Volume 4 Issue 9, September 2011

Reluctance to deposit data is rife among researchers, despite broad agreement on the principle of data sharing. More and better information will reach hitherto empty archives, if professional support is given during data creation, not in a project's final phase.

The quantity of heat generated by radioactive decay in Earth's interior is controversial. Measurements of geoneutrinos emitted from the mantle during this decay indicate that this source contributes only about half of Earth's total outgoing heat flux.

An exotic arrow-shaped cloud was discovered in the atmosphere of Saturn's moon Titan last year. Numerical modelling shows how a large-scale atmospheric wave can naturally shape tropical clouds to such an arrow.

River systems have changed through time; the sinuous, stable channels common today developed relatively late in Earth's history. The rock record suggests that a specific type of fixed-channel river system arose after the expansion of arborescence.

Hydroelectric energy is renewable, but reservoirs contribute to climate change by releasing carbon dioxide and methane to the atmosphere. A global estimate suggests that young reservoirs in low latitudes produce the largest emissions.

Analysis of the first Apollo samples suggested that Earth's only satellite was bone dry. Spacecraft data and improved analysis techniques now indicate that the Moon is more volatile-rich and complex than previously thought.

Saturn’s moon Titan exhibits an active weather cycle that involves methane. An analysis of cloud observations and simulations with a general circulation model reveals that convection in Titan’s atmosphere is organized through an interplay of two wave modes, leading to local rates of precipitation of up to twenty times the average.

Reservoirs emit significant amounts of greenhouse gases. An analysis of data from 85 globally distributed hydroelectric reservoirs indicates that about 48 Tg carbon is emitted as carbon dioxide and 3 Tg carbon as methane, and that carbon emissions are correlated with reservoir age and latitude.

Ice flow acceleration has played a crucial role in the rapid retreat of calving glaciers in Alaska, Greenland and Antarctica. High-frequency measurements of ice speed and basal water temperatures from a calving glacier in Patagonia show that changes in basal water pressure by a few per cent can significantly affect ice flow speed.

Additions of reactive nitrogen to terrestrial ecosystems have more than doubled since 1860 as a result of human activities. Model simulations suggest that the climatic benefits of nitrogen-induced carbon sequestration are offset by increased nitrous oxide emissions.

Oceanic uptake of carbon dioxide reduces the rate at which anthropogenic carbon accumulates in the atmosphere. Trends in oceanic and atmospheric carbon dioxide concentrations converge on a multidecadal timescale, according to an analysis of North Atlantic surface waters.

The El Niño–Southern Oscillation is the largest source of interannual variability in the tropical Pacific Ocean. A multidecadal reconstruction of the Southern Oscillation Index for the past 2,000 years shows three prolonged periods of El Niño-dominated conditions.

Faults are generally assumed to be more complicated at the surface than at depth. Analysis of the 2010 El Mayor–Cucapah earthquake, in contrast, reveals that the surface trace is nearly straight but the fault must be highly segmented at depth, thus the characteristics of this earthquake could not have been anticipated from surface geology.

Stretching of the continental crust can double its surface area, but it is unknown whether similar amounts of extension occur at depth. Seismic results from the central Basin and Range province, western USA, reveal a thick root of lithospheric mantle that has not been extended and indicates that crustal stretching is decoupled from extension at depth.

Movement of the down-going oceanic plate in subduction zones is accommodated by earthquakes, slow slip and free slip with increasing depth. Analysis of accompanying tremor reveals a continuum of slow-slip events in the Cascadia subduction zone, which suggests that deep free slip of the subducted plate may cause stress to be gradually transferred up the plate interface towards the seismogenic zone.

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.

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.

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.

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.