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.

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.

Modeling tabular icebergs submerged in the ocean in JAMES

 Schematic showing how tabular icebergs are constructed using Lagrangian elements. (a) Hierarchy of ice elements’ physical structure: (i) Previous iceberg models represent icebergs using non-interacting point-particle elements; (ii) In the new framework ice elements are given finite extent so that they are able to interact with the ocean across multiple grid cells, and can interact with other elements; (iii) These finite extent elements can be joined together by numerical bonds (magenta lines) to form larger structures such as tabular icebergs. (b) Areal photograph of a tabular iceberg with elements superimposed over it to illustrate how the Lagrangian elements can be used to model tabular icebergs. In this schematic, the ice elements (purple dots) are initialized in a staggered lattice covering the surface area of the iceberg. For purposes of mass aggregation, the ice elements are assumed to have hexagonal shape (red hexagons). For purposes of element interactions, the ice elements are assumed to be circular (black circles). Elements are initially bonded to adjacent elements using numerical bonds (magenta lines). These numerical bonds form equilateral triangles which give the shape rigidity. An ocean grid has been included (dashed cyan lines). The background photo is an areal photograph of iceberg PIIB (Area5 42 km2) taken in Baffin Bay in 2012. A red ship can be identified on the bottom of the photo for scale.

Detection of diffuse seafloor venting using a structured light laser sensor: 1. Development of a classification based detection method in Earth and Space Science

In Smart et al., image shows results of the updated classification algorithm at Shrimp Vent with the main area of sampling indicated by the dashed white circle. (a) 2D photomosaic of the Shrimp Vent area showing the distribution of bacterial mats and seafloor characteristics. (b) Gridded results of the SVM classification method showing seafloor (blue), bacteria (green) and active venting (yellow). (c)Classification algorithm results showing only areas of active venting in red indicating the spatial distribution of active venting.

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

Using large eddy simulations to reveal the size, strength, and phase of updraft and downdraft cores of an Arctic mixed-phase stratocumulus cloud in JGR: Atmospheres

In Roesler et al., total condensate (precipitating rain and snow and nonprecipitating water and ice) and the vertical velocity at 12 h into the simulation for the (left) 1.5 TKE scheme and the (right) CLUBB scheme. The total condensate is shown in the rainbow color bar, and the vertical velocity is shown with the blue-to-red color bar.

Seasonal and interannual variability of the Eastern Tropical Pacific Fresh Pool in JGR: Oceans

Guimbar et al., investigated the eastern tropical fresh pool (EPFP) spatial and temporal dynamics. The maximal surface extension of the EPFP exhibits a very large interannual variability. Over the past decade, two extreme events occurred, clearly related to the El Niño-Southern Oscillation (ENSO) phases with associated anomalies of precipitation, surface currents, and trade wind in the central Pacific. In particular, changes of the atmospheric freshwater fluxes and ocean surface currents during winter 2014 seems to trigger the onset of an abnormal fresh event related to the strong El Niño 2014–2015, leading to these unprecedented maximum values of the EPFP maximum extent (October-November) in 2014 and 2015.

The tropical rain belts with an annual cycle and a continent model intercomparison project: TRACMIP in JAMES

annual-mean precipitation response between 40N and 40S to increased CO

in aquaplanet and land
simulations. (a) Zonal-mean response in the aquaplanet setup, (b) longitude-latitude response of the model-median precipitation in the land setup, (c) zonal-
mean response in the land setup, and (d) dierence between zonal-mean response in the land versus aquaplanet setup. In Figures 15a, 15c, and 15d models
are colored according to the color coding introduced in Figure 2; the model median is shown by the thick black line. In Figure 15b, the black line is the model-
median ITCZ in LandControl.

40Ar/39Ar geochronology reveals rapid change from plume-assisted to stress-dependent volcanism in the Newer Volcanic Province, SE Australia in G-Cubed

In Oostingh et al., image shows examples of volcanic alignment and geomorphology interpretations. (a) Satellite image of Mt Eccles and (b) interpreted alignment direction. (c) Satellite image of Lake Cartcarrong (maar) and (d) interpreted elongation of the maar structure with preferred orientation.

Carbonate buffering and metabolic controls on carbon dioxide in rivers in GBC

In Stets et al., Stets et al. investigated the effects of carbonate buffering and metabolism on carbon dioxide (CO2) and dissolved inorganic carbon (DIC) concentrations in river networks. Carbonate buffering is less prominent in low alkalinity (a.) as compared with high alkalinity (b.) watersheds. Carbonate buffering decreases the rate of CO2 exchange across the air-water interface by decreasing the CO2 gradient, thereby affecting both the CO2 and DIC pools. Increased buffering and lags in CO2 exchange cause excess dissolved inorganic carbon (ΔDIC) to be higher in the small streams of high alkalinity watersheds (c.) as inputs from groundwater and negative net ecosystem production in small streams equilibrate more slowly in the high alkalinity watersheds. CO2 excess (ΔCO2) is high in the smallest streams of low alkalinity watersheds (d.). Rapid exchange with the atmosphere depletes CO2 pools, causing ΔCO2 to be lower in mid-sized streams of low alkalinity watersheds. Differences in carbonate buffering create spatial differences in CO 2 and DIC dynamics at the landscape scale.

Pyroclastic Eruption Boosts Organic Carbon Fluxes Into Patagonian Fjords in GBC

Mohr et al. estimated how much organic carbon was released, stored, and evacuated from disturbed temperate rainforest into the Patagonian fjords after the explosive eruption of the Chaitén volcano in Chilean Patagonia (A). By quantifying fluxes of large wood (B) and organic rich topsoils (C) from the headwaters to the delta fans (D), they showed for the first time that Patagonian rainforests may temporarily switch from regional carbon sinks to carbon sources. Their finding demonstrates that infrequent volcanic eruptions may be one previously overlooked disturbance for generating spiked terrestrial organic carbon inputs from small mountain rivers and potentially account for large fractions of terrestrial carbon burial rates in the fjords.

Building the Pamir-Tibetan Plateau—Crustal stacking, extensional collapse, and lateral extrusion in the Central Pamir: 1. Geometry and kinematics in Tectonics

In Rutte et al., image shows (a–d) Panoramic views of the Muskol dome. Distortion increases toward the image edges. Figures 4a and 4b are along section A in Figure 8. Thrusts and north vergent, recumbent, isoclinal folds in Figure 4d are in left part of Figure 4c. (e–h) Fault scarps in colluvial and alluvial deposits and range front normal faults along the active Sarez-Karakul graben system.

Ceres's obliquity history and its implications for the permanently shadowed regions in GRL

Ceres has plenty of permanently shadowed regions (mapped in blue) at the present day when its obliquity is small. However, due to obliquity changes in the past, only few permanent shadows remain.

Cartograms Facilitate Communication of Climate Change Risks and Responsibilities in Earth's Future

Cartogram set “Natural resources under stress”: visualizing current and future per-capita renewable groundwater resources as affected by CC and population growth. Distorter variables are indicated in curly brackets. The left column shows per-capita groundwater resources, in m3/(cap yr), under current conditions (1971–2000, population in 2010) by a global equal-area map (a), and by a gridded cartogram with population in 2010 as distorter (b), and per-capita groundwater resources under future conditions as affected by climate and population change (2070–2099, population in 2085), with population in 2085 as distorter (c). The right column shows percent change of per-capita groundwater resources between current and future conditions due to both climate and population change (d), and due to CC only (e). Cartograms (c), (d), and (e) use population in 2085 according to SSP 2 for computation of per-capita groundwater resources in 2085 as distorter, and the total land area is enlarged by 45% as compared to maps (a) and (b), proportional to the increase of world population from 6.9 to 9.9 billion. Groundwater resources as computed by WaterGAP driven by five bias-adjusted climate models, high emissions scenario RCP 8.5 (Portmann et al., 2013).

Evaluation of deep convective transport in storms from different convective regimes during the DC3 field campaign using WRF-Chem with lightning data assimilation in JGR: Atmospheres

In Li et al., three-dimensional renderings of 3h forward trajectories from (a–c) 500m, (d–f) 1.5km, (g–i) 2.5km of the 21 May air mass case (Figures11a,11d, and11g), the 29 May supercell case (Figures11b,11e, and11h), and the 11 June MCS case (Figures11c,11f, and11i), and (j–l) backward trajectories from the LMD of the three cases. Each trajectory line consists of 18 arrows with each arrow representing 10min air trajectory. The color of the arrows represents the ending height of the trajectories. The horizontal resolution of the trajectory seeds is 5km for all three cases.

Issue Information in JGR: Space Physics

Sumatra tsunami amplitude map with travel time shown by contours in 30 min time intervals. Bagiya et al., explain ahead-of-tsunami ionospheric disturbances from tsunami-generated acoustic gravity waves.

Stable isotopes in atmospheric water vapor and applications to the hydrologic cycle in Reviews of Geophysics

Galewsky et al. reviews how the isotopic composition of water vapor is impacted by deep convection and how it behaves within

several tropical weather and climate features. a) Deep convection depletes the lower troposphere through convective downdrafts and diffusive exchanges between rain
drops and vapor, and enriches the upper troposphere through condensate detrainment. b) In the context of a monsoon system, deep convection depletes the water
vapor along the monsoon flow, whereas continental recycling acts to reenrich it. c) In the context of the Madden-Julian Oscillation, the lower and middle tropospheric
water vapor is most enriched before the active phase due to the effect of shallow convection. It becomes more depleted during the active phase due to the effect of deep
convection. Finally, it is most depleted after the active phase when the cloud systems are dominated by their stratiform components. d) In tropical cyclones, diffusive
exchanges between rain drops and vapor lead to strongly depleted water vapor in the rain bands, whereas evaporation and sea spray explain the local maximum in the
eye. Galewsky et al reviews the implications of these properties to better understand convective processes and more generally the hydrological cycle.

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.

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.

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.

Continental-scale variation in controls of summer CO2 in United States lakes in JGR: Biogeosciences

In Lapierre et al., based on an analysis of 1080 lakes distributed across the continental U.S., the image shows that surface water CO2 responds to contrasting drivers related to aquatic primary production, respiration by microorganisms, or terrestrial loadings of carbon depending on the climate and landscape context where these lakes are found. These results show that controls on lake CO2

vary geographically, and that
considering that variation will be important for creating accurate global carbon models as well as to understand how changes in climate and terrestrial
landscapes could alter the pathways responsible for the widespread emissions of CO2
by lakes globally.