Articles in 2010

The mechanisms by which debris flows acquire mass and momentum as they entrain material are unclear. Large-scale experiments suggest that the pore pressure of wet bed sediment increases as the flow moves over the bed, leading to reduced friction and progressive scouring of the base.

The origins of Alpine valleys are controversial. Topographic data from the Swiss Alps suggest that the valleys have been incised progressively during consecutive glacial–interglacial cycles.

Initially, the devastating 12 January 2010 Haiti earthquake seemed to involve straightforward accommodation of the motion between the Caribbean and North American plates. A combination of seismological observations, geologic field data and space geodetic measurements shows that the rupture process may have involved slip on multiple faults, but lacked significant surface deformation.

Volcanic fields at the eastern margin of the Red Sea rift were regarded as seismically quiet until a swarm of 30,000 earthquakes struck in 2009. Geological analyses reveal the intrusion of a volcanic dyke and indicate that rift-related extension is spread over a broad region far from the rift axis.

Hydrographic properties of the North Atlantic Ocean have changed significantly over the past decades. A combination of changes in seawater density, calculated from observed properties of sea water and a numerical ocean model, reveals that the strength of the meridional overturning circulation has changed in different directions in the subpolar and subtropical basins, respectively.

European heatwaves have raised interest in the impact of land-cover conditions on temperature extremes. Analyses of observations from an extensive network of flux towers in Europe reveal a difference in the response of forests and grassland to extreme or long-lasting heat.

The photosynthetic production of oxygen in the ocean is thought to have begun at least 2.7 billion years ago. The geochemistry of marine sediments deposited 2.6 billion years ago suggests that ocean margins were oxygenated at least 100 million years before the first significant increase in atmospheric oxygen concentrations.

The Trezona Formation of South Australia pre-dates the 635-million-year-old Marinoan glaciation. Fossils found at this location are up to several millimetres in size, and share morphological characteristics with sponge-grade animals.

Present-day changes in the thickness of ice sheets and glacial isostatic adjustment both affect space geodetic measurements. A combination of gravity measurements and geodetic data of surface movement with a data-assimilating model of ocean bottom pressure allows the simultaneous estimation of present-day water transport and glacial isostatic adjustment.

The western Pacific warm pool and the Indonesian throughflow affect tropical climate and atmospheric convection. Marine sediment records reveal uniformly elevated temperatures from 10,000 to 7,000 years ago, despite the initiation of modern Indonesian throughflow circulation about 9,500 years ago.

Ice ages during the Palaeozoic era are marked by glacial–interglacial cycles thought to be driven by variations in the Earth’s orbit. Numerical simulations suggest that the response of vegetation to the varying insolation may be an important factor in the associated climate response.

The termination of the last glacial period was punctuated by the collapse and resumption of Atlantic meridional overturning circulation. Sedimentary records from the South Atlantic Ocean indicate that an unusually deep limb of North Atlantic Deep Water formed after the resumption of overturning circulation during the Bølling–Allerød warm event.

The metal content of ore deposits formed during subduction-zone volcanism was thought to be established when the ore fluid separates from the parent magma. Analyses of metal concentrations in erupted melts and the volcanic gases emitted after an eruption in Indonesia reveal that metals can be added to the ore fluid later, during mixing with separated melts.

Seismotectonic studies seek to provide ways of assessing the timing, magnitude and spatial extent of future earthquakes. Numerical simulations of seismic and aseismic fault slip in a fully dynamical numerical model open the possibility of predicting a fault system’s seismic rupture patterns from observations of its slip properties.

Stratospheric water vapour affects Earth’s radiation budget. A 19-month record of the hydrogen isotopic composition of water in the tropical stratosphere, collected through remote sensing measurements, shows a clear seasonal cycle in the isotopic composition that propagates upwards in this region, and is most likely created in the tropical tropopause layer.

Mid-ocean ridges grow through tectonic and volcanic processes. Uranium-series dating of volcanic rocks at the ultraslow-spreading Southwest Indian Ridge reveals widely dispersed, young, off-axis volcanism that is spatially coincident with fault surfaces. Faults may therefore provide a mechanism for the wide dispersal of magma at ultraslow-spreading ridges.

Interactions between the atmosphere and ocean are mediated by the mixed layer at the ocean surface. Analyses of ocean temperature and salinity data from Argo floats show that changes in the Southern Annular Mode, including recent and projected trends attributed to human activity, drive variations in mixed-layer depth in the Southern Ocean.

Over 90% of calcareous nannoplankton species disappeared during the Cretaceous–Palaeogene mass extinction, which occurred after an impact event. Palaeontological analyses show that the extinction was most pronounced in the Northern Hemisphere oceans, possibly as a result of an increased concentration of particulates created by the impact in the north.

The southwest corner of Western Australia has been subject to a serious drought in recent decades, whose ultimate cause remains unclear. A comparison of precipitation records in the area of drought and an ice core from East Antarctica reveal a significant inverse correlation between precipitation in the two locations, and suggest that the current drought may be highly unusual compared with the past 750 years of variability.