Reviews & Analysis

Subglacial water can significantly affect the velocity of ice streams and outlet glaciers of ice sheets. Depending on the geometry and capacity of the subglacial hydrologic system, increased surface melting in Greenland over the coming decades may influence the ice sheet's mass balance. Furthermore, subglacial lakes in Antarctica can modulate ice velocities and act as nucleation points for new fast-flowing ice streams.

Extraction of the continental crust has left the Earth's mantle depleted in certain elements. Some rocks from the Arctic Ocean floor suggest that the extent of depletion and heterogeneity in the Earth's mantle may be greater than we thought.

Violent uplift of western Crete in AD 365 generated a Mediterranean-wide tsunami that tossed boats onto house-tops in Alexandria, Egypt. Although a similar earthquake may not recur for 5,000 years, contiguous fault segments could rupture sooner.

Because of difficulties in creating a radiocarbon calibration that covers the end of the last glaciation, defining the timing and duration of the Younger Dryas cold event has been a challenge. Linking related cosmogenic isotopes in tree rings and ice cores may provide new insights into abrupt climate changes.

All organisms require elements to live, grow and reproduce, but some of these are hard to find or take up. Nitrogen-fixing bacteria solve the problem by secreting compounds that allow them to acquire the metals they need.

Electrical discharges from thunderstorms include bolts-from-the-blue, blue jets and gigantic jets along with the more common intracloud and cloud-to-ground lightning. All these phenomena can be understood in a single framework.

Black carbon in soot is an efficient absorbing agent of solar irradiation that is preferentially emitted in the tropics and can form atmospheric brown clouds in mixture with other aerosols. These factors combine to make black carbon emissions the second most important contribution to anthropogenic climate warming, after carbon dioxide emissions.

Whether convection in the Earth's mantle extends through its entire depth or if the mantle is layered has long been debated. Recent research suggests that spatially and temporally intermittent or partial layering is the most likely solution.

Earthquake data seem to reveal a huge sausage-shaped slab of material detaching itself from the material subducting as two plates meet beneath the Hindu Kush. This largest-ever 'boudin' could tell us more about what happens when continents collide.

Numerous long, wall-like ridges can be observed in the Valles Marineris region of Mars. They probably represent fault zones cemented by water-deposited minerals and are indicative of ancient groundwater flow.

Deltas are among the most valuable coastal ecosystems, but they are very dynamic and the factors that influence their health are complex. The rate of compaction of underlying sediments might be a more significant factor than was thought.

Lakes dammed by ice will commonly spill in catastrophic outbursts. Lake Agassiz-Ojibway, at the margin of the Laurentide ice sheet, burst 8,470 years ago in a subglacial flood whose marks have been scratched into the seafloor of Hudson Bay.

Despite Titan's cold temperatures (about 93.7 K at the equator), fluvial and atmospheric processes are active on this moon of Saturn, with methane playing a similar role to water on Earth. However, Titan lacks a global methane ocean, and rainfall appears to be episodic.

The influence of global warming on temperature trends at higher altitudes has been hotly debated. Stratospheric ozone depletion is another piece in the remaining tropical climate puzzle.

Ice-sheet stability is affected by a complex interplay between meltwater and the geological characteristics of the bedrock under the ice. The identification of a recently active subglacial volcano in Antarctica adds uncertainty to this system.