Articles in 2014

A slowing Atlantic overturning circulation during the last deglacial warming caused abrupt cooling in the Northern Hemisphere. Lake sediment records suggest that hydrological change in Europe lagged the temperature drop by almost 200 years.

Upwelling mantle plumes are thought to be sheared by the motions of the overlying tectonic plates. Seismic imaging of a hotspot beneath the Galápagos Islands, however, identifies a plume that is not deflected in the direction of plate motion and whose characteristics are instead controlled by multistage melting processes.

Carbon is removed from the Earth’s surface through the formation and burial of carbon-bearing rocks and minerals. An analysis of pore water profiles collected from marine sediments around the globe suggests that the precipitation of authigenic calcium carbonate accounts for around 10% of the carbonate that accumulates in marine sediments globally.

During the Younger Dryas cold event about 12,800 years ago, environmental change in western Europe seems to occur 170 years after cooling over Greenland. Lake sediment analyses confirm this delay, and suggest European hydrological and vegetation change occurred only after the build-up of sea ice in the North Atlantic pushed the westerly wind system south.

The dynamics of Earth’s mantle are difficult to constrain. Analysis of GOCE satellite gravity data can be used to identify gravity anomalies to mid-mantle depths and hence to identify regions of tectonic-plate subduction and plume upwelling in the mantle.

Volcanic plumes can be hazardous to aircraft. A correlation between plume height and ground deformation during an eruption of Grímsvötn Volcano, Iceland, allows us to peer into the properties of the magma chamber and may improve eruption forecasts.

Several periods of massive iceberg discharge into the North Atlantic and widespread cooling marked the last glacial period. Reconstructions of northward flow along the Florida margin suggest that not all cold events were associated with a change in the strength of the Atlantic meridional overturning circulation.

The dynamics of dune evolution under bimodal wind regimes are poorly understood owing to a lack of long-term wind records and the limitations of most experimental set-ups. A 4-year landscape-scale experiment in the Tengger Desert, Mongolia, demonstrates that the orientation of oblique dune crests is controlled by the wind regime.

The 2011 eruption of a 20-km-high volcanic plume from Grímsvötn Volcano, Iceland, led to the closure of northern European airspace. Geodetic measurements from the volcano reveal a correlation between plume height, surface deformation and magma-chamber pressure, with a delay of an hour, implying that volcanic-plume behaviour can be predicted before eruption onset.

Chlorine radicals function as a strong atmospheric oxidant, particularly in polar regions, where levels of hydroxyl radicals are low. Measurements in the Arctic reveal high levels of molecular chlorine during the day, consistent with a photochemical source.

Eruptions come in a range of magnitudes. Numerical simulations and laboratory experiments show that rare, giant super-eruptions and smaller, more frequent events reflect a transition in the essential driving forces for volcanism.

The global frequency of volcanic eruptions is inversely proportional to the volume of magma erupted in a single event. Numerical modelling of magma reservoirs evolving in Earth’s crust shows that frequent, small eruptions are triggered by injections of magma into the reservoir, but rare, giant supervolcano eruptions are triggered by magma buoyancy.

Supervolcano eruptions dwarf all historical eruptions, but their trigger mechanisms are unclear. Experimental measurements of magma density at high pressures and temperatures show that the buoyancy of magma alone can impose sufficient pressure at the roof of a supervolcano magma chamber to induce an eruption.