Julia Rosen explains how to extract ancient air from ice samples in OSU’s Ice Core Laboratory (Photo: Jeff Basinger)

A shard of ice sits on the black surface of the lab desk, buoyed in a growing puddle. Three small heads hover above in a tight huddle. “It’s cold,” notes one of the kids. Somehow, this obvious observation always catches me off guard, as if I’ve forgotten the most fundamental quality of water’s solid phase. “That’s true,” I reply, “it’s also 10,000 years old.”

“Wow!” the students chorus, and their eyes widen as they look again with renewed awe at this innocuous specimen that could have come from an ice-cube tray in their freezer. Whether I am visiting loquacious third-graders or shyly curious middle-schoolers, I am always touched by the unjaded willingness of youth to imagine and attempt to grasp the unseen. It’s the reason every scientist falls in love with science.

I analyze ice cores in the Oregon State University Ice Core Laboratory and no longer think about their cool touch. I have learned that, like people, the most interesting things about them lie hidden inside. And, like people, it takes time and patience to understand them. When we succeed, these frozen time capsules from Greenland and Antarctica allow us to reconstruct climate far into the past so that by understanding its natural rhythms and quirks, we can predict what kind of future awaits these students.

But let’s start with the obvious: a clear, smooth cylinder of ice glittering with tiny bubbles like a flute of frozen champagne. Stunningly boring to behold, only an occasional band of volcanic ash or the subtle cloudy layers formed during dusty polar winters break its translucent monotony. However, this continuity is actually an ice core’s greatest strength. It provides a complete, unbroken record of past climates, one that is unavailable in almost any other natural archive.

As detectives of Earth’s history, geologists reconstruct stories from snapshots of ancient seas and whispers of long-dead creatures, piecing together a hazy story of our planet’s past. Ice cores are the long-lost diaries of climate. Every day, they recorded the temperature, sniffed the air and noted the snowfall. They sensed changes far from their polar homes — the amount of dust lofted from Asia, the gurgle of tropical volcanoes and much more. From the top to the bottom of a core lie flakes that witnessed every moment of geologic time that elapsed in between.

Thin Air

Physicists, chemists and geologists have spent 60 years learning to translate the primordial language of ice. Early pioneers of ice-core science discovered that they could estimate temperature using the chemistry of rain and snow. As the air warms, precipitation gathers more heavy molecules and fewer light molecules (known as isotopes) of water. The ratio of these isotopes thus provides a record of temperature. These scientists had the transformative idea of using old ice to reconstruct climate by exploiting this valuable relationship.

Each new analytical tool that becomes available to scientists provides another Rosetta Stone for decoding long-lost archives of the ice. Today, we can measure trace amounts of chemical impurities deposited on the ice sheets as dust and aerosols. They tell us how sea ice waxed and waned and which way the wind blew. They reveal the fingerprints of individual volcanic eruptions. While only the pristine inner core provides suitably clean ice for these highly sensitive measurements, the “snow dust” from cutting and cleaning the core does not go to waste. It can be used, for example, to reconstruct concentrations of a rare element, beryllium-10. Produced by cosmic rays high in the atmosphere, the abundance of this element reflects shifts in solar radiation.

Lit by an Arctic midnight sun, this iceberg was spawned by one of Greenland’s fastest moving glaciers near Illulissat. About 400 feet high, it covered an area larger than a city block. (Photo: Julia Rosen)

Of all the stories that ice cores tell, however, the bubbles of air embedded within them actually contain the most impressive secrets. As snow accumulated over thousands of years, slowly hardening into solid ice and forming the massive polar ice sheets, it sealed off little breaths of ancient air between the grains of snow — the very same air we would have inhaled if we had stood on top of the ice sheet 8,000 years ago, or 80,000 or 800,000. From those microscopic samples, we can retrace the evolution of our planet’s atmosphere across almost a million years of Earth history, a period that encompasses nearly all of human existence.

Revelations

In Antarctica, where extreme cold and meager snowfall limit the flow of ice, these cores stretch back across eight glacial cycles. During each, the Earth oscillated between periods of cold climate and expansive ice, including a vast glacial blanket that smothered northern North America, and a time of balmy warmth with ice sheets comparable in size to those on Earth today. Wobbles in the planet’s orbit periodically brought it closer to and farther from the sun’s furnace, setting the rhythm of the climatic metronome.

Across these dramatic changes, carbon dioxide and other greenhouse gases rose and fell with the global temperature as the Earth’s oceans and biosphere adjusted to a changing environment. These gases both responded to climate change and amplified it through their potent ability to trap the Earth’s outgoing energy. But never in the past 800,000 years did these gases reach concentrations even remotely approaching current levels, and never did they rise so quickly, or shoot up at the end of an interglacial period when the receding sun should have lulled the Earth back into an icy slumber.

At the other pole, ice cores in Greenland felt those same changes, although the records of climate before 120,000 years ago crept away through the unstoppable march of glaciers to the sea. Nonetheless, these cores tell us something else completely new. Throughout the last cold period on Earth, which our ancestors waited out in the mild climates of Africa, the Northern Hemisphere experienced a barrage of climate changes so swift and so huge that certain places on Earth warmed by 20 degrees Fahrenheit in a matter of decades. The cause of these dramatic jolts remains a mystery, but their power to radically reorganize the Earth system attests to the inherent volatility of the world in which modern civilization has only recently made a home.

We are slowly beginning to understand the anatomy of global climate and how it changes, its geographic fingerprint and its tempo. Ice cores paint a complex and sometimes surprising picture, one that generations of scientists will spend decades trying to fully understand. We now know the correct greenhouse gas concentrations to feed into our calculations as we simulate past climates in order to validate models for the future.

Ice cores have made one thing abundantly clear: Humans are in uncharted territory. In 800 millennia of records, no entries document a climate like the one we live in today. Even as you read this, we are busy writing the next page of the ice-core diaries.

Illustration by Hank Osuna

Time to Listen

These observations from opposite poles forewarn a perilous future for our planet. We know without question that we’ve entered a period in geologic history for which there is no natural analog, and we know that the Earth’s climate can respond dramatically to perhaps even the smallest nudge.

However, the most terrifying lesson I learned from ice cores did not come from drilling into the past, but from just standing on the surface. At 80 degrees North, well above the Arctic Circle in the empty white wilds of the Greenland ice sheet, I watched a supply plane on skis repeatedly try to lift off. First the crew dumped cargo and then off-loaded all their fuel except what they needed to get home. Finally, on their seventh attempt, they succeeded.

The problem? The snow had warmed to the freezing point, and microscopic drops of water on the surface made the friction between the skis and the ice too great to break. Last summer, 97 percent of the surface of Greenland experienced temperatures above freezing, more than any year in NASA’s 30 years of satellite observations.

The ice cores have told us all they know, and now it’s up to us to listen.

Editor’s note: Julia Rosen is working toward her Ph.D. in the Oregon State University Ice Core Laboratory under the guidance of Ed Brook, professor in the College of Earth, Ocean, and Atmospheric Sciences and a Fellow of the American Association for the Advancement of Science. Support for the lab has come from the National Science Foundation’s Office of Polar Programs.

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For more information:

Analysis of Greenland Ice Cores Adds to Historical Record and May Provide Glimpse into Climate’s Future (Jan. 24, 2013)

Antarctic Ice Core Contains Unrivaled Detail of Past Climate, (Feb. 5, 2013)

Inside the Hinkle Creek Project

Hinkle Creek researchers are measuring water flows, trapping insects, tracking fish and monitoring amphibians.

Read more…

To the list of problems for watershed research, add dam-building beavers. Last fall, in the rippling waters of Flynn Creek near the Coast Range town of Toledo, Oregon, scientists had placed a probe to take continuous measurements of dissolved oxygen. When the instrument shut down abruptly, hydrologist George Ice went to check. “I saw that the cord was cut,” he says. “A beaver had gnawed it off and stuffed the probe into its dam.” The amused vendor, the Hach Company, provided a free replacement.

Ice and other researchers are updating a pivotal forest science project in Flynn Creek and the surrounding Alsea River watershed. Here, from 1959 to 1973, scientists conducted the first comprehensive forest watershed study in North America. “That was a very important, seminal piece of work,” says Arne Skaugset, Oregon State University hydrologist and director of the Watersheds Research Cooperative. “It set the standard for stream temperature research. It was one of the few watershed studies that had a robust fisheries component.”

The results provided the scientific basis for forest management regulations and contributed to the Oregon Forest Practices Act

In the 1960s, studies of Alsea River watershed logging led to the nation’s first water-quality regulations on forest management. (photo courtesy of the Oregon Forest Resources Institute)

of 1971, the first in the nation to address water quality protection. Back then, harvesting activities weren’t particularly kind to aquatic systems. Fish-bearing streams were literally buried in wood debris, says Ice. Logs might be dragged across or even down channels without regard for the bed and banks. Loggers sometimes removed and burned debris because of concerns that it would impede fish movement. Without riparian vegetation to hold soil and shade streams, sedimentation and water temperatures increased.

But the Alsea study, which documented the consequences of those operations, has become outdated by the modern practices — riparian buffers, better road-building techniques, debris treatment — that it helped to set in motion. “We really need to evaluate how today’s forest practices are working,” says Skaugset. “We have results from these original studies, but the old data are not terribly relevant for what’s going on right now.”

To update the scientific basis for forest management practices, teams of scientists from OSU, federal and state agencies have joined forest landowners in a three-pronged initiative. In the watersheds of the Alsea River, Trask River (east of Tillamook) and Hinkle Creek (east of Sutherlin in the Cascades), they are installing monitoring equipment and collecting water-quality data. They are measuring water flows, sediment concentrations and changes in water chemistry and stream temperature. In headwater streams and below tributary junctions, they are evaluating aquatic food webs by studying organisms from the smallest midges and stoneflies to the steelhead, salmon and cutthroat trout that have run in these waters for eons.

At Hinkle Creek, scientists and landowners are evaluating the impact of contemporary logging practices on water quality. (Photo courtesy of the Watersheds Research Cooperative)

These aren’t majestic, old-growth tracts. They are the kind of working industrial forests that comprise just under half of Western Oregon’s forestlands. For scientists and land managers, the questions are about more than the complexity of forest ecosystems. They’re also about balancing environmental quality with economic value, the health of fish populations with tree harvesting, the quality of water downstream with the need to build roads in steep terrain.

“We’re always developing new management tools,” says Ice, who received his Ph.D. at OSU in 1978 and works for an industry-supported environmental science organization, the National Council for Air and Stream Improvement. “Now we’re looking at more subtle questions: Where and how wide should those buffers be? What types of road systems should we install? Can we enhance streams by opening portions of the stream (to sunlight) or putting wood in those channels to increase productivity?”

Reliable answers to such questions will take time. In the Trask River Watershed, studies began in 2006, and harvesting won’t occur until 2012. In the Alsea watershed, monitoring has been conducted off and on since 1959, and no harvesting is projected until 2009 or 2010. However, at Hinkle Creek, the first answers are starting to trickle in. Three master’s students have completed their theses on summertime stream temperatures, cutthroat trout survival and down-stream propagation of temperature effects. Scientists have accumulated five years of data at nearly 50 locations. In the winter of 2005-06, the landowner, Roseburg Forest Products, cut the first trees, and researchers are beginning to analyze stream ecosystem changes.

“We’re passionate about science-based forestry,” says Phil Adams, timberlands manager for the company. “We understand the need for regulation to protect water and fish resources in Oregon through our Forest Practices Act. As we go forward, it needs to continue being efficient and based in science.”

The 4,534-acre Hinkle Creek watershed was last harvested in the 1940s. A continuing round of cuts is planned for the South Fork, but Roseburg Forest Products has agreed not to harvest trees on the North Fork until 2011, thus leaving it as an undisturbed control.

The experimental design is known as paired watersheds. During the pre-harvest phase, researchers confirmed that the two watersheds can be used as predictors of each other. To date, researchers have installed nearly a quarter-million dollars’ worth of equipment.

In the winter of 2005-06, the company harvested 380 acres in five units in the South Fork, enough to deliver 3,281 truckloads of logs to local mills. Harvest blocks were located in non-fish-bearing headwaters, where regulations do not require riparian buffers. Next winter, harvesting operations are scheduled for land along downstream fish-bearing reaches.

Batteries Not Included

When Kelly Kibler was looking for graduate schools, the Pacific Northwest caught her fancy. Within days of arriving in Corvallis in June 2005, the dreadlock-wearing forest engineering master’s student from North Carolina hustled down I-5 to Sutherlin to join Skaugset’s hydrology crew at Hinkle Creek. Mornings began with loading sample bottles, fluorescent dye, batteries and other gear into a pickup. Once past a yellow gate a half-hour outside of town, the crew left the pavement on Roseburg Forest Products’ gravel logging roads.

Kibler threw herself into the project, serving as a crew member and focusing her own thesis on water temperature impacts from logging. “It was exactly the kind of work I wanted to do. Multi-disciplinary across the sciences, physical and ecological, policy and management. Pretty applied. Just the ticket,” she says.

Working with Skaugset, Amy Simmons (faculty research assistant), Tim Otis (master’s student in forest engineering) and Nick Zegre (Ph.D. candidate, forest hydrology), Kibler helped to maintain computerized water-sampling devices and data recorders that monitor water temperature. She ran tests on water samples containing fluorescent dyes to determine how much groundwater was entering streams. She carried 40-pound marine batteries sometimes as far as a half-mile from the road to keep equipment operating. She reached under slash, logging debris left over headwater streams, to take measurements of light reaching the water.

For her master’s thesis, Kibler analyzed stream temperature profiles in six streams, four located just below clearcuts in the South Fork and two in the unharvested North Fork. She controlled for changes in weather and other conditions and compared data from pre- and post-harvest periods. Her findings were mixed and unexpected. In the South Fork, daily maximum temperatures dropped in one stream, rose in another and remained unchanged in two. However, mean temperatures decreased in all four, possibly reflecting the influence of slash cover and increased groundwater flow into the streams. Branches left by logging operations cast shade over the streams roughly equivalent, she found, to the original tree canopy cover. “Without that slash, all four streams might have been significantly warmer after harvest,” says Kibler.

Moving Targets

In addition to being a research lab, Hinkle Creek provides an educational setting for more than 600 Roseburg fifth-graders who visit the watershed every year, says consulting forester Javier Goirigolzarri. High school students and the Oregon Board of Forestry have also toured the research sites.

“The Watersheds Research Cooperative is probably the leading effort (in the United States) to look at the effectiveness of contemporary practices,” says Ice. The future of forest policy is at stake. Results from the Hinkle Creek, Alsea and Trask projects may guide regulation as attention is focused more on watersheds than on single pollutants, more on how watersheds respond to disturbance than to whether pollutants such as sediment and organic materials exceed a threshold level.

“Sediment, temperature, dissolved oxygen and nutrients are highly variable in time,” says Skaugset. “You can go out to a highly degraded watershed and collect a water sample at the right place and time, and it would look great. If you go out into the middle of the Santiam Wilderness Area during the middle of a large winter storm, there will be muddy water. So you have to capture that variability if you want to look for changes due to timber harvesting.”

“It’s a very tough problem,” he concludes. “All three of these studies and other studies in the Pacific Northwest are right on the forefront.”

Falkner is no stranger to such risks. Over the last ten years, she has helped to establish Arctic monitoring stations and flown to remote areas to collect water samples. As a professor in the College of Ocean and Atmospheric Sciences, she traces the origins and changing circulation of Arctic waters by analyzing water chemistry.

“Ten percent of the world’s river water drains into the Arctic, which represents just one percent of the world’s ocean volumes,” Falkner says. “The water flowing out of the Arctic can have impacts on ocean circulation, and thus climate, throughout the world.”

“During our 2003 cruise to Nares Strait (between Greenland and Ellesmere Island), we were able to get our ship further into the Petermann Gletscher Fjord than any ship has ever gone before. This is because the floating tongues of the continental ice sheet are retreating all around Greenland more than they ever have in recorded human history.”

Since 1978, when satellite measurements of Arctic ice first became available, the overall ice cap has shrunk more than eight percent each decade.