. Scientific Frontline: Environmental
Showing posts with label Environmental. Show all posts
Showing posts with label Environmental. Show all posts

Tuesday, March 12, 2024

Range-shifting fishes are climate-change losers, according to new research

Pouting (Trisopterus luscus)
Photo Credit: Diego Delso
(CC BY-SA 4.0 DEED)

The warming of the Earth’s oceans due to climate change is affecting where the world’s fishes live, eat and spawn — and often in ways that can negatively impact their populations. That’s according to a new paper in the journal Nature Ecology and Evolution.

The researchers write that populations that experience rapid-range shift decline noticeably, up to 50 per cent over a decade. The populations affected most are those living on the northern poleward edges of their species’ range.

“There is a conventional wisdom among many climate-change biologists that species that shift their ranges quickly by moving northward should provide a mechanism to sustain healthy populations — that shifting species should be climate-change winners. Our results show the exact opposite,” says paper co-author Jean-Philippe Lessard, a professor in the Department of Biology.

“Species that are shifting their range quickly experience little change in their population size in their core range. But some of them experience a major collapse in their populations at the northern edges.

“In fact, the population collapse is mostly driven by the northern poleward populations,” he adds. “We were expecting that many individuals from the core of the range would be moving up north due to climate change and maintain these northern populations. But the northern-edge populations are the ones most likely to collapse.”

Rainforest’s next generation of trees threatened 30 years after logging

Logged forests have reduced seedling density, reducing the probability for the next generation to emerge.
Photo Credit David Bartholomew

Rainforest seedlings are more likely to survive in natural forests than in places where logging has happened – even if tree restoration projects have taken place, new research shows.

Scientists monitored over 5,000 seedlings for a year and a half in North Borneo.

They studied a landscape containing both natural forest and areas logged 30 years ago – some of which were recovering naturally, while some had been restored by methods including tree planting.

A drought had triggered “mast fruiting” across the region, with trees simultaneously dropping fruit en masse and new seedlings emerging.

At first, both natural forest and restored forest had similarly high numbers of seedlings, compared to naturally recovering forest – suggesting restoration activities enhanced fruit production.

But these benefits did not last: low seedling survival in the restored forest meant that, by the end of the study, similarly low numbers of seedlings remained in restored and naturally recovering forest. Seedling populations remained higher in natural forests.

Together, these results show that regeneration may be challenged by different factors depending on the restoration approach – seed availability in naturally recovering sites and seedling survival in sites where planted trees have matured. These differences may have longer-term implications for how forests can deliver key ecosystem services such as carbon sequestration.

Monday, March 11, 2024

Unprecedented heatwaves revealed by marine lab’s historic data

Photo Credit: Courtesy of University of Auckland

A unique record at the University of Auckland's Leigh marine lab shows dramatic change in the Hauraki Gulf.

A thermometer dipped in a bucket of sea water on New Year’s Day in 1967 began a unique record which shows the dramatic intensification of warming in the Hauraki Gulf.

Sea-surface readings at the Leigh Marine Laboratory north of Auckland since that time indicate the “unprecedented nature of recent marine heatwaves,” according to Dr Nick Shears of the University of Auckland, Waipapa Taumata Rau.

The number of marine heatwave days and their cumulative intensity has increased sharply since 2012, Shears and his co-authors write in a paper published in the New Zealand Journal of Marine and Freshwater Research.

In past decades, some years had no heatwaves, but that hasn’t happened since 2012. Sponges `melting,’ becoming detached from rocks and dying, along with seaweed and kelp die-offs, are among temperature effects.

Especially warm autumns and winters have likely facilitated an increase in subtropical and tropical species such as the long-spined sea urchin Centrostephanus rodgersii, a voracious herbivore which can lay waste to deep reef environments.

Halloween toy among plastics swallowed by sea turtles

A rubber witches' finger found inside a dead sea turtle.
Photo Credit: University-of-Exeter

A Halloween toy was among hundreds of plastic items found in the guts of dead sea turtles in the Mediterranean, a new study reveals.

Researchers examined 135 loggerhead turtles either washed up or killed as “bycatch” (accidentally caught) in fishing nets off northern Cyprus.

More than 40% of the turtles contained “macroplastics” (pieces larger than 5mm), including bottle tops and the Halloween toy – a rubber witch’s finger.

The research team, led by the University of Exeter and the North Cyprus Society for the Protection of Turtles (SPOT), say loggerheads are a potential “bioindicator” species that could help them understand the scale and impact of plastic pollution.

“The journey of that Halloween toy – from a child’s costume to the inside of a sea turtle – is a fascinating glimpse into the life cycle of plastic,” said Dr Emily Duncan, from Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall.

“These turtles feed on gelatinous prey such as jellyfish and seabed prey such as crustaceans, and it’s easy to see how this item might have looked like a crab claw.”

Saturday, March 9, 2024

Loss of nature costs more than previously estimated

Photo Credit: Christian Heitz

Researchers propose that governments apply a new method for calculating the benefits that arise from conserving biodiversity and nature for future generations.

The method can be used by governments in cost-benefit analyses for public infrastructure projects, in which the loss of animal and plant species and ‘ecosystem services’ – such as filtering air or water, pollinating crops or the recreational value of a space – are converted into a current monetary value.

This process is designed to make biodiversity loss and the benefits of nature conservation more visible in political decision-making.

However, the international research team says current methods for calculating the values of ecosystem services “fall short” and have devised a new approach, which they believe could easily be deployed in Treasury analysis underpinning future Budget statements.

Their approach, published in the journal Science, takes into consideration the increase in monetary value of nature over time as human income increases, as well as the likely deterioration in biodiversity, making it more of a scarce resource.

Friday, March 8, 2024

Improving Wood Products Could Be a Key to Reducing Greenhouse Gas Emissions

Corrugated cardboard boxes are one of the most important products made from loblolly pine
Photo Credit: Aleksandar Pasaric

Harnessing the ability of wood products to store carbon even after harvest could have a significant effect on greenhouse gas emissions and change commonly accepted forestry practices, a new study from NC State researchers suggests.

The new study published in the journal Carbon Balance and Management uses carbon storage modeling to link the carbon stored in wood products with the specific forest system from which the products originated. Wood products and the forests they come from store different amounts of carbon, and being able to compare the two more specifically would help forest managers better understand these tradeoffs and plan for better carbon storage.

By tracing carbon in southern loblolly pine plantations from planting to harvest, the study also identified specific wood products that are important to improving carbon storage and reducing greenhouse gas emissions. Chief among them were corrugated carboard boxes.

“Corrugated cardboard boxes are one of the most important products made from loblolly pine,” said Sarah Puls, NC State graduate assistant and corresponding author of the study. “If we can extend the effective lifetime of products like these boxes, it could have a significant impact on the carbon storage associated with southern loblolly pine plantations.”

Tuesday, March 5, 2024

Researchers provide unprecedented view into aerosol formation in Earth’s lower atmosphere

Researchers identified evidence of Criegee intermediate oligomerization in the Amazon rainforest.
 Image Credit: Argonne National Laboratory
Eighty-five percent of the Earth’s air resides in the lowest layer of its atmosphere, or troposphere. Yet, major gaps remain in our understanding of the atmospheric chemistry that drives changes in the troposphere’s composition.

One especially important gap in knowledge is the formation and prevalence of secondary organic aerosols (SOAs), which impact the planet’s radiation balance, air quality and human health. But that gap is closing — due to the groundbreaking discoveries of an international team of researchers led by the U.S. Department of Energy’s (DOE) Argonne National Laboratory, Sandia National Laboratories and NASA’s Jet Propulsion Laboratory (JPL).

The scientists detail their findings in a new paper published in Nature Geosciences

The team focused on a class of compounds known as Criegee intermediates (CIs). Researchers suspect that CIs play a critical role in the formation of SOAs when they combine via a process called oligomerization. But no one had ever directly identified the chemical signatures of this process in the field — until now.

Can ‘Super Volcanoes’ Cool the Earth in a Major Way? A New Study Suggests No.

Quizapu Volcano, Chile
Photo Credit: Kevin Krajick / Earth Institute

Some 74,000 years ago, the Toba volcano in Indonesia exploded with a force 1,000 times more powerful than the 1980 eruption of Mount St. Helens. The mystery is what happened after that.

When it comes to the most powerful volcanoes, researchers have long speculated how post-eruption global cooling—sometimes called volcanic winter—could potentially pose a threat to humanity after a so-called super eruption. Previous studies have agreed that some planet-wide cooling would occur, but they have diverged on how much. Estimates have ranged from 3.6 to 14 degrees F (2 to 8 degrees C).

In a new study published in the Journal of Climate, a team from NASA’s Goddard Institute for Space Studies, an affiliate of the Columbia Climate School, used advanced computer modeling to simulate super eruptions like the Toba event. They found that post-eruption cooling would probably not exceed 2.7 degrees F (1.5 C) for even the most powerful blasts.

“The relatively modest temperature changes we found most compatible with the evidence could explain why no single super eruption has produced firm evidence of global-scale catastrophe for humans or ecosystems,” said lead author Zachary McGraw, a postdoctoral researcher at Goddard and Columbia.

To qualify as a super eruption, a volcano must release more than 240 cubic miles (1,000 cubic kilometers) of magma. These eruptions are extremely powerful, and rare. The most recent super eruption occurred more than 22,000 years ago in New Zealand. The best-known example may be the eruption that blasted Yellowstone Crater in Wyoming about 2 million years ago.

Harmful ‘forever chemicals’ removed from water with new electrocatalysis method

Per- and polyfluoroalkyl substances (PFAS) are often referred to as “forever chemicals” because they break down very slowly. Rochester scientists have developed nanocatalysts that can more affordably remediate a specific type of PFAS called Perfluorooctane sulfonate (PFOS).
Photo Credit: J. Adam Fenster / University of Rochester 

A novel approach using laser-made nanomaterials created from nonprecious metals could lay the foundation for globally scalable remediation techniques.

Scientists from the University of Rochester have developed new electrochemical approaches to clean up pollution from “forever chemicals” found in clothing, food packaging, firefighting foams, and a wide array of other products. A new Journal of Catalysis study describes nanocatalysts developed to remediate per- and polyfluoroalkyl substances, known as PFAS.

The researchers, led by assistant professor of chemical engineering Astrid Müller, focused on a specific type of PFAS called Perfluorooctane sulfonate (PFOS), which was once widely used for stain-resistant products but is now banned in much of the world for its harm to human and animal health. PFOS is still widespread and persistent in the environment despite being phased out by US manufacturers in the early 2000s, continuing to show up in water supplies.

How Does a River Breathe?

Scientists at Pacific Northwest National Laboratory have been studying processes that affect how rivers and streams breathe, particularly in the Columbia River Basin, to help prepare for future changes related to water quality and climate change. 
Photo Credit: Andrea Starr | Pacific Northwest National Laboratory

Take a deep breath.

Pay attention to how air moves from your nose to your throat before filling your lungs with oxygen.

As you exhale your breath, a mix of oxygen and carbon dioxide leaves your nose and mouth.

Did you know that streams and rivers “breathe” in a similar way?

The United States is home to more than 250,000 of these flowing bodies of water that connect to coastal zones and oceans. They vary in size, from small streams to large rivers, but all take in oxygen and give off carbon dioxide and other greenhouse gases like methane. 

Over recent years, a team of scientists led by Pacific Northwest National Laboratory (PNNL) has been immersed in crucial research around the processes and interactions that contribute to greenhouse gas dynamics. Their work focuses on whole networks of streams and rivers, as well as the land surrounding these systems.       

Their work also includes factors that can disturb how streams and rivers breathe. Some of these disturbances happen beyond streams, like wildfires, but still impact how streams breathe by changing how material enters streams. Understanding these impacts is key to addressing challenges related to water quality, global carbon cycling, and climate change.

A Larger Area of Arctic Seafloor is Exposed to Sunlight

Photo Credit: © Ignacio Garrido

Most of the sunlight reaching the Arctic Ocean is reflected by sea ice, shielding ocean ecosystems from light. As Arctic sea ice continues to melt, larger areas of the ocean and seafloor become exposed to sunlight, potentially allowing more photosynthesis to occur and making the Arctic Ocean more productive. However, this does not seem to be occurring uniformly across the Arctic Ocean.

Over the past 25 years, the amount of summer Arctic sea ice has diminished by more than 1 million square kilometers. As a result, vast areas of the Arctic Ocean are now, on average, ice free in summer. Scientists are closely monitoring how this impacts sunlight availability and marine ecosystems in the far north.

Many questions arise when such large areas become ice-free and can receive sunlight. A prevailing paradigm suggests that the Arctic Ocean is rapidly becoming more productive as sunlight becomes more abundant in the marine environment. However, it is unclear how ecosystems will evolve in response to increasing sunlight availability and how different parts of the marine ecosystem will be affected, says Karl Attard, a marine scientist and Associate Professor at the Department of Biology.

Attard has led an international research team investigating sunlight availability and photosynthetic production on the understudied Arctic seafloor. Their study has been published in the scientific journal Proceedings of the National Academy of Sciences (PNAS).

Monday, March 4, 2024

Producing Hydrogen from Rocks Gains Steam as Scientists Advance New Methods

Researchers are studying chemical catalysts that can produce hydrogen gas from iron-rich rocks.
Photo Credit: Toti Larson / UT Austin.

In a project that could be a game changer for the energy transition, researchers at The University of Texas at Austin are exploring a suite of natural catalysts to help produce hydrogen gas from iron-rich rocks without emitting carbon dioxide.

If the scientists are successful, the project could jump-start a brand-new type of hydrogen industry: geologic hydrogen.

“We’re producing hydrogen from rocks,” said Toti Larson, a research associate professor at the UT Jackson School of Geosciences Bureau of Economic Geology and the lead researcher on the project. “It’s a type of non-fossil fuel production of hydrogen from iron-rich rocks that has never been attempted at an industrial scale.”

The research team recently received a $1.7 million grant from the Department of Energy and is collaborating with scientists at the University of Wyoming’s School of Energy Resources to explore the feasibility of this process on different rock types across the United States.

Humans have driven the Earth’s freshwater cycle out of its stable state

For example, the Nile river basin has experienced exceptionally dry streamflow and wet soil moisture conditions, indicating changes driven by irrigation.
Photo Credit: Ron Porter

A new analysis of freshwater resources across the globe shows that human activity has pushed variation in the planet’s freshwater cycle well outside of its pre-industrial range. The study shows that the updated planetary boundary for freshwater change was surpassed by the mid-twentieth century. In other words, for the past century, humans have been pushing the Earth’s freshwater system far beyond the stable conditions that prevailed before industrialization. 

This is the first time that global water cycle change has been assessed over such a long timescale with an appropriate reference baseline. The findings, published in Nature Water, show that human pressures, such as dam construction, large-scale irrigation and global warming, have altered freshwater resources to such an extent that their capacity to regulate vital ecological and climatic processes is at risk.

The international research team calculated monthly streamflow and soil moisture at a spatial resolution of roughly 50x50 kilometers using data from hydrological models that combine all major human impacts on the freshwater cycle. As a baseline, they determined the conditions during the pre-industrial period (1661-1860). They then compared the industrial period (1861-2005) against this baseline.

Thursday, February 29, 2024

Lake Ecosystems: Nitrogen has been underestimated

Algae growth in shallow lakes around the world is affected not only by phosphorus but also by nitrogen
Photo Credit: Liz Harrell

An ecological imbalance in a lake can usually be attributed to increased nutrient inputs. The result: increased phytoplankton growth, oxygen deficiency, toxic cyanobacterial blooms and fish kills. Until now, controls in lake management have focused primarily on phosphorus inputs to counteract this effect. Now, this dogma is shaken by a study performed by the Helmholtz Centre for Environmental Research (UFZ) in collaboration with the University of Aarhus (Denmark) and the University of Life Sciences (Estonia) and published in Nature Communications. The researchers show that nitrogen is also a critical driver for phytoplankton growth in lakes worldwide. 

The input of phosphorus and nitrogen from agricultural sources and sewage treatment plants can have a strong effect on phytoplankton growth in rivers and lakes. "However, it was previously assumed that phytoplankton growth in lakes is mostly limited and driven by the availability of phosphorus," says lead author Dr. Daniel Graeber from the UFZ. The underlying theory: If only small quantities of phosphorus are available in a lake, phytoplankton growth is correspondingly limited. In contrast, large quantities of phosphorus will massively drive phytoplankton growth. "In this explanatory model, nitrogen plays no role," says Graeber. "This is based on the fact that specific cyanobacteria in the water can bind the nitrogen contained in the air and introduce it into the lake. This would therefore preclude a long-term nitrogen deficiency in lakes." Nor could an excess supply of nitrogen promote phytoplankton growth - and therefore could not ultimately give rise to eutrophication. "This model forms the basis for lake management worldwide, where the emphasis has been on controlling phosphorus inputs to counteract lake eutrophication," explains Dr. Thomas A. Davidson, limnologist at Aarhus University and last author of the study. "Reducing phosphorus inputs repeatedly fails to prevent eutrophication. This therefore gave rise to the question of whether the water equation included yet another unknown." In its present study, the research team has now clearly identified nitrogen as such a factor, and is thus indicating new directions for inland water science (limnology) and lake management. 

Wednesday, February 28, 2024

Study finds drought fuels invasive species after wildfires

Parry’s Phacelia, native to Southern California, grows beneath burnt brush, at the Loma Ridge site where UCI’s Sarah Kimball conducted the research.
Photo Credit: Jessica Rath / UCI

In a study recently published in the journal Ecology, University of California, Irvine scientists uncover the intricate dance between drought, wildfires and invasive species in Southern California’s coastal sage scrub ecosystems.

Titled “Long-term drought promotes invasive species by reducing wildfire severity,” the research, led by Sarah Kimball, Ph.D., director of the Center for Environmental Biology at UCI, sheds light on the critical interplay of these factors and its profound implications for ecosystem health.

The research, conducted at the Loma Ridge Global Change Experiment, showcases how prolonged drought acts as a catalyst, influencing not only the severity of wildfires but also paving the way for invasive species to take center stage. By simulating drought conditions, the study clarifies connections between climate change, wildfire dynamics, and shifts in plant communities.

Reduced fire severity associated with drought creates an environment conducive to invasive species. Non-native grasses, in particular, thrive in these conditions, potentially leading to a transformation of the landscape and abundance and diversity of native species.

80 mph speed record for glacier fracture helps reveal the physics of ice sheet collapse

In this illustration, seawater flows deep below the surface into an actively opening ice shelf rift in Antarctica. New research shows that such rifts can open very quickly, and that the seawater rushing in helps control the speed of ice shelf breakage.
Illustration Credit: Rob Soto

There’s enough water frozen in Greenland and Antarctic glaciers that if they melted, global seas would rise by many feet. What will happen to these glaciers over the coming decades is the biggest unknown in the future of rising seas, partly because glacier fracture physics is not yet fully understood.

A critical question is how warmer oceans might cause glaciers to break apart more quickly. University of Washington researchers have demonstrated the fastest-known large-scale breakage along an Antarctic ice shelf. The study, recently published in AGU Advances, shows that a 6.5-mile (10.5 kilometer) crack formed in 2012 on Pine Island Glacier — a retreating ice shelf that holds back the larger West Antarctic ice sheet — in about 5 and a half minutes. That means the rift opened at about 115 feet (35 meters) per second, or about 80 miles per hour.

“This is to our knowledge the fastest rift-opening event that’s ever been observed,” said lead author Stephanie Olinger, who did the work as part of her doctoral research at the UW and Harvard University and is now a postdoctoral researcher at Stanford University. “This shows that under certain circumstances, an ice shelf can shatter. It tells us we need to look out for this type of behavior in the future, and it informs how we might go about describing these fractures in large-scale ice sheet models.”

Scientists provide first detailed estimates of how much sediment is supplied to coral islands from the reef system

The island of Dhigelabadhoo in the Maldives is the main field site of the ARISE program
Credit: University of Plymouth

Scientists have produced the first detailed estimates of how much sediment is transported onto the shores of coral reef islands, and how that might enable them to withstand the future threats posed by climate change.

Coral reef islands are low-lying accumulations of sand and gravel-sized sediment deposited on coral reef surfaces.

The sediments are derived from the broken down remains of corals and other organisms that grow on the surrounding reef. Therefore, the rate of supply of sediment from reefs is a critical control on island formation and future change.

The international team of researchers used data available for 28 reef islands in the Indian and Pacific Oceans, widely acknowledged to be among the world’s most vulnerable environments to rising seas.

By identifying the amount of sediment present within reef islands, and comparing this against the known age of the islands, they were able to determine the average amount of sediment delivered to the islands from surrounding coral reefs over their histories.

Tuesday, February 27, 2024

Walleye struggle with changes to timing of spring thaw

Within a few days of ice-off, when a lakes’ frozen lid has melted away, walleye begin laying eggs and fertilizing them. When lakes thaw earlier than usual, the young walleye that hatch in Midwestern waters may have a more difficult time surviving.
Image Credit: Copilot AI

Walleye are one of the most sought-after species in freshwater sportfishing, a delicacy on Midwestern menus and a critically important part of the culture of many Indigenous communities. They are also struggling to survive in the warming waters of the Midwestern United States and Canada.

According to a new study published in the journal Limnology and Oceanography Letters, part of the problem is that walleye are creatures of habit, and the seasons — especially winter — are changing so fast that this iconic species of freshwater fish can’t keep up.

The timing of walleye spawning — when the fish mate and lay their eggs — has historically been tied to the thawing of frozen lakes each spring, says the study’s lead author, Martha Barta, a research technician at the University of Wisconsin–Madison. Now, due to our changing climate, walleye have been “unable to keep up with increasingly early and more variable ice-off dates,” Barta says.

Within a few days of ice-off, when a lakes’ frozen lid has melted away, walleye begin laying eggs and fertilizing them. In a normal year, that timing sets baby fish up for success once they hatch. But, Barta says, “climate change is interrupting the historical pairing of ice-off and walleye spawning, and that threatens the persistence of walleye populations across the Upper Midwest.”

You may be breathing in more tiny nanoparticles from your gas stove than from car exhaust

Brandon Boor, a Purdue associate professor of civil engineering, studies how everyday activities like cooking on a gas stove can affect indoor air quality.
Photo Credit: Kelsey Lefever / Purdue University

Cooking on your gas stove can emit more nano-sized particles into the air than vehicles that run on gas or diesel, possibly increasing your risk of developing asthma or other respiratory illnesses, a new Purdue University study has found.

“Combustion remains a source of air pollution across the world, both indoors and outdoors. We found that cooking on your gas stove produces large amounts of small nanoparticles that get into your respiratory system and deposit efficiently,” said Brandon Boor, an associate professor in Purdue’s Lyles School of Civil Engineering, who led this research.

Based on these findings, the researchers would encourage turning on a kitchen exhaust fan while cooking on a gas stove. 

The study, published in the journal PNAS Nexus, focused on tiny airborne nanoparticles that are only 1-3 nanometers in diameter, which is just the right size for reaching certain parts of the respiratory system and spreading to other organs. 

Recent studies have found that children who live in homes with gas stoves are more likely to develop asthma. But not much is known about how particles smaller than 3 nanometers, called nanocluster aerosol, grow and spread indoors because they’re very difficult to measure.

“These super tiny nanoparticles are so small that you’re not able to see them. They’re not like dust particles that you would see floating in the air,” Boor said. “After observing such high concentrations of nanocluster aerosol during gas cooking, we can’t ignore these nano-sized particles anymore.”

Glacier melting destroys important climate data archive

Corbassière glacier at Grand Combin in the canton of Valais
Photo Credit: Peter Meyer-Herzog

As part of the Ice Memory initiative, PSI researchers, with colleagues from the University of Fribourg and Ca’ Foscari University of Venice as well as the Institute of Polar Sciences of the Italian National Research Council (CNR), analyzed ice cores drilled in 2018 and 2020 from the Corbassière glacier at Grand Combin in the canton of Valais. A comparison of the two sets of ice cores published in Nature Geoscience shows: Global warming has made at least this glacier unusable as a climate archive.

Reliable information about the past climate and air pollution can no longer be obtained from the Corbassière glacier in the Grand Combin massif, because alpine glacier melting is progressing more rapidly than previously assumed. This sobering conclusion was reached by researchers led by Margit Schwikowski, head of the Laboratory for Environmental Chemistry at PSI, and Carla Huber, PhD student and first author of the study, when they compared the signatures of particulate matter locked in the annual layers of the ice. Glaciers are invaluable for climate research. The climatic conditions and atmospheric compositions of past ages are preserved in their ice. Therefore, they can serve, in much the same way as tree rings and ocean sediments, as a so-called climate archive for research.

Normally, the amount of particle-bound trace substances in ice fluctuates with the seasons. SubstPeter Meyer-Herzogances such as ammonium, nitrate, and sulfate come from the air and are deposited on the glacier through snowfall: The concentrations are high in summer and low in winter, because lower amounts of polluted air can rise from the valley when the air is cold. The 2018 ice core, which was drilled from depths of up to 14 meters during a preliminary study and contains deposits dating back to 2011, shows these fluctuations as expected. But the core from 2020, from a depth of up to 18 metres – drilled under the leadership of PSI researcher Theo Jenk – shows those fluctuations only for the upper three or four annual layers. Deeper in the ice – that is, farther in the past – the curve indicating the concentration of trace substances becomes noticeably flatter, and the total amount is lower. Schwikowski’s team reports on this in the current issue of the journal Nature Geoscience.

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