Volume 3 Issue 6, June 2010

Aquifers are the primary source of drinking water for up to two billion people. To avoid overexploitation, lengthy renewal periods of some aquifers must be taken into account.

The Triassic/Jurassic boundary was marked by widespread environmental changes, including greenhouse warming. Palaeoecological reconstructions from East Greenland reveal a dramatic rise in fire activity, driven by vegetation shifts and climate change.

The duration of Earth's creation remains unknown. Elegant modelling of the Earth's core formation reaffirms that the bulk of accretion occurred within a few tens of millions of years, but another 100 million years or so were needed to finish the job.

The ocean's nitrogen budget has escaped quantification. A modelling study shows how a small shift in the nitrate-to-phosphate uptake ratio of phytoplankton has a large effect on calculated nitrogen fixation rates.

Greenland's ice sheet does not look like an alpine glacier. However, it behaves like one in the way its meltwater lubricates basal motion, suggesting that projections of sea-level change will require unified knowledge of basal processes in glaciers and ice sheets.

Low atmospheric carbon dioxide concentrations during glacial periods must have been accompanied by changes in surface-ocean carbonate chemistry. But it is unclear whether concurrent changes in the deep sea contributed to the glacial carbon dioxide decline.

The rate at which new marine animals evolve has varied through time, but the factors that ultimately drive these fluctuations are unclear. A statistical analysis shows that global changes in abiotic factors play an important role.

The El Niño–Southern Oscillation is a naturally occurring fluctuation that originates in the tropical Pacific region and affects the lives of millions of people worldwide. An overview of relevant research suggests that progress in our understanding of the impact of climate change on many of the processes that contribute to El Niño variability is considerable, but projections for the phenomenon itself are not yet possible.

Climate-change projections suggest that European summer heatwaves will become more frequent and severe during this century. An analysis of a set of high-resolution regional climate simulations reveals consistent geographical patterns in these changes, with the most severe health impacts in southern European river basins and along the Mediterranean coasts.

Vertical motions of the rocky margins of Greenland and Antarctica respond to mass changes of their respective ice sheets, but these motions can be obscured by ancient episodes of glacial advance or retreat. An analysis of the acceleration of vertical motion indicates that accelerated ice loss in western Greenland started in the late 1990s.

An acceleration of ice-mass loss has been observed near the margin of the Greenland ice sheet, partly as a result of faster ice motion. Observations by GPS receivers reveal high seasonal variability in ice motion, with summer motion up to 220% higher than winter background levels.

The ratio of nitrogen to phosphorus in phytoplankton varies greatly with taxa and growth conditions. An ecosystem model suggests that the relative abundance of fast- and slow-growing phytoplankton controls the amount of new nitrogen added to the ocean.

The decay of soil and sedimentary organic matter yields organic compounds with a high molecular weight, termed humic substances. Sediment-incubation experiments suggest that microbial reduction of solid-phase humics can accelerate iron(III) oxide reduction in wetland soils.

Lake Tanganyika has become warmer, increasingly stratified and less productive over the past 90 years. Analyses of lake sediments show that this recent warming is unprecedented within the past 1,500 years.

An episode of climate warming 200 Myr ago was associated with catastrophic environmental changes. Experimental and palaeontological data suggest that a climate-driven shift to more flammable leaf shapes contributed to increased fire activity in East Greenland at this time.

The diversity of marine life has varied throughout the past 500 million years. Statistical analyses suggest that fluctuations in the availability of marine nutrients has been one important regulator of rates of origination during this time.

The global geoid is characterized by a semi-continuous belt of minima that surround the Pacific Ocean. Simulations with mantle flow models suggest that these geoid lows are correlated with high-velocity anomalies near the base of the mantle and low-velocity anomalies in the mid-to-upper mantle.

The Earth formed through accretion of many planetary embryos that were probably differentiated into a metallic core and a silicate mantle. The metals and silicates were assumed to fully mix during accretion, but models of Earth’s formation that assume only partial mixing are found to be equally compatible with geochemical observations.

In their pursuit of palaeoclimatic reconstruction, Andrew Cohen and colleagues experienced the 'Eureka!' highs and dangerous lows of sediment coring in Lake Tanganyika, East Africa.