A new study that provides surprising details on changes in Earth's climate from more than 100,000 years ago indicates that the last interglacial--the period between "ice ages"--was warmer than previously thought and may be a good analog for future climate, as greenhouse gases increase in the atmosphere and global temperatures rise.
The edge of the Greenland ice sheet is shown.
The research findings also indicate that melting of the massive West Antarctic ice sheet may have contributed more to sea-level rise at that time than melting of the Greenland ice sheet.
The new results from the North Greenland Eemian Ice Drilling (NEEM) project were published in the Jan. 24 edition of Nature.
Members of the research team noted that they were working in Greenland during the summer of 2012 during a rare modern melt event similar to those discussed in the paper.
"We were quite shocked by the warm surface temperatures observed at the NEEM ice camp in July 2012," said Dorthe Dahl-Jensen, of the University of Copenhagen, the NEEM project leader.
"It was simply raining, and, just as during the Eemian period, meltwater formed subsurface ice layers. While this was an extreme event, the present warming over Greenland makes surface melt more likely, and the predicted warming over Greenland in the next 50-100 years will potentially have Eemian-like climate conditions."
The Eemian interglacial period began about 130,000 years ago and ended about 115,000 years ago.
The project logistics for NEEM are managed by Denmark's Centre for Ice and Climate. The Arctic Sciences Section in the National Science Foundation's Division of Polar Programs manages the U.S. support for the project.In addition to Denmark and the United States, researchers from Belgium, Canada, China, France, Germany, Iceland, Japan, the Netherlands, South Korea, Sweden, Switzerland and the United Kingdom are also partners in NEEM.
"The new findings reveal higher temperatures in Northern Greenland during the Eemian than paleo-climate models have estimated," said Dahl-Jensen.
The researchers looked at surface elevation and ice thickness in the early and later parts of the Eemian. Following the previous glacial period, 128,000 years before present, the surface elevation in the vicinity of NEEM was 200 meters higher than the present and the ice thickness decreased at a very high rate of 6 centimeters per year. Some 122,000 years before the present, the surface elevation was 130 meters below the present. In the late Eemian, 122,000 to 115,000 before present, the surface elevation remained stable at a level of 130 meters below the present with an ice thickness of 2,400 meters.
The research team estimated the Greenland ice sheet's volume reduced by no more than 25 percent over 6,000 years. The rate of elevation change in the early part of the Eemian was high and the loss of mass from the Greenland ice sheet was likely on the the same order as changes observed during the last ten years.
"The good news from this study is that Greenland is not as sensitive as we thought to temperature increases in terms of disgorging ice into the ocean during interglacial periods," said Dahl-Jensen. "The bad news is that if Greenland did not disappear during the Eemian, Antarctica, including the more dynamically unstable West Antarctica, must be responsible for a significant part of the 4-8 meters of sea-level rise."
Jim White, director of the Institute of Arctic and Alpine Research at the University of Colorado, Boulder, and the lead U.S. investigator on the NEEM project, said that while three previous ice cores drilled in Greenland in the last 20 years recovered ice from the Eemian, the deepest layers were compressed and folded, making the data difficult to interpret.
With this study, although there was some folding of the lowest ice layers in the NEEM core, sophisticated ice-penetrating radar helped scientists sort out and interpret the individual layers to paint an accurate picture of the warming of Earth's Northern Hemisphere as it emerged from the previous ice age.
"When we calculated how much ice melt from Greenland was contributing to global sea rise in the Eemian, we knew a large part of the sea rise back then must have come from Antarctica," said White. "A lot of us had been leaning in that direction for some time, but we now have evidence that confirms that the West Antarctic ice sheet was a dynamic and crucial player in global sea rise during the last interglacial period."
The intense surface melt in the vicinity of NEEM during the warm Eemian period was seen in the ice core as layers of re-frozen meltwater. Meltwater from surface snow had penetrated the underlying snow, where it re-froze. Such melt events during the past 5,000 years are very rare by comparison, confirming that the surface temperatures at the NEEM site during the Eemian were significantly warmer than today, said the researchers.
The Greenland ice core layers--formed over millennia by compressed snow--are being studied in detail using a big suite of measurements, including stable water isotope analysis that reveals information about temperature and moisture changes back in time. Lasers are used to measure the water stable isotopes and atmospheric gas bubbles trapped in the ice cores to better understand past variations in climate on a year-by-year basis--similar in some ways to a tree-ring record.
"It's a great achievement for science to gather and combine so many measured ice core records to reconstruct the climate history of the past Eemian," said Dahl-Jensen. "It shows what a great team of researchers we have assembled and how valuable these findings are."
Dorthe Dahl-Jensen, University of Copenhagen’s Centre of Ice and Climate 011-45 22 894 537 email@example.com
For B-roll of the NEEM project and last summer's melt in Greenland, please contact Dena Headlee, firstname.lastname@example.org / (703) 292-7739
The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2012, its budget is $7.0 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives over 50,000 competitive requests for funding, and makes about 11,000 new funding awards. NSF also awards nearly $420 million in professional and service contracts yearly.
Peter West | EurekAlert!
Further reports about: > Analysis > Antarctic Predators > Antarctic ice > Antarctic ice sheet > Antarctica > Arctic Ocean > Climate change > Colorado river > Greenland > Greenland ice > Greenland ice sheet > Northern Lights > crystalline > glacial period > global temperature > greenhouse gas > ice age > ice cores > ice sheet > ice thickness > interglacial period > sea-level rise > surface temperature
Fossil coral reefs show sea level rose in bursts during last warming
19.10.2017 | Rice University
NASA finds newly formed tropical storm lan over open waters
17.10.2017 | NASA/Goddard Space Flight Center
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
19.10.2017 | Materials Sciences
19.10.2017 | Materials Sciences
19.10.2017 | Physics and Astronomy