Crystal Rao, a geoscience graduate student at Princeton University, bases her research on the environmental changes and climate impacts on the species in clues from nitrogen isotopes in fossils.
Rao uses the ratio of two common forms of nitrogen as a standard, and compares it with the nitrogen inside the tooth of the megalodon shark. She has reconstructed a picture of when and where megalodon sharks topped the food chain in Arctic waters. Rao said this fierce predator could “basically eat anything in the ocean”.
Yet this 50-foot long shark, went extinct some 3.5 million years ago. Rao said the food source the sharks relied on to fuel their massive bodies caused their downfall.
“As climate shifts, maybe the production in the ocean could change,” Rao said. “And depending on what the ecosystem responded to, there could be less food availability” for marine life today just as those causing the demise of the megalodon sharks.
And that’s where the nitrogen fingerprint in the teeth comes in. The nitrogen isotope levels change in warm spells compared to ice ages so that Rao can track climate change in the distant past. Nitrogen isotopes from the Atlantic and Pacific Oceans mix during warm spells but ice ages lower sea levels, cutting off Atlantic from Pacific waters and and leaving a distinct isotope in each ocean. ,
Rao shared her research at the Comer Climate Conference this fall, an annual gathering of global climate scientists held virtually for the third year due to COVID-19. Comer conference veteran climate scientists, graduate students and post-docs investigate the effect of climate change from ancient life forms to theoretical models.
While Rao’s work examines a species belonging to an ancient era, another Comer scientist’s work takes estimations of the possibilities for the future.
Edmund Derby, a climate science Ph.D. student at Oxford University, utilizes simple models of Arctic sea ice from his past research in 2009 to examine the bifurcation or tipping point accompanying ice cover changes throughout the season.
Derby’s research presents climate from basic principles to its core behavior. In the scientific model, when atmospheric carbon dioxide exceeds a certain point, after all the Arctic ice melts, it is no longer possible to gain back the ice. His research presented at the conference investigates this tipping point under a model when the Arctic is covered in ice all year round.
“When you’ve reached this tipping point, you don’t get a reversible change once you’ve lost your ice cover,” Derby said.
The temperature of the Arctic is intrinsically connected with global warming across the rest of the world. In a phenomenon known as Arctic Amplification where the Arctic warms twice as fast as the rest of the world, which has warmed in excess of 1 degree Celsius (1.8 degrees F) with global warming due to emissions from human reliance on petroleum-based fuels.
The ice has the light reflective property that redirect the heat. But as it melts, the heat-absorbent ocean water takes its place, according to Derby.
With heat transport to lower latitudes, as the Arctic warms up, the transfer of heat to the Arctic would be expected to decrease.
However, in a changing climate, the transport of water vapor or clouds into the Arctic can counteract the cooling of the heat transport. The water vapor causes local temperature in the Arctic to rise.
In his research, Derby is adding more factors into the model to make it more realistic to the Arctic ice cover, and to investigate how the global rise of greenhouse gas will impact the ice melt at a local level.
Rao said, in her field of geoscience, the past informs the present and the future. Studying the ancient past of Earth’s environment builds a better understanding of the complex systems involved.
“Only when we can really understand or estimate the future better, then we can come up with better plans in terms of how we do climate adaptation and climate mitigation,” Rao said.
The numbers of climate change may seem small, but a small change now may mean a colossal shift into the future. <The changes are occurring now – we don’t want to suggest this is a problem for the next millennium.
Through Rao and Derby’s research of both the past and the future, concerns of climate change continue to loom in both the vanishing fabric of the Arctic and the demise of a species.
Photo at top: Arctic water and the atmosphere help scientists reconstruct the past climate record and inform models for the future. (Photo by Kai Boggild, distributed via imaggeo.egu.eu.)
Columbia University Ph.D. student Celeste Pallone devotes her research time observing Eastern Equatorial Pacific dwelling planktonic foraminifera – very tiny creatures that can give huge clues into the pace of ocean climate change.
“Marine sediment cores act as an archive of sea surface temperatures, past environments, including past temperatures, and general environmental factors, such as past global ice volume,” she said of the single-celled, shelled organisms she studies at Columbia’s Lamont-Doherty Earth Observatory high in the Palisades outside New York City. “I examine these proxies, which can be biological or chemical or physical, and then using them I reconstruct oceanographic conditions in the past helping craft record of the El Niño-Southern Oscillation [ENSO].”
Climate change threatens El Nino and other ages-old weather systems with severe disruptions. ENSO varies on 2–7 year timescales and has major influences on temperature, wind patterns, biological productivity and rainfall across the tropical Pacific and far beyond. This also includes crop yields, floods and droughts at multiple locations, said Jerry McManus, field researcher and professor at Columbia’s Department of Earth and Environmental Sciences and Lamont-Doherty. Understanding the baseline influences on this system is key to gauging how it may be altered through climate changes.
The latest report from the U.N.’s International Panel on Climate Change expresses continued uncertainty about how the El Niño-Southern Oscillation will respond to continued warming, although the consequences that play out in the global water cycle are likely to be greater (more rain and flooding in some areas, with increased drought in others). South American countries such as Peru rely on the periodic El Niño to bring warmer ocean waters and rainfall. The uncertainly over El Niño is unsettling. Additionally, the Special Report on the Ocean and Cryosphere in a Changing Climate projected that over the 21st century, the ocean will transition to unprecedented conditions with increased temperatures, further acidification and oxygen decline. It predicts more frequent marine heatwaves along with extreme El Niño and La Niña events.
Pallone is seeing how she can reconstruct the oceanography of the eastern equatorial Pacific Ocean (the region of the open ocean directly south of Mexico and Central America) during a particularly interesting time in Earth’s past as she reported at the annual Comer Climate Conference, an international gathering hosted in southern Wisconsin but held virtually this fall.
According to WHO, the warming of the central to eastern tropical Pacific Ocean in the El Niño 2015-2016 event is affecting more than 60 million people, particularly in eastern and southern Africa, the Horn of Africa, Latin America and the Caribbean and the Asia-Pacific region.
El Niño is an oceanic climate pattern that characterizes unusual warming of surface waters in the eastern tropical Pacific Ocean. Considered the warm phase of a larger phenomenon called the El Niño-Southern Oscillation, the system marks a periodic warming of ocean surface temperatures. Its opposite, La Niña, is marked by an unusual cooling of oceanic surface temperatures. El Niño brings drier warmer weather to the northern United States and wetter conditions to the south. Arriving in the Americas around Christmas time in the cycle described below, it was given the name El Niño (meaning Little Boy or the Christ child) by Spanish fishermen.
Each climate pattern lasts about 9-12 months, and both tend to develop during the spring (March-June), reach peak intensity during the late autumn or winter (November-February) and then weaken during the spring or early summer (March-June) according to the National Oceanic and Atmospheric Administration.
“If you have a strong El Niño event, that might be followed by a strong La Niña event as well – but it is a consistent oscillation that we’ve observed,” Pallone said.
El Niño/La Niña’s hydrological effects are the most important implications on the human population. It can affect rainfall patterns impacting agriculture or even flooding and monsoonal seasons. With satellite measurements of sea surface temperature since the 1980s, there are historical records that indicate the same kind of variability that we observe today suggesting that the ENSO system has been occurring for certain at least the past several thousand years, perhaps even more.
“If we can kind of identify periods that had recurrent warming episodes, for example, or a really large range of temperature variability, we can associate those periods with stronger or more frequent El Niño events,” Pallone said.
McManus highlighted the importance of why Pallone chose to focus on a particular time period, Marine Isotope Stage 5. The marine isotope stages offer a way of tracking ice ages and the periods between them based on the oxygen isotopes found in sediment cores.
“MIS5 was approximately 130,000 to 70,000 years ago and the last interglacial interval that was subsequently followed by a major global ice age, and then the deglacial warming that led to the Holocene interglacial interval of the last 10 or 11 thousand years, the time when all of human agriculture and civilization has developed,” McManus said.
He emphasized that MIS5 is the interval of time when Earth was last as warm as it is today before the most recent ice age, offering the potential to provide insights into natural variability during a warm interval. “The 60,000 years of MIS5 were characterized by three large cycles in the seasonal distribution of sunlight based on the progression of the seasons around Earth’s elliptical orbit,” he said. This time period can help differentiate between natural climate events and what is going on now because of the climate similarities between the time periods of past and present.
Pallone’s research is tri-fold. She uses multiple methodologies to reconstruct the surface and subsurface oceanography of the eastern equatorial Pacific Ocean during a particularly interesting time in Earth’s past, according to McManus.
“She makes many measurements of the oxygen isotope ratios in individual specimens of surface-dwelling planktonic foraminifera shells preserved in deep-sea sediments deposited at that time to learn about the temperature each one experienced during its month or so lifetime, and to compare the range of temperatures that characterized different intervals in the past,” he said. “That tells us something about El Niño-Southern Oscillation (ENSO) variability.”
Another piece of her research is an analysis of multiple specimens of foraminifera species that live at a range of depths below the sea surface to assess their shells and biology as a way to assess where and how fast the temperature changes beneath the surface ocean, hallmarks of El Niño and La Niña events. She studies thermocline structure as another clue to temperature change. The thermocline is the transitional layer between warmer mixed water at the ocean’s surface and cooler deep water below.
Pallone also measures uranium, thorium and protactinium isotopes in the bulk sediment to estimate the amount of material that rained down due to biological productivity in the past.
“A shallower thermocline means that more nutrient-rich waters were moving toward the surface ocean at a particular time, potentially enhancing productivity,” McManus said.
Ultimately, by combining these three main methods, this enables Pallone to make a richer and more robust reconstruction of the ocean state in the EEP at different times throughout history.
The strength or frequency of an El Niño event can be influenced by small changes in Earth’s orbital geometry, with the main factor being changes in solar insulation that are driven by orbital shifts. Teleconnections, climate anomalies related to each other over long distances, also come into play because of how the atmosphere and oceans talk to each other.
“Because of the global circulation of the atmosphere in the ocean, if you have an event happening in the equatorial Pacific, for example, you’ll have effects in other parts of the world,” Pallone said.
Pallone started her research thinking that by using the foraminifera as a proxy and the MIS5 time period, she could create a good analog for modern warning.
“If we can reconstruct the environment during [MIS5], maybe it will inform about what changes could be coming in the future,” she said. “This, with most comparisons between the paleo record and the modern, we’re going to have kind of changes in temperature that might have been or that might be quicker than anything that we’ve seen in the past. But the past is still a useful analog for what could happen in the system.”
For the future, global efforts are needed to curb climate change. At the 2021 Glasgow Climate Conference, the United Nations called for a worldwide response to accelerate climate action to limit global temperature rise at a 1.5 degree C tipping point. The goal called for cutting global fossil fuel emissions by 45% compared to 2010 levels and doing so by 2030. The goal was not adopted.
Going forward, U.N. Secretary-General António Guterres deemed that the world is in emergency mode, meaning we must end fossil fuel subsidies, phase out coal, put a price on carbon, protect vulnerable communities, and deliver the $100 billion climate finance commitment.
Pallone’s research is a small but crucial step in reaching toward this goal.
El Niño events are the dominant source of like this kind of decades scale climate variability today,” Pallone said. “It’s unsettling that we’re not so confident in what could happen to them in the coming years or in the coming century.”
Photo at top: El Niño is anchored in the tropical Pacific, but it affects climate “downstream” in the United States. This shows the U.S. impacts of the climate patterns. (NOAA)
Carly Menker is a health, environment and science reporter for the Medill News Service and a Comer Scholar at Medill. Follow her on Twitter @carlymenker.
By Christian Elliott and Brittany Edelmann, Dec. 8, 2021 –
Nearly 20 years ago, then Ph.D. student Gina Moseley walked into a bar in Bristol to meet fellow members of the University of Bristol Spelæological Society caving club. An older caver talked with her over drinks about some small caves in northeastern Greenland he’d always dreamed of organizing an expedition to explore. But, “logistically, it’s a nightmare to get out there,” said Moseley, now a professor in the Institute of Geology at the University of Innsbruck in Austria. The caver gave her all the papers he’d collected on the caves, and for years she kept them filed away.
Much later, a 1960 article by U.S. military geologists among the papers caught her eye. In their search for prime airfield locations, the geologists discovered caves with interesting geological features — crystalline calcite, stalagmites and flowstone deposits. To Moseley, that was proof Greenland’s caves contained something critical to scientists’ understanding of Earth’s ancient climate.
Moseley took her first steps into caving years earlier with her mom on a holiday trip when she was 12. She loved it. As she started grad school in Bristol, she discovered she could bring together her fascination with caves and her interest in studying paleoclimate to understand how future climate change — pushed by fossil fuel emissions of human activities — will affect the Earth.
Caves are normally “not altered or impacted by other processes” and “they’re so well-preserved over thousands of years,” Moseley said. That makes them a great location for climate research and creating records that can function as important analogs for future climate change.
The 2021 Comer Climate Conference on Oct. 4 – 5 brought together scientists from around the world, including Moseley and fellow paleoclimate researcher Kathleen Wendt.
“Devils Hole was where it all began. That was the start of cave paleoclimate research,” Moseley said. Paleoclimate scientists first rappelled down into the deep, narrow cave in the Amargosa Desert in southwest Nevada in the late 1980s.
Using cores of the thick calcite crusts on the cave walls, which accumulated steadily over time, researchers reconstructed 500,000 years of climate history here with Uranium-thorium dating. Uranium-thorium dating provides insight into when a rock was formed– giving a date to the origin of the rock.
Devil’s Hole was also where Moseley and Wendt, who has her Ph.D. from the University of Innsbruck in Austria, got their start in cave paleoclimate science. In 2017, they returned to Devils Hole to extend the climate record further and validate the older results.
In their research Moseley and Wendt focused on oxygen isotopes, which provide temperature information about historic temperatures. During ice ages, a heavier isotope of oxygen forms at higher levels than during warm spells.
Wendt is getting ready to submit a new paper on the oxygen isotope record from Devils Hole. By showing the fluctuation in types of isotopes, heavier versus lighter forms of oxygen, this will give “clues into changes in temperature and a little bit about the source of precipitation over time,” Wendt said.
They found the water table dropped below modern levels during the last interglacial, 120,000 years ago, when Earth’s orbit brought the planet closer to the sun. That time period is an analog for southern Nevada’s hotter and drier future that will be accelerated beyond natural planetary fluctuations with human-forced extremes of climate change.
“Studying the paleoclimate tells us what nature is capable of,” Wendt said.
The Greenland caves
Paleoclimatologists who focus on caves often study speleothems — mineral deposits formed by dripping water. Protected within caves from the elements, these dripstones (stalagmites and stalactites) and flowstones grow as layers of calcium carbonate carried by rainwater add up over hundreds of thousands of years.
One of the flowstones Moseley found in the caves was specifically mentioned in the 1960 paper that inspired the expedition.
In Greenland, now a rainless polar desert, speleothems formed during a time when the island’s climate was warmer and wetter. By collecting and sampling speleothems, Moseley can reconstruct that ancient climate period as an analog for the future, when Greenland will once again be warmer and wetter.
Over millions of years due to orbital changes, Earth’s climate alternates between warm and cold periods — interglacials and ice ages called glacials. Paleoclimatologists rely on air bubbles in cores taken from ice sheets in Greenland and the Antarctic to study the composition of the ancient climate’s atmosphere, but there’s a problem — during warm periods, the ice sheet melts. That’s where the caves come in.
“So the caves offer the polar opposite of what the ice cores do because the ice cores tend to be cold-based climate records and the caves can give us warm-based climate records. So, we get to the two different parts together,” Moseley said.
That’s a common theme in paleoclimatology — no one climate proxy shows the big picture. To fully understand Earth’s ancient climate, scientists must piece together hundreds of pieces from data from sources across the world.
“If you have one cave in one location, that’s kind of interesting. But if you can relate that to other caves in other locations, ice cores in other locations, deep sea sediments in other locations and get the whole picture, that’s where it really gets interesting. That’s where we can answer the big questions and tackle the big issues,” Moseley said.
As the Arctic continues to warm at twice the rate of the rest of the world, understanding what warm and wet historic climate periods were like can help scientists know what to expert in the imminent future.
This leads to Moseley’s next adventure in 2023, where she will explore completely untouched caves in Northern Greenland. This was only made possible with an award from Rolex — which provides funding for such an endeavor.
Christian Elliott and Brittany Edelmann are science and environmental reporters at Medill. You can follow them on Twitter at @csbelliott. and @brittedelmann.
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.
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