I. Atmospheric Sciences

1.A More Powerful Reality Test for Climate Models

Studies of geomagnetic polarity reversals have generated some of the biggest and most interesting debates in the paleomagnetic and wider solid Earth geophysics communities over the last 25 years.

2.Becoming Habitable in the Habitable Zone

Ambient Noise Tomography Workshop (MIMOSA); Tucson, Arizona, 17–23 January 2016

4.Impacts Might Have Made Ancient Mars Briefly Hospitable to Life

Richard P. Von Herzen, a pioneer of marine heat flow studies who helped validate plate tectonics and discover oceanic hydrothermal vents, passed away on 28 January 2016. He was 85.

III. Hazards & Disasters

1.Visiting the Volcano

Shell's drilling activities in the Arctic drew the world's eyes to the far north and to issues like climate change and oil spills, the U.S. special representative for the Arctic said in a recent talk.

2.Eating Less Meat, Wasting Less Food Could Save Water Worldwide

The minerals identified by the Mars Reconnaissance Orbiter provide more evidence that the planet may have once been habitable.

VII. Climate Change

1.Climate Change Influences the Dynamics Behind Tropical Cyclones

Impact Relevance and Usability of High Resolution Climate Modeling and Datasets; Aspen, Colorado, 2–7 August 2015

3.Rapidly Activated Satellite Completes A European Constellation

After unveiling major planned cuts to climate science early this year, Australia's main science agency proposes a center to coordinate remaining projects. Many decry the proposal as an empty gesture.

VIII.Earth and Space Science

1.New study explains source of mysterious radar echoes2. Mantle control of the geodynamo: Consequences of top-down regulation

The mantle global circulation, including deep subduction and lower mantle superplumes, exerts first-order controls on the evolution of the core, the history of the geodynamo, and the structure of the geomagnetic field. Mantle global circulation models that include realistic plate motions, deep subduction, and compositional heterogeneity similar to the observed large low seismic velocity provinces in the lower mantle predict that the present-day global average heat flux at the core-mantle boundary (CMB) exceeds 85 mW m−2. This is sufficient to drive the present-day geodynamo by thermochemical convection and implies a very young inner core, with inner core nucleation between 400 and 1000 Ma. The mantle global circulation also generates spatially heterogeneous heat flux at the CMB, with peak-to-peak lateral variations exceeding 100 mW m−2. Such extreme lateral variability in CMB heat flux, in conjunction with the high thermal conductivity of the core, implies that the liquid outer core is thermally unstable beneath the high seismic velocity regions in the lower mantle but thermally stable beneath the large low seismic velocity provinces. Numerical dynamo simulations show how this pattern of heterogeneous boundary heat flux affects flow in the outer core, producing localized circulation patterns beneath the CMB tied to the mantle heterogeneity and long-lived deviations from axial symmetry in the geomagnetic field. This article is protected by copyright. All rights reserved.

3. Seasonal trends of Amazonian rainforest phenology, net primary productivity, and carbon allocation.

The seasonality of solar irradiance and precipitation may regulate seasonal variations in tropical forests carbon cycling. Controversy remains over their importance as drivers of seasonal dynamics of net primary productivity in tropical forests. We use ground data from nine lowland Amazonian forest plots collected over three years to quantify the monthly NPP of leaves, reproductive material, woody material, and fine roots over an annual cycle. We distinguish between forests that do not experience substantial seasonal moisture stress (“humid sites”) and forests that experience a stronger dry season (“dry sites”). We find that forests from both precipitation regimes maximise leaf NPP over the drier season, with a peak in production in August at both humid (mean 0.39 ± 0.03 Mg C ha-1 mo-1 in July, n = 4) and dry sites (mean 0.49 ± 0.03 Mg C ha-1 mo-1 in September, n = 8). We identify two distinct seasonal carbon allocation patterns (the allocation of NPP to a specific organ such as wood leaves or fine roots divided by total NPP). The forests monitored in the present study show evidence of either: (i) constant allocation to roots and a seasonal trade-off between leaf and woody material; or (ii) constant allocation to wood and a seasonal trade-off between roots and leaves. Finally, we find strong evidence of synchronised flowering at the end of the dry season in both precipitation regimes. Flower production reaches a maximum of 0.047 ± 0.013 and 0.031 ± 0.004 Mg C ha-1 mo-1 in November, in humid and dry sites respectively. Fruitfall production was staggered throughout the year, probably reflecting the high variation in varying times to development and loss of fruit amongst species.

4. A new view for the geodynamics of Ecuador: implication in seismogenic sources definition and seismic hazard assessment

A new view of Ecuador's complex geodynamics has been developed in the course of modeling seismic source zones for probabilistic seismic hazards analysis (PSHA). This study focuses on two aspects of the plates’ interaction at a continental scale: (a) age-related differences in rheology between Farallon and Nazca plates –marked by the Grijalva rifted margin and its inland projection– as they subduct underneath central Ecuador, and (b) the rapidly changing convergence obliquity resulting from the convex shape of the South American northwestern continental margin. Both conditions satisfactorily explain several characteristics of the observed seismicity and of the interseismic coupling. Intermediate-depth seismicity reveals a severe flexure in the Farallon slab as it dips and contorts at depth, originating the El Puyo seismic cluster. The two slabs position and geometry below continental Ecuador also correlate with surface expressions observable in the local and regional geology and tectonics. The interseismic coupling is weak and shallow south of the Grijalva rifted margin and increases northward, with a heterogeneous pattern locally associated to the Carnegie ridge subduction. High convergence obliquity is responsible for the North Andean Block northeastward movement along localized fault systems. The Cosanga and Pallatanga fault segments of the Block–South America boundary concentrate most of the seismic moment release in continental Ecuador. Other inner-block faults located along the western border of the Interandean Depression also show a high rate of moderate-size earthquake production. Finally, a total of nineteen seismic source zones were modeled in accordance with the proposed geodynamic and neotectonic scheme.

X.AUG Newsroom

1. OCEAN ACIDIFICATION MAY BE IMPACTING CORAL REEFS IN THE FLORIDA KEYS

WASHINGTON, DC—Limestone that forms the foundation of coral reefs along the Florida Reef Tract is dissolving during the fall and winter months on many reefs in the Florida Keys, according to a new study. The research showed that the upper Florida Keys were the most impacted by the annual loss of reef.