A ribbon of ice more than 600 kilometers long that drains about 12 percent of the gigantic Greenland Ice Sheet has been smaller than it is today about half of the time over the past 45,000 years, a new study suggests.
Interestingly, the loss of ice from the Northeast Greenland Ice Stream (NEGIS) took place not only during the warm Holocene period, but also during a period thought to be very cold preceding the last glacial maximum, the researchers say.
This is ice calving of the Zachariae Isstrøm in Northeast Greenland. The icebergs can be up to 1 km in diameter and the ice front up to 100 m high.
Credit: Nicolaj Krog Larsen
The findings suggest that NEGIS is particularly sensitive to environmental changes, which may exacerbate the influence of anthropogenic climate change. Results of the study are being published today in Nature Communications.
"There are some parts of the ice sheet that are relatively stable and others that show evidence of very rapid retreating - a pattern we're seeing today as well as thousands of years ago," said Anders Carlson, an Oregon State University geologist and co-author on the study. "Some of it relates to bed topography - when the bed is below sea level, it stabilizes that part of the ice sheet. In low spots, it is unstable."
Carlson said different factors may help explain the ice mass loss, including orbital forcing and warm summer temperatures. The path of the Earth's orbit put it closer to the sun some 9,000 years ago, breaking the planet out of its glacial maximum. NEGIS showed significant ice loss.
Yet it also showed a loss of ice during the period preceding that maximum, about 41,000 to 26,000 years ago, which is thought to have been very cold. OSU paleoclimatologist Christo Buizert, also a co-author on the study, reconstructed air temperatures from that period using ice core analysis and found that air temperatures indeed were much colder than average, but summer temperatures were warmer, which may have contributed to the ice loss.
"That period was also quite dry and there wasn't nearly as much snowfall," Carlson said, "which may have driven the ice margin to be smaller."
The researchers were able to determine where the ice sheet margins were essentially by analyzing the rocks for "sunburn," Carlson said. When ice has retreated, the rocks become exposed to cosmic rays that hit the quartz in the rock and split the elements, creating beryllium-10. This cosmic bombardment leaves an elemental fingerprint that allows the researchers to reconstruct ice-free times over thousands of years.
"The anthropogenic forcing we are seeing today is having a significant impact on the ice sheet and it already has retreated to levels that weren't predicted to occur until the end of the century," Carlson said.
A team of Danish and American researchers conducted much of the fieldwork, studying three fast-flowing marine-terminating "outlet" glaciers on the Greenland Ice Sheet.
"Modern observations have shown that the NEGIS is very susceptible to changes in both air and ocean temperatures and is presently in a phase of rapid ice retreat," said Nicolaj Larsen of Aarhus University in Denmark, lead author on the study. Larsen spent much of the past year on sabbatical at Oregon State, where he collaborated with the OSU researchers.
Carlson and Buizert are with Oregon State University's College of Earth, Ocean, and Atmospheric Sciences. The study was supported by the Villum Foundation, Aarhus University's Arctic Research Center, and the U.S. National Science Foundation.
Sean Nealon | EurekAlert!
Geomagnetic jerks finally reproduced and explained
23.04.2019 | CNRS
"Flight recorder" of rocks within the Earth’s crust
16.04.2019 | Universität Bern
The human eye is particularly sensitive to green, but less sensitive to blue and red. Chemists led by Hubert Huppertz at the University of Innsbruck have now developed a new red phosphor whose light is well perceived by the eye. This increases the light yield of white LEDs by around one sixth, which can significantly improve the energy efficiency of lighting systems.
Light emitting diodes or LEDs are only able to produce light of a certain colour. However, white light can be created using different colour mixing processes.
Researchers led by Francesca Ferlaino from the University of Innsbruck and the Austrian Academy of Sciences report in Physical Review X on the observation of supersolid behavior in dipolar quantum gases of erbium and dysprosium. In the dysprosium gas these properties are unprecedentedly long-lived. This sets the stage for future investigations into the nature of this exotic phase of matter.
Supersolidity is a paradoxical state where the matter is both crystallized and superfluid. Predicted 50 years ago, such a counter-intuitive phase, featuring...
A stellar flare 10 times more powerful than anything seen on our sun has burst from an ultracool star almost the same size as Jupiter
A localization phenomenon boosts the accuracy of solving quantum many-body problems with quantum computers which are otherwise challenging for conventional computers. This brings such digital quantum simulation within reach on quantum devices available today.
Quantum computers promise to solve certain computational problems exponentially faster than any classical machine. “A particularly promising application is the...
The technology could revolutionize how information travels through data centers and artificial intelligence networks
Engineers at the University of California, Berkeley have built a new photonic switch that can control the direction of light passing through optical fibers...
17.04.2019 | Event News
15.04.2019 | Event News
09.04.2019 | Event News
24.04.2019 | Life Sciences
24.04.2019 | Life Sciences
24.04.2019 | Life Sciences