Articles in 2012

The West Antarctic Ice Sheet is contributing to sea-level rise, but temperature trends in the region have remained uncertain. A complete temperature record for Byrd Station in central West Antarctica, spanning from 1958 to 2010, establishes West Antarctica as one of the fastest-warming regions globally.

The recurrence times of great Himalayan earthquakes are difficult to assess because they rarely rupture the surface. Field mapping and ¹⁴C dating of offset fluvial deposits are used to identify two great Himalayan quakes that ruptured the surface along the main plate boundary fault in AD 1255 and 1934.

The current mountain pine beetle infestation in forests in British Columbia ranks among the largest ecological disturbances recorded to date. An analysis of remote sensing data suggests that the resultant forest loss has led to a 1 °C rise in summertime surface temperatures.

The mantle plume beneath Hawai’i shifted southwards by about 15° between 80 and 50 million years ago. Palaeomagnetic inclination data from four South Pacific seamounts along with Ar/Ar dating reveal that by contrast the Louisville hotspot—Hawai’i’s southern hemisphere counterpart—remained within 3° of its present latitude between 70 and 50 million years ago.

The efficiency with which the oceans take up heat has a significant influence on the rate of global warming. An analysis of observations of heat uptake into the deep North Atlantic shows that the propagation of density-compensated temperature anomalies is an important mechanism for this heat uptake, and depends on high salinity in the subpolar gyre.

Subtropical high-pressure systems influence atmospheric circulation and global climate. Model simulations and reanalysis data suggest that summertime high pressure systems in the Northern Hemisphere subtropics will intensify as a result of climate change.

The persistence of dendritic drainage patterns implies that rivers reorganize after a tectonic perturbation, preserving no long-term record of that tectonic event. Numerical simulations of the evolution of drainage patterns in the Southern Alps, New Zealand, however, reveal rivers that resist reorganization and thus preserve a record of plate tectonic strain over 10 million years.

Santorini Volcano in Greece was thought to be continually charged by small injections of magma. Measurements of surface deformation show that magma equivalent to 10–50% of that emitted in previous small eruptions has been injected beneath Santorini since January 2011, implying that the volcano is instead charged by rapid, episodic fluxes of melt.

Hydrous clay minerals detected on the ancient martian crust have been proposed to have formed by aqueous weathering on a warm, wet early Mars. However, analyses of terrestrial clay minerals and comparisons to Mars suggest that the Noachian clays could have alternatively formed by precipitation from magmatic fluids.

The end of the Triassic period was marked by a mass extinction. Biomarkers in black shales that formed at the time suggest that the repeated poisoning of shallow seas by hydrogen sulphide delayed the early Jurassic recovery.

Arsenic contamination of groundwater threatens the health of millions of people in southeast Asia. Measurements in an arsenic-contaminated aquifer in Vietnam point to sediment age as a key determinant of groundwater arsenic concentrations.

The nature of the atmospheric sulphur cycle on the early Earth has been difficult to reconstruct. An analysis of sulphur isotopes from 3.2-billion-year-old volcanic rocks suggests that episodic volcanism released pulses of sulphur dioxide that was then broken down by ultraviolet photodissociation.

The Southern Ocean makes a substantial contribution to the oceanic carbon sink. Observationally based estimates of carbon subduction suggest that carbon sequestration depends on physical properties, such as mixed layer depth, ocean currents, wind and eddies, that are potentially sensitive to climate variability and change.

The great distance travelled by long-runout landslides, observed previously on the Earth and Mars, requires a mechanism of friction reduction. Identification and analysis of long-runout landslides on Saturn’s moon Iapetus suggests that the Iapetian landslides are enabled by flash heating of the icy sliding surface.

Both marine- and land-terminating glaciers in southeast Greenland have experienced dramatic recent retreat. An 80-year record of historical aerial photographs and satellite imagery shows that many land-terminating glaciers in this region retreated more rapidly in the 1930s than today, whereas marine-terminating glaciers have retreated faster in the 2000s.

Seagrass meadows are some of the most productive ecosystems on Earth. An analysis of organic carbon data from just under one thousand seagrass meadows indicates that, globally, these systems could store between 4.2 and 8.4 Pg carbon.

In the Arctic, permafrost and glaciers form a ‘cryosphere cap’ that traps methane leaking from hydrocarbon reservoirs, restricting flow to the atmosphere. Aerial surveys and ground-based measurements reveal the release of radiocarbon-depleted methane along boundaries of permafrost thaw and retreating glaciers in Alaska and Greenland.

Human activities, including industry and mining, have increased inorganic mercury deposition in terrestrial and aquatic ecosystems. Model simulations indicate that circumpolar rivers deliver large quantities of mercury to the Arctic Ocean during summer.

The vast majority of Earth’s volcanoes are under water, but little is known of the structure and evolution of submarine volcanoes. A bathymetric survey mapping the Monowai submarine volcano in the Tonga–Kermadec Arc twice within 14 days reveals dramatic changes in bathymetry of up to 71.9 m, associated with volcanic activity.

Carbon capture and geological storage represents a potential means of managing atmospheric carbon dioxide levels. An analysis of a 135,000 palaeorecord shows that pulses of carbon dioxide leakage from a natural reservoir in Utah are associated with episodes of glacial unloading.