Articles in 2014

The composition of mid-ocean ridge basalts varies with the properties of the mantle that feeds the ridges. Thermodynamic calculations of melt evolution suggest that most of the mantle melting occurs by an overlooked mechanism, focused melting.

Atmospheric phosphorus contributes to terrestrial biogeochemical cycles. Estimates of phosphorus emissions from combustion suggest that anthropogenic emissions represent more than 50% of atmospheric sources of phosphorus.

Plumes are thought to transport water-rich material from the deep mantle to Earth’s surface. High-pressure experiments identify a hydrous mineral phase that is stable under lower-mantle conditions and could provide a source for this water.

Nitrous acid cycling contributes significantly to the atmospheric oxidation capacity. Flow tube experiments and field monitoring reveal a night-time nitrous acid sink in soils, and subsequent release during the day.

In situ measurements of sea-ice thickness off Antarctica have limited spatial coverage. Surveys of ten floes by autonomous underwater vehicles suggest that Antarctic sea ice is thicker and more deformed than previously thought.

Landslide deposits are often interpreted as the consequence of precipitation. A millennial-scale record of landslides, inferred from river cobbles in the arid Andes, is instead consistent with earthquake triggering.

Elevated CO₂ is known to fertilize plant growth, resulting in greater uptake of atmospheric CO₂ by plants. However, CO₂ fertilization in a perennial grassland is absent when plants are jointly limited by both water and nitrogen.

The volume of the East Antarctic ice sheet is influenced by changes in the Earth’s orbit. Ice-rafted debris accumulation between 4.3 and 2.2 million years ago suggests precession affected the extent of the marine margins of the ice sheet.

Glaciers in the Karakoram mountains have been stable in mass, whereas in nearby regions, mass loss has prevailed. Climate model simulations reveal a unique seasonal cycle in Karakoram snowfall that contributes to this pattern.

Despite widespread evidence for extension, there have been few signs of contraction on the icy surface of Jupiter’s Europa. Evidence for a subduction-like convergent boundary suggests that Europa may have active plate tectonics.

Stratospheric water vapour is a powerful greenhouse gas. Merging individual satellite data sets with a chemistry–climate model reveals that water vapour levels in the lower and mid-stratosphere have been decreasing since 1988.

Narrow river gorges are often short-lived features. Images of a bedrock gorge in Taiwan, which was carved after 1999, reveal rapid widening where the upstream floodplain meets the gorge, an erosional front that propagates downstream as the gorge is erased.

Sea surface temperatures in the tropical oceans were thought to have remained stable during a period of warmth about five million years ago. Reconstructions of the sea surface temperature from the Caribbean and Pacific suggest that tropical temperatures have in fact changed in concert with global mean temperatures over the past five million years.

Marine sediments deposited beneath the eastern Pacific upwelling margin are a substantial sink for silica. The geochemistry of these sediments suggests that periods of intense upwelling result in iron limitation, which enhances the export of silica from the surface to the deep ocean and sediments.

The high elevation in Earth’s topography of hard rocks, such as granites and basalts, was thought to be caused by their inherent resistance to erosion. Numerical modelling now demonstrates, counterintuitively, that erosion-induced isostatic rebound of rocks, which is density dependent, causes granites and basalts to occupy high elevations because they are more dense than surrounding rocks.

The Changbaishan volcanic complex in China cannot be easily explained as the consequence of a mantle plume. Seismic images from the region identify buoyant mantle material that may have been entrained and dragged downwards by the subducting Pacific Plate, but is now escaping upwards through a gap in the plate and producing the intraplate volcanism.

The observed depletion of the stratospheric ozone layer from the 1980s onwards is attributed to halogens released through human activities. Model simulations show that stratospheric ozone loss has declined by over 10% since stratospheric halogen loading peaked in the late 1990s, indicating that the recovery of the ozone layer is well under way.

During the last glacial termination, climate changes associated with the Bølling–Allerød warming were seen throughout much of the Northern Hemisphere. A combination of ice-core records and box modelling shows that this climate change was nearly synchronous across high and temperate latitudes.

The explosive style of volcanic eruptions has been linked to gas separation from magmas in the shallow crust. Geochemical analysis of magmas erupted over the past 600 years at Kīlauea Volcano, Hawai‘i, now reveal a link between eruption style and the geochemistry of magmas formed at greater depths, implying that some magmas are predisposed towards explosivity.

Ethanol-based vehicles are thought to generate less pollution than gasoline-based vehicles. An analysis of pollutant concentrations in the subtropical megacity of São Paulo, Brazil, reveals that levels of ozone pollution fell, but levels of nitric oxide and carbon monoxide rose, during periods of prevailing gasoline use relative to ethanol use.