Volume 6 Issue 6, June 2013

Allowing authors of research papers to be anonymous to referees has long been recommended. We will offer such an option, as a trial, from 10 June 2013.

In areas of the developing world that have benefited only marginally from the intensification of agriculture, foreign investments can enhance productivity. This could represent a step towards greater food security, but only if we ensure that malnourished people in the host countries benefit.

Patches of deposits containing unusual mafic minerals are observed in and around some large lunar impact craters. Numerical simulations suggest that in the slowest of these impacts, asteroidal material, alien to the Moon, could have survived.

The amount of carbon stored in the deep ocean varied over glacial–interglacial cycles. Southern Ocean sediments from the past 360,000 years show that carbon storage also fluctuated within glacial periods, in concert with the fertilization of the Southern Ocean by wind-borne dust.

Different measurements of inner core rotation have delivered inconsistent results. An analysis of seismic data provides a resolution of this discrepancy by suggesting decadal variations in inner core rotation rate.

High-temperature water–rock reactions produce large quantities of hydrogen, which must be transported to cooler settings to sustain life. Lower-temperature hydrogen generation could potentially support life in situ and free subsurface microbes from photosynthetic constraints.

A 500,000-year-long period of warmth in the middle Eocene was marked by high atmospheric carbon dioxide concentrations and prolonged dissolution of carbonate in the deep oceans. Numerical simulations attempting to capture these features identify gaps in our understanding of the causes of this and similar perturbations.

Unusual minerals observed in lunar craters were thought to originate from beneath the Moon’s surface. Numerical simulations show that rather than being vaporized, much of the impactor material can survive in the crater, implying that the unusual minerals come from the impactor and may not be indigenous to the Moon.

Atmospheric aerosol particles can significantly influence the climate system. Analyses of observations and observation-based modelling data reveal that biogenic aerosol emissions soar in response to warming, exerting a cooling effect in a negative feedback loop.

The brightness and lifetime of clouds is determined by cloud droplet number concentration, which is in turn dictated by the number of available seed particles. Model simulations suggest that condensation of semi-volatile organic compounds enhances the formation of cloud droplets, with consequences for cloud dynamics.

Predicting the response of tropical rainfall to climate change remains a challenge. An analysis of climate model simulations suggests that in an emission scenario without mitigation, a large fraction of tropical precipitation change will be independent of global surface warming over the twenty-first century.

Climate change can be thought of in terms of geographical shifts in climate properties. Tracking the geographical movement of analogous climate conditions between historical and future climate model simulations, and calculating the impact of such shifts on vegetation carbon storage, suggests that boreal forests will lose carbon as low-carbon ecosystems shift in.

In the Southern Ocean, the biological cycling of dissolved CO₂ is thought to be influenced by the delivery of iron by dust particles. Reconstructions of nutrient utilization from the South Atlantic Ocean show millennial-scale links between dust flux and the efficiency of the biological pump.

Ridges on the down-going plate in a subduction zone can segment the seismogenic zone and influence earthquake occurrence, but the role of the overriding plate is unclear. InSAR and GPS satellite measurements indicate that segmentation of the subduction zone in northern Chile correlates with a 1-km-high coastal scarp, implying that overriding plate structure can influence seismicity.

Slow earthquakes form part of a spectrum of fault behaviour between steady creep and fast rupture during a normal earthquake. Laboratory simulations of slow slip in rock samples taken from the Nankai subduction zone, Japan, reveal similar characteristics to fast earthquakes, implying that some slow slip events could be prematurely arrested earthquakes.

Carbon is carried into the Earth at subduction zones. Geochemical analysis of subducted sediments now exhumed in Alpine Corsica, France, reveal the formation of graphite during shallow subduction, implying that carbonate transformation to graphite aids transport into the deeper Earth.

Hydrogen is commonly produced during the high-temperature hydration of mafic and ultramafic rocks. Laboratory experiments suggest that water–rock reactions also generate hydrogen at lower temperatures, potentially fuelling microbial life in ultramafic aquifers in oceanic and terrestrial crust.

The Indo-Pacific warm pool is the largest source of heat and moisture vapour to the atmosphere. Proxy reconstructions and model simulations suggest that during the Last Glacial Maximum, the exposure of the Sunda Shelf of Southeast Asia weakened deep convection over the warm pool.

Earth’s crust is thought to eventually rebound following an earthquake so that deformation is not permanent. Field analysis in the Atacama Desert, northern Chile, however, identifies numerous large cracks in the crust, implying that the crust here has been permanently deformed by thousands of earthquakes that have occurred over the past million years.

Earth’s inner core rotates at a different rate than the mantle, and discrepancies exist between rotation rates derived from geophysical observations and geodynamical simulations. An inverse analysis of seismic data from repeating earthquakes over the past 50 years suggests that the rotation rate of the inner core fluctuates on decadal timescales.