Volume 3 Issue 4, April 2010

Online publishing has blurred the boundary between accepted and published articles.

Twitter messages offer first-hand accounts of earthquakes within minutes. Analyses of their content and geographic distribution can be a useful supplement to instrument-based estimates of quake location and magnitude.

Anna Armstrong reviews Dirty Oil by Leslie Iwerks, Dogwoof: 2010. UK release date: 19 March 2010.

The fragmentation of continents at convergent plate boundaries is thought to be influenced by the subducting lithosphere. Numerical modelling suggests that instead, the forces exerted by the underlying mantle can drive the formation of continental microplates.

The surface layer of the Southern Ocean connects the atmosphere with the deep subtropical ocean. Ocean observations reveal that the thickness of this layer — important for biological productivity — is controlled by the strength and position of the southern circumpolar winds.

Many species of nannoplankton with carbonate shells vanished during the mass extinction 65 million years ago. An analysis of extinction rates from the world's oceans reveals a geographic bias in the demise and recovery of nannoplankton species.

Oceanic crust forms through the addition of volcanic rock to mid-ocean ridges. Widely dispersed, young lavas observed at an ultraslow-spreading ridge provide impetus for the redevelopment of models of oceanic magmatism.

Decision makers are in need of decadal climate forecasts, for example, to help plan infrastructure investments. When — or whether — climate modellers will be able to deliver is not yet clear.

Ice clouds in the tropical tropopause layer have a key role in dehydrating air that is entering the stratosphere. Cloud-chamber measurements suggest that their high humidity can be explained if heterogeneous ice nucleation on glassy aerosols is a significant nucleation mechanism in this region.

Nanoparticles are a key component of atmospheric aerosols, growing rapidly under ambient conditions. Exposure of nanoparticles to organic vapours shows that various organic species can enhance the growth of nanoparticles.

The five interglacial periods that occurred after the Mid-Brunhes Event 430,000 years ago were longer and warmer than the preceding interglacials. Climate modelling indicates that a change in the seasonality of insolation following the event, in conjunction with higher greenhouse-gas concentrations, could have caused the relative warmth.

Landslide erosion is a primary control of landscape relief. A wide-ranging analysis of landslide geometry shows that soil-based landslides are generally less voluminous than landslides that involve the failure of bedrock, and provides refined metrics for estimating the volume of a landslide from the area of the failure

Mineral dust and marine sediment resuspension are generally considered the primary sources of the nutrient iron to the oceans. Numerical model results suggest that iron released by hydrothermal activity is also an important source of dissolved iron, particularly in the Southern Ocean.

The evolution of Cordilleran-type orogens is controlled by a balance between forces that result in uplift and forces that destabilize the crustal growth. Numerical modelling indicates that the buoyancy of the underlying mantle wedge is an important factor in the collapse and fragmentation of Cordilleran orogens.

Stratospheric water vapour affects Earth’s radiation budget. A 19-month record of the hydrogen isotopic composition of water in the tropical stratosphere, collected through remote sensing measurements, shows a clear seasonal cycle in the isotopic composition that propagates upwards in this region, and is most likely created in the tropical tropopause layer.

The southwest corner of Western Australia has been subject to a serious drought in recent decades, whose ultimate cause remains unclear. A comparison of precipitation records in the area of drought and an ice core from East Antarctica reveal a significant inverse correlation between precipitation in the two locations, and suggest that the current drought may be highly unusual compared with the past 750 years of variability.

Interactions between the atmosphere and ocean are mediated by the mixed layer at the ocean surface. Analyses of ocean temperature and salinity data from Argo floats show that changes in the Southern Annular Mode, including recent and projected trends attributed to human activity, drive variations in mixed-layer depth in the Southern Ocean.

Over 90% of calcareous nannoplankton species disappeared during the Cretaceous–Palaeogene mass extinction, which occurred after an impact event. Palaeontological analyses show that the extinction was most pronounced in the Northern Hemisphere oceans, possibly as a result of an increased concentration of particulates created by the impact in the north.

Mid-ocean ridges grow through tectonic and volcanic processes. Uranium-series dating of volcanic rocks at the ultraslow-spreading Southwest Indian Ridge reveals widely dispersed, young, off-axis volcanism that is spatially coincident with fault surfaces. Faults may therefore provide a mechanism for the wide dispersal of magma at ultraslow-spreading ridges.

After dodging icebergs and flying fish, Jeff Standish and colleagues collected a suite of basalts from the Southwest Indian Ridge, to try and determine the mechanisms of mid-ocean-ridge formation.