Articles in 2011

The world is undergoing a phenomenally fast wave of urban growth. Research that can help tackle some of the ensuing problems is likely to originate in cities themselves.

Phytoplankton form the base of the marine food web, but their growth in nutrient-depleted surface waters has remained a puzzle. Two complementary studies suggest that ocean eddies help to control phytoplankton growth and distribution in unexpected ways.

Volcanic activity is much more common beneath the oceans than on land, yet has been observed only rarely. Direct measurements of an eruption in the southwest Pacific Ocean reveal unexpectedly explosive activity at great depths.

At the southern boundary between India and Tibet, the Indian tectonic plate subducts northwards beneath the Tibetan Plateau. Seismic imaging shows that at the northern boundary of Tibet, the Asian plate is also subducting southwards beneath the plateau, and the Tibetan lithosphere is separate.

Two competing models have been suggested to explain the recovery of ecosystems from mass extinctions. An analysis of the recovery of marine pelagic communities from the Cretaceous–Palaeogene mass extinction supports a model of contingent recovery, rather than one based on trophic structure.

Seismic data have identified large-scale compositional heterogeneities in Earth’s deep mantle, but their origin is debated. Numerical modelling demonstrates that seismological and geochemical constraints on the character of these heterogeneities can be satisfied if they are composed of primitive material formed early in Earth’s history.

Eutrophication increases the acidity of coastal waters. Model simulations suggest that the drop in pH in coastal waters of the northern Gulf of Mexico since pre-industrial times is greater than that expected from eutrophication and ocean acidification alone.

Anthropogenic emissions of ozone-depleting gases cause marked changes in surface climate, in addition to rising levels of anthropogenic greenhouse gases. A Review of the influence of the Antarctic ozone hole on Southern Hemisphere surface climate finds that its signature closely resembles the negative phase of the southern annular mode.

Current estimates of carbon dioxide evasion from inland waters are based on incomplete spatial coverage. Streams and rivers in the United States release 97 Tg of carbon to the atmosphere each year, according to an analysis of chemical and morphological data.

Pronounced warming in the Arctic region is an important feature of observed and modelled climate change. Simulations with a coupled climate model show that the thermal inversion at the surface that predominates in Arctic winter amplifies Arctic warming by lowering the ability of the warming surface layer to radiate to space.

The Ganges–Brahmaputra drainage basin represents one of the largest sources of terrestrial biospheric carbon to the ocean. Radiocarbon analyses suggest that 20% of the carbon exported from this system has an average age of more than 15,000 years.

The stability over time of the zonal jets on the giant planets has been debated. An analysis of observations from the Cassini spacecraft reveals an acceleration of wind velocities in Saturn’s high-altitude equatorial jet between 2004 and 2009, by 20 m s⁻¹ at tropopause level and by 60 m s⁻¹ in the stratosphere.

The impact of solar activity on climate has been debated heatedly. Simulations with a climate model using new observations of solar variability suggest a substantial influence of the Sun on the winter climate in the Northern Hemisphere.

Elevated concentrations of arsenic are common in shallow groundwater in many parts of South and Southeast Asia. Field experiments and model simulations suggest that adsorption of arsenic to sediments could help to limit contamination of deep groundwater.

An influence of solar irradiance variations on Earth’s surface climate has been repeatedly suggested. Simulations with a climate model driven by satellite measurements of solar ultraviolet irradiance show an atmospheric response to the solar minimum that resembles the negative phase of the North Atlantic Oscillation.

Ocean circulation patterns during the Late Cretaceous greenhouse interval remain disputed. Marine sediment geochemistry suggests that the end of the greenhouse interval coincided with the onset or intensification of deep-water formation in the North Atlantic Ocean.

Boninite lavas are erupted during the early stages of subduction, however they have previously been found only in the ancient geological record. Discovery of an active boninite eruption shows that abundant volatile gases derived from the subducting slab drive this violent eruptive activity, even in the deep sea.