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Nearly 40% of the Earth’s ice-free surface area is cropland or pasture. Measurements of dissolved organic matter along a gradient of agricultural land use suggest that agricultural watersheds contain less complex, more microbially derived dissolved organic matter than natural wetlands.
Seismic anisotropy in Earth’s oceanic lithosphere and in the mantle wedge above subduction zones is associated with crystallographic preferred orientations of olivine. Experiments at high pressure and temperature suggest that a pressure of ∼3 GPa can induce the same changes in the crystal structure of olivine as high water activity at lower pressures.
The effect of volcanism on low-latitude climate has been difficult to quantify. A compilation of tropical and subtropical annually resolved climate reconstructions shows a correlation between low sea surface temperatures and low-latitude volcanic activity over the past four centuries.
Climate variability in the tropical Pacific Ocean influences climate across much of the planet. A diatom-based record of sea surface temperatures from El Junco lake, Galapagos, reveals that the most recent half-century is the warmest 50-year period in the past 1,200 years.
The Earth constantly loses matter, mostly in the form of H+ and O+ ions. Analysis of measurements from the Cluster spacecraft reveals that the total loss of cold ions, below 1 eV in thermal energy, is larger than the previously observed, more energetic, outflow.
The break-up of an asteroid led to the rapid delivery of meteorites to Earth around 470 million years ago. The widespread occurrence of sedimentary megabreccias deposited at the same time suggests this high influx of meteorites could have triggered mass wasting — downslope movement of rock and sediment — at continental margins, by inducing the destabilization of sedimentary slopes.
The rising abundance of greenhouse gases in the atmosphere has been associated with a change in the stratospheric circulation and a decrease in the mean age of stratospheric air. Balloon-borne measurements of trace gases over 30 years suggest that, in contrast to model predictions, there have been no significant trends (at a 90% confidence limit) in the age of stratospheric air.
As a single-plate planet, Mars cannot support large-scale motion of the lithosphere, according to the standard theory of stagnant-lid convection, but such motion is required to explain the position of the Tharsis Rise. Modelling work suggests that differential rotation of the lithosphere can resolve this problem.
Observational studies show a clear response in European climate to El Niño/Southern Oscillation in late winter. Simulations with an atmospheric general circulation model identify a long-distance pathway connecting climate variability in the Pacific region and Europe via the stratosphere, the upper layer of the atmosphere.
Impacts of extraterrestrial objects were frequent on the early Earth. Shock experiments suggest that the impact of the most common type of meteorites into sea water could have synthesized the organic molecules that served as the building blocks of life.
Biological nitrogen fixation limits plant growth and carbon exchange at local to global scales. Long-term nutrient manipulation experiments in forests and short-term manipulation experiments in microcosms suggest that the micronutrient molybdenum, a component of the nitrogen-fixing enzyme nitrogenase, limits nitrogen fixation by asymbiotic bacteria in tropical soils in Panama.
Stephen Rintoul and an international team of oceanographers headed south on the Australian icebreaker, Aurora Australis, to discover how Southern Ocean currents influence climate and biodiversity.
