FOLLOWING THE BREADCRUMBS: GLACIERS DROPPING BOULDERS CLUE US INTO CLIMATE CHANGES

FOLLOWING THE BREADCRUMBS: GLACIERS DROPPING BOULDERS CLUE US INTO CLIMATE CHANGES

By Kelly Calagna –

Aaron Putnam of the Climate Change Institute at the University of Maine is searching for clues to climate change at altitutdes of 15,000 feet in China this summer. What caused the Earth to lurch out of the last Ice Age and how does knowing that help predict the impact of human activities pushing at Earth’s climate now? Climate levers are not yet well understood, and what causes them is still a mystery Putnam is continuing to unravel.To weave together the clues, Putnam is finding data on the Tibetan Plateau. He was awarded an Early Career Award by the National Science Foundation to pursue this work. Medill Comer Foundation Scholar Kelly Calagna is embedded with Putnam and the research team for the length of the field season and is blogging about the experience.

A glacial valley on the Tibetan Plateau; this summer’s field site for a team of paleoclimate geologists from the University of Maine. (Kelly Calagna/Medill)

TIBETAN PLATUEAU, CHINA, AUG. 6,Throughout our planet’s existence, Earth has experienced periods of warming and cooling, with glaciers expanding and receding according to this natural variation in the climate system. However, our current climate flux accelerated by human use of fossil fuels is not so typical, and glacially deposited boulders can prove it.

“The landscape’s morphology tells a story,” said Aaron Putnam, paleoclimatology professor at the University of Maine’s Climate Change Institute. And the story it tells is the history of our planet’s climate.

Moraines, or hills formed at the points of a glacier’s maximum reach, are the footprints left behind by glaciers of past ice ages, acting as visual timelines for a glacier’s history through periods of climate changes. Boulders perched on moraines were deposited there by glaciers at an equilibrium, neither expanding nor shrinking during periods of stable climate. Boulders scattered up the valley were tossed there as the climate warmed and the melting glacier retreated up mountain.

By comparing the deposit dates and locations of these glacially abandoned boulders, scientists are able to calculate the rate of recessions of the glacier – the rate of past global warmings.

How do scientists calculate such a date as when a glacier dropped a boulder?

Beryllium 10.

A researcher clears dust out of holes that were drilled into a boulder as part of the sample removal process. (Kelly Calagna/Medil)

Beryllium 10 is a unique isotope that is collected in the surface of the boulders as they are exposed to cosmic rays in our atmosphere. “It starts building and building over the years as an archive—it acts as a cosmic clock,” said Putnam.

The boulders the scientists sample originated high up in the mountains as rock debris ripped off the mountainside by compacting snow at the top of the glacier. The force of ice sent the rock on a grinding journey down the mountain: shaving it down, rounding its edges and polishing the surface.

After years in frozen darkness, the boulders reemerged from their icy prison, fresh-faced and, theoretically, with any beryllium 10 deposits from its past life on a mountainside eliminated.

Their reemergence starts a new exposure to cosmic rays, and the beryllium 10 begins collecting like tick marks in the progression of time. “That boulder is capturing the moment that the glacier left it there,” said Putnam.

At Putnam’s field site high up on the Tibetan Plateau, the boulders retain roughly 70 atoms of beryllium 10 in every gram of quartz per year—the lower density atmosphere at the high elevation allows for more cosmogenic rays to interact with the boulder than at lower altitudes—and the scientists can use this information to measure for an absolute deposit date for each boulder sample.

By looking into our planet’s climate history, we gain a better understanding on where we stand today with our warming planet. “We can look at the past and piece together the puzzle of how the climate system works,” said Putnam, “And then from that, be able to predict how perturbing it with greenhouse gasses the way that we are may influence change.”

HOW DRONES ARE ADVANCING CLIMATE SCIENCE

University of Maine graduate student Mariah Radue pilots a drone as it maps a geological field site that can give us clues to climate change. (Kelly Calagna/Medill)

Drones have proven themselves to be multidimensional little devices: from shooting HD video for the film industry, to potentially becoming Amazon’s future means of merchandise delivery. But beyond videographers and curriers, these little robots can also be scientists.

A geological research group from the University of Maine’s Climate Change Institute has adopted drones as part of the team, using the devices to map their field sites—this summer on the Tibetan Plateau.

“I find it a game changer,” said Mariah Radue, a graduate student at the University of Maine who is piloting the DJI Phantom IV drone this field season in China, “It helps in that I can revisit the field area really well.”

The team of paleogeologists uses the drone to collect images of glacial landscapes through series of pre-planned flight routes, which they can later synthesize into highly detailed maps and gain insights into the area’s past changes in climate.

“Our two main goals are to create aerial photographs, which are really detailed—we can see our boulders on them—and then the second goal is to create digital elevation models, which are basically topographic maps,” said Radue.

At 13 cm per pixel, the maps developed by the drone footage are at far higher resolution than available satellite data. The images are so detailed that “we will be able to see the height of our tents,” said Radue.

These images help the scientists relate the morphology of the landscape to the boulders they are sampling, allowing for better understanding of the boulder’s history. Boulders set upon moraines, or hills formed by the points of a glacier’s maximum ice extent, suggest that they were deposited there during a time of climate stability, where the glacier was at equilibrium, neither growing or shrinking. Boulders in more sporadic locations suggest a time of global warming when they were dumped on the landscape as the glacier was melting and receding up the valley. By comparing the dates of the different glacially deposited boulders, the scientists can better understand our planet’s climate history, as well as project how human influence will affect it in the future.

“One of the most important things that we do in this type of work is mapping the perimeter of the former ice age glacier,” said Aaron Putnam, professor of paleoclimatology at the University of Maine and principal researcher of the project. “It’s the geometry of those paleo glaciers that can help us reconstruct past climate,” said Putnam, “The droning has opened up a whole new world for us.”

Research assistant and Comer College Prep High School student Maya Sheriff catches the Phantom IV drone as it returns from mapping a glacial valley near Litang, China. (Kelly Calagna/Medill)

SCIENCE AT 15,000 FEET

Scientists extract a sample from a boulder on a glacial moraine near Litang, China, to determine when the glaciers retreated. (L to R) Paleoclimatology Professor Aaron Putnam, graduate student Peter Strand and undergraduate student Ben Lindsay of the University of Maine, and Xianghui Kong and Guocheng Dong, post-doctorate students with the Chinese Academy of Sciences Institute of Earth Environment. (Kelly Calagna/Medill)

LITANG, CHINA JULY 17, 2017.  Less than 2 percent of the world’s population lives above 8,200 feet, and we are almost doubling that baseline elevation, for climate research in China this summer.

This field season, scientists from the University of Maine in a collaboration with the Institute of Earth Environment of the Chinese Academy of Sciences, have set their sights high on geological field sites on the Tibetan plateau to gain insight into our planet’s climate history. I am along for the ride to document this important research.

Fieldwork can be grueling—long days, heavy packs, inclement weather—and at this elevation, the lack of oxygen can be stifling.

We passed the subalpine zone days ago on our ascent from Kangding to Litang; It was a sudden rise out of the tree line as we wound up the valley road, the air too thin for the tall Chinese pines.

At over 13,000 feet, the air pressure in Litang is 39 percent less than it is at sea level, meaning less oxygen available to saturate the body’s hemoglobin, which carries oxygen from our lungs to our body’s tissues.

This interruption of homeostasis causes the body to find ways to compensate but it can take days, or even weeks, for people to acclimate. The heart rate increases, as does respiration, while hunger can seemingly disappear as your body puts digestion on a backburner as it deals with the cellular challenge it is facing. If the body cannot adapt, it can be fatal.

“I’m actually doing better than I expected,” said Jessica Stevens, an environmental science teacher from Gary Comer College Prep High School in Chicago, who is assisting in the field. “I have to stop every so often and [blows] shove out all the carbon dioxide. The problem I’m having more is the side effect of our altitude medication,” said Stevens.

Stevens, as well as many others in the group, have reported a tingling sensation in their limbs, and even their faces, as a result of taking Acetazolamide. Acetazolamide, more commonly known as Diamox, is a medication that helps the body acclimate and can ward off acute mountain sickness, or AMS.

What makes this science worth the journey above the clouds?

“Well, it’s of great scientific interest. It’s a site that captures a remarkable period in Earth’s history that’s trying to tell us about how the climate system works,” said climate scientist Aaron Putnam, principal researcher from the University of Maine and the research team leader.

The Tibetan Plateau is in a unique location, receiving energy in the air masses that come off of the Indo-Pacific region—the warmest waters on Earth. Putnam calls the planet’s “heat engine.”

“The reason we came here is because it is one of the closest places you can get to that warm pool and also find glaciers and spectacular records in the landscape.” The morphology of the valleys act as a visual timeline, indicating the progression and recession of glaciers through the ice ages by leaving behind carved out ridges, called moraines.

While the research team has acclimated well this past week in Litang, tomorrow we all face a new challenge. We are continuing our assent northeast of Batang, to an elevation of over 15,000 feet—nearly reaching the same altitude as the Mount Everest base camp. At that elevation, oxygen is at half the concentration as it is at sea level.

“We have several plans in order in case someone becomes ill from the altitude, but I think everyone is adjusting well,” said Putnam, “I spent a semester in Iceland when I was in college and they had a saying: ‘There is no such thing as bad weather, only being poorly prepared,’” he said. “For the most part, if you come prepared, you can enjoy yourself, and do good science. Even with the wide range of conditions we can experience out here.”

Onwards and upwards.

PHOTO AT TOP: University of Maine paleoclimatology Professor Aaron Putnam extracts a sample from a glacially deposited boulder on the Tibetan Plateau to find clues to climate change. (Kelly Calagna/Medill)


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