91̽»¨ glaciologists are co-authors on two papers that analyzed Antarctic ice cores to understand the continent’s air temperatures during the most recent glacial period. The results help understand how the region behaves during a major climate transition.

In one , an international team of researchers, including three at the UW, analyzed seven ice cores from across West and East Antarctica. The results published June 3 in Science show warmer ice age temperatures in the eastern part of the continent.

The team included authors from the U.S., Japan, the U.K., France, Switzerland, Denmark, Italy, South Korea and Russia.

“The international collaboration was critical to answering this question because it involved so many different measurements and methods from ice cores all across Antarctica,â€� said second author , a 91̽»¨assistant research professor of Earth and space sciences.

Antarctica, the coldest place on Earth today, was even colder during the last ice age. For decades, the leading science suggested ice age temperatures in Antarctica were on average as much as 9 degrees Celsius cooler than the modern era. By comparison, temperatures globally at that time averaged 5 to 6 degrees cooler than today.

Previous work showed that West Antarctica was as cold as 11 degrees C below current temperatures. The new paper in Science shows that temperatures at some locations in East Antarctica were only 4 to 5 degrees cooler, about half previous estimates.

“This is the first conclusive and consistent answer we have for all of Antarctica,� said lead author , an assistant professor at Oregon State University. “The surprising finding is that the amount of cooling is very different depending on where you are in Antarctica. This pattern of cooling is likely due to changes in the ice sheet elevation that happened between the ice age and today.�

The findings are important because they better match results of global climate models, supporting the models’ ability to reproduce major shifts in the Earth’s climate.

Another , accepted in June in the Journal of Geophysical Research: Atmospheres and led by the UW, focuses on data from the recently completed South Pole ice core, which finished drilling in 2016. The Science paper also incorporates these results.

“With its distinct high and dry climate, East Antarctica was certainty colder than West Antarctica, but the key question was: How much did the temperature change in each region as the climate warmed?â€� said lead author , who recently completed a 91̽»¨doctorate in Earth and space sciences.

That paper, focusing on the South Pole ice core, found that ice age temperatures at the southern pole, near the Antarctic continental divide, were about 6.7 degree Celsius colder than today. The Science paper finds that across East Antarctica, ice age temperatures were on average 6.1 degrees Celsius colder than today, showing that the South Pole is representative of the region.

“Both studies show much warmer temperatures for East Antarctica during the last ice age than previous work — the most recent ‘textbook’ number was 9 degrees Celsius colder than present,â€� said , a 91̽»¨professor of Earth and space sciences who is a co-author on both papers. “This is important because climate models tend to get warmer temperatures, so the data and models are now in better agreement.â€�

“The findings agree well with climate model results for that time period, and thus strengthen our confidence in the ability of models to simulate Earth’s climate,� Kahle said.

Previous studies used water molecules contained in the layers of ice, which essentially act like a thermometer, to reconstruct past temperatures.  But this method needs independent calibration against other techniques.

The new papers employ two techniques that provide the necessary calibration. The first method, , takes temperatures at various depths inside the hole left by the ice drill, measuring changes through the thickness of the ice sheet. The Antarctic ice sheet is so thick that it keeps a memory of earlier, colder ice age temperatures that can be measured and reconstructed, Fudge said.

The second method examines the properties of the snowpack as it builds up and slowly transforms into ice. In East Antarctica, the snowpack can range from 50 to 120 meters (165 to 400 feet) thick, including snow from thousands of years which gradually compacts in a process that is very sensitive to the temperature.

“As we drill more Antarctic ice cores and do more research, the picture of past environmental change comes into sharper focus, which helps us better understand the whole of Earth’s climate system,� Fudge said.

Fudge, Steig and Kahle are among 40 authors on the Science paper. Other co-authors on the JGR: Atmospheres paper are Michelle Koutnik, Andrew Schauer, C. Max Stevens, Howard Conway and Edwin Waddington at the UW; Tyler Jones, Valerie Morris, Bruce Vaughn and James White at the University of Colorado, Boulder; and Buizert and Jenna Epifanio at Oregon State University.

Both papers were supported by the U.S. National Science Foundation. Both papers made use of the , a project that in 2016 completed a 1.75 kilometer (1.09 mile) deep ice core at the South Pole. That project was funded by the NSF and co-led by Steig and Fudge with colleagues at the University of California, Irvine, and the University of New Hampshire.

For more information, contact Fudge at tjfudge@uw.edu, Kahle at eckahle@uw.edu and Steig at steig@uw.edu.

Part of this article were adapted from an OSU .

But there are a few potential brakes. One was supposed to be heavier snowfall over the vast continent of Antarctica. Warmer air will hold more moisture and thus generate more snow to fall inland and slightly rebuild the glacier, according to climate model projections.

Not so fast, says a 91̽»¨ published in Geophysical Research Letters, a journal of the American Geophysical Union. The authors looked at evidence from the to get a first clear look at how the continent’s snowfall has varied over 31,000 years.

“It’s allowed us to look at the snow accumulation back in time in much more detail than we’ve been able to do with any other deep ice core in Antarctica,” said lead author , a 91̽»¨postdoctoral researcher in Earth and space sciences. “We show that warmer temperatures and snowfall sometimes go together, but often they don’t.”

For example, the record includes periods before 8,000 years ago, as Earth was coming out of its last ice age, when the air temperature went up by several degrees without any boost in the amount of snowfall.

“Our results make it clear that we cannot have confidence in projections of future snowfall over Antarctica under global warming,” said co-author , a 91̽»¨professor of Earth and space sciences.

The plateau of East Antarctica, the site of most previous ice cores, is relatively high and dry. About 80 percent of the continent’s precipitation falls on the lower, stormier edges, like where this core was drilled in 2006-2011. (To prepare scientists for conditions during a West Antarctic snowstorm, Fudge notes, researchers had to practice navigating outside with a bucket over their heads.)

The 2.1-mile, or 3.5-kilometer, ice core preserves climate history in enough detail to show individual snow years.

Many climate models predict that warming temperatures will mean more snow in Antarctica in the future. When more snow falls inland at the upper edge of the flowing ice sheet, it counteracts mass lost to melting or calving at the edges. This extra snowfall would reverse 2 to 4 centimeters, or about 1 inch, of global sea-level rise by 2100, researchers said.

“It’s not a huge component,” Fudge acknowledges, “but if you live close to sea level, centimeters certainly matter.”

The new study, however, shows that temperature is an unreliable predictor of Antarctic snowfall.

“Depending on what part of the record you look at, you can draw different conclusions,” Fudge said. “During some of the more abrupt climate changes, from when we had ice sheets to our current climate state, there’s actually no relationship between temperature and snowfall.”

The large variation seen in the historical record probably reflects shifts in atmospheric patterns and how storm tracks reach Antarctica, Fudge said. Research is increasingly showing that winds play a big role in Antarctic temperature, sea ice and weather patterns, especially on shorter timescales, and that the gale-force winds that whip around the continent are connected to weather patterns in the tropics.

“For sea-level rise, we’re not really interested in what happens over thousands of years,” Fudge said. “We’re interested in what happens over the next few hundred years. At that shorter timescale, the variability in how the storms reach the continent matters much more than a few degrees of warming.”

The snowfall record may help to understand how winds affect Antarctic weather, and how influence the amount of relatively warm ocean water that laps at the frozen continent’s edge.

“By getting models to better capture the variability in our snowfall record, we actually will get a better idea of how the warm ocean is going to interact with the ice sheets at the edge, and those will have an even bigger impact on sea level, eventually,” Fudge said.

The study, published online April 28, was funded by the National Science Foundation and NASA. Other co-authors are 91̽»¨doctoral student ; 91̽»¨faculty members , and ; Kurt Cuffrey at the University of California, Berkeley; Christo Buizert at Oregon State University; and Kendrick Taylor at Nevada’s Desert Research Institute.

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For more information, contact Fudge at tjfudge@uw.edu or 650-743-5227 and Steig at steig@uw.edu or 206-685-3715.

NSF grants: 0944197, 0944191, 1043518

Drilling continues through the end of January for the first of two years of a joint project by the 91̽»¨ and the University of California, Irvine. The National Science Foundation is funding the to dig into climate history at the planet’s southernmost tip.

The 40,000-year record will be the first deep core from this region of Antarctica, and the first record longer than 3,000 years collected south of 82 degrees latitude.

“The cold temperatures in the ice, about -50 C, have caused some surprises with drilling since certain aspects of the drill perform differently even than during the test in Greenland at -30 C,” said , a 91̽»¨postdoctoral researcher who is chief scientist for this month.

The location is just 2.7 km (1.7 miles) from the South Pole. The thick, uncontaminated layers of ice there will help answer questions about how Antarctic climate interacts with the rest of the world. The period between 40,000 years ago and 10,000 years ago includes sudden swings in temperature, ending with warming at the end of the last ice age.

Scientists were attracted by conditions at the pole, which are cold even by Antarctic standards.

“Most of the other places where we’ve worked the ice is -25 C to -30 C, and that’s too warm for rare organic molecules and other trace gases that our colleagues are interested in measuring,” said co-leader , a 91̽»¨professor of Earth and space sciences.

“This is basically the coldest ice that we have drilled in,” said principal investigator , a UC Irvine researcher who was chief scientist from setup of the field camp in early November through the end of December. “Everything is harder in the cold.”

All three scientists were part of a team that collected a from West Antarctica, a five-year effort that ended in 2011. Analysis of that ice is still ongoing at the UW, UC Irvine and many other labs around the country.

“South Pole is part of the East Antarctic Ice Sheet, yet is influenced by storms coming across the West Antarctic Ice Sheet,” Fudge said. “This core will help us figure out how the two sides of Antarctica communicate during climate changes in the past.”

The project at the South Pole is using a new intermediate-depth drill based on a Danish design, that is lighter than the one used in West Antarctica, and a new drilling fluid. The team reached a depth of 1/2 kilometer (1/3 mile) on Jan. 14. Researchers hope to pass 700 meters by the end of this season and 1,500 meters (almost a mile down) by the end of next season.

“We’re not just trying to punch through the ice sheet, the most important objective is to bring up the highest-quality ice possible,” Aydin said.

After the core is drilled, three-foot sections will be flown to and transferred to a ship. Scientists will then converge on Denver’s this summer to process the samples and ship pieces to labs across the country.

In the UW’s , Steig will analyze different types of oxygen molecules in the ice to determine the temperature. This will provide a record of climate changes for that region and help to evaluate the large-scale climate patterns across the Southern Hemisphere.

“The South Pole is one of the very few places in Antarctica that has not warmed up in the past 50 years,” Steig said. “That’s interesting, and needs to be better understood.”

The UC Irvine group will look at ultra-trace gases from air bubbles trapped in the ice. Aydin is interested in gases that are one in a billion to one in a trillion molecules in the atmosphere, but provide clues about the productivity of land-based plants and the extent of tropical wetlands in previous eras.

So far, looking at the core shows that the researchers think is tied to a volcanic eruption in the South Sandwich Islands.

“Otherwise, the core has been beautifully clear,” Fudge said.

Scientists work inside a field tent at about -20 C, the same temperature as the national ice core lab. Extra-curricular highlights of this year’s season included the Christmas Day , and participating in the New Year’s annual .

Partners on the project include the University of New Hampshire and NASA. This season’s field team includes at NASA; at the University of Dartmouth; Mindy Nicewonger, a graduate student at UC Irvine; and members of the U.S. group.

The NASA team includes , a 91̽»¨graduate and affiliate professor in Earth and space sciences. Steig plans to be in the field next season with a 91̽»¨graduate student.

http://vimeo.com/72499614

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For more information, contact Steig at steig@uw.edu and Fudge at 206-543-0162 or tjfudge@uw.edu.

Note: Fudge is at the South Pole until February but has satellite phone connection before 2 p.m. EDT. Steig is on sabbatical in Scotland and is best reached via email.