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John West and colleagues struggled with widely held misconceptions and computer hackers in their attempt to explain mantle processes beneath the Great Basin in the United States.
A dramatic oceanic biotic shift from eukaryotic phytoplankton to bacteria occurred about 740 million years ago. Microfossil and geochemical data from the Chuar Group in the southwestern United States link this biotic turnover to widespread eutrophication of surface waters.
The interglacial period that occurred about 400,000 years ago—Marine Isotope Stage 11—was the longest out of the past five glacial cycles. A proxy-based alignment of this interglacial with the Holocene, and a subsequent analysis of carbon isotopic data from marine sediments, indicates that the unusual length may have been driven by strong poleward oceanic heat transport.
Seismic anisotropy data for the Great Basin region of the western United States, coupled with tomographic images, help delineate a northeast-dipping lithospheric drip. Numerical experiments suggest that the drip could have formed owing to gravitational instability triggered by a density increase of about 1% and a temperature increase of about 10%.
Structures formed during ancient tectonic events are commonly reactivated during subsequent tectonism. Numerical models point to mechanical anisotropy arising from the inherited orientation of crystals of the mineral olivine in the lithospheric mantle as the cause of this behaviour.
The impact of aerosol particles on the formation and properties of clouds is one of the largest remaining sources of uncertainty in climate change projections. Now, aircraft-aerosol time-of-flight spectroscopy measurements of ice residues indicate that biological particles trigger ice formation in high-altitude clouds.
Tectonic activity severely restricted the seaway connecting the tropical Pacific and Indian oceans sometime between about 3 and 4 million years ago. Ocean temperature and salinity reconstructions indicate that the Indonesian Gateway reached its present configuration about 2.95 million years ago, leading to the cooling and freshening of subsurface water in the tropical eastern Indian Ocean.
Seismic data show that the Earth’s inner core is structurally complex. Numerical simulations suggest that whereas the deeper structure may be inherited from past episodes of inner-core growth, the origin of the shallow structure is due to ongoing deformation.
The myriad bodies that occur in the Solar System show a wide range of physical properties. Exploration by spacecraft during the past four decades has shown that volcanism — a major mechanism by which internal heat is transported to the surface — is common on many of these bodies.
Some aerosol particles—known as ice nuclei—initiate ice formation in clouds, thereby influencing precipitation, cloud dynamics and incoming and outgoing solar radiation. Measurements of the concentration and elemental composition of ice nuclei in the Amazon basin indicate that local bioparticles and Saharan dust could explain the presence of almost all ice nuclei during the wet season.
The overflows from the Nordic seas maintain the deep branch of the North Atlantic circulation that is an important part of the global climate system. An analysis of observed ocean temperatures and salinities between 1950 and 2005 shows that the Atlantic water circulating in the Nordic seas is the main source for change in the overflow waters.
The period of relatively warm climate from 11,000 to 5,000 years ago was marked by considerable temporal and spatial variability. Model simulations relate this complexity to the influence of the waning Laurentide ice sheet.
The necessity of establishing boundaries between nationally and internationally administered areas of the sea floor has long been recognized. The UN-approved demarcation line must be scientifically inevitable to gain practical importance.
Iron can stimulate productivity in many regions of the world ocean, but only if it exists in a readily dissolvable form. Chemical analyses of typical aerosol particles show that the mineralogy of iron-containing particles largely determines their solubility.
Atmospheric deposition of nitrogen can, but does not always, speed up the sequestration of carbon in trees and forest soil. This complexity may arise from the spatial variations in each of the three mechanisms by which nitrogen affects carbon storage.
