Earth-like environment likely on ancient Mars

A research team using the ChemCam instrument onboard NASA's Curiosity rover discovered higher-than-usual amounts of manganese in lakebed rocks within Gale Crater on Mars, which indicates that the sediments were formed in a river, delta, or near the shoreline of an ancient lake. The results were published today in Journal of Geophysical Research: Planets.

"It is difficult for manganese oxide to form on the surface of Mars, so we didn't expect to find it in such high concentrations in a shoreline deposit," said Patrick Gasda, of Los Alamos National Laboratory's Space Science and Applications group and lead author on the study. "On Earth, these types of deposits happen all the time because of the high oxygen in our atmosphere produced by photosynthetic life, and from microbes that help catalyze those manganese oxidation reactions.

"On Mars, we don't have evidence for life, and the mechanism to produce oxygen in Mars's ancient atmosphere is unclear, so how the manganese oxide was formed and concentrated here is really puzzling. These findings point to larger processes occurring in the Martian atmosphere or surface water and shows that more work needs to be done to understand oxidation on Mars," Gasda added.

ChemCam, which was developed at Los Alamos and CNES (the French space agency), uses a laser to form a plasma on the surface of a rock, and collects that light in order to quantify elemental composition in rocks.

The sedimentary rocks explored by the rover are a mix of sands, silts, and muds. The sandy rocks are more porous, and groundwater can more easily pass through sands compared to the muds that make up most of the lakebed rocks in the Gale Crater. The research team looked at how manganese could have been enriched in these sands -- for example, by percolation of groundwater through the sands on the shore of a lake or mouth of a delta -- and what oxidant could be responsible for the precipitation of manganese in the rocks.

On Earth, manganese becomes enriched because of oxygen in the atmosphere, and this process is often sped up by the presence of microbes. Microbes on Earth can use the many oxidation states of manganese as energy for metabolism; if life was present on ancient Mars, the increased amounts of manganese in these rocks along the lake shore would have been a helpful energy source for life.

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This salt battery harvests osmotic energy where the river meets the sea

Estuaries -- where freshwater rivers meet the salty sea -- are great locations for birdwatching and kayaking. In these areas, waters containing different salt concentrations mix and may be sources of sustainable, "blue" osmotic energy. Researchers in ACS Energy Letters report creating a semipermeable membrane that harvests osmotic energy from salt gradients and converts it to electricity. The new design had an output power density more than two times higher than commercial membranes in lab demonstrations.

Osmotic energy can be generated anywhere salt gradients are found, but the available technologies to capture this renewable energy have room for improvement. One method uses an array of reverse electrodialysis (RED) membranes that act as a sort of "salt battery," generating electricity from pressure differences caused by the salt gradient. To even out that gradient, positively charged ions from seawater, such as sodium, flow through the system to the freshwater, increasing the pressure on the membrane. To further increase its harvesting power, the membrane also needs to keep a low internal electrical resistance by allowing electrons to easily flow in the opposite direction of the ions. Previous research suggests that improving both the flow of ions across the RED membrane and the efficiency of electron transport would likely increase the amount of electricity captured from osmotic energy. So, Dongdong Ye, Xingzhen Qin and colleagues designed a semipermeable membrane from environmentally friendly materials that would theoretically minimize internal resistance and maximize output power.

The researchers' RED membrane prototype contained separate (i.e., decoupled) channels for ion transport and electron transport. They created this by sandwiching a negatively charged cellulose hydrogel (for ion transport) between layers of an organic, electrically conductive polymer called polyaniline (for electron transport). Initial tests confirmed their theory that decoupled transport channels resulted in higher ion conductivity and lower resistivity compared to homogenous membranes made from the same materials. In a water tank that simulated an estuary environment, their prototype achieved an output power density 2.34 times higher than a commercial RED membrane and maintained performance during 16 days of non-stop operation, demonstrating its long-term, stable performance underwater. In a final test, the team created a salt battery array from 20 of their RED membranes and generated enough electricity to individually power a calculator, LED light and stopwatch.

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New approach needed to save Australia's non-perennial rivers

Non-perennial rivers, which stop flowing at some point each year, dominate surface water movement across Australia, yet monitoring the continued health of these vital waterways demands a new type of research attention.

More than 70% of this nation's rivers are non-perennial due to a combination of ancient landscape, dry climates, highly variable rainfall regimes, and human interventions that have altered riverine environments.

An extensive review of current research incorporating geomorphology, hydrology, biogeochemistry, ecology and Indigenous knowledges identifies prevailing factors that shape water and energy flows in Australia's non-perennial rivers -- but the review also points to research deficiencies that must be addressed if these river systems are to be preserved and protected.

"Australia relies on our rivers, and has a strong history of research to understand river flows and ecosystems and the human impacts on them. Now, we must address emerging threats to river systems due to climate change and other anthropogenic impacts," says lead author of the review, Dr Margaret Shanafield, from Flinders University's College of Science and Engineering.

"We have to work together to tackle emerging threats to our rivers. If we are going to plug gaps in existing knowledge, which this review identifies, then a new style of inter-disciplinary scientific research is necessary to achieve the required outcomes."

While dominant research themes in Australia focus on drought, floods, salinity, dryland ecology and water management, four other areas of research attention are urgently needed, namely:

•     Integrating Indigenous and western scientific knowledge;
•     Quantifying climate change impacts on hydrological and biological function;
•     Clarifying the meaning and measurement of "restoration" of non-perennial systems;
•     Understanding the role of groundwater.

Addressing these areas through multi-disciplinary efforts supported by technological advances will provide a map for improved water research outcomes that the rest of the world can follow.

"Australia is globally unique in its spread and diversity of non-perennial rivers spanning climates and landforms -- but most, if not all, of the classes of non-perennial rivers found in Australia also occur in other regions of the world with similar climates and geology," says Dr Shanafield.

"Therefore, the evolving body of knowledge about Australian rivers provides a foundation for comparison with other dryland areas globally where recognition of the importance of non-perennial rivers is expanding."

The review authors are concerned that Australian non-perennial river research has been driven by the needs of its inhabitants for survival, agriculture, resource economics, environmental concern and politics.

"Considering the continent's ancient geological history and its harsh, arid climate, it comes as no surprise that significant attention has been directed toward water resource management during drought periods, the reduction of salinisation, and gaining insights into the intricate dynamics of the transient rivers that are a defining feature of central Australia," says the review.

"The prevalence of prolonged drought periods has had a marked impact on driving research -- so it is critical to address the knowledge gaps this review has identified, given that increasing trends in hydrological droughts are projected to negatively impact streamflow not just in Australia, but also in South America, southern Africa, and the Mediterranean."

The review authors -- a multi-disciplinary collective of scientists from across more than two dozen institutions and government departments -- say more investment in long-term hydrological monitoring is desperately needed to increase water management knowledge that can address the competing water needs of communities, agriculture, mining and ecosystems in a dry environment -- not only in Australia, but throughout the world.

"We anticipate that changing global water fluxes and continued groundwater pumping will cause more of the world's rivers to become non-perennial, accelerating our need to understand these systems across many disciplines," says Dr Shanafield.

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Land under water: What causes extreme flooding?

If rivers overflow their banks, the consequences can be devastating -- just like the catastrophic floods in North Rhine-Westphalia and Rhineland-Palatinate of 2021 showed. In order to limit flood damage and optimise flood risk assessment, we need to better understand what factors can lead to extreme forms of flooding and to what extent. Using methods of explainable machine learning, researchers at the Helmholtz Centre for Environmental Research (UFZ) have shown that floods are more extreme when several factors are involved in their development. The research was published in Science Advances.

There are several factors that play an important role in the development of floods: air temperature, soil moisture, snow depth, and the daily precipitation in the days before a flood. In order to better understand how individual factors contribute to flooding, UFZ researchers examined more than 3,500 river basins worldwide and analysed flood events between 1981 and 2020 for each of them. The result: precipitation was the sole determining factor in only around 25% of the almost 125,000 flood events. Soil moisture was the decisive factor in just over 10% of cases, and snow melt and air temperature were the sole factors in only around 3% of cases. In contrast, 51.6% of cases were caused by at least two factors. At around 23%, the combination of precipitation and soil moisture occurs most frequently.

However, when analysing the data, the UFZ researchers discovered that three -- or even all four -- factors can be jointly responsible for a flood event. For example, temperature, soil moisture, and snow depth were decisive factors in around 5,000 floods whilst all four factors were decisive in around 1,000 flood events. And not only that: "We also showed that flood events become more extreme when more factors are involved," says Dr Jakob Zscheischler, Head of the UFZ Department "Compound Environmental Risks" and senior author of the article. In the case of one-year floods, 51.6% can be attributed to several factors; in the case of five- and ten-year floods, 70.1% and 71.3% respectively can be attributed to several factors. The more extreme a flood is, the more driving factors there are and the more likely they are to interact in the event generation. This correlation often also applies to individual river basins and is referred to as flood complexity.

According to the researchers, river basins in the northern regions of Europe and America as well as in the Alpine region have a low flood complexity. This is because snow melt is the dominant factor for most floods regardless of the flood magnitude. The same applies to the Amazon basin, where the high soil moisture resulting from the rainy season is often a major cause of floods of varying severity. In Germany, the Havel and the Zusam, a tributary of the Danube in Bavaria, are river basins that have a low flood complexity. Regions with river basins that have a high flood complexity primarily include eastern Brazil, the Andes, eastern Australia, the Rocky Mountains up to the US west coast, and the western and central European plains. In Germany, this includes the Moselle and the upper reaches of the Elbe. "River basins in these regions generally have several flooding mechanisms," says Jakob Zscheischler. For example, river basins in the European plains can be affected by flooding caused by the combination of heavy precipitation, active snow melt, and high soil moisture.

However, the complexity of flood processes in a river basin also depends on the climate and land surface conditions in the respective river basin. This is because every river basin has its own special features. Among other things, the researchers looked at the climate moisture index, the soil texture, the forest cover, the size of the river basin, and the river gradient. "In drier regions, the mechanisms that lead to flooding tend to be more heterogeneous. For moderate floods, just a few days of heavy rainfall is usually enough. For extreme floods, it needs to rain longer on already moist soils," says lead author Dr Shijie Jiang, who now works at the Max Planck Institute for Biogeochemistry in Jena.

The scientists used explainable machine learning for the analysis. "First, we use the potential flood drivers air temperature, soil moisture, and snow depth as well as the weekly precipitation -- each day is considered as an individual driving factor -- to predict the run-off magnitude and thus the size of the flood," explains Zscheischler. The researchers then quantified which variables and combinations of variables contributed to the run-off of a particular flood and to which extent. This approach is referred to as explainable machine learning because it uncovers the predictive relationship between flood drivers and run-off during a flood in the trained model. "With this new methodology, we can quantify how many driving factors and combinations thereof are relevant for the occurrence and intensity of floods," adds Jiang.

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Scientists propose new method for tracking elusive origins of CO2 emissions from streams

A team of researchers from the University of Massachusetts Amherst that specializes in accounting for the carbon dioxide release by streams, rivers and lakes recently demonstrated that the chemical process known as "carbonate buffering" can account for the majority of emissions in highly alkaline waters. Furthermore, carbonate buffering distorts the most commonly used method of tracking the origins of CO2 in streams. The research, published in Global Biogeochemical Cycles, proposes a better method for tracking the origin of riverine CO2 emissions.

Inland waters, including streams, rivers and lakes, account for roughly 5.5 gigatons of CO2 emissions annually -- about 15% of what humans emit.

But current climate models have trouble accounting for this carbon, in part because, says Matthew Winnick, assistant professor of Earth, Geographic and Climate Sciences at UMass Amherst and the paper's lead author, much of this carbon seems to be produced cryptically, through carbonate buffering.

"The process is a little weird," says Winnick. "It acts as a kind of hidden reserve pool of CO2, replenishing carbon that is lost to the atmosphere, and ultimately increasing the amount of CO2 available for off-gassing."

To show how this hidden pool operates, Winnick and his co-author, then-UMass graduate student Brian Saccardi, looked to studies that focused on the carbon content of the oceans.

"Carbonate buffering is a really well-known phenomenon in the ocean," says Winnick, "and even though oceans work differently from inland waters, we were able to borrow the geochemical equations to build a series of models that could account for a wide range of river and stream conditions."

So what is carbonate buffering? It begins with CO2 -- which is everywhere: in the air, in the soil and in water.

When CO2 dissolves in water, it can react to form carbonic acid, which, through further reactions, can then become bicarbonate and carbonate.

This reaction can also run in reverse, which means that high levels of bicarbonate and carbonate can act as reserve pools of CO2, driving emissions.

This entire balance of CO2, water and carbonate is called "carbonate buffering," and the carbonate reserves can be emitted as a greenhouse gas from stream systems.

Indeed, Winnick and Saccardi found that this hidden pool can account for more than 60% of CO2 emissions under alkaline conditions.

There's yet another trick that carbonate buffering has up its sleeve.

In the era of global warming, it is critically important to know both how much carbon is being emitted overall and where this carbon is coming from.

"While we don't think stream emissions contribute to global warming, there is a big question about whether these emissions will change as climate warms, which could amplify warming in the future. To predict changes, we need to know where the CO2 is coming from," says Winnick.

But figuring out which molecule of CO2 came from which source is not a simple task.

To track carbon, especially carbon emitted by bodies of water, scientists often use carbon isotopes, or versions of carbon with different masses, which act as a sort of forensic signature that can indicate the carbon's origin.

However, Winnick and Saccardi discovered that isotope signals in streams are highly sensitive to carbonate buffering reactions.

"The primary way we use isotopes to track sources is through their relationship with CO2 concentrations, but carbonate buffering causes these relationships to break down," says Winnick.

This breakdown can point to the wrong carbon culprit if not properly accounted for.

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Three years later, search for life on Mars continues

In the three years since NASA's Perseverance rover touched down on Mars, the NASA science team has made the daily task of investigating the red planet seem almost mundane.

The rover and its helicopter sidekick Ingenuity have captured stunning images of Mars and collected 23 unique rock core samples along 17 miles of an ancient river delta.

One science team member, University of Cincinnati Associate Professor Andy Czaja, said he sometimes has to remind himself that the project is anything but ordinary.

"This is so cool. I'm exploring another planet," he said.

Czaja teaches in the Department of Geosciences in UC's College of Arts and Sciences. He is a paleobiologist and astrobiologist helping NASA look for evidence of ancient life on Mars using a rover outfitted with custom geoscience and imaging tools with three of his UC graduate students, Andrea Corpolongo, Brianna Orrill and Sam Hall.

Three years into the mission, the rover has performed like a champ, he said.

"Perseverance has excelled. It's been fantastic. It has such capable instrumentation for doing the geology work. It's able to explore distant objects with its zoom lens cameras and can focus on tiny objects at incredible resolution," Czaja said.

Along the way, the mission has recorded a number of firsts: first powered flight, first recorded sounds of Mars, the longest autonomous drive (nearly a half-mile) and new discoveries about the planet's geology, atmosphere and climate.

Czaja was part of the NASA team that decided where on Mars to land the rover. And he remained on the science team that would pore over its daily data and discoveries to decide what the rover should do next.

Among the new discoveries was finding primary igneous rocks in Jezero Crater. These rocks are the hardened result of liquid magma. They offer scientists promising clues about refining the known age of the planet.

Scientists suspect Mars once had long-lived rivers, lakes and streams. Today, water on Mars is found in ice at the poles and trapped below the Martian surface.

Czaja and his student Corpolongo were co-lead authors of a paper published in the Journal of Geophysical Research, Planets that revealed that Mars also may have had hydrothermal systems based on the hydrated magnesium sulfate the rover identified in the volcanic rocks.

"When those rocks cool off and fracture, they become a habitable environment for life," Czaja said.

Corpolongo also led a similar research paper in the same journal co-authored by Czaja detailing the results of the rover's analysis of samples using the SHERLOC deep ultraviolet Raman and fluorescence instrument. Both papers featured contributions from dozens of their fellow NASA researchers on the project.

Samples collected by the rover may finally answer the question about whether we are alone in the universe.

"We have not found any definitive evidence of life in these deposits yet. But if there were fossil microorganisms trapped in the rocks, they would be too small to see with the rover," Czaja said.

Czaja is hopeful funding will be approved for the anticipated Mars Sample Return mission to retrieve the hermetically sealed titanium tubes scientists have spent three years filling with interesting rock cores.

"These hydrated minerals trap water within themselves and record the history of how and when they formed," the study said. "Returning samples of these minerals to Earth would allow researchers to explore the history of Mars' water and climate and possibly evidence of ancient life with the most sensitive instruments possible."

But that was just the beginning. Perseverance began its deliberate exploration from the floor of the crater to the front of the delta, formed by an ancient river or drainage channel where it encountered sedimentary rocks that often contain trapped minerals and another avenue for evidence of ancient life.

And last year the rover made it to the crater's margin in what used to be an enormous lake where it is exploring deposits of magnesium carbonate, which can form geologically or biologically from bacteria.

Czaja said the decision to send Perseverance to Jezero Crater appears to be paying off.

"Absolutely. There were other places we could have gone that might have been just as good," he said. "You won't know until you explore them all. But Jezero was picked for good reason and it has been completely justified."

The helicopter Ingenuity's flying days appear to be over after it sustained rotor damage in January after landing on its 72nd flight. But Perseverance is still going strong. It still has 15 sample tubes at its disposal to capture additional interesting geologic specimens.

Next the rover will make its way out of Jezero Crater to explore the wider area. Czaja said they are likely to find rocks dating back 4 billion years or more. And Mars could harbor stromatolites or rocks that contain evidence of ancient layered mats of bacteria visible to the naked eye. On Earth, these rocks are sometimes found in extreme environments such as geyser basins.

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Researchers shed light on river resiliency to flooding

Researchers at theUniversity of Nevada, Renohave completed one of the most extensive river resilience studies, examining how river ecosystems recover following floods. They developed a novel modeling approach that used data from oxygen sensors placed in rivers to estimate daily growth in aquatic plants and algae. The researchers then modeled the algal and plant biomass in 143 rivers across the contiguous U.S. to quantify what magnitude of flooding disturbs the biomass and how long the rivers take to recover from floods. Increased understanding of rivers' resiliency is important to maintaining healthy rivers, as human actions can affect flood regimes and change the conditions in rivers for other aquatic life that may rely on algae and plants as a food source.

Assistant Professor Joanna Blaszczak and Postdoctoral Scholar Heili Lowman, both in the University'sCollege of Agriculture, Biotechnology & Natural ResourcesandGlobal Water Centerled the research, which was published in two separate journal articles. The preliminary work, led by Blaszczak andpublished in Ecology Letters last June, first studied six rivers and laid the groundwork and methodology for the second study, which Blaszczak hired Lowman to conduct, examining the 143 rivers. The results of that research were justpublished last month in PNAS (the Proceedings of the National Academy of Sciences).

The research is unique because it estimates changes in biomass in rivers more frequently than ever before without needing to directly sample rivers. This is done by using both data from oxygen sensors placed in the rivers by the U.S. Geological Survey and a population model of algal and plant biomass -- similar to a human population model that models change in the number of people over time, but instead modeling the change in the amount of algae and plants. The oxygen sensors began collecting data in 2007, and the most recent Nevada-led study of 143 rivers includes some data that are for nine years running, among the longest such records on file for rivers across the globe.

"Previously, you would have to go to a river and scrub rocks to measure the algae, and do that several times for an extended period of time in order to estimate changes in biomass growth and loss," Blaszczak said. "This is very time consuming, so the data have been extremely limited relative to how extensive our sensor networks are."

Blaszczak said that with the oxygen sensors that take data as frequently as every five minutes, the team found that they could use statistical models to extract the amount of photosynthesis that occurs daily and estimate daily changes in the amount of biomass in a river over time.

"The dissolved oxygen sensors show the peak during the day, and the low during the night, and from those patterns, you can estimate how much new algae and other biomass grew that day," she said. "With the sensors measuring data continuously in hundreds of rivers for years now, we can get a much bigger, clearer picture. The data is there, and we can use it to model the size of flood needed to disturb the biomass in a river, as well as the rate at which a river recovers from flood disturbances, which can help us manage rivers more effectively."

Getting started

In the first study, Blaszczak used two years of data from oxygen sensors placed in six rivers. She found that she could successfully use this data to model the flood threshold specific to a river that disturbed the underlying biomass, and that generally, the magnitude of flood necessary to disturb biomass and reduce ecosystem productivity was lower than the disturbance flow threshold necessary to mobilize river bed sediment, a metric of disturbance commonly used by those studying rivers. In other words, instead of estimating the disturbance of the river by the movement of the rocks on the river bed, this study used the biology -- the changes in algae and plant growth -- to quantify disturbance to the river and found that the biological disturbance threshold was lower.

"The amount of biomass is important for water quality and a food source for everything that lives in a river," Blaszczak explained, "so it is more important than rock movement, in terms how a river ecosystem is affected by a disturbance."

Blaszczak, a freshwater ecologist, began this work with Robert O. Hall Jr. of the Flathead Lake Biological Station at the University of Montana and enlisted the help of her colleague Assistant Professor Robert Shriver, a plant ecologist, for both research projects to complete the biomass growth modeling. Blaszczak, Shriver, and Lowman all conduct research as part of the College'sDepartment of Natural Resources & Environmental Science, as well as the College'sExperiment Stationresearch unit. The College's faculty often take interdisciplinary approaches to meet research challenges, Blaszczak said.

Expanding out to a continental scale

Blaszczak wanted to delve further by applying this approach to more rivers over a longer period of time to shed light on how various factors may be influencing both a river's thresholds for flood disturbance and its resilience to floods. Thus, she recruited Lowman to embark on the second, more extensive study. Lowman's research examined landscape and river characteristics that affected the rivers' resiliency to floods.

"We've never had such great insight into the resilience of rivers, and because of the amount of data and our modeling, we now understand the natural variation in resilience, and that the widest rivers without dams upstream recover the most quickly," Lowman said.

The fact that wide rivers without dams recover more quickly than wide rivers with dams upstream was not immediately obvious, she said, and is one example of how rivers can be affected and/or managed by our actions. Most of the rivers Lowman researched had three to four years of data, with some having as much as nine years, and a handful having less than a year.

"Having three to four years' worth of data is way more than we've ever been able to use before," Lowman said. "And, we used rivers of various sizes with various climates and land characteristics."

Besides wider rivers without dams being more resilient, Lowman said those rivers that had more frequent floods also tended to recover more quickly.

"It could be that they have had a long history of frequent flooding, so their algae and plant communities have developed the ability to adapt to more frequent disturbance," she said.

Overall, Lowman said the new model results are consistent with other previous approaches. But, she said that some sites took much longer, a month or more, to recover from floods than other sites, regardless of river size.

"It might be the composition of the algal and plant communities, the structure of the river bed, or other factors," she said. "The thresholds and recovery times are very likely partially dependent on the slope, the grain size of the sediment, and possibly other factors that aren't as well documented. Those are some next steps for future research."

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Curiosity rover finds new evidence of ancient Mars rivers, a key signal for life

New analysis of data from the Curiosity rover reveals that much of the craters on Mars today could have once been habitable rivers.

"We're finding evidence that Mars was likely a planet of rivers," said Benjamin Cardenas, assistant professor of geosciences at Penn State and lead author on a new paper announcing the discovery. "We see signs of this all over the planet."

In a study published in Geophysical Research Letters, the researchers used numerical models to simulate erosion on Mars over millennia and found that common crater formations -- called bench-and-nose landforms -- are most likely remnants of ancient riverbeds.

The study was the first to map the erosion of ancient Martian soil by training a computer model on a combination of satellite data, Curiosity images and 3D scans of the stratigraphy -- or layers of rock, called strata, deposited over millions of years -- beneath the Gulf of Mexico seafloor. The analysis revealed a new interpretation for common Martian crater formations which, until now, have never been associated with eroded river deposits.

"We have everything to learn about Mars by better understanding how these river deposits can be interpreted stratigraphically, thinking about rocks today as layers of sediment deposited over time," Cardenas said. "This analysis is not snapshot, but a record of change. What we see on Mars today is the remnants of an active geologic history, not some landscape frozen in time."

Prior studies of satellite data from Mars had identified erosional landforms called fluvial ridges as being possible candidates for ancient river deposits. Using data collected by the Curiosity rover at Gale crater, the team found signs of river deposits that are not associated with fluvial ridges, but rather bench-and-nose landforms that have never been linked to ancient river deposits.

"This suggests that there could be undiscovered river deposits elsewhere on the planet, and that an even larger section of the Martian sedimentary record could have been built by rivers during a habitable period of Mars history," Cardenas said. "On Earth, river corridors are so important for life, chemical cycles, nutrient cycles and sediment cycles. Everything is pointing to these rivers behaving similarly on Mars."

In designing their computer model, Cardenas and his team found a new use for 25-year-old scans of Earth's stratigraphy. Collected by oil companies, the scans of beneath the Gulf of Mexico seafloor provided an ideal comparison to Mars, Cardenas explained.

The team simulated Mars-like erosion using the 3D scans of actual, recorded stratigraphy on Earth. When they ran the simulation, the model revealed erosional Martian landscapes that formed topographic benches and noses, rather than fluvial ridges, appearing almost identical to landforms observed by the Curiosity rover inside the Gale crater.

"Our research indicates that Mars could have had far more rivers than previously believed, which certainly paints a more optimistic view of ancient life on Mars," Cardenas said. "It offers a vision of Mars where most of the planet once had the right conditions for life."

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Even treated wastewater affects our rivers

Effluents from wastewater treatment plants have a dual effect: Some species disappear, while others benefit. Especially certain insect orders, such as stonefly and caddisfly larvae, are decimated. Certain worms and crustaceans, by contrast, can increase in number. A team from Goethe University Frankfurt led by Daniel Enns and Dr. Jonas Jourdan has corroborated this in a comprehensive study, which has now been published in the journal Water Research. They examined 170 wastewater treatment plants in Hesse in relation to species composition.

Wastewater treatment plants are an indispensable part of our modern infrastructure; they have made a significant contribution to improving the quality of our surface waters. However, their ability to completely remove what are known as micropollutants from wastewater is mostly limited. These substances include, for example, active ingredients from pharmaceuticals and personal care products, pesticides and other synthetic substances enter waterbodies via the treated wastewater, placing an additional burden on rivers and streams. This exacerbates the challenges faced by already vulnerable insect communities and aquatic fauna. Previous studies -- which have primarily focused on single wastewater treatment plants -- have already shown that invertebrate communities downstream of such effluents are generally dominated by pollution-tolerant taxa.

Until now, however, it was unclear how ubiquitous these changes are. That is why a team of biologists from Goethe University Frankfurt has now studied extensively how wastewater from 170 wastewater treatment plants in Hesse has an impact on the species composition of invertebrates. This has prompted a change in the common conception that human-induced stressors reduce the number of species in a habitat and thus their diversity: Rather, the findings indicate that a shift in species composition can be observed. The researchers were able to identify significant shifts in the composition of the species community between sites located upstream and downstream of wastewater treatment plants. Some species were particularly affected by effluents from wastewater treatment plants -- such as stonefly and caddisfly larvae, which disappear entirely in some places. Other taxa, such as certain worms and crustaceans, by contrast, benefit and are found in greater numbers. This change can be observed especially in streams and smaller rivers. Overall, wastewater treatment plants alter conditions downstream to the advantage of pollution-tolerant taxa and to the disadvantage of sensitive ones.

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Study examines Earth and Mars to determine how climate change affects the paths of rivers

In a new study published in Nature Geosciences, researchers, led by a Tulane University sedimentologist , investigated why the paths of meandering rivers change over time and how they could be affected by climate change.

Chenliang Wu, PhD, a postdoctoral researcher at Tulane University School of Science and Engineering, began this research by looking at the Mississippi River before adding other rivers on Earth and ancient riverbeds on Mars to the study.

The study specifically looks at river sinuosity, or how much rivers curve. The sinuosity of rivers changes over time, depending on the age of the river and environmental changes. Some of these changes include sediment and water supply and riverbank vegetation, all of which are affected by climate change. The study found that river sinuosity is related to the changes in how much water flows through the river. Rivers have different water levels depending on environmental factors, like precipitation levels.

The researchers looked at maps of the rivers on Earth over time by using historical data from as early as the fifth century and images from as early as 1939. They used data of 21 lowland meandering rivers. For the ancient riverbeds on Mars, they used previously identified ancient river channels from remote sensing data.

The ancient riverbeds on Mars, untouched by human influence, gave Wu and his team a system to test their hypotheses on how the river systems migrated and what their sinuosity looked like by the time they dried up. Their analysis is also a step toward understanding what the hydroclimate on Mars was like when there was still surface water.

"It really lays the foundation for more advanced topics," Wu said, "like, were the environmental conditions suitable for life on Mars?"

After performing analysis on the rivers, the researchers separated them into two categories: variable-sinuosity and constant-sinuosity. The variable-sinuosity rivers never reached a steady state, meaning their sinuosities continue changing, and the constant sinuosity rivers did reach a steady state, meaning their average sinuosity remained relatively constant. Of the 21 Earth rivers studied, 13, including the Mississippi River, had variable sinuosity, while 8 had constant sinuosity.

Understanding what factors affect the sinuosity of rivers will give researchers and engineers insight into how to manage rivers in the future. It can help with river restoration, future infrastructure projects and flood management. This insight can be invaluable in attempts to mitigate the impacts of climate change.

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River erosion can shape fish evolution

New findings could explain biodiversity hotspots in tectonically quiet regions.

If we could rewind the tape of species evolution around the world and play it forward over hundreds of millions of years to the present day, we would see biodiversity clustering around regions of tectonic turmoil. Tectonically active regions such as the Himalayan and Andean mountains are especially rich in flora and fauna due to their shifting landscapes, which act to divide and diversify species over time.

But biodiversity can also flourish in some geologically quieter regions, where tectonics hasn't shaken up the land for millennia. The Appalachian Mountains are a prime example: The range has not seen much tectonic activity in hundreds of millions of years, and yet the region is a notable hotspot of freshwater biodiversity.

Now, an MIT study identifies a geological process that may shape the diversity of species in tectonically inactive regions. In a paper appearing in Science, the researchers report that river erosion can be a driver of biodiversity in these older, quieter environments.

They make their case in the southern Appalachians, and specifically the Tennessee River Basin, a region known for its huge diversity of freshwater fishes. The team found that as rivers eroded through different rock types in the region, the changing landscape pushed a species of fish known as the greenfin darter into different tributaries of the river network. Over time, these separated populations developed into their own distinct lineages.

The team speculates that erosion likely drove the greenfin darter to diversify. Although the separated populations appear outwardly similar, with the greenfin darter's characteristic green-tinged fins, they differ substantially in their genetic makeup. For now, the separated populations are classified as one single species.

"Give this process of erosion more time, and I think these separate lineages will become different species," says Maya Stokes PhD '21, who carried out part of the work as a graduate student in MIT's Department of Earth, Atmospheric and Planetary Sciences (EAPS).

The greenfin darter may not be the only species to diversify as a consequence of river erosion. The researchers suspect that erosion may have driven many other species to diversify throughout the basin, and possibly other tectonically inactive regions around the world.

"If we can understand the geologic factors that contribute to biodiversity, we can do a better job of conserving it," says Taylor Perron, the Cecil and Ida Green Professor of Earth, Atmospheric, and Planetary Sciences at MIT.

The study's co-authors include collaborators at Yale University, Colorado State University, the University of Tennessee, the University of Massachusetts at Amherst, and the Tennessee Valley Authority (TVA). Stokes is currently an assistant professor at Florida State University.

Fish in trees

The new study grew out of Stokes' PhD work at MIT, where she and Perron were exploring connections between geomorphology (the study of how landscapes evolve) and biology. They came across work at Yale by Thomas Near, who studies lineages of North American freshwater fishes. Near uses DNA sequence data collected from freshwater fishes across various regions of North America to show how and when certain species evolved and diverged in relation to each other.

Near brought a curious observation to the team: a habitat distribution map of the greenfin darter showing that the fish was found in the Tennessee River Basin -- but only in the southern half. What's more, Near had mitochondrial DNA sequence data showing that the fish's populations appeared to be different in their genetic makeup depending on the tributary in which they were found.

To investigate the reasons for this pattern, Stokes gathered greenfin darter tissue samples from Near's extensive collection at Yale, as well as from the field with help from TVA colleagues. She then analyzed DNA sequences from across the entire genome, and compared the genes of each individual fish to every other fish in the dataset. The team then created a phylogenetic tree of the greenfin darter, based on the genetic similarity between fish.

From this tree, they observed that fish within a tributary were more related to each other than to fish in other tributaries. What's more, fish within neighboring tributaries were more similar to each other than fish from more distant tributaries.

"Our question was, could there have been a geological mechanism that, over time, took this single species, and splintered it into different, genetically distinct groups?" Perron says.

A changing landscape

Stokes and Perron started to observe a "tight correlation" between greenfin darter habitats and the type of rock where they are found. In particular, much of the southern half of the Tennessee River Basin, where the species abounds, is made of metamorphic rock, whereas the northern half consists of sedimentary rock, where the fish are not found.

They also observed that the rivers running through metamorphic rock are steeper and more narrow, which generally creates more turbulence, a characteristic greenfin darters seem to prefer. The team wondered: Could the distribution of greenfin darter habitat have been shaped by a changing landscape of rock type, as rivers eroded into the land over time?

To check this idea, the researchers developed a model to simulate how a landscape evolves as rivers erode through various rock types. They fed the model information about the rock types in the Tennessee River Basin today, then ran the simulation back to see how the same region may have looked millions of years ago, when more metamorphic rock was exposed.

They then ran the model forward and observed how the exposure of metamorphic rock shrank over time. They took special note of where and when connections between tributaries crossed into non-metamorphic rock, blocking fish from passing between those tributaries. They drew up a simple timeline of these blocking events and compared this to the phylogenetic tree of diverging greenfin darters. The two were remarkably similar: The fish seemed to form separate lineages in the same order as when their respective tributaries became separated from the others.

"It means it's plausible that erosion through different rock layers caused isolation between different populations of the greenfin darter and caused lineages to diversify," Stokes says.

Read more at Science Daily

River longer than the Thames beneath Antarctic ice sheet could affect ice loss

An unexpected river under the Antarctic ice sheet affects the flow and melting of ice, potentially accelerating ice loss as the climate warms.

The 460km-long river is revealed in a new study, which details how it collects water at the base of the Antarctic ice sheet from an area the size of Germany and France combined. Its discovery shows the base of the ice sheet has more active water flow than previously thought, which could make it more susceptible to changes in climate.

The discovery was made by researchers at Imperial College London, the University of Waterloo, Canada, Universiti Malaysia Terengganu, and Newcastle University, with the details published today in Nature Geoscience.

Co-author Professor Martin Siegert, from the Grantham Institute at Imperial College London, said: "When we first discovered lakes beneath the Antarctic ice a couple of decades ago, we thought they were isolated from each other. Now we are starting to understand there are whole systems down there, interconnected by vast river networks, just as they might be if there weren't thousands of metres of ice on top of them.

"The region where this study is based holds enough ice to raise the sea level globally by 4.3m. How much of this ice melts, and how quickly, is linked to how slippery the base of the ice is. The newly discovered river system could strongly influence this process."

Water can appear beneath ice sheets in two main ways: from surface meltwater running down through deep crevasses, or by melting at the base, caused by the natural heat of the Earth and friction as the ice moves over land.

However, the ice sheets around the north and south poles have different characteristics. In Greenland, the surface experiences strong melting over the summer months, where immense amounts of water channel down through deep crevasses called moulins.

In Antarctica, however, the surface doesn't melt in sufficient quantities to create moulins, as the summers are still too cold. It was thought this meant that there was relatively little water at the base of the Antarctic ice sheets.

The new discovery turns this idea on its head, showing there is sufficient water from basal melt alone to create huge river systems under kilometres-thick ice.

The discovery was made through a combination of airborne radar surveys that allow researchers to look beneath the ice and modelling of the ice sheet hydrology. The team focussed on a largely inaccessible and understudied area that includes ice from both the East and West Antarctic Ice Sheets and reaches the Weddell Sea.

That such a large system could be undiscovered until now is testament to how much we still need to learn about the continent, says lead researcher Dr Christine Dow from the University of Waterloo.

She said: "From satellite measurements we know which regions of Antarctica are losing ice, and how much, but we don't necessarily know why. This discovery could be a missing link in our models. We could be hugely underestimating how quickly the system will melt by not accounting for the influence of these river systems.

"Only by knowing why ice is being lost can we make models and predictions of how the ice will react in the future under further global heating, and how much this could raise global sea levels."

For example, the newly discovered river emerges into the sea beneath a floating ice shelf - where a glacier extending out from the land is buoyant enough to begin floating on the ocean water. The freshwater from the river however churns up warmer water towards the bottom of the ice shelf, melting it from below.

Co-author Dr Neil Ross, from the University of Newcastle, said: "Previous studies have looked at the interaction between the edges of ice sheets and ocean water to determine what melting looks like. However, the discovery of a river that reaches hundreds of kilometres inland driving some of these processes shows that we cannot understand the ice melt fully without considering the whole system: ice sheet, ocean, and freshwater."

The existence of large under-ice rivers also needs to be taken into account when predicting the possible consequences of climate change in the region. For example, if summers warm enough to cause enough surface melt that the water reaches the base of the ice sheet, it could have large effects on the river systems, potentially tipping Antarctica to a Greenland-like state, where ice loss is much faster.

There are also potential feedback loops that would accelerate ice loss. For example, if the ice starts to flow faster as water accumulated at the base, then this will increase friction where the ice runs over dry land, which could increase the amount of basal melting and water produced.

Read more at Science Daily

The entire planet's ecosystems classified

A global cross-disciplinary team of scientists led by UNSW Sydney researchers has developed the first comprehensive classification of the world's ecosystems across land, rivers and wetlands, and seas. The ecosystem typology will enable more coordinated and effective biodiversity conservation, critical for human wellbeing.

The extensive collaboration includes the International Union for Conservation of Nature (IUCN), which comprises about 1400 member organisations, including countries; the IUCN Commission on Ecosystem Management; the PLuS Alliance -- Arizona State University, King's College London and UNSW Sydney; and more than 100 specialist ecosystem scientists around the world.

The study, published today in Nature, explores the science that underpins the typology, as well as how it can help achieve objectives in global policy that flow to individual countries. With UNSW's support, IUCN launched the first public version of the typology in 2020 and, since then, the researchers have refined and updated it.

The research team was led by Professor David Keith with Professor Richard Kingsford from UNSW's Centre for Ecosystem Science, and Professor Emily Nicholson from Deakin University.

"For the first time, we have a common platform that identifies, defines and describes the full suite of the whole planet's ecosystems," said Professor Keith.

"It may seem rather odd that we haven't had this before, but historically scientists have forged advances by working somewhat separately in marine, freshwater and terrestrial ecosystems. This is the first time that all of this detailed knowledge has been brought together into a single framework taking advantage of common theory across the disciplines."

The typology allows us to understand broad global patterns, including the transformation of ecosystems by people. Ten per cent of ecosystems are artificially created and maintained by humans but occupy more than 30 per cent of the Earth's land surface -- what is left is home to 94 per cent of threatened species on the IUCN Red List.

At a policy level, this is the first time we've had this kind of overview, Professor Kingsford said.

"It's very hard to see the big picture on a jigsaw puzzle until you have all the pieces in place -- and that's what we now have. We have a much more substantial foundation to move ahead with a new era of ecosystem conservation and management policy."

At a more general level, the overview allows policymakers and industry to plan their initiatives in full context. For governments and non-government organisations (NGOs) working in a range of countries, the overview can inform decisions about how ecosystem protection and restoration efforts can achieve maximum conservation benefit, and where development infrastructure is best placed to minimise impact.

"Efforts on biodiversity conservation have largely centered at the species level, because it's seen to be more tangible," said Professor Keith. "But a broader focus on both ecosystems and species is more likely to succeed in conserving all plants and animals, as well as the essential services that nature provides people."

Globally, countries coordinate their efforts under the umbrella of the United Nations Convention on Biological Diversity (CBD), which is coming up for renewal at the end of 2022. Delegates from 193 countries will meet in December at the 15th Conference of Parties in Montreal, Canada, to agree on the post-2020 agenda for CBD. Preparations for that meeting indicate a stronger emphasis on ecosystem conservation and management in the coming decades.

"The global ecosystem typology will make it possible to account for ongoing ecosystem change, identify threatened ecosystem types, and plan better preventative action and restoration under a renewed agenda for the CBD," said Professor Nicholson.

This typology marks a breakthrough for sustainable management of the world's ecosystems, said Dr Angela Andrade, Chair of IUCN's Commission on Ecosystem Management and one of the authors.

"It will enable real progress on United Nations Sustainable Development Goals and Environmental Accounting, and should help place ecosystems at the forefront of the United Nations' post-2020 agenda for conserving biological diversity."

To make that a reality, we need a full set of high quality maps for all major ecosystem types, Professor Keith said.

"We are already well down that path, but we need help to surmount the considerable challenges by exploiting recent advances in computer and satellite technology, along with global networks of citizen scientists."

The ecosystem typology

Ecosystems provide homes and vital life support for all plants and animals, and supply essential ecosystem services that sustain business, culture and human wellbeing. Those services -- such as provision of clean air and water, carbon sequestration, reduced risks of disasters and outdoor recreational opportunities that sustain mental health -- are sometimes regarded as free, but ecosystem degradation incurs costs for tapping alternative resources, disaster relief and reconstruction, and to health budgets.

All of the world's ecosystems show hallmarks of human influence, and many are under acute risks of collapse, with consequences for habitats of species, genetic diversity, ecosystem services, sustainable development and human wellbeing.

The global ecosystem typology describes the diversity of tropical forests, big rivers, coral reefs and other ecosystems that have typically been the focus of public attention. But it also includes little-known ecosystems of deep ocean trenches, seamounts, lakes beneath the ice sheets and microscopic ecosystems within rocks.

"We don't think often about what's in the deep oceans, for example," said Professor Keith. "There's a tremendous variety of life down there and it's organised into a number of different ecosystems. And those ecosystems are beginning to feel the impact of human expansion.

"The deep trenches in the ocean are filling up with microplastics, and we're starting to look at mining volcanic vents for minerals. We need to make decisions about those kinds of environments, just as we do about coral reefs and rainforests."

A hierarchical structure

The new typology has a hierarchical structure with six levels. The top level divides the planet into major realms, including terrestrial, freshwater, marine and subterranean ecosystems. The second and third levels include 25 biomes and 110 ecosystem functional groups, based on the ecological processes that shape different ecosystems and the functions that their key components perform. These functional groups will frame blueprints for sustainable ecosystem management.

The lower levels of the hierarchy are based on finer ecosystem features and enable the integration of existing national classifications. These national ecosystem classifications and maps benefit from detailed scientific observations and considerable investment over many years. They are critical to conservation because many countries have built their environmental governance and regulations around them, as well as their protected area networks. For the first time, a globally agreed typology enables these many different systems to be reconciled across national borders, while supporting their ongoing use in each country.

Read more at Science Daily

Surprise finding suggests 'water worlds' are more common than we thought

Water is the one thing all life on Earth needs, and the cycle of rain to river to ocean to rain is an essential part of what keeps our planet's climate stable and hospitable. When scientists talk about where to search for signs of life throughout the galaxy, planets with water are always at the top of the list.

A new study suggests that many more planets may have large amounts of water than previously thought -- as much as half water and half rock. The catch? All that water is probably embedded in the rock, rather than flowing as oceans or rivers on the surface.

"It was a surprise to see evidence for so many water worlds orbiting the most common type of star in the galaxy," said Rafael Luque, first author on the new paper and a postdoctoral researcher at the University of Chicago. "It has enormous consequences for the search for habitable planets."

Planetary population patterns

Thanks to better telescope instruments, scientists are finding signs of more and more planets in distant solar systems. A larger sample size helps scientists identify demographic patterns -- similar to how looking at the population of an entire town can reveal trends that are hard to see at an individual level.

Luque, along with co-author Enric Pallé of the Institute of Astrophysics of the Canary Islands and the University of La Laguna, decided to take a population-level look at a group of planets that are seen around a type of star called an M-dwarf. These stars are the most common stars we see around us in the galaxy, and scientists have catalogued dozens of planets around them so far.

But because stars are so much brighter than their planets, we cannot see the actual planets themselves. Instead, scientists detect faint signs of the planets' effects on their stars -- the shadow created when a planet crosses in front of its star, or the tiny tug on a star's motion as a planet orbits. That means many questions remain about what these planets actually look like.

"The two different ways to discover planets each give you different information," said Pallé. By catching the shadow created when a planet crosses in front of its star, scientists can find the diameter of the planet. By measuring the tiny gravitational pull that a planet exerts on a star, scientists can find its mass.

By combining the two measurements, scientists can get a sense of the makeup of the planet. Perhaps it's a big-but-airy planet made mostly out of gas like Jupiter, or a small, dense, rocky planet like Earth.

These analyses had been done for individual planets, but much more rarely for the entire known population of such planets in the Milky Way galaxy. As the scientists looked at the numbers -- 43 planets in all -- they saw a surprising picture emerging.

The densities of a large percentage of the planets suggested that they were too light for their size to be made up of pure rock. Instead, these planets are probably something like half rock and half water, or another lighter molecule. Imagine the difference between picking up a bowling ball and a soccer ball: they're roughly the same size, but one is made up of much lighter material.

Searching for water worlds

It may be tempting to imagine these planets like something out of Kevin Costner's Waterworld: entirely covered in deep oceans. However, these planets are so close to their suns that any water on the surface would exist in a supercritical gaseous phase, which would enlarge their radius. "But we don't see that in the samples," explained Luque. "That suggests the water is not in the form of surface ocean."

Instead, the water could exist mixed into the rock or in pockets below the surface. Those conditions would be similar to Jupiter's moon Europa, which is thought to have liquid water underground.

"I was shocked when I saw this analysis -- I and a lot of people in the field assumed these were all dry, rocky planets," said UChicago exoplanet scientist Jacob Bean, whose group Luque has joined to conduct further analyses.

The finding matches a theory of exoplanet formation that had fallen out of favor in the past few years, which suggested that many planets form farther out in their solar systems and migrate inward over time. Imagine clumps of rock and ice forming together in the cold conditions far from a star, and then being pulled slowly inward by the star's gravity.

Read more at Science Daily

Dynamic rivers contributed to Amazon's rich bird diversity

 One of the most contentious questions in evolutionary biology is, how did the Amazon become so rich in species? A new study focused on birds examines how the movements of rivers in the Amazon have contributed to that area's exceptional biological diversity. The research team, led by the American Museum of Natural History, found that as small river systems change over time, they spur the evolution of new species. The findings also reveal previously unknown bird species in the Amazon that are only found in small areas next to these dynamic river systems, putting them at high risk of imminent extinction. The study is detailed today in the journal Science Advances.

The lowland rainforests of the Amazon River basin harbor more diversity than any other terrestrial ecosystem on the planet. It is also a globally important biome containing about 18 percent of all trees on Earth and carrying more fresh water than the next seven largest river basins combined. Researchers have long wondered and hotly debate how the Amazon's rich biodiversity arose and accumulated.

"Early evolutionary biologists like Alfred Russel Wallace noticed that many species of primates and birds differ across opposite riverbanks in the Amazon, and ornithologists now know that rivers are associated -- in one way or another -- with the origin of many avian species," said the study's lead author Lukas Musher, a postdoctoral researcher at the Academy of Natural Sciences of Drexel University and a recent comparative biology Ph.D. graduate of the American Museum of Natural History's Richard Gilder Graduate School. "Moreover, accumulating geological evidence has suggested that these rivers are highly dynamic, moving around the South American landscape over relatively short time periods, on the order of thousands or tens of thousands of years."

To investigate how the movement of rivers across the landscape has influenced the accumulation of bird species in the Amazon, the researchers sequenced the genomes of six species of Amazonian birds.

"Even though birds can fly, our study confirmed that current rivers across the Southern Amazon rainforest, even relatively small ones, are highly effective at isolating populations of these six species, which leads to genomic divergence and ultimately speciation," said the study's senior author Joel Cracraft, Lamont Curator and curator-in-charge in the Museum's Department of Ornithology.

However, because these rivers move around the landscape at different time scales, their movements can have varying outcomes for bird species: when river rearrangements occur quickly, populations of birds on each side can merge before they've had time to differentiate; when river changes happen slowly, species have a longer time to diverge from one another; and when rivers change at intermediate rates, bird populations diverge and then join back together and co-occur when a river moves.

The scientists also identified distinct populations of birds that should be described as separate species but have been considered a single species until now.

"Though we know Amazonian biodiversity is unmatched by any other terrestrial ecosystem, we demonstrated that its species richness may be greatly underestimated even in well-studied groups such as birds," Musher said. "Our results corroborate those of other studies that have reported fine-scale patterns of diversity across the southern Amazon basin -- a region threatened by rapid and ongoing deforestation -- yet this diversity is generally unrecognized. Many of the distinct populations are relatively young and endemic to a small Amazonian region, meaning that a large portion of the Amazon's birds may be threatened with loss to imminent extinction."

Read more at Science Daily

Rivers speeding up Arctic ice melt at alarming rate

Irina Panyushkina grew up in Siberia, near the Arctic Circle. She was raised on stories of explorers trudging through seas of ice to reach the North Pole.

Now, she is a climate scientist and associate research professor of dendrochronology in the University of Arizona Laboratory of Tree-Ring Research. And she is trying to understand how a warming world is transforming the place she once called home.

Someday, the Arctic Ocean may no longer host ice, since the northern regions of the world are warming are faster than the rest -- a trend scientists refer to as Arctic amplification. As Arctic ice melts, new opportunities and challenges for humans will arise, researchers say.

Freshwater flowing into the Arctic Ocean from the continent is thought to exacerbate Arctic amplification, but the extent of its impact isn't fully understood. New research led by Panyushkina measures how the flow of the Yenisei River -- the largest freshwater river that flows into the Arctic Ocean -- has changed over the last few hundred years, and describes the impact freshwater has had on the Arctic.

Previous studies have attributed recent changes in wintertime freshwater flow into the Arctic to warming air temperature, seasonal precipitation changes or snowpack. But more recent research, including Panyushkina's study, suggests that the primary driver is actually degradation of permafrost -- or frozen ground -- as well as forest fires across southern Siberia.

Panyushkina's research, funded by the National Science Foundation Polar Office, is published in the journal Environmental Research Letters.

What trees can tell us

Data collected by instruments at the upper reaches of the Yenisei River in Tuva, in southern Siberia, only goes back so far. To overcome this, Panyushkina and her team used tree-ring data to double the number of years' worth of the stream flow data they had, allowing them to look back 300 years.

Stream flow, or the amount of water that moves through a certain area of a river over time, can be inferred by measuring changing tree-ring thickness over the years. Measurements of stream flow over specific seasons can even be teased out of the data.

Annual stream flow information is commonly used by water managers to reveal the average changes in stream flow trends. But Panyushkina and her team did something novel when they decided to also investigate winter stream flow specifically.

"We found an unprecedented increase in the winter flow rate over the last 25 years," Panyushkina said. This winter flow rate is nearly 80% above the average seen over approximately 100 years.

"In contrast, annual flow fluctuated normally during the 300-year period, with only a 7% increase over the last 25 years," Panyushkina said.

The winter stream flow data revealed the role of permafrost melt on Arctic ice.

Since ice covers rivers during winter in Siberia, the team's stream flow measurements only captured information about river waterthat originated underground rather thanfrom the sky. That includes water from thawing permafrost, as well as water from sub-permafrost aquifers, as permafrost loss leads to an increased exchange of water between the river and aquifers. These two sources of groundwater are warm compared to the frigid air above, and when they eventually flow into the Arctic Ocean, they melt the ice.

An uncertain future

Forest fires are also thought to be a driver of Arctic ice melt.

"We know the frequency and intensity of forest fires in Siberia have been increasing," Panyushkina said. "When fires happen in forests with permafrost, there is deep thawing under the fire event, and the affected area often doesn't recover for up to 60 years. When we have large-scale fires and long-burning fires and more frequent fires, we're maybe hitting the critical point when permafrost degradation cannot return to normal. Forest fires are also another process that increases connectivity between aquifers and stream flow."

The combined effects of permafrost degradation and fires are very strong at the Yenisei River basin, with more fresh water and heat flowing into the Arctic Ocean in recent decades, according to the study. In turn, melting sea ice also exacerbates global warming.

"Research interest in the region is booming because the surface temperature is warming much faster here than anywhere else in the world," Panyushkina said. "It's a hot spot for climate research, and because I grew up there and understand how the system works, it's a natural topic of study for me. I'm also very interested in knowing the impact of an ice-free Arctic on the surrounding landscape. Humans have never seen an ice-free Arctic before, ever. My mind still cannot comprehend how the Arctic Ocean can be free of ice."

By the middle of the century, changing sea ice conditions are expected to lead to greater navigability for open water-vessels crossing the Arctic. A future trans-Arctic shipping route called the Supra Polar Route will link the Atlantic and Pacific Oceans through the Arctic, potentially paving the way for more trans-Arctic commerce.

There is a need to quantify the Arctic amplification impacts to manage and regulate Arctic seas of the future, Panyushkina said.

"This strong prospect of the global trade fleet entering the Arctic opens the Pandora's box of near-future geopolitical and environmental issues and reinforces the urgency for a new regulatory framework by international organizations to ensure adequate environmental protections and vessel safety standards," she said.

Read more at Science Daily

Global river database documents 40 years of change

A first-ever database compiling movement of the largest rivers in the world over time could become a crucial tool for urban planners to better understand the deltas that are home to these rivers and a large portion of Earth's population.

The database, created by researchers at The University of Texas at Austin, uses publicly available remote sensing data to show how the river centerlines of the world's 48 most threatened deltas have moved during the past 40 years. The data can be used to predict how rivers will continue to move over time and help governments manage population density and future development.

"When we think about river management strategies, we have very little to no information about how rivers are moving over time," said Paola Passalacqua, an associate professor in the Cockrell School of Engineering's Department of Civil, Architectural and Environmental Engineering who leads the ongoing river analysis research.

The research was published today in Proceedings of the National Academy of Sciences.

The database includes three U.S. rivers, the Mississippi, the Colorado and the Rio Grande. Although some areas of these deltas are experiencing migration, overall, they are mostly stable, the data show. Aggressive containment strategies to keep those rivers in their place, especially near population centers, play a role in that, Passalacqua said.

Average migration rates for each river delta help identify which areas are stable and which are experiencing major river shifts. The researchers also published more extensive data online that includes information about how different segments of rivers have moved over time. It could help planners see what's going in rural areas vs. urban areas when making decisions about how to manage the rivers and what to do with development.

The researchers leaned on techniques from a variety of disciplines to compile the data and published their methods online. Machine learning and image processing software helped them examine decades' worth of images. The researchers worked with Alan Bovik of the Department of Electrical and Computer Engineering and doctoral student Leo Isikdogan to develop that technology. They also borrowed from fluid mechanics, using tools designed to monitor water particles in turbulence experiments to instead track changes to river locations over the years.

"We got the idea to use tools from fluid mechanics while attending a weekly department seminar where other researchers at the university share their work," said Tess Jarriel, a graduate research assistant in Passalacqua's lab and lead author of the paper. "It just goes to show how important it is to collaborate across disciplines."

Rivers that have high sediment flux and flood frequency move more as it is in their nature and part of an important tradeoff that underpins Passalacqua's research.

By knowing more about these river deltas where millions of people live, planners can have a better idea of how best to balance these tradeoffs. Passalacqua, as well as researchers in her lab, have recently published research about these tradeoffs between the need for river freedom and humanity's desire for stability.

Passalacqua has been working on this topic for more than eight years. The team and collaborators are in the process of publishing another paper as part of this work that expands beyond the centerlines of rivers and will also look at riverbanks. That additional information will give an even clearer picture about river movement over time, with more nuance, because sides of the river can move in different directions and at different speeds.

Read more at Science Daily

Meanders in river beds help the climate

It takes about 8500 years for a grain of sand from the Andes to be washed across the Argentine lowlands into the Río Paraná. The 1200-kilometer journey in the river called Río Bermejo is interrupted by many stops in river floodplains, where the grain is deposited, sometimes over thousands of years, and then washed free again. The sand is accompanied by organic carbon, washed in from soil and plants. The transport in water thus gains relevance for the climate: Rivers carry the carbon, which was previously removed from the atmosphere via photosynthesis, as sediment into the sea, where it is stored for thousands of years without harming the climate.

Researchers at the GFZ German Research Centre for Geosciences have now quantified the individual processes of the journey for the first time and report on them in the journal Nature Geoscience. An important result of the work: It is in particular undisturbed meandering sections of a river where carbon is deposited and reabsorbed, and then transported further into the sea. In river sections with straight, stable banks, on the other hand, only the suspended particle load passes through, while the carbon in the river floodplains is slowly decomposed again to CO2 by microorganisms. GFZ working group leader Dirk Sachse says, "The Río Bermejo was an ideal natural laboratory for us because it has no significant tributaries." Sachse is also director of the "Landscapes of the Future" topic in the Helmholtz program "Changing Earth -- Sustaining Our Future." He says, "This means that natural river courses that have space to erode floodplains can remove more carbon from the atmosphere than straight river sections. In this respect, straightening of rivers by humans could also contribute to the increase in atmospheric CO2 concentration. What's exciting now is answering the question of whether we can help the climate by giving rivers more space again and not impeding natural river meandering."

The international team led by first author Marisa Repasch of GFZ studied the processes in the river and its floodplains with a diverse set of instruments. Analyses of cosmogenic beryllium-10 content, for example, indicated the duration of sediment transport. Dating based on the unstable carbon isotope 14C, in turn, allowed conclusions to be drawn about the age of the particles of organic origin. During fieldwork in Argentina, samples were taken from the river at multiple stations along the source-to-sink pathway. "Naturally meandering rivers erode material from floodplains and transport it to the sea, where it remains for a long time," says Marisa Repasch, summarizing the results, "in contrast, artificially stabilized river courses are far less effective carbon sinks."

From Science Daily

Runoff, sediment flux in High Mountain Asia could limit food, energy for millions

Rivers flowing from the Tibetan Plateau and the surrounding high Asian mountains which support one-third of the world's population have experienced rapid increases in annual water and sediment runoff since the 1990s, and the volume of sediment washed downstream could more than double by 2050 under the worst-case scenario, a team of scientists has found.

The cause is "amplified warming": Since 1950, the High Mountain Asia area, or the region of Asia containing five mountain ranges including the Himalaya and Hindu Kush around the Tibetan Plateau, has warmed by about 2 degrees Celsius, twice the amount of warming worldwide. That warming is precipitating more glacier melt, permafrost thaw while annual rainfall is also increasing, the researchers note.

"These findings have far-reaching implications for the region's hydropower, food and environmental security," the researchers observe. The findings also highlight the under-appreciated importance of sediment fluxes and have implications for potential changes in the global carbon cycle, they add.

The research, published today in the journal Science, is led by the National University of Singapore and includes three researchers from the University of Colorado Boulder, including Irina Overeem, Jaia Syvitski and Albert Kettner, all researchers in the Institute of Arctic and Alpine Research. Overeem is also a CU Boulder associate professor of geological sciences, and Syvitski is professor emeritus of geological sciences.

The scientists analyzed observational data of runoff and sediment fluxes from 28 headwater basins over the past six decades.

Sediment flux is the mass of sediment that passes through a specific point in a river basin over a given time period, "like truckloads of sand being transported, in this case by water," Overeem said. Although river runoff, the amount of water entering a river system, and sediment flux are both increasing, they are rising at different rates.

In the river basins the scientists studied, runoff increased by about 5% per decade, while sediment flux increased about 12% per decade.

Overeem explained the variability is affected in two ways: "With glacial melt and permafrost thaw there are new sources of sediment, that previously had been frozen in place in the landscape now can slump into the river. In addition, if more rainfall triggers bigger floods, you suddenly have exceeded a threshold and you can pick up so much more sediment" compared to average conditions. "If you increase the source and the proportion of a couple of these extreme events, you'll get disproportionally much more sediment. So that is maybe what's going on in this system."

River-borne sediment can benefit highly populated areas like Bangladesh, where sediment helps maintain the coastal zone. But in other areas such as Tibet or Nepal, which have hydro-electric power plants, rising levels of sediment can wear out the dams' turbines and fill reservoirs with sand and silt.

By harming existing or planned hydropower projects and reducing irrigation capacity, rising sediment fluxes can thus "threaten the region's food and energy security," the authors write. Additionally, the rising levels of sediment, which can carry nutrients, pollutants and organic carbon, can have implications for water quality and flooding, potentially affecting millions of people.

Research on the High Mountain Asia watershed was facilitated by the area's unusually good, long-term records of streamflow and sediment flux, Overeem said, adding that datasets of similar quality do not exist for Greenland or the whole Arctic.

In the Arctic, scientists have also recorded increases in water discharge from melting ice and increasing rainfall but have few measurements of sediment flux.

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Titan’s river maps may advise Dragonfly’s 'sedimental' journey

With future space exploration in mind, a Cornell-led team of astronomers has published the final maps of Titan's liquid methane rivers and tributaries -- as seen by NASA's late Cassini mission -- so that may help provide context for Dragonfly's upcoming 2030s expedition.

The fluvial maps and details of their accuracy were published in the Planetary Science Journal (August 2021.) In addition to the maps, the work examined what could be learned by analyzing Earth's rivers by using degraded radar data -- similar to what Cassini saw.

Like water on Earth, liquid methane and ethane fill Titan's lakes, rivers and streams. But understanding those channels -- including their twists and branch-like turns -- is key to knowing how that moon's sediment transport system works and the underlying geology.

"The channel systems are the heart of Titan's sediment transport pathways," said Alex Hayes, associate professor of astronomy in the College of Arts and Sciences. "They tell you how organic material is routed around Titan's surface, and identifies locations where the material might be concentrated near tectonic or perhaps even cryovolcanic features.

"Further, those materials either can be sent down into Titan's liquid water interior ocean, or alternatively, mixed with liquid water that gets transported up to the surface," Hayes said.

Larger than the planet Mercury and fully shrouded in a dense nitrogen and methane atmosphere, Titan is the only other place in the solar system with an active hydrologic system, which includes rain, channels, lakes and seas.

"Unlike Mars, it's not 3.6 billion years ago when you would have seen lakes and channels on Titan. It's today," Hayes said. "Examining Titan's hydrologic system represents an extreme example comparable to Earth's hydrologic system -- and it's the only instance where we can actively see how a planetary landscape evolves in the absence of vegetation."

Julia Miller '20 led the detailed work of examining Cassini's Synthetic Aperture Radar (SAR) images of Titan's surface, looking for fluvial characteristics and then comparing those images to those available on Earth.

On Earth, fluvial geomorphology is typically studied with topographic data and high-resolution visible images, but that was not available for Titan. Instead, Miller used Earth-based radar images and degraded them to match the Cassini radar images of Titan.

This way, Miller could understand the limits of the Cassini dataset and know which results are robust for analysis using low, roughly 1-kilometer resolution data.

"Although the quality and quantity of Cassini SAR images put significant limits on their utility for investigating river networks," Miller said, "they can still be used to understand Titan's landscape at a fundamental level."

River shapes say a lot. "You can use sort of what the river looks like to try to say some things about the type of material that it's flowing through, or like how steep the surfaces, or just what went on in that region," Miller said. "This is using the rivers as a starting point, to then, ideally, learn more about the planet."

The Dragonfly mission to Titan is slated to launch in 2027 and is scheduled to arrive at Titan in 2034.

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