Articles in 2012

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 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.

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.

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.

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.

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.

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.

Subtropical highs influence climate over extensive regions of the planet. These maritime high-pressure systems are set to intensify in boreal summer over the coming century, as a result of an increase in the land–sea thermal contrast.

River regulation and sea-level rise have damaged deltaic ecosystems as well as the sedimentological processes that support them. More scientific effort needs to be directed towards restoring land-building processes in our vanishing deltas.

Research in Asia, and particularly in China, is catching up with the traditional hotbeds of science. The next step towards a more even geographical distribution of research will be a higher proportion of top-level publications led by scientists at Chinese labs.