Research articles

Methylmercury is a neurotoxin that poses significant health risks to humans. Laboratory experiments suggest that the activity of methylating and non-methylating bacteria may together enhance the formation of methylmercury in anaerobic environments.

Greater Himalayan glaciers are retreating and losing mass. A combination of the latest ensemble of climate models combined with a glacio-hydrological model suggests that in two contrasting watersheds in the Greater Himalaya, glaciers will recede but net glacier melt runoff is on a rising limb until at least 2050.

The mode of carbon storage in Earth’s mantle is unclear. High-pressure laboratory experiments on mantle analogue materials reveal that significant quantities of carbon can be stored in tiny defects within the minerals, providing an efficient mechanism for carbon storage in the mantle.

Sediment grains in rivers are often bound together and stabilized by bacterial films. Experiments and mathematical models show that sediments bound by biofilms behave like a single elastic membrane that can rip catastrophically if the river flows fast enough.

Methane is abundant in marine sediments. Analysis of sediment cores and seismic images of marine sediments obtained off the coast of Pakistan show fracturing of gas hydrates and an increase in upward methane flux in the decades following a large earthquake in the Arabian Sea in 1945, suggesting that quakes can trigger hydrocarbon seepage.

Sea level during the last interglacial period reached a peak of between 5 and 9 m above the present-day level. A detailed reconstruction of sea level and isostatic rebound from Western Australia indicates a prolonged period of sea-level stability at 3–4 m above present, followed by an abrupt sea-level rise of 5–6 m.

Submarine seeps release substantial amounts of methane into the overlying water column at continental margins, leading to the formation of calcium carbonate deposits. Analyses of methane-derived carbonate build-ups on the Nile Delta suggest that their formation coincided with the development of deep-water anoxic or suboxic conditions.

As a moist atmosphere warms, it will reach a limit after which it is unable to radiate incoming solar radiation back to space, and a runaway greenhouse will occur. Calculations suggest that this limit is lower than previously thought and, for a water-saturated atmosphere, a runaway greenhouse can occur under present-day solar radiation.

The precise location of the mantle plume upwelling beneath Hawaii is debated. Seismic data reveal a thick layer of melt in the mantle beneath western Hawaii, implying that the upwelling plume may be deflected around an ancient, resistive root beneath the island.

The Lusi mud eruption in Indonesia has been ongoing since 2006. Numerical simulations show that a parabolic-shaped layer in the rock surrounding the site of the Lusi eruption could have amplified and focussed incoming seismic energy from an earthquake, which then triggered the mud eruption.

Iceberg calving—implicated in the retreat of ice shelves—is a complex process constrained by few observations. Numerical simulations suggest that the pattern of iceberg calving is controlled by the geometry of the glacier, and that regions of Greenland and Antarctica may be particularly vulnerable to catastrophic calving-driven retreat.

The East Antarctic ice sheet is considered to be largely insensitive to temperature changes in the Southern Ocean. Marine sediment records indicate the East Antarctic ice sheet repeatedly retreated by several hundred kilometres during intervals of Pliocene warmth.

The Greenland and Antarctic ice sheets have been reported to be losing mass at accelerating rates. Comparison of mass loss trends over the past decade with reconstructions of past mass loss indicates that the existing satellite record is too short to separate long-term mass loss trends from natural variability.

During the last deglaciation, the North Pacific Ocean was characterized by a spike in primary productivity, which has been attributed to iron input. Marine sediment analyses suggest that, instead, the productivity may have been fuelled by deep convection and subsequent stratification.

Volcanic tremor can be caused by small earthquakes occurring within the volcano. Mechanical modelling of volcanic tremor generated at Redoubt Volcano, Alaska, suggests that high-frequency tremor is the result of stick–slip motion in faults within the volcano conduit.

Owing to the turbulent nature of the ocean, mesoscale eddies are omnipresent. An analysis of atmospheric conditions associated with several hundred thousand eddies in the Southern Ocean suggests that the transitory sea surface temperature fronts associated with these eddies alter near-surface winds, clouds and rainfall.

Ocean Anoxic Event 2 was marked by rapid global warming and loss of O₂ from the ocean. Lithium isotope data suggest that the warming was accompanied by enhanced silicate weathering, which stimulated marine productivity and helped stabilize atmospheric CO₂ levels.

Over the twentieth century, droughts in southwestern North America have been linked to sea surface temperature variability in the North Pacific Ocean. Speleothem data from southern California suggest that links between the North Pacific and drought were less pronounced during the past millennium.

Large earthquakes in subduction zones can affect nearby volcanoes. Analysis of ground deformation following the 2010 earthquake in Maule, Chile, shows that some volcanoes subsided by up to 15 cm, probably because of quake-triggered release of hydrothermal fluids.

The 2011 Tohoku earthquake caused high levels of crustal deformation in Japan. Analysis of satellite radar and GPS data show that the earthquake caused nearby volcanic regions to subside instantaneously, creating elliptical depressions that are parallel to the direction of quake-induced crustal extension.