Volume 5 Issue 12, December 2012

Not enough young people enter the geosciences. A passion for the subject should be sparked early on.

Multiple factors determine how much water is and will be available in the river basins of Asia. To expose hotspots and help adaptation, these factors must be assessed together at the basin level.

Ocean acidification is predicted to harm the ocean's shell-building organisms over the coming centuries. Sea butterflies, an ecologically important group of molluscs in the Arctic and Southern oceans, are already suffering the effects.

The catastrophic drainage of glacial Lake Agassiz about 8,500 years ago is linked to abrupt climate change. A layer of sediments deposited during the previous interglacial period suggests that such outburst flooding is not unique to the Holocene epoch.

Carbon dioxide cools the upper atmosphere. Satellite measurements suggest that concentrations of this greenhouse gas have risen in the thermosphere over the past decade, with implications for the energy balance of the upper atmosphere.

Solar forcing has been invoked to explain persistent, millennial-scale climate variations during the Holocene. Two climate reconstructions, one based on sea-ice drift and one on North Atlantic storminess, call this link into question.

The world's largest freshwater resource is groundwater. A review of our understanding of groundwater depletion suggests that although the problem is global, solutions must be adapted to specific regional requirements at the aquifer scale.

Magma erupted at subduction-zone volcanoes contains mantle rocks and a mixture of fluids and sediments derived from the subducted slab. A synthesis of work over past years provides an integrated physico-chemical framework for subduction zones with mixing at the slab–mantle interface and transport towards the surface volcanoes by buoyant diapirs.

Above an altitude of about 50 km, carbon dioxide is the primary radiative cooling agent. Carbon dioxide and carbon monoxide mixing ratios derived from satellite-based solar occultation spectra document an estimated increase in global CO_x concentrations of about 23.5 ppm per decade at an altitude of 101 km.

In contrast to the dramatic decline of Arctic sea ice, Antarctic sea ice has increased over recent decades. A 19-year satellite record of sea-ice motion shows that winds are driving decadal trends in Antarctic ice concentrations.

The West Antarctic Ice Sheet is sensitive to ocean warming and contains enough ice to significantly raise sea level. Direct oceanographic measurements in the Amundsen Sea during 2010 show continuous inflow of warm water towards the thinning ice shelves in West Antarctica.

As a result of ocean acidification, aragonite may become undersaturated by 2050 in the upper layers of the Southern Ocean. Analyses of sea snail specimens, extracted live from the Southern Ocean in January and February 2008, show that the shells of these organisms are already dissolving.

Diatoms—unicellular algae that form substantial blooms in cold, nutrient-rich waters—are thought to be responsible for the export of marine silica to depth. An analysis of the elemental composition of marine cyanobacteria suggests that picocyanobacteria also accumulate significant quantities of silicon.

Considerable climatic variability on decadal to millennial timescales has been documented for the Holocene epoch. A reappraisal of estuarine and coastal sediment records reveals five periods of enhanced storminess during the past 6,500 years, at a frequency of approximately every 1,500 years and unrelated to solar irradiance variations.

Decadal- to centennial-scale variability has been identified in the Arctic Oscillation, but less is known about variations on the millennial scale. A record of sea-ice drift from off the Alaskan coast shows a 1,500-year cycle in the phase of the Arctic Oscillation.

Episodes of ice sheet disintegration and meltwater release over glacial–interglacial cycles are recorded in the sediments of the Labrador Sea. Analyses of sediment cores along the Labrador and Greenland margins reveal a layer of red material that was probably carried to the Labrador Sea during a glacial outburst flood through the Hudson Strait, early in the last interglacial period.

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.

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.