Articles in 2011

Ocean warming during the last deglaciation decreased the solubility of oxygen. A global compilation of marine sediment records shows that the deglacial trend of deoxygenation was overprinted by changes in ocean circulation and marine productivity.

Wetlands cover more than 6% of the global ice-free land area, and represent an important arsenic sink. Laboratory experiments suggest that natural organic matter plays an active role in the immobilization of arsenic in anoxic wetlands.

Peatlands store vast amounts of organic carbon, owing to anoxic conditions, which prevent decay. Laboratory and field experiments suggest that drought-induced increases in oxygen stimulate microbial growth and the breakdown of peatland carbon.

Atmospheric carbon dioxide levels rose at the end of the last glacial period, but the sources of this carbon are uncertain. Ice-core data and carbon-cycle modelling suggest that the disappearance of a terrestrial inert carbon pool may have contributed to the rise.

Atmospheric aerosols can both suppress and foster the development of clouds and precipitation, depending on meteorological conditions. Ten years of observations, together with model simulations, suggest that aerosols stimulate the vertical development of warm-base mixed-phase clouds.

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.

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.

Eddies and other mesoscale processes are thought to enhance biological production in the ocean, particularly in nutrient-limited regions. Satellite data and model simulations suggest that eddies suppress production in eastern boundary upwelling systems.

Noble gases from the atmosphere are carried into Earth’s mantle through subduction. Geochemical analyses of rocks that record slab dehydration during progressively deeper stages of subduction indicate that noble gases incorporated into hydrous minerals close to the sea floor are efficiently transported to mantle depths of at least 200 km.

Low levels of biologically available forms of nitrogen can limit phytoplankton growth. Isotopic analyses of seawater samples collected from the Sargasso Sea in the summer suggest that small phytoplankton obtain half of their nitrogen from upwelled nitrate.

The largest dense-water plume feeding the lower limb of the Atlantic meridional overturning circulation from the Nordic seas comes from Denmark Strait overflow water. Measurements of hydrography and water velocity north of Iceland and ocean model simulations indicate that a significant part of this water is supplied by the North Icelandic Jet.

The expansion of land plants led to the development of new river and floodplain morphologies. Field studies suggest that the expansion of tree habitats in the Carboniferous period caused the development of river systems dominated by multiple channels and stable alluvial islands.

Lavas erupted above subduction zones commonly show evidence for recycling of subducted sediments. Geochemical analyses of sedimentary rocks that experienced subduction indicate that trace elements in the sediments can be efficiently recycled, because metamorphosed sediments rise buoyantly from the subducting plate and undergo partial melting at high temperatures in the overlying mantle wedge.

The Longmen Shan Mountains rise up 6,000 m over a distance of just 100 km, but the mechanisms driving formation of this striking topography are debated. Analyses of crustal movements during the 2008 Wenchuan earthquake suggest that fault-induced uplift plays a role in building the high topography.

Non-basaltic volcanism is rare on the Moon and has been found predominantly on the lunar nearside. Analysis of Lunar Reconnaissance Orbiter Camera images and spectral data reveal the presence of compositionally evolved, non-basaltic volcanism on the lunar farside.

Relative contributions to Earth’s total heat flux from the radioactive decay of isotopes versus primordial heat are debated. Measurements of geoneutrino particles emitted during radioactive decay in the Earth’s interior indicate that radiogenic isotopes contribute only about half of the total heat flux.

The southern San Andreas fault terminates in a stepover zone — several small faults that separate major fault segments — beneath the Salton Sea. Analysis of movements on the stepover zone faults indicates that periodic flooding of the palaeo-Salton Sea during the late Holocene could have triggered earthquakes on the San Andreas fault.

Cave deposits from China are commonly used to reconstruct the intensity of the East Asian monsoon precipitation. Numerical modelling indicates that these deposits may instead reflect changes in the strength of Indian monsoon precipitation and the isotopic signature of water vapour exported from India to China.

Hydrothermal vents along mid-ocean ridge systems host highly productive communities of microbes. Measurements along the Juan de Fuca ridge suggest that subsurface microbes consume hydrogen in low-temperature hydrothermal fluids, before discharge of these fluids at the sea floor.

A brief period of warming 55.9 Myr ago has been attributed to the release of massive amounts of carbon. Geochemical and model data suggest the peak rate of carbon emission during this interval was relatively slow, and significantly lower than present-day levels of carbon emissions to the atmosphere.