2,000 years of genetic history in Scandinavia elucidates Viking age to modern day

Peer-Reviewed Publication

CELL PRESS

 

IMAGE: UNDERWATER KRONAN EXCAVATIONS view more 

CREDIT: LARS EINARSSON

A new study reported in the journal Cell on January 5 captures a genetic history across Scandinavia over 2,000 years, from the Iron Age to the present day. This look back at Scandinavian history is based on an analysis of 48 new and 249 published ancient human genomes representing multiple iconic archaeological sites together with genetic data from more than 16,500 people living in Scandinavia today.

Among other intriguing findings, the new study led by Stockholm University and deCODE genetics (Reykjavik) offers insight into migration patterns and gene flow during the Viking age (750–1050 CE). It also shows that ancestries that were introduced into the area during the Viking period later declined for reasons that aren’t clear.

“Although still evident in modern Scandinavians, levels of non-local ancestry in some regions are lower than those observed in ancient individuals from the Viking to Medieval periods,” said Ricardo Rodríguez-Varela of Stockholm University. “This suggests that ancient individuals with non-Scandinavian ancestry contributed proportionately less to the current gene pool in Scandinavia than expected based on the patterns observed in the archaeological record.”

 “Different processes brought people from different areas to Scandinavia [at different times],” added Anders Götherström, Stockholm University.

The researchers hadn’t originally planned to piece together Scandinavian history over time and space. Rather, they were working on three separate studies focused on different archaeological sites.

“When we were analyzing the genetic affinities of the individuals from different archaeological sites such as the Vendel period boat burials, Viking period chamber burials, and well-known archaeological sites like the Migration period Sandby borg ringfort, known for the massacre that occurred there [in] 500 CE, and individuals from the 17th century royal Swedish warship Kronan, we start to see differences in the levels and origin of non-local ancestry across the different regions and periods of Scandinavia,” Rodríguez-Varela explained.

“Initially, we were working with three different studies,” Götherström said. “One on Sandby borg, one on the boat burials, and one on the man-of-war Kronan. At some point it made more sense to unite them to one study on the Scandinavian demography during the latest 2,000 years.”

The goal was to document how past migrations have affected the Scandinavian gene pool across time and space to better understand the current Scandinavian genetic structure. As reported in the new study, the researchers found regional variation in the timing and magnitude of gene flow from three sources: the eastern Baltic, the British Irish Isles, and southern Europe.

British Irish ancestry was widespread in Scandinavia from the Viking period, whereas eastern Baltic ancestry is more localized to Gotland and central Sweden. In some regions, a drop in current levels of external ancestry suggests that ancient immigrants contributed proportionately less to the modern Scandinavian gene pool than indicated by the ancestry of genomes from the Viking and Medieval periods.

Finally, the data show that a north-south genetic cline that characterizes modern Scandinavians is mainly due to differential levels of Uralic ancestry. It also shows that this cline existed in the Viking Age and possibly even earlier.

Götherström suggests that what the data reveal about the nature of the Viking period is perhaps most intriguing. The migration from the west impacted all of Scandinavia, and the migration from the east was sex biased, with movement primarily of female people into the region. As the researchers write, the findings overall “indicate a major increase [in gene flow] during the Viking period and a potential bias toward females in the introduction of eastern Baltic and, to a lesser extent, British-Irish ancestries.

“Gene flow from the British-Irish Isles during this period seems to have had a lasting impact on the gene pool in most parts of Scandinavia,” they continued. “This is perhaps not surprising given the extent of Norse activities in the British-Irish Isles, starting in the 8th century with recurrent raids and culminating in the 11th century North Sea Empire, the personal union that united the kingdoms of Denmark, Norway, and England. The circumstances and fate of people of British-Irish ancestry who arrived in Scandinavia at this time are likely to have been variable, ranging from the forced migration of slaves to the voluntary immigration of more high-ranking individuals such as Christian missionaries and monks.”

Overall, the findings show that the Viking period in Scandinavia was a very dynamic time, they say, with people moving around and doing many different things. In future work, they hope to add additional genetic data in hopes of learning more about how the ancestries that arrived during the Viking period were later diluted. They’d also like to pinpoint when the north-south cline was shaped based on study of larger ancient datasets from the north.

“We need more pre-Viking individuals form north Scandinavia to investigate when the Uralic ancestry enter in this region,” Rodríguez-Varela said. "Also, individuals from 1000 BCE to 0 are very scarce, [and] retrieving DNA from Scandinavian individuals with these chronologies will be important to understand the transition from the Bronze Age to the Iron Age in this part of the world. Finally, more individuals from the Medieval period until the present will help us to understand when and why we observe a reduction in the levels of non-local ancestry in some current regions of Scandinavia.”

“There is so much fascinating information about our prehistory to be explored in ancient genomes,” Götherström said.

Sandby borg archaeological excavations

CREDIT

Daniel Lindskog

Underwater Kronan excavations

CREDIT

Lars Einarsson

This research was supported by the Swedish Research Council project ID 2019-00849_VR and ATLAS (Riksbankens Jubileumsfond). Part of the modern dataset was supported by a research grant from Science Foundation Ireland (SFI), grant number 16/RC/3948, and co-funded under the European Regional Development Fund and by FutureNeuro industry partners.

Cell, Rodríguez-Varela et al.: “The genetic history of Scandinavia from the Roman Iron Age to the present” https://www.cell.com/cell/fulltext/S0092-8674(22)01468-4

Cell (@CellCellPress), the flagship journal of Cell Press, is a bimonthly journal that publishes findings of unusual significance in any area of experimental biology, including but not limited to cell biology; molecular biology; neuroscience; immunology; virology and microbiology; cancer; human genetics; systems biology; signaling; and disease mechanisms and therapeutics. Visit http://www.cell.com/cell. To receive Cell Press media alerts, contact press@cell.com.

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JOURNAL

Cell

DOI

10.1016/j.cell.2022.11.024 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

The genetic history of Scandinavia from the Roman Iron Age to the present

ARTICLE PUBLICATION DATE

5-Jan-2023

DNA from archaeological remains shows that immigration to Scandinavia was exceptional during the Viking period

Peer-Reviewed Publication

STOCKHOLM UNIVERSITY

 

IMAGE: KRONAN UNDERWATER EXCAVATIONS. PHOTO: LARS EINARSSON view more 

CREDIT: PHOTO: LARS EINARSSON

A new study based on 297 ancient Scandinavian genomes analysed together with the genomic data of 16,638 present day Scandinavians resolve the complex relations between geography, ancestry, and gene flow in Scandinavia – encompassing the Roman Age, the Viking Age and later periods. A surprising increase of variation during the Viking period indicates that gene flow into Scandinavia was especially intense during this period.

An international study coordinated from Stockholm and Reykjavik investigates the development of the Scandinavian gene pool over the latest 2000 years. In this effort the scientists relied on historic and prehistoric genomes, and from material excavated in Scandinavia. These ancient genomes were compared with genomic data from 16,638 contemporary Scandinavians. As the geographical origin and the datings were known for all these individuals, it was possible to resolve the development of the gene pool to a level never realised previously.

Dr Ricardo Rodríguez Varela at the Centre for Palaeogenetics*, who analysed all the data and extracted some of the ancient DNA used in the study, explains: “With this level of resolution we not only confirm the Viking Age migration. We are also able to trace it to the east Baltic region, the British-Irish Isles and southern Europe. But not all parts of Scandinavia received the same amounts of gene flow from these areas. For example, while British-Irish ancestry became widespread in Scandinavia the eastern-Baltic ancestry mainly reached Gotland and central Sweden.”

The gene pool bounced back after the Viking period
Another new discovery in this study was what happened to the gene pool after the Viking period. The scientists were surprised to find that it bounced back in the direction of what it looked like before the Viking period migration.

Professor Anders Götherström at the Centre for Palaeogenetics, who is a senior scientist on the study, is intrigued: “Interestingly, the non-local ancestry peaks during the Viking period while being lower before and after. The drop in current levels of external ancestry suggests that the Viking-period migrants got less children, or somehow contributed proportionally less to the gene pool than the people who were already in Scandinavia.”

Yet a new discovery was the history of the northern Scandinavian gene pool. There is a genetic component in northern Scandinavia that is rare in central and western Europe, and the scientists were able to track this component in northern Scandinavia through the latest 1000 years.

Dr Ricardo Rodríguez Varela comments, “We suspected that there was a chronology to the northern Scandinavian gene pool, and it did indeed prove that a more recent influx of Uralic ancestry into Scandinavia define much of the northern gene pool. But if it is recent, it is comparatively so. For example, we know that this Uralic ancestry was present in northern Scandinavia as early as during the late Viking period”.

Based on well-known Swedish archaeological sites
The study is based on a number of well-known Swedish archaeological sites. For example, there are genomes from the 17th century warship Kronan, from the Viking and Vendel period boat burials in the lake Mälaren Valley, and from the migration period ring fortress Sandby borg on Öland.

Anders Götherström conclude: “We were working on a number of smaller studies on different archaeological sites. And at some point it just made sense to combine them into a larger study on the development of the Scandinavian gene pool.

The study, published today in Cell, is an international effort with several collaborators, but it was led by Dr Ricardo Rodríguez Varela and Professor Anders Götherstörm at Stockholm University, and Professor Agnar Helgason, and Kristján Moore at deCODE in Reykavijk.

*The Centre for Palaeogenetics (CPG) is a joint venture between Stockholm University and the Swedish Museum of Natural History.

CAPTION

Sandby Borg archaeological site. Photo: Daniel Lindskog

DNA lab at Stockholm University.

CREDIT

Photo: David Díaz del Molino.

More information:
The article “The genetic history of Scandinavia from the Roman Iron Age to the present” is published in Cell. https://www.cell.com/
This research was supported by The Swedish Research Council Project ID 2019-00849_VR and ATLAS (Riksbankens Jubileumsfond).

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JOURNAL

Cell

DOI

10.1016/j.cell.2022.11.024 

ARTICLE TITLE

The genetic history of Scandinavia from the Roman Iron Age to the present

ARTICLE PUBLICATION DATE

5-Jan-2023

Research could simplify process for calculating soil carbon credits

Study led by the University of Illinois Agroecosystem Sustainability Center provides new insights for quantifying cropland carbon budgets and credits, two important metrics for mitigating climate change

Peer-Reviewed Publication

UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN INSTITUTE FOR SUSTAINABILITY, ENERGY, AND ENVIRONMENT

 

IMAGE: ILLUSTRATION OF SOIL CARBON CREDITS CALCULATION BASED ON PROCESS-BASED MODELS. THE UNCERTAINTY IN THE CALCULATED CARBON CREDITS IS MUCH SMALLER THAN THE UNCERTAINTY IN THE INITIAL SOIL CARBON STOCK. SOURCE: GEODERMA view more 

CREDIT: GEODERMA

A study led by researchers at the Agroecosystem Sustainability Center (ASC) at the University of Illinois Urbana-Champaign provides new insights for quantifying cropland carbon budgets and soil carbon credits, two important metrics for mitigating climate change.

The results, outlined in a paper published in the soil science journal Geoderma, could simplify the process for calculating soil carbon credits, which reward farmers for conserving soil carbon through crop rotation, no-tillage, cover crops, and other conservation practices that improve soil health. The project was funded by the U.S. Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E).

Agricultural activity causes a significant amount of soil organic carbon (SOC) to be released into the atmosphere as carbon dioxide, a greenhouse gas that contributes to climate change. Several conservation practices have been suggested to help sequester that carbon in the soil, but their potential to enhance the total SOC in a soil profile, known as SOC stock, needs to be assessed locally. Such assessments are key to the emerging agricultural carbon credit market.

Accurately calculating cropland carbon budgets and soil carbon credits is critical to assessing the climate change mitigation potential of agriculture as well as conservation practices. Those calculations are sensitive to local soil and climatic conditions, especially the initial SOC stock used to initialize the calculation models. However, various uncertainties exist in SOC stock datasets, and it’s unclear how that can affect cropland carbon budget and soil carbon credit calculations, according to lead author Wang Zhou, Research Scientist at the ASC and the Department of Natural Resources and Environmental Sciences (NRES) at Illinois.

In this study, researchers used an advanced and well-validated agroecosystem model, known as ecosys, to assess the impact of SOC stock uncertainty on cropland carbon budget and soil carbon credit calculation in corn-soybean rotation systems in the U.S. Midwest.

They found that high-accuracy SOC concentration measurements are needed to quantify a cropland carbon budget, but the current publicly available soil dataset is sufficient to accurately calculate carbon credits with low uncertainty.

“This is a very important study that reveals counter-intuitive findings. Initial soil carbon data is very important for all the downstream carbon budget calculation. However, carbon credit measures the relative soil carbon difference between a new practice and a business-as-usual scenario. We find that the uncertainty of initial soil carbon data has limited impacts on the final calculated soil carbon credit,” said ASC Founding Director Kaiyu Guan, Blue Waters Professor in NRES and the National Center for Supercomputing Applications (NCSA) at Illinois and lead of the DOE-funded SMARTFARM project at iSEE, which featured several co-authors on this paper.

The results indicate that expensive in-field soil sampling may not be required when focusing only on quantifying soil carbon credits from farm conservation practices – a major benefit for the agricultural carbon credit market.

“Uncertainty in SOC concentration measurements has a large impact on cropland carbon budget calculation, indicating novel approaches such as hyperspectral remote sensing are needed to estimate topsoil SOC concentration at large scale to reduce the uncertainty from interpolation. However, uncertainty in SOC concentration only has a slight impact on soil carbon credit calculation, suggesting solely focusing on quantifying soil carbon credit from additional management practices may not require extensive in-field soil sampling – an advantage considering its high cost,” Zhou said.

“The approach in this study can be applied to other models and used to assess important uncertainties of the carbon sequestration potential of various conservative land management practices,” said Bin Peng, the other primary author of the study and Senior Research Scientist at ASC and NRES.

The ASC was jointly established by the Institute for Sustainability, Energy and Environment (iSEE), the College of Agricultural, Consumer and Environmental Sciences (ACES), and the Office of the Vice Chancellor for Research and Innovation at Illinois.

Co-authors on the study included ASC Associate Director Andrew Margenot, Assistant Professor of Crop Sciences; DoKyoung Lee, Professor of Crop Sciences and ASC founding faculty member; Even DeLucia, Professor Emeritus of Plant Biology and ASC founding faculty member; Sheng Wang of ASC and NRES Research Assistant Professor; Ziqi Qin of ASC and graduate student in NRES; NRES Professor Michelle Wander; Jinyun Tang, Staff Scientist of the Earth and Environmental Sciences Area, Lawrence Berkeley National Laboratory; Zhenong Jin, Assistant Professor in the Department of Bioproducts and Biosystems Engineering, University of Minnesota; and Robert Grant, Professor in the Department of Renewable Resources, University of Alberta, Edmonton, Canada.

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JOURNAL

Geoderma

DOI

10.1016/j.geoderma.2022.116254 

METHOD OF RESEARCH

Computational simulation/modeling

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

How does uncertainty of soil organic carbon stock affect the calculation of carbon budgets and soil carbon credits for croplands in the U.S. Midwest?

ARTICLE PUBLICATION DATE

1-Jan-2023

New York City’s greenery absorbs a surprising amount of its carbon emissions

Previously unrecognized vegetation in backyards and on curbs does outsize work

Peer-Reviewed Publication

COLUMBIA CLIMATE SCHOOL

 

IMAGE: ZOOMING IN ON SEVERAL COMPLETELY BUILT-UP BLOCKS IN THE PROSPECT HEIGHTS NEIGHBORHOOD OF BROOKLYN, PINK AREAS ARE BUILDINGS; PURPLE ONES ARE PAVED SURFACES INCLUDING SIDEWALKS AND PARKING AREAS. IN BACKYARDS AND ALONG THE STREETS, DARK GREENS SIGNIFY TREE CANOPY; LIGHT GREENS, SHRUBS OR GRASS. view more 

CREDIT: WEI ET AL., ENVIRONMENTAL RESEARCH LETTERS, 2022

A study of vegetation across New York City and some densely populated adjoining areas has found that on many summer days, photosynthesis by trees and grasses absorbs all the carbon emissions produced by cars, trucks and buses, and then some. The surprising result, based on new hyper-local vegetation maps, points to the underappreciated importance of urban greenery in the carbon cycle. The study was just published in the journal Environmental Research Letters.

Using fine-grained vegetation maps, the researchers documented large amounts of previously unrecognized greenery scattered in small spots even in highly developed areas, and found it is performing an outsize role in the exchange of atmospheric gases. They reached their conclusions by modeling carbon uptake of every bit of lawn and tree canopy, and studying data from instrument towers that measure the air’s carbon dioxide content on a continuous basis.

The findings are significant because urban areas account for more than 70 percent of human carbon dioxide emissions; New York City is the United States’ number one emitter, and third largest in the world.

“There is a lot more greenery than we thought, and that’s what drives our conclusion,” said lead author Dandan Wei, a postdoctoral researcher at the Columbia Climate School’s Lamont-Doherty Earth Observatory. “This tells us that the ecosystem matters in New York City, and if it matters here, it probably matters everywhere else.”

Most previous studies have calculated carbon uptake of vegetation by looking mainly at contiguous tracts of forest and grassland, but these comprise only about 10 percent of the metro area. Using newly available aerial radar imagery of New York City that mapped vegetation in unprecedented 6-inch grids, Wei and her colleagues included developed areas—the other 90 percent of the region, left out in most models. Here, they were able to pick out individual street trees, little backyard gardens, overgrown vacant lots and other small features. Outlying areas beyond the five boroughs—about a third of the 2,170-square kilometer study area—were broken down into 30-meter grids, which is still relatively fine resolution.

“Most people have assumed that New York City is just a grey box, that it’s biogenically dead,” said Lamont-Doherty atmospheric chemist Roísín Commane, who coauthored the paper. “But just because there’s a concrete sidewalk somewhere doesn’t mean there’s not also a tree that’s shading it.”

The researchers determined that tree canopies cover some 170 square kilometers of New York City, or about 22 percent of its area; grasses account for another 94 square kilometers, or 12 percent. To figure out how the greenery interacted with carbon emissions, they looked at June through August 2018, when the metro area emitted a total of some 14.7 million tons of carbon dioxide. The largest sources were the power industry and energy for buildings; road transport accounted for about 1.2 million tons. Global average CO2 levels are currently about 417 parts per million, but around New York, they routinely reach 460 or more, said Commane.

Levels would be even higher were it not for all the vegetation, especially that in the newly mapped developed areas; they accounted for nearly 85 percent of the daily carbon uptake, according to the study. On many summer days, total uptake equaled up to 40 percent of a summer afternoon’s total emissions from all sources. The scientists saw carbon dioxide levels swing up in the morning in tandem with traffic and other activities, and come down somewhat in afternoon, as grass and trees went to work.

The caveat: carbon uptake of course occurs only during the local growing season, which in relatively chilly New York runs mid-April to mid-October. Vegetation in cities situated in warmer climates probably plays a bigger role in carbon uptake, said Wei.

New York City is actively pushing to increase its tree cover. One of the team’s next projects: characterizing coverage by species, and helping figure out the relative benefits of different ones. Hardy, fast-growing oaks are a common choice for this region, but research has found they also give off a fair amount of isoprene, a volatile compound that reacts with emissions from vehicles to create polluting ozone. Sweet gums, another common tree, produce a similar amount of isoprene, but have different growth characteristics. “More trees are always going to be better, no matter what they are,” said Wei. “But we could use an assessment of which ones are the best.”

The study was coauthored by Andrew Reinmann of the City University of New York and Luke Schiferl of Lamont-Doherty.

Researchers studied carbon uptake by vegetation in New York City and parts of the surrounding area. Greens show areas of contiguous forest, marsh or grassland. The rest is developed, with purple areas at highest intensity, but a surprising amount of vegetation is found there, too, along sidewalks, in backyards and other small features.

CREDIT

Wei et al., Environmental Research Letters

JOURNAL

Environmental Research Letters

DOI

10.1088/1748-9326/aca68f 

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

High resolution modeling of vegetation reveals large summertime biogenic CO2 fluxes in New York City

Team projects 2 out of 3 glaciers could be lost by 2100

COLLEGE OF ENGINEERING, CARNEGIE MELLON UNIVERSITY

 

IMAGE: GLACIERS FROM A RESEARCH EXPEDITION view more 

CREDIT: CARNEGIE MELLON COLLEGE OF ENGINEERING

Assistant Professor David Rounce of Civil and Environmental Engineering led an international effort to produce new projections of glacier mass loss through the century under different emissions scenarios. The projections were aggregated into global temperature change scenarios to support adaptation and mitigation discussions, such as those at the recent United Nations Conference of Parties (COP 27). His work showed that the world could lose as much as 41 percent of its total glacier mass this century—or as little as 26 percent—depending on today’s climate change mitigation efforts.

Specifically, Rounce and his team found that in a future scenario with continued investment in fossil fuels, over 40 percent of the glacial mass will be gone within the century, and over 80 percent of glaciers by number could well disappear. Even in a best-case, low-emissions scenario, where the increase in global mean temperature is limited to +1.5° C relative to pre-industrial levels, over 25 percent of glacial mass will be gone and nearly 50 percent of glaciers by number are projected to disappear. A majority of these lost glaciers are small (less than one km2) by glacial standards, but their loss can negatively impact local hydrology, tourism, glacier hazards, and cultural values.

His work provides better context for regional glacier modeling, and he hopes it will spur climate policymakers to lower temperature change goals beyond the 2.7° C mark that pledges from COP-26 are projected to hit. Smaller glacial regions like Central Europe and Western Canada and the United States will be disproportionately affected by temperatures rising more than 2° C. At a 3° C rise, glaciers in these regions almost disappear completely.

Rounce noted that the way in which glaciers respond to changes in climate takes a long time. He describes the glaciers as extremely slow-moving rivers. Cutting emissions today will not remove previously emitted greenhouse gasses, nor can it instantly halt the inertia they contribute to climate change, meaning even a complete halt to emissions would still take between 30 and 100 years to be reflected in glacier mass loss rates.

Many processes govern how glaciers lose mass and Rounce’s study advances how models account for different types of glaciers, including tidewater and debris-covered glaciers. Tidewater glaciers refer to glaciers that terminate in the ocean, which causes them to lose a lot of mass at this interface. Debris-covered glaciers refer to glaciers that are covered by sand, rocks, and boulders. Prior work by Rounce has shown that the thickness and distribution of debris cover can have a positive or negative effect on glacial melt rates across an entire region, depending on the debris thickness. In this newest work, he found that accounting for these processes had relatively little impact on the global glacier projections, but substantial differences in mass loss were found when analyzing individual glaciers.

The model is also calibrated with an unprecedented amount of data, including individual mass change observations for every glacier, which provide a more complete and detailed picture of glacier mass change. The use of supercomputers was thus essential to support the application of state-of-the-art calibration methods and the large ensembles of different emissions scenarios.

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JOURNAL

Science

New approach to predicting glacier response to climate change shows significant impacts of every temperature increase

Peer-Reviewed Publication

AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE (AAAS)

In a study that represents “a substantial step forward in predictive modeling” of glacier response to climate change, researchers present predictions for the fate of all Earth’s mountain glaciers, which total more than 215,000 under various policy-relevant climate scenarios. They report that even under the most optimistic scenarios, glaciers globally will lose substantially more mass and contribute to more sea-level rise than current estimates, including those published in the most recent IPCC report, indicate. “[E]very increase in temperature has significant consequences with respect to glacier contribution to sea level rise, the loss of glaciers around the world, and changes to hydrology, ecology, and natural hazards,” these authors, led by David Rounce, say. In a related Perspective, Guðfinna Aðalgeirsdóttir and Timothy James reflect on how recent studies have revealed that positive opportunistic framing of climate change is more effective at inciting public support for climate policies than focusing on urgency and consequences. They say the authors of this study, “while issuing a stark warning about the consequences of insufficient action, achieve this framing with an important message: Although it is too late to avoid losing many glaciers, any effort to limit global mean temperature rise will have a direct effect on reducing how many glaciers will be lost.”

Rates of glacier melt have increased over the past few decades, and the continued decline of these vulnerable features will affect sea level rise, freshwater availability for nearly 2 billion people, and risk from glacier-related hazards. Projecting glacier mass loss is critical to future global climate adaptation and mitigation efforts. However, a comprehensive understanding of how Earth’s more than 215,000 individual glaciers (excluding the Greenland and Antarctic ice sheets) will respond under various climate warming scenarios remains challenging. Existing projections are limited to regional scales and neglect key physical processes controlling glacier mass loss. To address these limitations, Rounce and colleagues took advantage of new datasets to produce a set of global glacier projections that explicitly account for glacier dynamics. They produced projections for all of Earth’s individual glaciers under +1.5°Celsius (C), +2°C, +3°C, and +4°C temperature change scenarios by 2100 relative to pre-industrial levels. The findings suggest that glaciers are projected to lose 26±6% to 41±11% of their total mass by 2100, relative to 2015, under temperature increases of 1.5°C to 4°C, respectively. This means that even under the best-case scenarios, where global mean temperature rise is limited to 1.5°C, as many as half of the planet’s glaciers will be lost by 2100. Based on recent climate pledges from COP-26, which project global mean temperature to increase by 2.7°C over the next century, Earth will likely experience a near-complete deglaciation of entire mid-latitude regions, including Central Europe, Western Canada and United States, and New Zealand; this will result in a much greater glacial contribution to sea-level rise than currently estimated.

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JOURNAL

Science

DOI

10.1126/science.abo1324 

ARTICLE TITLE

Global glacier change in the 21st century: Every increase in temperature matters

ARTICLE PUBLICATION DATE

6-Jan-2023

Spring sunny heat waves caused record snow melt in 2021, adding to severe water supply impacts across the Western US

A new study highlights how persistent high pressure in April 2021 drove widespread rapid snow loss

Peer-Reviewed Publication

DESERT RESEARCH INSTITUTE

 

IMAGE: SNOWMELT ON PEAVINE PEAK ABOVE RENO, NV. view more 

CREDIT: PHOTO BY JESSE JUCHTZER/DRI SCIENCE

Reno, Nev. (Jan. 5, 2023) - Snow-capped mountains aren’t just scenic – they also provide natural water storage by creating reservoirs of frozen water that slowly melt into watersheds throughout the spring and summer months. Much of the Western U.S. relies on this process to renew and sustain freshwater supplies, and new research underscores the impacts of extreme weather conditions on this annual cycle.  

In a study published Jan. 5th in Environmental Research Letters, DRI researchers examine the role of spring heatwaves on the melting rates of mountain snowpacks across the West. They found that in April 2021, record-breaking snowmelt rates occurred at 24% of all mountain snowpack monitoring sites in the region, further compounding the impacts of extended drought conditions. Rapid snowmelt increases the time when our natural snowpack reservoir is emptied and when this water is most needed later in the warm season.

“One thing that stood out was the spatial pattern,” says Daniel McEvoy, Ph.D., DRI climatologist and co-author of the new study. “It wasn't just one single mountain range or one part of the West – there were snowmelt records across the entire Western U.S., in all 11 states.” 

By examining data from mountain snowpack monitoring stations, the researchers found that between April 1 and May 1, record high temperatures caused dramatic decreases in snowpacks. Although record snowmelt rates occurred throughout the entire month of April, two heatwaves stood out. The first week of April saw maximum temperatures 4-6 degrees Celsius above average, driving the most widespread record snow melt centered on the Rocky Mountains. Another heatwave the third week of April centered on the Pacific Northwest, with maximum temperatures 5-8 degrees Celsius above average, primarily in the Cascade Range.   

“Summer heat waves are studied extensively, but people don't often care as much about a spring heatwave because the actual air temperatures don't usually lead to human health impacts,” McEvoy says. “But at the same time, they are creating these hydrological and climatological extreme impacts.” 

Several factors contributed to the rapid rate of snowmelt in the spring of 2021. On top of record high maximum temperatures, record high minimum temperatures prevented snowpacks from re-freezing at night, and clear, sunny skies exposed snow to the melting energy of the sun’s rays. The ongoing drought, already widespread in late 2020, also created parched soils that absorbed more of the spring snowmelt in 2021 before it could run off into streams and reservoirs or replenish groundwater.  

“What really motivated this study was that in May and June of 2021, I kept hearing from other climatologists, meteorologists, hydrologists, and even skiers, that ‘the snow really came off the mountains fast this year,’” McEvoy says. “I kept hearing that over and over again.” 

Although many snowpacks across the West were below average due to low winter snowfall, water resource managers were unable to forecast the exacerbating effects of the rapid spring snowmelt on water supplies. With reservoirs below expected levels based on early-season snowpack predictions, less water flowed to downstream users. Reduced water availability also impacted hydropower production, which made providing energy during the summer and fall heatwaves more challenging. By the end of summer 2021, 76% of the West was in severe drought, according to the U.S. Drought Monitor.

“This was one of several extreme climate events over the course of that year,” McEvoy says of the spring 2021 heatwave. “There was a compounding set of climate extremes that all contributed to this rapid expansion and intensification of the drought across the Western U.S. during the late spring and summer.” 

The researchers say these spring heatwaves are consistent with the long-term trend of spring warming across the West, and that because of this, April 1 may no longer be a reliable benchmark for evaluating snowpack levels and their seasonal contributions to western water supplies. 2021 was also an active wildfire season in California and the Pacific Northwest, consistent with previous research linking reduced mountain snowpacks and spring heatwaves with increased wildfire potential.

McEvoy says that future research will examine the impacts and frequency of spring heatwaves, as well as ways to predict them by looking at global atmospheric circulation patterns, such as the ones that cause La Niña.  

“Understanding the predictability of these types of snowmelt events would be helpful for both drought early warning and water resource management,” says McEvoy.  

 

More information:

The full study, Spring heat waves drive record western United States snow melt in 2021, is available from Environmental Research Letters:  
https://iopscience.iop.org/article/10.1088/1748-9326/aca8bd 

Study authors include Daniel McEvoy and Benjamin Hatchett, both at DRI.  

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About DRI

The Desert Research Institute (DRI) is a recognized world leader in basic and applied environmental research. Committed to scientific excellence and integrity, DRI faculty, students who work alongside them, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge on topics ranging from humans’ impact on the environment to the environment’s impact on humans. DRI’s impactful science and inspiring solutions support Nevada’s diverse economy, provide science-based educational opportunities, and inform policymakers, business leaders, and community members. With campuses in Las Vegas and Reno, DRI serves as the non-profit research arm of the Nevada System of Higher Education. For more information, please visit www.dri.edu.

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JOURNAL

Environmental Research Letters

DOI

10.1088/1748-9326/aca8bd 

METHOD OF RESEARCH

Data/statistical analysis

ARTICLE TITLE

Spring heat waves drive record western United States snow melt in 2021

ARTICLE PUBLICATION DATE

5-Jan-2023