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.

Holocene history of deep-seated landsliding in the North Fork Stillaguamish River valley from surface roughness analysis, radiocarbon dating, and numerical landscape evolution modeling in JGR: Earth Surface

 In Booth et al., image (a–e) slope maps of the surface evolution of the Oso landslide predicted by a nonlinear model of hillslope sediment flux (equation(1)). Figure6a is 2014 lidar data, while Figures 6b–6e are model results. For comparison, (f) a lidar-derived slope map of the landslide directly southeast of the Oso landslide with a similar size and shape and a predicted age of ~5000 cal years B.P. is presented.

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

Three-dimensional numerical modeling of thermal regime and slab dehydration beneath Kanto and Tohoku, Japan in JGR: Solid Earth

Two errors were discovered in the originally published version. The units specified in the first footnote of Table A1 have been corrected. In addition, all instances of “(cm^2 s str)^-1” on page 19 have been replaced with “(cm^-2 sr)”. The corrected paper should be considered the version of record.

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.

Global ULF waves generated by a hot flow anomaly in GRL

A hot flow anomaly generates global ULF waves in the magnetosphere. Reflected ions (white arrows) from Earths bow shock are trapped by a tangential discontinuity (purple dashed line) and drift along it, interact with the incident solar wind ions and form a hot plasma region (yellow region) called Hot Flow Anomaly (HFA). The hot plasma region expands and form shocks (blue arrows) on two sides of the structure. In this study, an HFA was observed by Cluster 1 spacecraft, generating ULF waves in the magnetosphere globally (the red dashed lines represent the undisturbed magnetic field lines, the red solid lines represent the magnetic field lines with ULF waves).

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.

Wind‐Driven Erosion and Exposure Potential at Mars 2020 Rover Candidate‐Landing Sites in JGR: Planets

Wind-blown dune sand can wear away the Martian surface and uncover geologic units, which haven’t been exposed to prolonged spa

ce radiation.
Locations that show evidence for high erosion rates maybe favo
rable for the preservation of ancient life and organics for sampl
ing by future Mars missions,
including the Mars 2020 mission. Here, migrating sand dunes are shown near Mawrth Vallis, a Mars 2020 candidate landing site, u
sing data returned from
the High Resolution Imaging Science Experiment (HiRISE). Several candidate sites showed the strong evidence for ongoing sand tr
ansport and erosion
potential. Color perspective view of HiRISE image ESP_045312_2020 is ~800-m-wide and derived using HiRISE digital terrain model
DTEEC_036859_2020_036569_2020_A01.

Full‐Wave Seismic Tomography in the Northeastern United States: New Insights Into the Uplift Mechanism of the Adirondack Mountains in GRL

A 3D view of the newly-discovered low seismic speed volume (with shear wave velocity below 4.4 km/s) beneath the northeastern United States in red color. This low-speed column below the Adirondack Mountains may come from the asthenosphere at greater depth. This buoyancy  of this column, together with possible thermal expansion, may have provided the primary force that uplifted the Adirondack Mountains.

Reducing Disparity in Radio-Isotopic and Astrochronology-Based Time Scales of the Late Eocene and Oligocene in Paleoceanography & Paleoclimatology

Overview of sampled outcrops: A = the Monte Cagnero section, with approximate locations of the
Rupelian-Chattian boundary (RCB) and the biotite-rich layer (BRL) at 142.8 m; B = BRL at 145.8 m in the Monte Cagnero section;
C = the Massignano
section, with approximate locations of the Eocene-Oligocene boundary (EOB), and sampled BRL; D = BRL at 5.8 m in the Massignano
section; E = the
Pieve d’Accinelli section with approximate location of the B2 BRL (sample PAC-B2 in this study) and the RCB.

Relative linkages of stream water quality and environmental health with the land use and hydrologic drivers in the coastal-urban watersheds of southeast Florida in GeoHealth

The estimated linkages of stream water quality with the land use and hydrologic drivers identify the management targets and priorities to achieve healthy coastal-urban stream ecosystems.

Controls of inherited lithospheric heterogeneity on rift linkage: Numerical and analog models of interaction between the Kenyan and Ethiopian rifts across the Turkana depression in Tectonics

image shows alternative model results. We vary the initial conditions by scanning through different configuration
of initial thicknesses of lithosphere, full crust, and upper crust within the transverse inherited domain of the Turkana region
. (a) Initial crustal thickness of 30 km. (b) Initial
crustal thickness of 25 km. All other parameters and layer thicknesses are kept identical to model A1. Images show strain rate
patterns after 15 Myr of stretching, equivalent
to 60 km of extension. In the lower left corner of each image we plot the yield strength profile of the transverse central regi
on at the onset of rifting. Lithospheric strength
is controlled by the interplay of lithospheric thickness and radiogenic heat production within the upper crust. The initial str
ength controls rift localization and leads to five
different types of rift linkage after 15 Myr indicated in the upper right corner of each image. Initial strength of each layer
within the central domain of all models is also
provided in supporting information Table S2. Animations of six characteristic models representing key aspects of rift linkage a
re given in the supporting information as Movies
S1 to S6.

Decline in Antarctic Ozone Depletion and Lower Stratospheric Chlorine Determined From Aura Microwave Limb Sounder Observations in GRL

A view of Earth’s atmosphere from space overlaid by figures showing change in ozone levels above Antarctica from the beginning
to the end of southern
winter—early July to mid-September—computed daily from Microwave Limb Sounder (MLS) measurements every year from 2005 to 2016. Strahan and Douglas find that levels of ozone-destroying chlorine are declining, resulting in less ozone depletion. Image credit: NASA.

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.

Holocene Event Record of Aysén Fjord (Chilean Patagonia): An Interplay of Volcanic Eruptions and Crustal and Megathrust Earthquakes in JGR: Solid Earth

 Offshore sedimentary trace of the Quitralco Fault, showing vertical stratigraphic offset.
(a) Multibeam bathymetry map where the gray shading of the fault trace represents the offset at the seafloor, which is consistent with “surface” rupture of the bedrock below the fjord’s sedimentary infill following the Mw6.2 earthquake’s (epicenter indicated by red star) moment tensor (Legrand et al., 2011): Black, no vertical offset, where fault trace is parallel to along-fault movement; white, largest offset, at an angle with movement along the fault. Location of deltaic sediments dated in Vargas et al. (2013) is indicated (white dot), (b) zoom from part of TOPAS profile 024 (dashed line, where offset is maximal) that shows the seismic expression of the fault, with indication of fault offset values for each stratigraphic level. The shaded area indicates the megaturbidite that levels vertical offset at SL-F.

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.

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

2
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.

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.

Increased water yield due to the hemlock woolly adelgid infestation in New England in GRL

Two eddy-covariance flux towers at the Harvard Forest in New England where the hemlock woolly adelgid (Adelges tsugae) infestation has resulted in eastern hemlock (Tsuga canadensis) mortality (photo by David A. Orwig).

A model for stealth coronal mass ejections in JGR: Space Physics

(left) STA-COR1 observation with representative PFSS field lines overplotted showing the faint white-light signature of the eruption X point [adapted from Lynch et al., 2010]. (right) Synthetic white-light ratio image at t = 174 h from ϕSTA perspective showing the stealth CME simulation X point structure.