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Atmospheric concentrations of nitrous oxide, a greenhouse gas, have increased since 1860. A regression model indicates that conversion of 2% of manure nitrogen and 2.5% of fertilizer nitrogen could explain the pattern of increasing nitrous oxide concentrations between 1860 and 2005, including a rise in the rate of increase around 1960.
The depth at which particulate organic carbon sinking from the surface ocean is converted back to carbon dioxide is known as the remineralization depth. A three-dimensional global ocean biogeochemistry model suggests that a modest change in remineralization depth can have a substantial impact on atmospheric carbon dioxide concentrations.
The oxidation of ammonia to nitrate, known as nitrification, is a key process in the nitrogen cycle. Real-time polymerase chain-reaction measurements show that nitrification is driven by bacteria rather than archaea in nitrogen-rich grassland soils in New Zealand.
Earthquakes often occur in areas that lack an array of seismometers, resulting in a scarcity of local measurements from some regions of great geological interest. In such regions, some earthquakes themselves may be turned into virtual seismometers that are capable of measuring strain caused by passing waves from other earthquakes.
It has been debated whether rivers or glaciers are more effective agents of erosion. A global compilation of erosion rates reveals that both are capable of generating rates of erosion that match or exceed the highest rates of rock uplift.
Gigantic jets emerge from the top of thunderstorms and extend all the way to the ionosphere at altitudes of 90 km. Simultaneous video images and magnetic field measurements of a gigantic jet demonstrate an electric charge transfer between the thunderstorm and the ionosphere that is comparable to that observed in cloud-to-ground lightning.
The formation of dunes is controlled by the direction of the prevailing winds and the characteristics of the sediments. Linear dunes in the Qaidam Basin, China, are shown to form from cohesive sediments, a model that could be applicable to dunes on Titan.
Slab fluids drive mantle melting and return ocean water to the Earth's surface through arc volcanism. New ways of estimating the temperature of slab fluids indicate relatively hot conditions, and hint at a shallow and fast return path for ocean water.
The sedimentary wedge in the Nankai Trough off the coast of Japan is cut by a landward-dipping thrust fault, which is an important plate boundary structure in this region. Geological and seismic reflection data indicate that the fault initiated ∼1.95 million years ago and underwent uplift and reactivation ∼1.55 million years ago.
The earliest fossils of cyanobacteria have been controversially reported from the 3,465-million-year-old Apex chert in Western Australia. Mineralogical analyses of the rock near the fossil site indicate that the site experienced repeated alterations at low and medium temperatures, and is therefore unlikely to have preserved any early forms of life.
The Australian–Indonesian summer monsoon affects rainfall variability across the Indo–Pacific region. Reconstructions of monsoon strength from stalagmites show that precipitation increased from 11,000 to 7,000 years ago, as rising global sea level caused the flooding of the Indonesian continental shelf.
The micronutrient molybdenum is necessary for nitrogen fixation, but is very rare and highly soluble in soils. X-ray spectroscopy analysis of forest soil samples indicates that most of the molybdenum in the litter layer binds to organic matter.
Palaeoclimate research increasingly portrays itself as a means to understanding future climate change. It would serve the science and scientists better to regard the study of the past as an end in its own right.
Comprehensive abatement strategies will be needed to limit global warming. A drastic reduction of black-carbon emissions could provide near-immediate relief with important co-benefits.
The Salton Sea is located in a sedimentary basin at the southern termination of the San Andreas fault. High-resolution seismic data indicate that the basin formed and grew by active subsidence at its southern end.
Modern terrestrial microbes have shown a puzzling ability to use reduced forms of phosphorus not commonly found on Earth. An examination of glasses formed in the ground by lightning suggests that lightning strikes can generate these phosphorus species.
