't have direct evidence for that before," Fudge said.He noted that the warming in West Antarctica 20,000 years ago is not explained by a change in the sun's intensity. Instead, how the sun's energy was distributed over the region was a much bigger factor. It not only warmed the ice sheet but also warmed the Southern Ocean that surrounds Antarctica, particularly during summer months when more sea ice melting could take place.
Changes in Earth's orbit today are not an important factor in the rapid warming that has been observed recently, he added. "Earth's orbit changes on the scale of thousands of years, but carbon dioxide today is changing on the scale of decades so climate change is happening much faster today," Fudge said.
Julie Palais, the Antarctic Glaciology Program director in NSF's Division of Polar Programs, said new findings will help scientists to "better understand not only what happened at the end of the last ice age but it should also help inform our understanding of what might be happening as the climate warms and conditions begin to change in and around the Antarctic continent."She added, "West Antarctica is currently experiencing some of the largest changes on the continent, such as the large calving events in the Amundsen Sea Embayment linked to warm ocean currents undercutting the outlet glaciers. The recent changes are consistent with the WAIS Divide results that show West Antarctica is sensitive to changes in ocean conditions in the past."
Peter West | EurekAlert!
Colorado River's connection with the ocean was a punctuated affair
16.11.2017 | University of Oregon
Researchers create largest, longest multiphysics earthquake simulation to date
14.11.2017 | Gauss Centre for Supercomputing
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
17.11.2017 | Physics and Astronomy
17.11.2017 | Health and Medicine
17.11.2017 | Studies and Analyses