What do Antarctic climate scientists and Nordic Vikings have in common?
More than you’d think.
After being cast out of Iceland for murdering his neighbor, Erik the Red, the notorious Viking who walked the Earth around 985 A.D., braved the unforgiving seas in search of a new home. That’s according to Christopher Klein’s History article “The Viking Explorer Who Beat Columbus to America.” Wrapped in layers of pelts, tools in hand, the Viking dropped anchor on new land. Gradually, he took control, founding the first European settlement in what is today Greenland.
An alpine forest turns into a desert within a mere 16,000 years – the geologic equivalent of a blink of an eye. The transformation is just one climate mystery waiting to be solved.
Wondering what drives local rainfall? Curious about tipping points for the entire global weather system? To find answers, you’ll have to go through the “lake mafia,” a disparate collection of scientists who study closed lake basins.
They admit they don’t have definitive explanations. But with the clues they collectively gather and assess, they’re are coming ever closer.
That’s why such a “mafia” even exists, or was jocularly referenced by Douglas Boyle, a climatologist at the University of Nevada, Reno, who identified his colleagues with that specific moniker during a presentation at the 2018 Comer Climate Conference this fall on climate in the Mono Lake basin.
The mafia members gathered at the annual conference to present their latest research findings. Yonaton Goldsmith, a geochemistry postdoc at the California Institute of Technology, studies lakes in China. Geochemist Sidney Hemming and her sixth-year Ph.D. student Guleed Ali with Columbia University’s Lamont-Doherty Earth Observatory, pursue fieldwork at Mono Lake in California. Adam Hudson, a geologist with the U.S. Geological Survey, studies the now nearly empty basin of ancient Lake Chewaucan in Oregon.
Lakes that don’t have an outlet are called closed basin lakes. These provide vital clues to understanding and developing theories of climate, Goldsmith said. “There are abrupt events where lakes rose rapidly and we would like to know the relationship of these events to climate changes,” Goldsmith says. “Why does this happen? How does it happen? This is still an enigma but we do really see these rapid changes in lake size and ultimately rainfall.” The big picture goal, Goldsmith says, is understanding the mechanisms of climate and how rainfall water availability respond to climate changes.
In the United States, the Great Basin watershed, an arid area that extends from California to Utah, is a hotbed of study for paleoclimatology – the study of climate past stretching back hundreds of thousands and even millions of years. These scientists are telling the story of how lake changes that occurred naturally inform our most pressing concerns about the pace and magnitude of climate change as human use of fossil fuels are pushing it now. But the history of these lake scientists, their relationships to each other, and their work tells a story as well about how science is conducted and how powerful hypotheses are developed over time.
“The lake scientists at this conference come from different institutions and we work in different places around the globe,” Goldsmith says. “Before this conference we weren’t really connected, it wasn’t an organic connection … and I think that for us this whole becoming a gang has happened here [at the Comer Conference]. Oh, we’re all doing the same thing! We’re all working on really similar questions! We should be talking to each other.”
Columbia University geochemist Wallace Broecker is the common thread among these lake researchers. They are his former students, students of his former students, or of past and present colleagues. His decades of research span oceanography and climate science. He is credited with discovering the global circulatory system of the Earth’s ocean and was a pioneer in radiocarbon dating. Broecker began investigating the geology of Pyramid Lake in Nevada over 60 years ago, when he was pulled aside by Phil Orr, a pipe-smoking scientist in cowboy boots who told him, “Look kid, I can tell you know a lot about math and science. But you don’t know a goldarn thing about the Earth. You come with me for three weeks and I’ll change your life.”
Pyramid Lake is where Broecker collected his first sample of lake limestone, towers of rock called tufas that jut out from the shoreline. “It was a tufa from the highest shore line of [ancient] Lake Lahontan,” Broecker explains. “So I got interested in those lakes. And dated quite a few samples and then had students that worked on it, and then more recently these other people appeared who, you know, are eager to work on it, so they created the ‘mafia’ … they were following in my footsteps in a way.”
Broecker’s work analyzing tufas and recording the history of Pyramid Lake and others as they expanded or receded helped develop current theories of how temperature, rainfall and evaporation are connected, and how quickly they respond to changes. If lakes can dry up in a matter of centuries, than our current pace of global warming can have a profound impact on local climates, threatening future water availability.
“Most precipitation that comes to the Great Basin falls as snow in the winter,” Hudson explains. “And it comes from the Pacific Ocean, and where it comes into the coast and how often it gets there is controlled by a variety of things.”
At the Comer Conference, the mafia presented new research on lake regions. Ali demonstrated Mono Lake’s historic fluctuations with new research. Hudson used ancient fossilized fish remains to map a more precise history of Lake Chewaucan’s past volume. And Goldsmith linked lakes in East Asia to water availability. “With geology, what’s going on today informs how we think about what see from the past record,” Hemming says. “I feel like I’ve done a second Ph.D. working on Mono Basin.”
Another equally important reason that scientists are drawn to these lakes and to the flowing ice of glaciers is because of their intrinsic and captivating beauty. Hudson Tufas in Mono Lakedescribes a section of mountain, a fault between two lava flows in Southeast Oregon, as “the walls of Mordor”; Hemming has been coming to Lake Mono for years.
“It’s really the only lake I ever studied,” Hemming says. “Every day is a discovery it is so beautiful and enigmatic and I’ve never not spent a single day that I went out in the field that I didn’t come back thinking: I really learned or discovered something that I hadn’t known before. It’s just that … field work in general just brings that level of discovery to your life. It’s way better than the lab.”
Photo at top: Geo-chemist Yonaton Goldsmith digs through lake sediments in Mongolia. (Courtesy of Yonaton Goldsmith/Caltech)
By Austin Keating,Video by Tiffany Chen and Austin Keating, Nov. 22, 2017 –
Scientists take to the field to study rapid warming and cooling events in Earth’s past. They find clues in ice and rock, lakes and sediment across the globe. Rebuilding climate change patterns from the past enhances predictions for the future as human use of fossil fuels accelerates global warming.
Leading geologists and climate researchers shared their latest discoveries and new developments at the Comer Abrupt Climate Change Conference in southwestern Wisconsin this fall.
The Comer Family Foundation has supported climate science researchers for 15 years now. This year, scientists presented a wide array of new discoveries, such as looking at how heavy rainfall in California over the past year and years of drought prior to that are depleting snowpack that streams water into the region.
Researchers also presented new data on glacial melt in Greenland, as well as melt in the Bhutan region of the Himalayas, where the lower-elevation faces of glaciers are thinning as much as 10 feet per year, according to research presented at the conference by Joerg Schaefer of Columbia University’s Lamont-Doherty Earth Observatory. Sea level rise as Greeenland glaciers melt and strained freshwater resources for several countries due to thinning Himilayan glaciers pose major concerns.
PHOTO AT TOP: A visualization of aerosols in the atmosphere above China recorded by satellites in 2006. Human-sourced aerosols and other greenhouse gases coming from China are rising, and scientists at the Comer Conference advocated for policy action to curb the trend (Courtesy of NASA).
NOTE: Tiffany Chen and Austin Keating are Comer Scholars, a Medill scholarship program supported by the Comer Family Foundation to promote graduate studies in Science and Environmental Journalism.
Climate change is an urgent threat linked to floods, drought and increasing heat waves. While carbon dioxide emissions continue to rise, President Donald Trump pulled the United States out of the Paris Climate Accord meant to cap emissions and the temperature rise due to them. Scientists gathered at the Comer Climate Change Conference in southwestern Wisconsin this fall to share their latest research and emphasize the critical need to fight climate change now.
Scientists agree that cutting back carbon dioxide emissions from fossil fuels and the investment in renewable energies might provide a solution. We have many alternative technologies already.
But one country can’t fight climate change on its own, it requires collaborations and communication among nations, scientist, law makers and the public.
PHOTO AT TOP: Climate change scientists gathered at the Comer Abrupt Climate Change Conference this fall to share their latest research and their deep concerns for the future ahead. (Tiffany Chen/MEDILL)
NOTE: Tiffany Chen is a Comer Scholar, a Medill Scholarship program supported by the Comer Family Foundation to promote graduate studies in science and environmental journalism
Methane, a greenhouse gas frozen by the megatons in Earth’s melting ice, holds the potential to dramatically turn up the thermostat for the planet. But new research shows that a bacterial hero from Earth’s soils and seas will keep the thawing gas at bay.
Methane-eating soil microbes will prevent large plumes of methane from reaching the atmosphere as frozen deposits of it begin to thaw due to climate change, according to a paper in Nature recently published by Vasilii Petrenko and Jeffrey Severinghaus of the Scripps Institution of Oceanography at the University of California, San Diego. While Severinghaus doesn’t study microbes directly, he’s able to show their effect on past climates by going to Antarctica and sampling ancient air, he told colleagues during a presentation at the Comer Abrupt Climate Change Conference in southwestern Wisconsin this fall.
Scientists previously thought thawing methane deposits may have caused an abrupt 50 percent rise in atmospheric methane concentration during a rapid warming period at the end of the Younger Dryas, a cold period that ended 11,600 years ago. The prospect raised alarms for a potentially devastating climate feedback from methane, which molecule for molecule, traps at least 25-times more heat in the atmosphere than carbon dioxide.
Through 10 years of sampling ancient air, Severinghaus, his graduate students and the rest of his team were able to show, however, that during the warming period, no detectable methane in the atmosphere came from thawed deposits.
They demonstrated this by looking at the radiocarbon content of 11,600-year-old Antarctic ice, exhuming a ton for each measurement at a precise and narrow vein of ancient ice originally deposited by snowfall on Younger Dryas glaciers. They gathered a corresponding control of modern-day air cleared of carbon-14 for each measurement as well.
Methane released from thawed deposits has no carbon-14, because it’s old and the radiocarbon content decayed long ago. But methane released from natural sources such as wetlands is fresh, and has detectable carbon-14. Carbon-14 builds up in the air and in all living organic things as cosmic rays bombard atoms in the atmosphere.
“If that 50 percent increase in methane concentration was actually caused by the tundra getting warm and burping out all of this methane, then the concentration of carbon-14 relative to the more abundant carbon-12 should have gone down by 30 percent,” Severinghaus said. “We should really see a huge signal if this idea is correct …and we don’t.”
He added that methane-consuming soil microbes at the time must have stopped most of the thawing methane from reaching the atmosphere—just as their oceanic cousins did when they ate 99.9 percent of the methane released during the Deepwater Horizon oil spill in 2010.
Wetlands, which belch methane when it rains, and other natural sources were the main culprits for the rise in methane during the Younger Dryas warming period, Severinghaus said.
“If it didn’t happen back then, it won’t happen now and it won’t happen in the future,” Severinghaus said. “We can focus our attention back on CO2 [carbon dioxide], which really is the problem, and not worry so much about methane. So check one thing off the list.”
Pennsylvania State Geology Professor Richard Alley concluded Severinghaus’s presentation by applauding the amount of work that went into the research.
“Jeff could stand up here and give five or six more talks that have come out of these samples, it’s just really spectacular,” Alley added.
PHOTO AT TOP: Vasilii Petrenko works in the Severinghaus lab, and went to Antarctica to measure radiocarbon in ancient glacial ice. This chamber melts the ice so he can capture and measure the methane content, as the ice traps air bubbles of the atmosphere as it existed 11,600 years ago during a rapid warming event.(Courtesy of Jeffrey Severinghaus)
Note: Austin Keating is a Comer Scholar, a Medill scholarship program supported by the Comer Family Foundation to promote graduate studies in environmental journalism.
Taiwan has faced water shortages for decades – and the Chicago area may face them within the next 20 years as aquifer levels for well water drop while Great Lakes water use is limited by by an interstate compact.
As drought conditions worsen worldwide due to global warming, improved water conservation and efficiency systems become increasingly necessary. National Taiwan University (NTU), a prestigious research institution located in Taipei, is seeking to harness the power of the international science community here and globally to propel cities into a more sustainable future.
The Dragon Gate Program of National Taiwan University, in collaboration with Argonne National Laboratory west of Chicago, and Northwestern University are pioneering water reclamation and reuse technologies. One is a filtration systems that produce clean water from salt water or wastewater. The project is in its third year.
Yupo Lin, an electrochemical engineer at ANL, is leading the research team to scale up a filtration technology called Resin Wafer Electrodeionization (RW-EDI). The process purifies wastewater by pushing it through a series of porous ion exchange membranes with an electric field on either side. The result is an energy-efficient and economically viable approach to water reclamation, Lin said.
“We don’t have many natural resources in Taiwan,” said Lin. So far, the Argonne RW-EDI process has only been demonstrated as a pilot program. But the team hopes to soon create systems that can be used commercially and improve water efficiency on a large scale. Plans are underway to do just that.
“We’re doing this research to solve problems that South Taiwan is facing,” said postdoctoral fellow Ming-Huang Wang. “We want to create a versatile technology.”
Wang works with the Carbon Cycle Research Center at NTU, but is now spending 10 months in the Energy Systems Division at ANL, where he is working with Lin on water reuse technologies that could be applied in Taiwan and elsewhere as water shortages spread due to climate change.
RW-EDI does not purify wastewater to the extent that it is drinkable. However, the brackish or semi-pure water that is extracted can still be used for numerous purposes.
“We tend to think that most of the water that’s used is what people drink, but that’s not true,” said Aaron Packman, professor of civil and environmental engineering at Northwestern University. He is partnering with Lin, Argonne, and NTU on the RW-EDI project. “One of the strategies that we’re looking at is to try to separate the drinking water from industrial water use,” he said. The technology could remove compounds that are problematic for industry to produce water that can be used for cooling and other purposes.
“You don’t have to treat water to drinking standards if it’s going to be used for industrial purposes,” said Packman, part of the Northwestern-Argonne Institute for Science and Engineering. “There are ways to be more efficient.”
Because power plants are the largest consumers of water in the U.S., using more efficient sources for cooling water would have a significant impact on the water supply. It’s hard to imagine that a place like Chicago, which sits right alongside Lake Michigan, could ever face water shortages, but estimates indicate that industrial and economic development could be limited in the city within the next 20 years. “If we find a way to reuse the wastewater that opens up a huge amount of new development potential,” said Packman.
The NTU-ANL-NU partnership and the Dragon Gate Program have created opportunities for scientists from both institutions to contribute to technologies that could improve resource management, not just in Chicago and Taipei, but across the globe.
A consortium of global scientists will gather Aug. 5 and 6 at a conference hosted by NTU to explore opportunities for new international collaborations. The symposium isl focusing on clean water technologies, the vital links between urban food, energy and water supplies, and green infrastructure. Lin and Packman will be addressing these topics at the symposium, along with Seth Snyder, a mechanical engineering professor at Northwestern, and scientists from several institutions.
“We are aiming for integrated water-energy solutions including a mixture of technological innovation and integration of engineered systems with natural systems,” said Packman. The collaboration between leading scientists in this field could produce the ingenuity that will allow cities to continue to function as resource scarcity becomes a more imminent threat.
Photo at Top: Eaglle Harbor (Abigail Foertner/Medill)
The scientists agree that as temperatures and carbon dioxide levels rise, the Earth faces increased threats of fresh water shortages, coastal flooding and extreme weather events. Trying to determine the speed and potential impact of a changing climate, Comer scientists representing institutions across the world pursue field research from Africa to the Swiss Alps.
“This ultimately comes down to a simple thing as it is easier to break something than to build it,” said Richard Alley, professor of geosciences at Pennsylvania State University. “When we think about what we are doing to the climate, cranking up CO2, it’s very, very unlikely that it turns the planet into Eden.”
The researchers found that much of their data from all over the globe seemed to coalesce around a few key ranges in time, suggesting that the researchers from across disciplines might be zeroing on a much more precise picture about the nature of climate change through the ages.
Much of the research on display looked to the past to better predict possible climate responses, from the collapse of ice sheets in Greenland and Antarctica to historical variations in volcanic activity. Presenters also discussed advances in green technology and how our ancestors adapted to previous changes in climate.
One of the major questions facing the scientific community is how researchers can effectively communicate the exponential nature of abrupt climate change. Current climate models are built on scientists’ best knowledge about climate indicators like sea level rise, glaciers and the chemical composition of the oceans, but there may be other drivers or effects scientists have yet to decipher. This means that while nearly 200 countries pledged in Paris to limit warming to well below 2 degrees Celsius (3.6 degrees Fahrenheit), the world may soon be reaching a tipping point where this will no longer be possible.
The uncertainties in climate change research should motivate the public and policymakers to do more, not less, to address the potentially devastating consequences of abrupt climate change, said Alley. People buy auto insurance to protect themselves from the uncertainties of having a car accident. The most important story we need to tell about climate change is that adaptation will help the economy, he added.
Author and consultant Philip Conkling told the audience of predominantly scientists that the secret is in telling “character-driven stories about how climate is affecting real people’s lives.” Conkling cofounded the Island Institute in 1983 to examine climate change through the lens of communities along Maine’s sensitive archipelago. Philip Conkling & Associates helps not-for-profits and implement communications goals and strategic plans.
Klaus Lackner, director of the Center for Negative Carbon Emissions and professor at Arizona State University, is already working on a promising technology to sequester carbon from the atmosphere. Mitigation, he said, has to be a solution in order to repair the considerable damage already done by burning carbon. “I am now convinced that we will have to do carbon storage, carbon sequestration or carbon disposal,” said Lackner.
Many of the other scientists at the conference are looking at to the past to see how ancient climate shifts played out, even without human interference. The scientific community is hoping to understand the conditions before, after and during previous warming periods in order to make better predictions about our planet’s future.
Christine Chen, a third-year Ph.D. student at the Massachusetts Institute of Technology, studies lakes in the Andes Mountains in order to predict future precipitation patterns. “Water availability is a huge issue there,” said Chen, referring to the Central Andes region where she conducted her fieldwork. “Reconstructing how precipitation patterns changed in the past is highly relevant to what is happening and what is going to happen in these regions in the future.”
University of Nevada Ph.D. candidate Ben Hatchett is pursuing research that could help us understand the future of drought and water shortages closer to home. His model identifying the influence of temperature and precipitation over time on water levels in western Nevada’s Walker Lake watershed found that drought severity doesn’t all come down to precipitation.
“We can see that the impact of temperature is very important,” Hatchett said. Ongoing drought conditions are “on par” with historic anomalies in terms of precipitation, he said, but warns that the same does not hold true for temperature where megadroughts don’t reflect an earlier precedent.
“The temperature [now] could be pushing us outside the realm of the natural variability,” Hatchett said. With the arid western U.S. projected to warm even more in the future, that means additional pressure applied to strained water resources.
Many presentations showed powerful evidence that something big happened to atmospheric circulation in the Southern Hemisphere approximately18,000 years ago, when glaciers last reached their maximum extent in the last major ice age. Mike Kaplan, geologist at Columbia University, has been working in Patagonia, at the southern tip of the Andes Mountains. Scientists had previously assumed the area only contained records of older ice masses. But during his 2013 field season, Kaplan and his colleagues found glacial deposits dating to that last glacial maximum. Kaplan’s work could provide crucial clues to when exactly the ice age started and ended in the Southern Hemisphere, furthering scientists’ understanding of how the climate system works.
With the world’s glaciers withering away, caves are emerging as an increasingly important setting for scientists to collect climate data. This past summer, Gina Moseley of the University of Innsbruck in Australia led the Northeast Greenland Caves Project. The group studied the mineral build-up in caves that creates formations such as stalagmites and stalactites, called speleothems, in order to try to fill in gaps in Greenland’s ice core records, especially around the last interglacial period – a stretch approximately 130,000 years ago, when warm temperatures disrupted ice formation.
Moseley and her spelunking colleagues are part of an increasingly popular field. The journal Science noted in 2006 that: “For paleoclimate, the past two decades have been the age of the ice core. The next two may be the age of the speleothem,” spire-like mineral deposits in caves that include stalagmites and stalactites.
While scientists have so far observed global warming of just less than a degree, the oceans could be distorting the true extent of the impact on the atmosphere of carbon dioxide emissions from fossil fuels, said Jeff Severinghaus, professor of geosciences at the Scripps Institution of Oceanography, part of the University of California at San Diego.
“The deep ocean is so enormous and it is a huge reservoir of cold water and it is becoming a little less cold right now. It means that it will take about 100 years to realize the full warming of 2 degrees. If we continue to burn fossil fuel we will be committing to more than 2 degrees.”
The implications of forces other than temperature make the climate puzzle even more challenging. Other presenters explored drivers of climate change that we could be missing. For example, Guleed Ali’s research on Mono Lake Basin in California suggested that scientists might have reframe current thinking about temperature and evaporation and consider other factors such as the jet stream.
Low temperatures during Earth’s ancient cold snaps should have meant decreased evaporation, and thus higher lake levels. But Ali’s research suggests that Mono Lake was likely as low as it is today. This data indicates that temperature and evaporation, both of which scientists consider drivers of the lake’s water level, seemed to have had a negligible role.
Ali has hypothesized that the North Atlantic Ocean’s circulation and its jet stream instead controlled climate then and now, “What I think might be controlling these lake levels is the state of the tropical circulation and the state of the North Atlantic Ocean’s circulation,” Ali said. “What I think is a possibility, just working hypothesis… is that the strength of the circulation in the North Atlantic Ocean is the controlling factor of the hydro-climate certainly in Mono Lake and much of western U.S.”
Some of the first scientists to lead the charge in researching climate change help organize the conference each year, including glaciologist George Denton of the University of Maine at Orono. Denton spoke on the collapse of the Antarctic ice sheets but, like other climate veterans at the conference, came to hear from the new generation of climate researchers. Many of them are Denton’s current or former students, presenting findings in a field where he has contributed several decades of research.
Climate change science pioneer Wally Broecker, the first scientist to use the term “global warming” in a 1975 paper for Science, is among the founders of the Comer Foundation’s climate change research program. In 2001, the late entrepreneur and philanthropist Gary Comer sought out Broecker, an oceanographer, geochemist and professor of geology at Columbia University. Partnering with Denton and Alley, the four men created a fellows program working with mentor scientists at 31 institutions to support the next generation of researchers and research on abrupt climate change. Seed money and grants also support seminal research in the field, with more than 125 global research projects on abrupt climate change supported since 2005.
In the opening remarks for the second day of talks, Alley spoke movingly on the origins of the conference and the Comer Family Foundation. Comer, founder of Lands’ End outfitting company and a native Chicagoan, started the foundation in 1986 to promote education, healthcare and the environment.
Dec. 22, 2015
Photo at top: Climate scientists Peter Strand (left) and Aaron Putnam (right) hike through the Altai Mountains of western Mongolia during their summer 2015 field season. Putnam and Strand’s research on the glaciers of central Asia is one of the many projects funded by the Comer Family Foundation. (Sarah Kramer/Medill)
Thousands of miles away from the Massachusetts Institute of Technology where she is a third-year doctoral student, Chen reached one of the most remote regions on Earth equipped with a knapsack, a rudimentary rock hammer and a burning question—can ancient lakes in the Andes Mountains shed light on past climate, clues that can then be used to predict future climate change?
The question is long established in the field of earth science and has prompted exploration into the world of “paleoclimates” (or “ancient” climates). As the planet currently undergoes unprecedented change in terms of rising global temperatures, scientists have long speculated that by critically analyzing past changes in Earth’s climate, they can develop climate models that can be used to predict temperature and precipitation changes of the future. Of greatest uncertainty is how rainfall patterns will change in the future.
“For the modern climate, we’ve got rain gauges and we can calculate rates of evaporation,” explained Chen at the annual fall Comer Conference on abrupt climate change. “But no one was around thousands of years ago to set up a rain gauge. Lake level changes are a proxy for water availability.”
Most of the work on lake levels and paleoclimate has been done on European and North American lakes, Chen said. South American lakes are markedly underrepresented in the scientific literature, and Chen hopes that her work in the Andes will bring South America to the global forefront of much needed data. She sees in the barren landscape as a treasure trove of ancient knowledge, revealing answers to ages-old mysteries of climates and precipitation patterns.
The lakes that Chen studies, Agua Caliente I, Laguna de Tara and Salar de Loyoques, are vestiges of much larger lakes from thousands of years ago. With no outlets such as streams or rivers from these lakes, they depend on the competing forces of rainfall and evaporation to maintain water levels. As a result, Chen hypothesizes that higher water levels indicate periods when rainfall was plentiful. By matching water levels with the time record, Chen can then evaluate how global temperature patterns affected past rainfall. This will provide important lessons that will shape current climate models on what changes we might expect in rainfall patterns in the future.
“Reconstructing past rainfall amounts is not easy; using lake levels is the best way to do this,” said Yoni Goldsmith, a doctoral student at the Lamont-Doherty Earth Observatory of Columbia University. “Using a variety of geochemical, geophysical and biological methods, it is possible to decode these climatic signals and reveal how climate changed in the past.”
A cursory glance at Google Earth images of Agua Caliente I, Laguna de Tara and Salar de Loyoques clearly shows that these lakes were once mighty bodies of water. Now, they are more like large salt flats.
“We can see awesome bathtub-like ring features,” Chen said, referring to a series of concentric circular patterns extending from the lakes. “These bathtub-like rings are essentially ancient abandoned shorelines,” she said.
On the ground, the bathtub ring pattern is not nearly as striking, and the ancient shorelines are marked by white rocky formations that to a lay person seem beautiful but not of great scientific import. But to Chen, the answers to her questions lie within these rocky formations coating the ancient shorelines. Chen calls these formations “tufas”, and thanks to their biological origin, their presence provides valuable insights into past conditions for these ancient lakes.
Tufas, fossilized remains of algae reefs, are made of calcium carbonate. When the algae making up these reefs were alive, they lived on the shore close to the water surface in order to get sunlight for photosynthesis. By analyzing the tufas back in a lab at MIT, Chen has figured out when these algal reefs were last alive, before they became fossilized into stone. And that gives her a timeline for the shrinking bathtub rings.
Many of the tufas—some located more than 60 meters away from the modern shoreline—fall between 15,000 to 25,000 years old. Based on those results, Chen can infer that thousands of years ago, these lakes were nearly four times larger than they are today, indicating that the barren landscape was once a lush terrain that was hospitable for more kinds of life.
Chen also looks at other formations known as ikaites, which are calcium carbonate crystals that form at the bottom of lakes within the mud only when the water is at very cold, near-freezing temperatures.
“Not only do the ikaite deposits give us a constraint on how high the lake was, but it also tells us the paleotemperature—how cold it was back then,” explained Chen. “This is pretty cool because usually proxies only give you one parameter, but we’ve got two. So that’s pretty exciting to find.”
Chen hopes to apply the same technique of finding the age of tufas and tracing abandoned shorelines to other ancient lakes in the Chilean Andes. She will then compare these data with temperature records from nearby ice cores from Andean glaciers to get a better idea of why these lakes were larger in the past.
“If we know what caused these lakes to get bigger, what caused these lakes to get smaller, then maybe we will have an insight on what these lakes will do in the future and what is causing them to shrink or expand,” said Chen.
Chen’s work comes at a time when the Central Andean region has been experiencing decreased rainfall and increased evaporation rates over the past 50 years, which has significantly strained local Andean communities. She hopes that her scientific contributions might help policymakers identify regions that are more sensitive to water availability issues, and divert resources to communities that are most likely to be adversely affected by future climate change.
Photo at top: A closed-basin lake in the beautiful barren landscape of the high Andes. Photograph by Christine Chen.