Current AGU Journal Covers

Current covers of AGU Journals.  For older covers, see the archives of each journal.  High resolution images are available in the issue information PDF of each issue.

in G-Cubed

In Aiuppa et al., image sequence showing evolution of Villarrica volcano throughout December 2014 to March 2015.

Dates are in the yyyy/mm/dd format. (a) Quiescent degassing activity in mid-December 2014; (b) and (c) more vigorous lava lake activity (seething magma) in early to mid-February 2015; (d) intense strombolian activity on 2 March 2015; (e) the paroxysmal lava fountaining activity in the night of 3 March; (f) the post-paroxysm summit of Villarrica on 4 March.

Interesting Equatorial Plasma Bubbles Observed by All-Sky Imagers in the Equatorial Region of China in JGR: Space Physics

Temperature perturbations at ~40 km, ~50 km, and ~60 km at 11:00LT 4 October 2013 in the data of Modern Era Retrospective Analysis for Research and Applications (MERRA), revealing atmospheric gravity wave oscillations that most likely initiated equatorial plasma bubbles in the
ionosphere. The red dotted lines represent the magnetic equator.

Potential rise in iron deficiency due to future anthropogenic carbon dioxide emissions in GeoHealth

Photograph of wheat prairie under clouds. See Smith et al. [DOI:10.1002/2016GH000018] to learn more about how increasing carbon dioxide levels over the coming century may reduce the iron content of many crops and impact global malnutrition

Seismicity, Deformation, and Metamorphism in the Western Hellenic Subduction Zone: New Constraints From Tomography in JGR: Solid Earth

Threedimensional block model of the subduction interface and seismicity based on the results obtained in this study. The subducting oceanic crust of the Ionian plate is dark blue, while the subducting continental crust of the Adriatic plate is in brown. Variable shading on the interfaces represents relief, with oblique illumination from a light source to the right of the model. The magenta solid lines mark large strike‐slip faults, including the Kephalonia Transform Fault and the western tip of the North Anatolian Fault. The magenta dashed line marks the putative boundary between oceanic and continental slabs based on the contrast in seismicity (though apparent changes in the slab‘s tomographic response could also be used to constrain this boundary, we refrain from doing so as there is a progressive change in resolution associated with the contrast in seismicity between north and south; see Figure 2). Relocated hypocenters are indicated by red spheres, with size corresponding to magnitude. The green spheres are hypocenters projected onto the slab top surface.

Red dashed lines indicate the outline of a V‐shaped seismic gap believed to be associated with a broad zone of deformation in the oceanic slab.

Fiber-Optic Network Observations of Earthquake Wavefields in GRL

The cover figure shows examples of local and regional seismic events observed using surface fiber-optic cables and distributed acoustic sensing (DAS).
Left: installation photographs from three sites with fiber optic cables including Richmond, CA (top), Fairbanks, AK (middle), and Stanford, CA (bottom). Right: a small catalog of seismic events observed using these surface DAS cables from 5 to 500
km epicentral distance. Events are color-coded to the site of observations.

Hydrothermal nontronite formation associated with microbes from low-temperature diffuse hydrothermal vents at the South Mid-Atlantic Ridge in JGR: Biogeosciences

Ta et al. reported the formation of hydrothermal nontronite associated with microbes from low-temperature diffuse
hydrothermal vents at the South Mid-Atlantic Ridge. NanoSIMS imaging reveals the bacteria cells (red) are surrounded by nontron
ite (green). The
formation of nontronite may begin with the adsorption of cationic iron in the hydrothermal fluid to anionic cellular surfaces.
Biologically induced
mineralization might be widely responsible for the formation of nontronit
e in modern low-temperature hydrothermal environments.

A miniature, low-power scientific fluxgate magnetometer: A stepping-stone to cube-satellite constellation missions in JGR: Space Physics

The Ex-Alta 1 Cube-Satellite, to be launched in late 2016 as part of the ESA QB50 constellation mission, will demonstrate the potential

for scientifically valuable magnetic field measurements from a Cube-Satellite. For more information on the magnetometer, boom, and satellite

Ultrafine particle number fluxes over and in a deciduous forest in JGR: Atmospheres

Pryor et al. [DOI: 10.1002/2016JD025854] computed fluxes of ultra-fine particles (UFP) above and below the canopy of a mature deciduous

forest during leaf-on and leaf-off periods (using the multi-level sampling design shown). The results indicate that despite a comparatively high
frequency of upward ultra-fine particle number fluxes, the forest is a net sink for UFP. Further, the majority of UFP that are deposited to the forest are
removed by the over-story even during leaf-off. Understanding the flux partitioning between the over-story and ground and the uptake of UFP by
forests is essential to improving the representation of atmospheric aerosol particles in Earth System Models.

Using Stereo Satellite Imagery to Account for Ablation, Entrainment, and Compaction in Volume Calculations for Rock Avalanches on Glaciers: Application to the 2016 Lamplugh Rock Avalanche in Glacier Bay National Park, Alaska in JGR: Earth Surface

Image shows (a) Raw elevation difference between preevent (15 June 2016) and postevent (16 July 2016) digital elevation models (DEMs) over the Lamplugh rock avalanche deposit. Dashed line indicates the extent of the source area, which is obscured by clouds in the image acquired on 16 July 2016. (b) Raw elevation difference between prevent (15 June 2016 and 14 August 2012) and postevent (27 September 2016) DEMs in the source area of the Lamplugh rock avalanche

(see Figure 2 for differentiation). The average thickness of depleted material in the headscarp was used to extrapolate the differenced elevation values
in areas of no data (shown in white).

Intersection Waves in JGR: Solid Earth

Intersection wave signal stacks for (a) constant load on the vertical fracture plane and increasing
load on the horizontal fracture plane for the long aluminum bars and (c) two steering loading cases (purple and orange) in the
small hexagonal
aluminum samples. Bulk shear, Rayleigh, and wedge waves are shown for comparison. (b) Predicted velocities of the intersection
wave in C2v
symmetry (unequal stiffness), at 1 MHz, for an orthogonal fracture intersection with varying stiffnesses for mode A1. The analo
gous mode in the
C4v symmetry is shown as the black line along the diagonal.

Interplay between spatially explicit sediment sourcing, hierarchical river-network structure, and in-channel bed material sediment transport and storage dynamics in JGR: Earth Surface

In Czuba et al. image shows Lidar hillshade highlighting major features (river, bluff, and ravine, each with relevant attributes) incorporated into the model. Inset image shows a 64m bluff; note the canoe for scale. Location and extent is shown in Figure3by a small red box.

SAPS-Associated Explosive Brightening on the Duskside: A New Type of Onset-Like Disturbance in JGR: Space Physics

Merged Polar/VIS Earth Camera image (orange-scale global image of Earth) with DMSP/OLS data (black and white high-resolution image), showing evening-sector brightening coincident with the strong convection regionof a subauroral polarization stream.

Fault-bound valley associated with the Rembrandt basin on Mercury in GRL

Mercurys great valley revealed in a 3D perspective view using a high-resolution digital elevation model derived from stereo images obtained by NASAs MESSENGER spacecraft. Below the perspective view is a high-incidence angle image mosaic of the region. Mercurys great valley is over 1,000 km long, extends into the Rembrandt basin, and is bound on one side by Enterprise Rupes, the largest fault scarp on Mercury. The vertical exaggeration is 20X. See also Watters et al., doi: 10.1002/2016GL070205. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/German Aerospace Center–DLR/Smithsonian Institution.

Integrating uncertainty propagation in GNSS radio occultation retrieval: From bending angle to dry-air atmospheric profiles in Earth and Space Science

 In Schwarz et al. [DOI: 10.1002/2016EA000234], image shows error correlation matrices from CP and MC methods: (a) Covariance propagated R and (b) Monte Carlo propagated R MC αs for statistically optimized bending angle, (c) propagated R r and (d) Monte Carlo R MC Nr for retrieved refractivity, (e) propagated R pdr and (f) Monte Carlo R MC pdr for retrieved dry pressure, and (g) propagated R Tdr and (h) Monte Carlo R MC Tdr for retrieved dry temperature.

The export and fate of organic matter in the ocean: New constraints from combining satellite and oceanographic tracer observations in GBC

In DeVries and Weber, DeVries and Weber combined satellite and oceanographic tracer data to estimate the flux of sinking organic carbon out of the ocean‘s euphotic zone, and the efficiency with which the carbon is transferred to the deeper ocean.

Their findings demonstrate that the highest rates of organic carbon export are found in upwelling regions along coasts, near the equator, and in the sub-polar oceans (light blue to red colors). This carbon is transferred into the deeper ocean most efficiently in the high latitudes and near oxygen minimum zones, where cold temperatures and reduced oxygen concentrations lead to slow respiration rates.

Atmospheric escape from unmagnetized bodies in JGR: Planets

 Venus, Mars, Titan, Pluto, and a comet are shown at the same scale to illustrate the relative sizes of the

interaction region (blue) produced by a flowing plasma—the solar wind (light green) in all cases but Titan that is sitting in the magnetosphere (red)—
impinging on the planetary exosphere (orange). The supersonic solar wind is slowed and compressed behind an upstream bow shock with the plasma
deflected around the obstacle in a sheath flow (dark green).

Observational properties of dayside throat aurora and implications on the possible generation mechanisms in JGR: Space Physics

Observational properties of a newly discovered auroral form near local noon, called throat aurora, revealing combined contributions from inside and outside of the magnetosphere on the generation. The image gives a schematic summarizing the physical process leading to the formation of throat aurora.

A decade of volcanic construction and destruction at the summit of NW Rota-1 seamount: 2004–2014 in JGR: Solid Earth

In Schnur et al., eruptive vents observed in 2010. (a) Map showing linear arrangement of vents. (b) Phantom vent. (c) Sulfur vent. (d) Brimstone vent. (e) Styx vent. (f) Charon vent.

Pacific-Atlantic Ocean influence on wildfires in northeast China (1774 to 2010) in GRL

Fire-scarred Dahurian larch from the Daxing’an Mountains in northeast China.

Sorting out compositional trends in sedimentary rocks of the Bradbury group (Aeolis Palus), Gale crater, Mars in JGR: Planets

In Siebach et al. MAHLI image examples of each of the textural classes of rocks in the Bradbury group and (h) the Murray mudstone in the Mount Sharp group. White scale bars are 1 cm across. Classes were divided on the basis of grain size and/or surface texture and coloring and include (Figure 2a) Sheepbed mudstone (10 APXS analyses; example is Wernecke_preDRT, sol 168), exposed in Yellowknife Bay with grains finer than the limit of resolution; (Figure 2b) fine sandstone (15 APXS analyses; example is Aillik1, sol 322), well-sorted siltstones to sandstones; (Figure 2c) sandstone (22 APXS analyses; example is Gillespie_Lake, sol 132), medium to pebbly sandstones; (Figure 2d) conglomerate (15 APXS analyses; example is Bardin_Bluffs, sol 394), primary grain sizes >1 mm, rounded grains, clasts up to 6 cm; (Figure 2e) uncertain (13 APXS analyses; example is Morehouse, sol 503), float rocks with poorly defined grain boundaries, sometimes weather like conglomerates; (Figure 2f) possible igneous (4 APXS analyses; example is Clinton, sol 512), small group of float rocks and one clast in a conglomerate with porphyritic textures, shortened to igneous in plot legends; (Figure 2g) diagenetic (36 APXS analyses; example is CumberlandNewRP_LIBs, sol 277), rocks with clearly diagenetic textures including preferential cementation and fracture fills; and (Figure 2h) Murray mudstone (27 APXS analyses; example is Punchbowl2, sol 813), mudstone observed at

Pahrump Hills in Mount Sharp group, fine grained with potential secondary crystal structures.