Plain Language Summaries Collection

Plain Language Summaries are published alongside a paper’s scientific abstract, and are a great way to communicate your work to a broader audience. Submitting a Plain Language Summary is now an option across all AGU Journals. We showcase some good examples here. Find out more about how to write a good Plain Language Summary.


Evaluating the Skill of Forecasts of the Near‐Earth Solar Wind using a Space Weather Monitor at L5 by S. R. Thomas, et al in Space Weather

A space weather monitor spacecraft has been proposed away from the Earth’s viewing direction which is likely to help improve the warning of solar events which could be heading towards Earth. In this study, we investigate whether such a spacecraft can improve our predictions of important physical values that are associated with the solar wind. To do this, we use times when two spacecraft have previously been in similar locations with respect to each other and map each value from one to the other, making several important considerations relating to the spacecraft’s motion and the movement of the plasma that they are embedded within. We have used ‘skill scores’ which are used to assess weather forecasts to quantify how well our forecast performs. We find that a spacecraft at this location predicts almost all important values better than are currently possible. This means that a detector of these parameters is essential for when the mission is commissioned.


The Search for Active Marsquakes Using Subpixel Coregistration and Correlation: Best Practice and First Results by Peter M. Grindrod, et al in JGR: Planets

It is currently unknown whether there are active ‘Marsquakes’ – earthquakes on Mars – despite past missions with seismometer instruments designed for their detection. In this study we compare images of Mars taken over eight and a half (Earth) years to look for changes at the surface that could have been caused by Marsquakes. We focused our study on the youngest fault system on Mars, Cerberus Fossae, as it is one of the areas that probably has the best chances of being active today. We developed a method that should be sensitive to small changes in the surface but have found no conclusive evidence of any Marsquakes. We dismissed one possible signal of change as the result of artefacts in the method and offer best practices for future studies of this kind. Identifying Marsquakes is important in understanding the tectonic and overall geologic evolution of Mars.

A new bathymetry for the southeastern Filchner‐Ronne Ice Shelf: implications for modern oceanographic processes and glacial history by S. H. R. Rosier, et al in JGR: Oceans

The Filchner‐Ronne Ice Shelf in Antarctica is the largest body of floating ice in the world and plays an important role in the global climate system through its interactions with the ocean and Antarctic Ice Sheet. Due to its thickness and remoteness, the shape of the large ocean cavity beneath this floating ice shelf is poorly understood, yet this information is crucial for ice and ocean models of the region. In this study we present recent measurements of the thickness of this ocean cavity and, in combination with previous measurements, produce a new map of the area. Several new features are revealed in this map and we discuss the implications for ocean currents within the cavity, as well as past and future ice sheet flow. 

Urban Water Conservation Policies in the United States by Jonathan M. Gilligan, et al in Earth's Future

As urban water supply systems confront growing populations, growing economies, and climatic stress, water conservation measures are often more effective and economical ways to assure reliable and sustainable access to water than building ever larger supply systems. We present the first analysis of a comprehensive index of urban water conservation policies for 195 cities in the contiguous United States. We find that the number of conservation measures a city adopts correlates both with environmental and societal factors, and with the characteristics both of the city itself and of the state in which it is located. Cities in drier states and cities that vote for Democratic candidates in greater numbers tend to adopt more conservation policies. By identifying characteristics associated with water conservation, these results can help planners and policy makers understand how different cities face different obstacles and opportunities for adopting conservation policies. 

The Threat of Multiyear Drought in Western Amazonia by L. A. Parsons, et al in WRR

The Amazon basin recently experienced multiple “once‐in‐a‐century” droughts that impacted the region’s water cycle, economy, vegetation, and carbon storage. However, the instrumental record in this region tends to be too short to determine if these droughts are abnormal in a long‐term context. Paleoclimate data can extend drought records that help water and land managers plan for these events in the face of climate change. To provide additional information about pre‐instrumental drought, here we present results from a new paleoclimate lake record based on sediments we recovered from Lake Limón in the Peruvian Amazon. We find that concentrations of elements in the Lake Limón sediment cores are likely recording past changes in rainfall variability. We use this elemental variability to generate a new, millennial‐length record of drought for the western Amazon. We show that this region has experienced multi‐year droughts at least twice a century over the last ~1400 years. The frequency and severity of these paleo‐inferred droughts exceed most climate model and instrumental‐era drought risk estimates. Our findings illustrate that the future sustainability of the Amazonian forest and its many ecosystem services may require management strategies that consider the likelihood of multi‐year droughts in addition to continued warming. 

Radar Sounding of Open Basin Lakes on Mars by E. S. Shoemaker, et al in JGR: Planets

Mars was once host to ancient lakes that can currently be observed as a topographic depression in the surface with channels where water is thought to have once flowed called an open basin lake. This flowing water transported sediments into the lake which was later covered by further sedimentary or volcanic deposits. The interface between layers of material in the subsurface can be detected from orbit using the Shallow Radar (SHARAD) instrument. Our survey of 61 open basin lakes revealed only one detectable interface in a single basin lake. We investigate possible factors that could contribute to the lack of identified interfaces through detailed analyses of available radar images and surface characteristics of the open basin lakes. We develop a method to characterize the degree of noise (clutter) in the radar images created by large surface features (>100 m) up to 25 km away from the position of the ground track of the spacecraft. However, this alone cannot explain the lack of detected interfaces. A rough subsurface or interface may be more likely. Further modeling will be necessary to characterize the radar characteristics of these basins as many are landing site candidates for future missions searching for formerly habitable environments. 

Interpreting precession driven δ18O variability in the South Asian monsoon region by Clay R. Tabor, et al in JGR: Atmospheres

Cave records suggest that there has been significant longterm climate variability in India related to changes in Earth’s orbit. However, these records are difficult to interpret because the signals can represent several different climate responses. Here, we use a climate model that directly simulates the isotopic data captured in the cave records to better interpret their physical meaning. From these model simulations, we show that a large portion of the orbital signals found in the cave records are due to changes in the amount of water vapor coming from different sources. Changes in the amount of local evaporation compared to precipitation also have a large effect on the signals found in the cave records

Exploring the Utility of IASI for Monitoring Volcanic SO2 Emissions by Isabelle A. Taylor, et al in JGR: Atmospheres

Gas emissions at volcanoes are dangerous to health and can alter the environment and climate. Monitoring the gases emitted is therefore important, and it gives volcanologists some insight into volcanic behavior. Ground‐based monitoring can be dangerous and is limited in remote regions, and so satellite imagery is used to detect and measure volcanic gas emissions (usually sulfur dioxide [SO2]) across the globe. This study focused on the Infrared Atmospheric Sounding Interferometer, which is an infrared sensor onboard two meteorological satellites. First, a fast tool was used to detect emissions of SO2 across the globe: including from explosive volcanic activity, smaller eruptions, and human pollution sources. Following this, a second method was applied to calculate the amount of SO2emitted from volcanoes in Ecuador and Kamchatka (Eastern Russia)—two regions with regular volcanic activity. This technique was shown to capture changing levels of volcanic activity in both areas. At Tungurahua, a volcano in Ecuador, comparisons could be made to another satellite and to measurements made on the ground. The three methods compared well suggesting that the technique developed for Infrared Atmospheric Sounding Interferometer can capture changing activity at this volcano and could be valuable for tracking and quantifying emissions.

Long‐lasting response of the global thermosphere and ionosphere to the 21 August 2017 solar eclipse by Jiuhou Lei, et al in JGR: Space Physics

The thermosphere is the layer of the Earth’s atmosphere above the mesosphere between about 60 and 1000 km, and the ionosphere is the ionized part of the atmosphere. In this region, the neutral gas and the ionized plasma have significant impact on low Earth orbiting determination and satellite radio communications. This work is the first to use a stateofart, firstprinciples model of the coupled thermosphere and ionosphere, with selfconsistent electrodynamics, to systematically investigate the dynamics and electrodynamic behavior of the global ionosphere and thermosphere after an eclipse. Although the solar eclipse is a transient local event, its impact on the ionosphere and thermosphere can persist for a long time over the entire globe, rather than just being an impulse event with a localized response as was previously expected. This effort paves the way for improving the understanding of the upper atmospheric variability.

Quantifying Debris Thickness of Debris‐Covered Glaciers in the Everest Region of Nepal Through Inversion of a Subdebris Melt Model by David R. Rounce, et al in JGR: Earth Surface

Debris‐covered glaciers are ubiquitous in the Himalaya and this debris significantly alters the evolution of these glaciers. Estimating the thickness of debris on these glaciers, however, remains a challenge. This study develops a novel method for estimating the debris thickness on three glaciers in the Everest region of Nepal based on digital elevation models, surface velocity data, ice thickness estimates, and a debris‐covered glacier energy balance model. The method was calibrated and validated on Ngozumpa Glacier, one of the largest debris‐covered glaciers in Nepal, and was found to accurately estimate debris thickness. Specifically, this method was able to estimate thick debris (> 0.5 m), which has been a major limitation of previous studies. This is important because thick debris significantly reduces glacier melt rates by insulating the underlying ice. This study creates a step‐change in our ability to model the past, present, and future evolution of debris‐covered glaciers. 

Episodes of aqueous flooding and effusive volcanism associated with Hrad Vallis, Mars by Christopher W. Hamilton, et al in JGR: Planets

The Elysium Volcanic Province of Mars includes major outflow channels that are interpreted to have been carved by either catastrophic aqueous floods or turbulent lava flows. Determining the origin of these channels is therefore important for determining the hydrological and volcanic history of the planet. This study focuses on Hrad Vallis, which is a geologically recent outflow channel within the Elysium Volcanic Province. Through a combination of mapping and modeling, we find evidence for both aqueous flooding and effusive volcanism associated with this channel, indicating a complex hydrologic and geologic history. However, lava flows are interpreted to be the products of pāhoehoe‐like lava flow emplacement, similar to terrestrial lava flows on Earth in New Mexico and Hawaii, and not highly turbulent flows as previously suggested. The identification of ~50 m thick pāhoehoe‐like lava flows near Hrad Vallis implies a gradual formation process over the course of decades and heat from these lava flows may have interacted with ground ice in the region to generate meltwater and steam. Associated lava‐water interactions are important because they could have developed habitable environments for microbial organisms adapted for survival within hydrothermal systems. 

Browning‐related decreases in water transparency lead to long‐term increases in surface water temperature and thermal stratification in two small lakes by Rachel M. Pilla, et al in JGR: Biogeosciences

Lakes provide key services to society ranging from drinking water and food to recreation and increased property value. But lakes are vulnerable to many environmental threats, including climate change. Two study lakes in Pennsylvania have experienced decreases in water clarity as the water has become more brown over the past three decades. As a result, sunlight and heat are more completely absorbed near the surface of the lake, with less light and heat reaching deeper waters. This leads to warmer surface waters and cooler deep waters. We attribute the reduced water clarity and changes in lake temperature to recovery from acid rain following the Clean Air Act amendments in the 1990s, combined with climate change‐induced increases in precipitation and storm events in the northeastern United States that increase runoff of organic matter into lakes. These changes are influencing other aspects of the lake ecosystem by accelerating oxygen depletion and altering the abundance of and habitat availability for algae, zooplankton, and fish. 

A Field Guide to Finding Fossils on Mars by S. McMahon, et al in JGR: Planets

This paper reviews the rocks and minerals on Mars that could potentially host fossils or other signs of ancient life preserved since Mars was warmer and wetter billions of years ago. We apply recent results from the study of Earth’s fossil record and fossilization processes, and from the geological exploration of Mars by rovers and orbiters, in order to select the most favored targets for astrobiological missions to Mars. We conclude that mudstones rich in silica and iron‐bearing clays currently offer the best hope of finding fossils on Mars and should be prioritized, but that several other options warrant further research. We also recommend further experimental work on how fossilization processes operate under conditions analogous to early Mars. 

Seasonal non‐tectonic loading inferred from cGPS as a potential trigger for the M6.0 South Napa Earthquake by Meredith L. Kraner, et al in JGR: Solid Earth

It is well established that earthquakes occur on fault systems where stress has accumulated over periods of centuries to millennia. The specific factors that trigger individual earthquakes are typically unknown, but researchers have recently found links between seasonal variations in earthquake occurrence and local changes in water storage and temperature. Using data from high‐precision continuous GPS stations in Northern California, we observed a small 3 mm horizontal expansion of the Earth’s crust prior to and in the vicinity of the August 2014 M6.0 South Napa earthquake. By analyzing the previous eight years of GPS data, we additionally found that a similar pattern of crustal motion repeats every summer. We have determined that this crustal expansion releases pressure on nearby faults, including those in the South Napa fault system, making them more likely to slip during the summer months. Large seasonal variability in the amount of groundwater in the Napa Valley and Sonoma subbasins may contribute to the observed changes. 

Understanding the Twist Distribution Inside Magnetic Flux Ropes by Anatomizing an Interplanetary Magnetic Cloud by Yuming Wang, et al in JGR: Space Physics

Magnetic Flux rope (MFR) is a fundamental structure in the universe filled with plasmas, and related to various eruptive phenomena, e.g., mass ejections, jets, etc. How the magnetic twist distributes in a MFR is key information in understanding many puzzles: e.g., (1) why a very-long (thousands of light-years long) and high-twist astrophysical jet can exist, (2) whether or not a seed MFR exists prior to coronal mass ejections, which is a long debate in the solar physics, and (3) when a MFR gets kink-unstable. Here, we try to address these puzzles by presenting a rare observed MFR, namely magnetic cloud, in interplanetary space. Four spacecraft near Mercury, Venus, Earth and Mars, respectively, observed the magnetic cloud sequentially in time and space. By analyzing the in-situ measurements of the magnetic cloud, we find that the axial flux and helicity decreased with the heliocentric distance but the twist increased. The ‘pancaking’ effect and ‘erosion’ effect may jointly cause such variations. The erosion effect suggests that the magnetic cloud might consist of a strong-twist core and a less-twisted outer shell, posing a great challenge to the current understanding on the solar eruptions as well as the formation and instability of MFRs. 

In situ microphysical observations of the 29‐30 May 2012 Kingfisher, OK supercell with a balloon‐borne video disdrometer by Sean M. Waugh, et al in JGR: Atmospheres

A microphysics instrument capable of measuring the number, size, shape, and composition of particles inside thunderstorms has been developed that flies on a weather balloon. The observations collected are compared to radar observations and some aspects of computer models that validate what these other tools are seeing and shows room for improvements. These observations are providing a unique and unprecedented look at the details of in situ particle concentrations. Understanding of the processes responsible for the formation and maintenance of these particles can lead to advances in forecasting ability and real time decision making. 

The impacts of Chinese wind farms on climate by Hongwei Sun, et al in JGR: Atmospheres

With the rapid development of wind energy, the impacts of wind farms on environment have attracted increasing attention. A new wind farm fleet scenario is designed in the study to analyze the climatic impacts of wind farms in China. The results show the local and regional climatic impacts of wind farms in China (e.g., changes within {plus minus}0.5 K for 2-m temperature and {plus minus}30 m2/s2 for 500-hPa geopotential height), which are much smaller than the natural climate variability. This research can provide China, as well as other countries and regions, with useful scientific advice for the environment-friendly development of wind energy. 

Interfacial Form Stress in the Southern Ocean State Estimate by Jessica Masich, et al in JGR: Oceans

Winds over the Southern Ocean blow towards the east, continuously inputting eastward momentum into the ocean. This eastward momentum is balanced by the landmasses and undersea ridges that block the Antarctic Circumpolar Current (ACC)’s eastward path around Antarctica. We analyze a high-resolution model of the Southern Ocean to map interfacial form stress (IFS), the mechanism by which momentum travels from wind source to topographic sink. We conduct this analysis in a new, unique way, by calculating the pressure exerted from one ocean layer to another for every day in the six-year model run; this analysis shows where lighter layers are ‘leaning’ against denser layers and thus transferring eastward momentum downward from lighter to denser ocean layers. We find that IFS mostly concentrates where there are large-scale meanders in the ACC, and to a lesser degree in regions where the Southern Ocean is mixed by eddies. 

Observations of Surface Wave Dispersion in the Marginal Ice Zone by Clarence Collins, et al in JGR: Oceans

The relationship between wavelength and wave period is known as the dispersion relation. The dispersion relation is well known for waves on the open ocean. The relationship is altered by shallow water and by changing currents at the surface, but we do not know if it is altered by ice cover. In this study we present measurements of the dispersion relation in the marginal ice zone, the transition zone between open areas of ocean and areas dominated by ice cover. The measurements were tricky, so there is a good deal of uncertainty involved. We found that dispersion of long period waves was not affected by ice in this zone, but under certain circumstances, the short period waves were slightly reduced in wavelength. This reduction in wavelength was consistent with a theory which adjust dispersion for the added weight of the ice.

Denali ice core methanesulfonic acid records north Pacific marine primary production by David J. Polashenski, et al in JGR: Atmospheres

The base of the marine food web is composed of single-celled photosynthetic organisms that are collectively termed primary producers. Because these microscopic organisms support all marine life, changes in their biomass can impact the entire food web. Over the past three decades, satellite data has shown that primary producers are declining around the world with some of the greatest declines occurring in the north Pacific Ocean. The reasons for these declines may include changes in ocean temperatures, nutrient availability, and wind-driven ocean mixing, all of which are related to climate. To place these changes within a longer-term context, we wanted to develop a proxy tool by measuring a chemical produced by phytoplankton, called methanesulfonic acid (MSA). MSA is transported through the atmosphere by storms, which deposit it on mountain glaciers in the north Pacific region. We measured MSA in a new ice core from Denali National Park, Alaska. We describe how we found strong, statistically significant correlations between ice core MSA concentrations and chlorophyll concentrations in the western Gulf of Alaska. We suggest that the ice core MSA proxy record can help us understand how primary production in this region has changed through time and put contemporary changes in context.