A Trek to the Giant Mongolian Glacier That Holds the Secrets to Global Warming

October 17th, 2016  |  Source: PS Magazine

Deep in the Altai mountains, American scholars are using drones to study glacier-formed ridges that could unlock the mysteries of abrupt climate change.

Thousands of years ago, near what is now the shared border of Mongolia, China, and Russia, water sat frozen in mountain glaciers that extended for miles. At the end of the Ice Age, with temperatures rising rapidly, the ice began to melt, and water poured across the landscape, carving out wide valleys. Granite silt and ice ground into the Earth, polishing smooth the sandstone bedrock.

As the ice receded, gray till, sediment, and boulders remained in the form of moraine ridges that describe where the glaciers once sat. Over millennia, these jagged landforms slowly weathered. Plants began to grow, and the grass fed newly arrived animals — yak, goats, and sheep, herded there by people who, like the vanished glaciers, have left signs of their own. Bands of early Turkic, Eurasian, and Mongol people came and left, nomadic groups who left burial mounds, memorials, and petroglyphs.

And now, in 2016, a different group is trudging up this valley wearing colorful jackets and carrying the latest technology. Up-valley, a team of men on horseback walk along a thin trail leading camels, carrying supplies for a month-long science expedition — drills, GPS units, and a carcass of a freshly slaughtered sheep. Aaron Putnam is an hour behind them, hiking with a team of students, research assistants, and local guides. He’s a glacial geologist from the University of Maine, and he and his team are here to collect the surface layer of granite boulders implanted in those moraines that formed at the margins of the glacier. I’m with them as an embedded reporter.

“This is the nexus of climate, humans, and geology, and it is all happening right here.”

The team hopes that data derived from the rock can tell them when the ice melted. “This was the singular most powerful, most important climate event in human history. It allowed us to flourish,” Putnam says. “But we don’t know why that happened.” Putnam is trying to determine what caused the Ice Age’s demise; the answer could help us identify the triggers that cause abrupt climate change.

The remaining ice is the Potanin Glacier, the country’s largest today. Putnam studies glaciers for what they can tell us about climate change of the past, but also for what they say about current warming. What caused the melting of ice sheets and alpine glaciers roughly 20,000 years ago is one of earth science’s most enduring questions, and Putnam is developing a chronology of glacial retreat at the end of the Ice Age. He believes information extracted here holds the key to unlocking this mystery. Solving this problem could reduce uncertainty in predictive models that forecast the impact of anthropogenic climate change and vastly improve our ability to adapt to future warming.

Here in the deep interior of Asia, the grassland steppe gives way to shrubby desert and, now and then, timberline. The moraines are perfectly preserved. There is no forest to obscure them from view. For a researcher interested in geomorphology, it’s a total playground — and one that has been minimally studied. Samples from the glacial moraines here approximate a record of summer temperatures spanning thousands of years — new information that scientists have never had before.

What caused the end of the Ice Age? For a time, researchers thought that CO2 may have been the trigger, but Putnam doesn’t think so. Neither does Michael Kaplan, a researcher at Columbia University who is also working on this problem. At least, they don’t think CO2 was the singular trigger. “We don’t think CO2 could be the initial smoking gun because some retreat happens before CO2 increases significantly,” Kaplan says. Researchers have a unified record of warming across the Southern Hemisphere, but, Kaplan says, “the outstanding question is to know what happened in the Northern Hemisphere” — precisely what Putnam hopes to learn from his work in Mongolia.

And it is with no small effort that he arrived here at all. More than five years ago, Putnam was scrutinizing pixilated satellite images to see if the place was right, unsure even if it would be politically feasible to collect samples. He worried that an American researcher would be denied the necessary permits to collect samples in a national park so near China and Russia. But local officials agreed to grant access, and 2016 marks his third consecutive field season.

As Putnam hikes past the margin of the modern glacier, a thick stream of milky water flows out of a field of gray rock. From this vantage, the moraine ridges expand outward, each one representing a moment in the past, carved into the landscape: a time when the climate was cooler and the ice expanded. The base camp is at an elevation higher than 10,100 feet. Over the coming days, we will walk the entire length of each moraine ridge, the team collecting dozens of rock samples.

“This is the nexus of climate, humans, and geology, and it is all happening right here,” Putnam says.

The expedition to the border of Mongolia in the Altai Mountains is a five-day drive across steppe lands — an expanse of semi-arid grassland — and begins on a single-lane, paved thoroughfare out of the capital city of Ulan Bator. Soon the road splits into sandy tracks, crisscrossing like the branches of a tree. Cars pass through the outer rings of the city along streets lined with brightly colored roofs — blues and reds. In the countryside, people live ingers, traditional homes insulated by felt and supported by wood.

We fill three SUVs outfitted with black snorkels for river crossings; a Russian gear van follows behind. At the glacier, our campsite is next to a towering moraine. On the first field day, Peter Strand and I cross a meltwater stream by stepping from rock to rock. He is Putnam’s Ph.D. student and is leading the field work. Wet sediment is the glacial equivalent of quicksand, and, after a few moments, I step in the muck, burying my foot.

“To understand climate dynamics, we need to understand why ice ages occur and why they end.”

Strand is looking for boulders embedded on the top of the moraine that show evidence of time spent in the glacier. “The ice acts like sandpaper,” Strand explains. Once he has identified a hard granite boulder — brushing it with his fingers to find a polished surface and identifying the spot with permanent marker — he takes a drill out of his pack.

When you’re working at 10,000 feet, you start to notice just how thin the air is. A few people are dizzy. Strand drills several holes, each about the width of a dime, into a granite boulder. Then he places wedges and shims in the holes. After several cracks with a hammer, the pressure of the wedges dislodges a hunk of rock the size of a plate.

The next step is for Mariah Radue, Putnam’s newest graduate student at the University of Maine, to measure the rock’s dimensions, collect GPS coordinates, and use a compass and clinometer to map the heights of surrounding mountains. They repeat this process on every sample, recording every detail in yellow field notebooks, of which Strand photographs each page.

The fieldwork is part of a technique called beryllium-10 surface-exposure dating. These granite boulders were once suspended in the ice, having been dislodged from the mountain peaks by the glacier’s formation. The ice melted and deposited the rock on the ridge. At that moment, the granite was exposed to a flux of secondary particles created when cosmic rays from outer space collided with Earth’s atmosphere.

The particles bombard the rock and affect oxygen and silicon in quartz, creating a cosmogenic byproduct, an isotope called beryllium-10. These atoms accumulate in the rock surface and can be measured to determine how long ago the boulder was freed from the ice and dropped on the land. The Altai samples will be sent back to Maine, where they will undergo chemical processing. Once dated, these samples can reconstruct glacier movement, and the researchers can then draw inferences about how Mongolia’s glaciers changed over thousands of years. “To understand climate dynamics, we need to understand why ice ages occur and why they end,” Putnam tells me.

The expedition to the border of Mongolia in the Altai Mountains is a five-day drive across steppe lands — an expanse of semi-arid grassland — and begins on a single-lane, paved thoroughfare out of the capital city of Ulan Bator. Soon the road splits into sandy tracks, crisscrossing like the branches of a tree. Cars pass through the outer rings of the city along streets lined with brightly colored roofs — blues and reds. In the countryside, people live ingers, traditional homes insulated by felt and supported by wood.

We fill three SUVs outfitted with black snorkels for river crossings; a Russian gear van follows behind. At the glacier, our campsite is next to a towering moraine. On the first field day, Peter Strand and I cross a meltwater stream by stepping from rock to rock. He is Putnam’s Ph.D. student and is leading the field work. Wet sediment is the glacial equivalent of quicksand, and, after a few moments, I step in the muck, burying my foot.

“To understand climate dynamics, we need to understand why ice ages occur and why they end.”

Strand is looking for boulders embedded on the top of the moraine that show evidence of time spent in the glacier. “The ice acts like sandpaper,” Strand explains. Once he has identified a hard granite boulder — brushing it with his fingers to find a polished surface and identifying the spot with permanent marker — he takes a drill out of his pack.

When you’re working at 10,000 feet, you start to notice just how thin the air is. A few people are dizzy. Strand drills several holes, each about the width of a dime, into a granite boulder. Then he places wedges and shims in the holes. After several cracks with a hammer, the pressure of the wedges dislodges a hunk of rock the size of a plate.

The next step is for Mariah Radue, Putnam’s newest graduate student at the University of Maine, to measure the rock’s dimensions, collect GPS coordinates, and use a compass and clinometer to map the heights of surrounding mountains. They repeat this process on every sample, recording every detail in yellow field notebooks, of which Strand photographs each page.

The fieldwork is part of a technique called beryllium-10 surface-exposure dating. These granite boulders were once suspended in the ice, having been dislodged from the mountain peaks by the glacier’s formation. The ice melted and deposited the rock on the ridge. At that moment, the granite was exposed to a flux of secondary particles created when cosmic rays from outer space collided with Earth’s atmosphere.

The particles bombard the rock and affect oxygen and silicon in quartz, creating a cosmogenic byproduct, an isotope called beryllium-10. These atoms accumulate in the rock surface and can be measured to determine how long ago the boulder was freed from the ice and dropped on the land. The Altai samples will be sent back to Maine, where they will undergo chemical processing. Once dated, these samples can reconstruct glacier movement, and the researchers can then draw inferences about how Mongolia’s glaciers changed over thousands of years. “To understand climate dynamics, we need to understand why ice ages occur and why they end,” Putnam tells me.

Read on here: https://psmag.com/trekking-potanin-glacier-mongolia-mystery-climate-change-5240b435f007#.y8mfz2xd9




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