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.

 

Coastal Erosion of Permafrost Soils Along the Yukon Coastal Plain and Fluxes of Organic Carbon to the Canadian Beaufort Sea by Nicole J. Couture, et al in JGR: Biogeosciences

The oceans help slow the buildup of carbon dioxide (CO2) because they absorb much of this greenhouse gas. However, if carbon from other sources is added to the oceans, it can affect their ability to absorb atmospheric CO2. Our study examines the organic carbon added to the Canadian Beaufort Sea from eroding permafrost along the Yukon coast, a region quite vulnerable to erosion. Understanding carbon cycling in this area is important because environmental changes in the Arctic such as longer open water seasons, rising sea levels, and warmer air, water and soil temperatures are likely to increase coastal erosion and, thus, carbon fluxes to the sea. We measured the carbon in different types of permafrost soils and applied corrections to account for the volume taken up by various types of ground ice. By determining how quickly the shoreline is eroding, we assessed how much organic carbon is being transferred to the ocean each year. Our results show that 36 × 106 kg of carbon is added annually from this section of the coast. If we extrapolate these results to other coastal areas along the Canadian Beaufort Sea, the flux of organic carbon is nearly 3 times what was previously thought.

Pancake Ice Thickness Mapping in the Beaufort Sea From Wave Dispersion Observed in SAR Imagery by P. Wadhams, et al in JGR: Oceans

It is known from work at open ocean boundaries such as Antarctica and the Greenland Sea that ocean waves interact with icefields to break up the ice and strip it away from the ice-water boundary, enhancing ice retreat. Also, in a wave field, new ice is forced to grow in the form of pancakes, an array of small cakes. The Beaufort Sea in late summer now counts as an open ocean boundary, and on the 2015 cruise of “Sikuliaq” it was found that vast fields of pancake ice were being created at the advancing edge as summer ended. We were able to map the thickness of these pancakes, and hence their contribution to the volume of the icefield, using a satellite technique developed by two of the authors in 1991. This uses synthetic aperture radar images of the ice to determine the frequency spectrum of wave energy, and since the speed of waves in ice depends on the frequency and the ice thickness, we can extract thicknesses from this analysis. The results were tested against direct measurements from the ship. This technique can be used worldwide to determine the overall contribution of pancake ice to the world’s sea ice.

Estimating Wetland Connectivity to Streams in the Prairie Pothole Region: An Isotopic and Remote Sensing Approach by J. R. Brooks, et al in WRR

Connectivity of wetlands within watersheds is critical to wetland function at local-to-landscape scales. However, actual measures of connectivity between wetlands and streams at the watershed scale are difficult to make, but critical for quantifying these functions, and for supporting policy and decision making. In this manuscript, we combine and compare direct field measurements of connectivity using stable isotopes of water, and remotely sensed measurements of connectivity using Landsat data. We found that prairie-pothole wetlands contributed significant amounts of water to the perennial stream from high to low-flow conditions. This wetland water flowed through surface water connections and not through groundwater flow paths. Hydrologic connectivity between prairie-pothole wetlands and the stream was dynamic, fluctuating with streamflow. Combining the isotopic and Landsat approaches to estimating contributing area appears to be a promising technique for determining potential and actual contributing areas in these flat wetland-dominated systems.

Effects of High-Latitude Forcing Uncertainty on the Low-Latitude and Midlatitude Ionosphere by N. M. Pedatella, et al in JGR: Space Physics

Geomagnetic storms produce large changes in the Earth’s ionosphere that can impact communications, navigation systems, and the electric power grid. The capability of numerical models to reproduce the ionospheric disturbance during a geomagnetic storm is partially dependent on accurately specifying the geomagnetic storm forcing at high latitudes. The forcing is, however, not known with complete accuracy due to imperfect observational knowledge and processes that occur at scales smaller than the model resolution. Numerical models typically neglect any forcing uncertainty, and it is unclear to what extent uncertainty in the forcing leads to uncertainty in the model response. In the present study, an ensemble of simulations in the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General Circulation Model are performed to understand how uncertainty in the forcing parameters during a geomagnetic storm are propagated into uncertainty in the low-latitude to midlatitude ionosphere disturbance. The ensemble simulations demonstrate that there can be large uncertainty in numerical simulations of the low-latitude to midlatitude ionosphere response to a geomagnetic storm due to uncertainty in the forcing. Understanding the impact of forcing uncertainty may be useful for space weather forecasting models since it can provide an estimate of the reliability of the simulations.

Multimodel Evidence for an Atmospheric Circulation Response to Arctic Sea Ice Loss in the CMIP5 Future Projections by G. Zappa, et al in GRL

How the atmospheric circulation will respond to climate change in the coming decades remains uncertain. The loss of Arctic sea ice has been identified as one of the factors that can influence atmospheric circulation, and a better understanding of this connection is important to improve our confidence in the regional impacts of climate change. To do this, we have analyzed future climate projections from computer simulations based on a large set of different climate models. Using a novel approach, we were able to demonstrate that Arctic sea ice loss exerts a consistent and nonnegligible impact on the atmospheric circulation response. In particular, in late winter and in the North Atlantic and Euro-Asian sector, Arctic sea ice loss tends to oppose the poleward shift of the midlatitude westerly winds, which is a common feature of the future projections of atmospheric circulation change. These results are important as they provide the first assessment that Arctic sea ice loss is important for the atmospheric circulation response to climate change based on a large number of climate models.

Cascadia Onshore-Offshore Site Response, Submarine Sediment Mobilization, and Earthquake Recurrence by J. Gomberg in JGR: Solid Earth

Earthquakes radiate seismic waves that shake the surface. The shaking at a site can be altered by nearby geologic structure (the sediments and rocks beneath the surface) and topography, amplifying and prolonging or diminishing the strength of the shaking. Scientists and engineers call these effects “site response” and measure and account for them in the design of shaking-resilient structures. Earthquake shaking also causes failures of slopes and redistributes sediments offshore, which can break communications cables, initiate local tsunamis, alters ecosystems, and even influences how the tectonic plates move. Deposits (called “turbidites”) left behind by past slope failures and transient sediment-laden currents also are useful, providing a record of previous earthquakes spanning millennia. I used unique seismic data from the seafloor and from permanent networks onshore, to derive estimates of site response throughout Cascadia (the Pacific Northwest’s subduction zone). Results show that the local geologic structure and topography strongly changes shaking from place to place, particularly offshore. The broad-scale, systematic nature of these changes should be considered in assessments of the vulnerability of submarine slopes to future shaking. Results also highlight the need to consider site response more carefully when interpreting the turbidite record to derive chronologies of past earthquakes.

The Influence of Eurasian Snow Extent on the Northern Extratropical Stratosphere in a QBO Resolving Model by Nicholas L. Tyrrell, et al in JGR: Atmospheres

The ability to predict European wintertime temperatures weeks or months in advance would have many positive implications for society. However, standard weather prediction techniques are unable to make accurate forecasts much more than a week in advance. For long-term seasonal forecasts we rely on the slowly changing features of the climate system to give us information about the future weather. These slowly changing features include the autumn snow cover over Siberia and winds high in the tropical atmosphere. Both of these can influence the stratospheric winds over the northern hemisphere pole in winter, which then affects the weather at the surface. In this study we simulate these slowly changing features and compare the simulated response of the polar winds to the observed response. We find that the simulated response is weaker than the observed response; however, we also find that the Siberian snow and the high tropical winds work together to influence the polar winds more than each factor individually. This combined effect may provide us with additional information when making long-term seasonal forecasts.

Empirical Modeling of the Quiet and Storm Time Geosynchronous Magnetic Field by V. A. Andreeva and N. A. Tsyganenko in Space Weather

A mathematical model has been developed to describe the magnetic field around the orbits of geosynchronous satellites. The model allows to map the magnetic field lines and represent their evolution during space storms. The model is based on results of spacecraft measurements of the geomagnetic field during last 20 years and makes it possible to help understand the dynamics of the Earth’s magnetic field and its relation to the space weather.

Correlations Between Extreme Atmospheric Hazards and Global Teleconnections: Implications for Multihazard Resilience by H. Steptoe, et al in Reviews of Geophysics

The likelihood of global extreme weather events occurring at the same time represents a significant source of uncertainty for organizations involved in responding to natural disasters. Understanding the risks posed by natural disasters is important in preparing for extreme events. Many public and private sector organizations play key roles in managing the impacts in the aftermath of natural disasters. However, to ensure that sufficient disaster resilience is in place, in the event of single or simultaneous extreme events, we need to understand the ways they connect with processes occurring in the Earth’s atmosphere and oceans. This review summarizes the connections between 16 regional extreme weather events and 10 key drivers of global weather and climate. Focusing on annual time scales, El Niño–Southern Oscillation has connections with 15 regional hazards, linking rainfall in China, the United States, Australia, South Asia, and South Africa. The Indian Ocean Dipole and the Southern Annular Mode provide additional significant sources of connections between hazards across North and South Hemispheres. We show how this understanding can be used to develop early-warning systems for multihazard disasters at a global scale, in support of sustainable development goals, and inform a coordinated response to multiple hazard occurrence.

Control of Delta Avulsion by Downstream Sediment Sinks by Gerard Salter, et al in JGR: Earth Surface

Deltas are low-lying coastal landscapes which form over time from sediment delivered by a river. Because they are low-lying, they are vulnerable to drowning from rising sea level. This drowning is counteracted, at least partially, by the formation of new land from river sediment. Bifurcations are locations where a river splits into two downstream branches and are common in deltas. They are important because they control how much sediment gets delivered to different parts of the delta, where it can form new land to counteract rising sea level. In this study, we solve mathematical equations to investigate how conditions at the shoreline influence how water and sediment are split between the branches of a bifurcation. We find that normally, the bifurcation switches repeatedly, sending more water and sediment down one branch, and then switching to the other. The switching happens because the branch carrying more sediment builds land faster, so the neglected branch becomes a shorter path to the sea. Alternatively, if the sediment gets lost into deeper water instead of forming new land, we find that one branch of the bifurcation becomes permanently favored. By better understanding delta bifurcations, we hope to inform efforts to save drowning coastal landscapes.

Identification of Tropical-Extratropical Interactions and Extreme Precipitation Events in the Middle East Based On Potential Vorticity and Moisture Transport by A. J. de Vries, et al in JGR: Atmospheres

Torrential rains lead almost every year to flooding and fatalities in the arid Middle East. At the same time, such heavy rainfall events can recharge scarce freshwater resources in the subtropical desert region. These events often occur when the atmospheric circulations of the midlatitudes and the tropics interact with another. More specifically, a disturbance from the midlatitudes intrudes into the subtropics and initiates an incursion of tropical moisture across the Middle East. In our study we developed an identification method for heavy rainfall events based on the combination of these two meteorological processes. This unique approach avoids dependency on rainfall data which is often poorly simulated in numerical weather and climate models, whereas the atmospheric circulation is much better represented. Our method successfully detects events that contribute to a large fraction of annual rainfall amounts (40–70%) and heavy rainfall days (50–90%) in the arid parts of the Levant and the Arabian Peninsula. Moreover, the characteristics and duration of the midlatitude disturbances and tropical moisture incursions strongly influence the rainfall severity. This knowledge and identification method can support weather prediction and early warnings for heavy rainfall events as well as future studies on their climatic changes due to global warming.

Using Forbush Decreases to Derive the Transit Time of ICMEs Propagating from 1 AU to Mars by Johan L. Freiherr von Forstner, et al in JGR: Space Physics

Eruptions from the Sun often containing a shock front followed by a magnetic ejecta may cause a depression in the omnipresent cosmic rays that can now be observed at Mars thanks to the radiation assessment detector (RAD) on board the Mars Science Laboratory. When both Earth (or other spacecraft like STEREOs that are located at Earth orbit) and Mars are closely aligned on the same side of the Sun, we have a great opportunity to observe such eruptions passing by and affecting both planets. Based on measurements from both Earth orbit and Mars, we have studied 15 solar events and their properties such as the speed and its evolution from the Sun to Mars. We found that most of these eruptions slow down considerably during their propagation from the Sun to Earth orbit and even beyond all the way to Mars.

Observation-Based Trends of the Southern Ocean Carbon Sink by R. Ritter, et al in GRL

The Southern Ocean plays an important role in regulating Earth’s climate as it takes up a substantial amount of carbon dioxide from the atmosphere, thereby limiting the effect of global warming. However, this part of the global ocean is also the least well observed and observational data are sparse. Therefore, to study Southern Ocean carbon uptake, data interpolation methods are used to estimate the variability of the carbon uptake from the few existing observations. This poses the question on how reliable these estimates are. The Surface Ocean CO2 Mapping intercomparison project aims to do exactly that, that is, test how reliable current estimates are by comparing results from different methods. Here we compare the results from nine data interpolation methods in the Southern Ocean from 1990 to 2010 and find a broad and encouraging agreement regarding decadal carbon uptake signals, whereas a spatially more refined analysis reveals much less agreement locally, illustrating the need to continue the measurement effort in the Southern Ocean.

Retrieval of Compositional Endmembers from Mars Exploration Rover Opportunity Observations in a Soil-filled Fracture in Marathon Valley, Endeavour Crater Rim by N. T. Stein, et al in JGR: Planets

The Opportunity rover investigated a region on the rim of Endeavour crater on Mars called Marathon Valley where a series of bright outcrops are cut by fractures. A scuff performed by one of the rover wheels on the fractures revealed the presence of three different compositional endmembers. A novel technique was applied to retrieve the composition of the endmembers using measurements by the rover’s Alpha Particle X-ray Spectrometer and Pancam instruments. The presence of a magnesium-sulfate-rich soil endmember and hematite-rich pebbles in the scuffed fracture imply alteration in an acid-sulfate environment. Results add to growing evidence of alteration along the rim of Endeavour crater that was concentrated along fractures, which likely provided a conduit for subsurface fluid flow. The timing of formation of these altered deposits is unclear; they could have formed during transient post-impact hydrothermal activity or perhaps significantly later utilizing groundwater from the southern highlands.

Rapid Water Transport by Long-Lasting Modon Eddy Pairs in the Southern Midlatitude Oceans by Chris W. Hughes and Peter I. Miller in GRL

The ocean’s equivalent of smoke rings has been found. They last for about 6 months and can carry water over distances of more than 1,000 km in different directions to the usual ocean currents and much faster than other eddies. This changes the way heat, nutrients, and carbon are transported in parts of the ocean. Most eddies drift to the west at or around a particular speed that depends on latitude, faster near the equator, and slower near the poles (about 1–2 km/d at midlatitudes). However, it has long been theoretically predicted that eddies can sometimes pair up in a way that allows them, like smoke rings, to travel much faster, to the east as well as west, staying together for a long time. For the first time, using satellite measurements of sea level, we have seen these eddy pairs, called “modons,” traveling over long distances in the oceans. Eight pairs are seen around Australia and one in the South Atlantic. They travel at about 10 times the typical eddy speed, over distances of 1,000 km or more, stirring up the surface temperatures as they pass and lasting for about 6 months before splitting up.

Cost-Loss Analysis of Ensemble Solar Wind Forecasting: Space Weather Use of Terrestrial Weather Tools by E. M. Henley and E. C. D. Pope in Space Weather

The space weather community is increasingly adopting a useful approach from terrestrial weather—running many slightly different versions of a model—to understand the uncertainty in model forecasts. However, space weather has made less progress on using the resulting information to improve forecast communication and relevance. Considering the decisions users must make is one way to improve forecast relevance. How certain must the forecast be before a user takes action? Discussing the expenses involved is a simple way to explore decisions—a power operator near a hurricane may wish to wait until more than 80% of the models predict a hit before shutting down the grid, because the associated cost will be high. Another user with lower costs may, however, be willing to make their decision at a 30% hit probability. Understanding the costs and losses that users face helps model developers assess the value of their forecasts, and how this changes between users. This commentary highlights a paper taking a cost-loss approach to solar wind forecasting, as it provides the space weather community with a useful guide to this terrestrial tool. The commentary also discusses the wider context of space weather’s general progress in adopting terrestrial techniques.

Potential for Changing Extreme Snowmelt and Rainfall Events in the Mountains of the Western United States by A. A. Harpold and M. Kohler in JGR: Atmospheres

Extreme precipitation can cause floods, landslides, and other natural hazards in the mountains of the western United States. Predicting extreme precipitation intensity is therefore a critical tool for protecting life and property. Most of our standard prediction tools do not differentiate snow and rain or track the effects of snowmelt. Deficiencies in standard estimates could be amplified by increased winter rainfall and slowing snowmelt rates that are expected from regional warming. We investigated 379 mountain sites over 30+ years to estimate the 100 year intensity (i.e., statistically a 1/100 likelihood of occurring in any given year) at 1, 2, and 30 day durations. We found that snowmelt and precipitation during the snow cover season were the main drivers of extreme water input intensity. Changes to slower snowmelt rates were more likely to affect extreme water input intensity at continental sites like the southern Rocky Mountains. Conversely, changes to rainfall during the snow cover season were more likely to affect water input intensity at maritime sites like the Cascades. These regional differences give a framework to understand vulnerability to changing extreme water input intensity that local resource managers and planners could use to adapt standard estimates to their areas.

Petrophysical, Geochemical, and Hydrological Evidence for Extensive Fracture-Mediated Fluid and Heat Transport in the Alpine Fault's Hanging-Wall Damage Zone by John Townend, et al in G-Cubed

The Alpine Fault produces large (magnitude ~8) earthquakes approximately every 300 years and last ruptured 300 years ago in 1717 AD. Understanding the state of the fault — the temperatures, pressures, stresses to which the fault is being subjected — ahead of an anticipated large earthquake is an important scientific challenge and the focus of the Deep Fault Drilling Project. In this paper, we report findings from scientific drilling in 2014 that reveal evidence for active fluid flow adjacent to the Alpine Fault. The transport of heat and mass near the fault appears to be controlled or modulated by earthquake shaking and rupture processes, and likely controls the build-up of pressure and stress in the shallow portions of the crust during the ~300 year earthquake cycle.

Plant Uptake of Atmospheric Carbonyl Sulfide in Coast Redwood Forests by J. E. Campbell, et al in JGR: Biogeosciences

The future resilience of coast redwoods (Sequoia sempervirens) is now of critical concern due to the detection of a 33% decline in coastal fog that sustains these forests. However, monitoring the potential impacts on redwood forests is challenging because the unique features of the coastal environment interfere with ecological measurement techniques. Here we propose a solution involving a new technique using carbonyl sulfide, an atmospheric chemical that is related to carbon dioxide. We found that the redwoods remove carbonyl sulfide from the atmosphere, which is a critical prerequisite for using this technique to explore redwood resiliency.

Vertical Distributions of Coccolithophores, PIC, POC, Biogenic Silica, and Chlorophyll a Throughout the Global Ocean by William M. Balch, et al in GBC

We use a global shipboard data set to describe the vertical distributions of coccolithophores (marine phytoplankton that produce microscopic calcium carbonate scales). These plants are responsible for over half of all the suspended calcium carbonate in the ocean, they can cause major increases in water reflectance in blooms spanning entire ocean basins, and they provide ballast to organic matter to the deep sea and thus are strong drivers of the ocean’s biological carbon pump (responsible for sequestering carbon in the deep sea). This paper describes global relationships that relate the surface concentrations of coccolithophores and their particulate inorganic carbon (as observed by satellite) to concentrations found over the upper 100 m of the ocean or the entire euphotic zone. These predictions function from highest productivity waters to the lowest productivity, “biological deserts” in the sea. We also include predictive relationships for biogeochemical variables related to other phytoplankton groups (e.g., diatoms) as well as more generic indicators of phytoplankton (e.g., chlorophyll and particulate organic carbon). The results provide new oceanographic insights into the ecology and biogeochemistry of these microalgal groups.