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.

Primary Production and Calcification Rates of Algae‐Dominated Reef Flat and Seagrass Communities in JGR: Biogeosciences

Field survey sites at (a) Heron Reef, southern Great Barrier Reef, Australia, and (b) Saipan
Lagoon, Commonwealth of the Northern Mariana Islands, where flow respirometry drifts were conducted. One site was surveyed in Shark Bay on the
east side of Heron Island. Two sites were surveyed in Saipan Lagoon off of Pau Pau Beach, an algae‐dominated, coral reef flat, and San Roque, a seagrass
community. The black lines denote flow respirometry tracks, the yellow point is where current meter and Wetlabs PAR sensor were placed, and the
yellow arrow is general current direction. WorldView 2 imagery provided by the Remote Sensing Research Centre at the University of Queensland and
CNMI Bureau of Environmental and Coastal Quality.

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.

First Estimate of Wind Fields in the Jupiter Polar Regions From JIRAM‐Juno Images in JGR: Planets

In Grassi et al., details from speed fields N1 (a and b) and S2 (c and d). A and a letters indicate anticyclonic areas. “a?” indicates possible locations of further anticyclonic areas. f and r indicate other features discussed in the text.

Fidelity of the Sr/Ca proxy in recording ocean temperature in the western Atlantic coral Siderastrea siderea in G-Cubed

In Kufner et al. [DOI: 10.1002/2016GC006640], image shows an example of one of the 39 Siderastrea siderea colonies included in this study (a) attached

to a calcication monitoring block with a temperature logger (black, on left) on the Fowey Rocks reef crest, and (b) slabbed in half showing Alizarin Red-S stain
lines (pink) marking 29 April 2011 (lower line) and 9 May 2012 (upper line). The upper surface of the slab marks the collection date of 16 May 2013. Scale bar
on left of Figure 1b is a cm ruler with mm markings. (c) Inset box from Figure 1b with annual cycle of Sr/Ca in two replicate drill-paths (blue and green lines)
between the stain lines. Y axis is reversed so that Sr/Ca values (mmol mol
–1
) indicating warmer values are up. X axis is time (decimal years).

Empirical modeling of plasma clouds produced by the Metal Oxide Space Clouds experiment in Radio Science

In Pedersen et al. [DOI: 10.1002/2016RS006079], overview of the experimental observation setup.

Interplanetary coronal mass ejection observed at STEREO-A, Mars, comet 67P/Churyumov-Gerasimenko, Saturn, and New Horizons en route to Pluto: Comparison of its Forbush decreases at 1.4, 3.1, and 9.9 AU in JGR: Space Physics

Image from instruments on SDO, STEREO, and SOHO of the CME that launched from the Sun on 14 October 2014. The CME was observed fromthe Sun all the way to New Horizons at 32 AU, en route to Pluto.

 

Mercury in the Black Sea: New Insights From Measurements and Numerical Modeling in GBC

 Rosati et al. found elevated concentrations of Hg and MeHg in the euxinic waters of the Black Sea. By integrating observations from the GEOTRACES cruise and 1D biogoechemical modeling along the extended redox gradient of the Black
Sea, the work highlights that the bulk of MeHg is produced in situ in anoxic sulfidic waters, and inputs from external sources (i.e. rivers, sediment and the Mediterranean Sea) are negligible. The investigation also stresses the significant role of Mn oxides that act as scavengers of Hg species in the suboxic water and mediate their cycling between suboxic and anoxic waters. In its present state, calculated HgT inputs to the Black Sea still exceed the outputs.

Advances in understanding river-groundwater interactions in Reviews of Geophysics

The figure illustrates river water and groundwater interactions at the reach scale (left) and the hyporheic scale (right). These interactions are at the core of a wide
range of major contemporary challenges, including the provision of high-quality drinking water in sufficient quantities, the loss of biodiversity in river ecosystems, or
the management of environmental flow regimes. Brunner et al. [10.1002/2017RG000556] review state of the art approaches in characterizing and modeling river and
groundwater interactions, including remote sensing to characterize the streambed, emerging methods to measure exchange fluxes between rivers and groundwater, and
developments in several disciplines relevant to the river-groundwater interface. These novel approaches show great potential to tackle the most critical water resources
challenges at the watershed scale.

Convection Enhances Mixing in the Southern Ocean in GRL

Instantaneous snapshot of a temperature isosurface, at Tˆ, colored by velocity magnitude. Sourced from an idealized model of Southern Ocean circulation used in Sohail et al.

Four-dimensional imaging of moisture dynamics during landslide reactivation in JGR: Earth Surface

In Uhlemann et al. [DOI: 10.1002/2016JF003983], image shows change in GMC from baseline model (Figure 7). Red colors indicate a relative

drying, while blue colors indicate wetting; opaque subvolumes highlight the areas where moisture contents change by more than ±10%. The years
2010 and 2011 show the typical seasonal characteristics: surficial wetting following prolonged winter rainfall (November–March) and surficial drying
during the summer months (May–September). Deeper wetting fronts at the base of the slope are indicative of regional groundwater dynamics, while
an area of surficial wetting close to the top of the hill coincides with a known location of a sag pond. In contrast, moisture levels in 2012 are generally
higher than imaged in previous years, especially in deeper parts of the back scarp and areas of the WMF. Strongly decreasing moisture contents in
parts of the lobes and back scarp indicate disturbances of the corresponding material, leading to higher crack volume and hence lower bulk GMC. Only
the upper 12 m bgl of the model is shown, corresponding to the depth of the most significant GMC changes.

Dry deposition of particles to canopies—A look back and the road forward in JGR: Atmospheres

Comparison of the nontransport processes that affect PM

2.5
concentration in the
lowest 100 m of the atmosphere as estimated from a regional-scale air quality model simulation for June 2013. The area over which the results
(averages) apply is about 500 km × 500 km, as indicated by the inner square of the CAMx domain illustration inset. The time scale markings indicate
noon (EST). The dry deposition estimates result from an assumption about the deposition velocity that is a focus of the current presentation. The time
period selected for this illustration was free of rainfall.

Dynamic Triggering of Mud Volcano Eruptions During the 2016–2017 Central Italy Seismic Sequence in JGR: Solid Earth

Examples of mud volcanoes that responded to the main earthquakes of the Central
Italy seismic sequence. (a) Satellite image and (b) lateral view show the S.M. in Paganico mud volcano after the
Mw 6.5 earthquake of 30 October.
(c) N-S trending fractures controlling the surface mud extrusion of the Valle Corvone mud volcano after the 30 October earthqua
ke. (d) Lateral view of the newly formed Contrada S. Salvatore mud volcano, which erupted the day after the 30 October earthquake. (e) N-S trending fracture along the so-called Case Tedeschi 2bis mud volcano, a newly formed seep south of the Monteleone di Fermo village. (f ) Stereoplot showing the trend of ground fractures controlling mud volcanism. An average value of N355°±5°E/90° is taken as input parameter for the normal stress
change calculation.

Contemporary glacier retreat triggers a rapid landslide response, Great Aletsch Glacier, Switzerland in GRL

Pictured is a measurement campaign in October 2015 using a portable radar interferometer on the Great Aletsch Glacier in Switzerland. The campaign

is part of a long term paraglacial slope stability investigation, aimed at studying the relationship between glacier retreat and rock slope response. The
radar utilizes a rotating fan beam antenna array, in this case, scanning a 170 degree field of view. The continuous series of radar images allow measurement
of deformations taking place on the glacier, and also the Moosfluh rock slope instability, located to the lower right of the photograph.

Diurnal and seasonal variability of Uranus's magnetosphere in JGR: Space Physics

The three-dimensional structure of Uranus global magnetosphere at solstice, including the upstream solar wind streamlines, the magnetic field lines, and the pressure. The magnetosphere alternates between an open structure and a closed one during rotation, which shows the “switch-like” effect discussed in Cao and Paty.

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.

How Much Information Is Required to Well Constrain Local Estimates of Future Precipitation Extremes? in Earth's Future

Rain begins to fall over a prairie.  In this issue, Li et al. use a large
ensemble of North American regional climate simulations to evaluate the relationship of temperature scaling to estimates of future extremes of
local precipitation accumulation.

CO2 flux from Javanese mud volcanism in JGR: Solid Earth

In Queißer et al. [10.1002/2017JB013968], snapshots of a bursting gas bubble of the main vent (vent II) at the Bledug Kuwu complex. The bursts had a duration of approximately ~2s.

A PV-approach for dense water formation along fronts: Application to the Northwestern Mediterranean in JGR: Oceans

Giordani et al. [DOI: 10.1002/2016JC012019], intense surface buoyancy losses (–400 W/m2, colour) occurred under the path of Mistral and Tramontane winds (black arrows, N/m2) in the Gulf of Lion (GL) during the ASICS-MED experiment (February 2013). These buoyancy fluxes and positive Ekman pumping (cyan positive, green negative wind-stress curl used as proxy of the Ekman pumping,  N/m3 x 10 5; interval 0.2 x 10–5 N/m3 x 1.105) are key atmospheric conditions for dense water formation (DWF) and preconditioning in the GL. DWF also occurs along the Catalan coast i.e. along the northern branch of the Liguro-Provençal Current where strong horizontal density gradients are present (see brown lines of surface density). DWF results from the coupling between the surface wind stress (black arrows) and lateral buoyancy gradients because this coupling leads to efficient destratification and PV-destruction in frontal regions. As consequence DWF cannot be reduced as a buoyancy flux problem.

Estimating refractivity from propagation loss in turbulent media in Radio Science

(a) Surface-based duct refractivity profile and math formulaCn2 profile. (b) Propagation loss (PL) of 1 GHz wave given refractivity and math formulaCn2 profiles in Figure 1a under no turbulence. PL calculated assuming homogeneous turbulence given (c) math formulaCn2=10−15 and (e) 10−14. PL calculated assuming inhomogeneous turbulence given (d) Cs=10−15 and (f) math formulaCn2=10−14.

Development and evaluation of a physics-based windblown dust emission scheme implemented in the CMAQ modeling system in JAMES

In Forouta et al., the emission of particulate matter with diameter less than 10 microns (PM10) due to dust outbreaks over the southwestern United States in March 7, 2011 (top left), March 21, 2011 (top right), April 3, 2011 (bottom left), and May 29, 2011 (bottom right). The results (in gm-3) are obtained using a newly developed windblown dust scheme implemented in the Community Multiscale Air Quality (CMAQ) modeling system