Articles in 2017

The radiative effect of desert dust depends in part on its size. An integrative analysis of observed and modelled dust size and abundance reveals that atmospheric dust is coarser, and less cooling, than previously thought.

The geological record preserves scant evidence for early plate tectonics. Analysis of eclogites — metamorphic rocks formed in subduction zones — in the Trans-Hudson mountain belt suggests modern-style subduction may have operated 1,800 million years ago.

Freezing and thawing of soils leads to large pulses of nitrous oxide release. An empirical model shows that cropland winter nitrous oxide emissions are substantial, calling for a revision of the global nitrous oxide budget.

The timing of onset of modern-style plate tectonics on Earth is unclear. Identification of eclogite rocks—typically formed during subduction—in the Trans-Hudson orogen implies modern-style tectonics may have been active 1,830 million years ago.

Magma movement is thought to trigger volcanic tremor. However, analysis of seismic data suggests that tremor prior to the Bárðarbunga eruption in Iceland instead marked the crust cracking open, whereas subsequent magma flow was seismically silent.

Grass species vary in their regulation of water use. Remote-sensing data reveal that productivity is more sensitive to atmospheric moisture than precipitation deficits, especially in grasslands where plants loosely regulate water use.

Large fluxes of nitrous oxide occur when frozen soils thaw. Field measurements and mathematical models suggest that freeze–thaw events are responsible for 17 to 28% of nitrous oxide emitted from agricultural soils globally.

Iron is an essential fuel for life in the oceans. The influence of this element on biogeochemistry — and nitrogen cycling in particular — varies across environments and time.

External metal inputs to oceans affect ocean productivity and metal cycling. A synthesis of researchreveals that internal processes such as metal retention, recycling and remineralizationare also important.

Hints from seismic tomography and geochemistry indicate that Earth's mantle is heterogeneous at large scale. Numerical simulations of mantle convection show that, if it started enriched in silicates, the lower mantle may remain unmixed today.

Dust-borne nutrients can enhance productivity in the surface ocean. Two years of sediment trap data reveal that dust enhances carbon export to depth by increasing surface nitrogen fixation, productivity and carbon sinking rates in the North Atlantic.

The dominant source for water in Earth’s mantle is unclear. Geochemical analyses of rock samples from mid-ocean ridges and ocean islands globally suggest the water is largely derived from seawater-altered crust introduced during subduction.

Seismic data are inconsistent with a compositionally homogenous lower mantle. Simulations show that viscosity variation with depth in Earth’s early mantle may have prevented efficient mixing and allowed ancient mantle domains to persist.

Mixing with non-black carbon can enhance the radiative effect of black-carbon aerosols. Lab and field measurements of aerosol properties reveal that the mass ratio of black to non-black carbon determines the amount of enhancement.

Dissolved iron is mysteriously pervasive in deep ocean hydrothermal plumes. An analysis of gas, metals and particles from a 4,000 km plume transect suggests that dissolved iron is maintained by rapid and reversible exchanges with sinking particles.

Variability of iron isotopes among planetary bodies may reflect their accretion or differentiation histories. Experiments suggest nickel may be the ingredient controlling iron isotope signatures, supporting fractionation during core formation.

Atmospheric rivers have been associated with extreme rainfall events. A global detection algorithm, applied to reanalysis data, suggests that they contribute substantially to extremes in wind as well as precipitation along coasts globally.

Planetary materials reveal variation in iron isotope composition across planetary bodies. Experiments suggest that this variation can be explained by varying degrees of fractionation during core formation, depending on temperature.

The largest known hydrothermal plume moves dissolved iron halfway across the Pacific. In situ measurements show that dissolved and particulate iron transport is facilitated by reversible exchange of dissolved iron onto organic compounds.

The crystal structure of iron under the extreme pressures and temperatures of Earth’s core is debated. Numerical simulations suggest that the body-centred cubic structure of iron is stable under inner-core conditions.