Volume 4 Issue 11, November 2011

The impact of solar activity on climate has been debated heatedly. Simulations with a climate model using new observations of solar variability suggest a substantial influence of the Sun on the winter climate in the Northern Hemisphere.

Volcanic activity is much more common beneath the oceans than on land, yet has been observed only rarely. Direct measurements of an eruption in the southwest Pacific Ocean reveal unexpectedly explosive activity at great depths.

Phytoplankton form the base of the marine food web, but their growth in nutrient-depleted surface waters has remained a puzzle. Two complementary studies suggest that ocean eddies help to control phytoplankton growth and distribution in unexpected ways.

Anthropogenic emissions of ozone-depleting gases cause marked changes in surface climate, in addition to rising levels of anthropogenic greenhouse gases. A Review of the influence of the Antarctic ozone hole on Southern Hemisphere surface climate finds that its signature closely resembles the negative phase of the southern annular mode.

The stability over time of the zonal jets on the giant planets has been debated. An analysis of observations from the Cassini spacecraft reveals an acceleration of wind velocities in Saturn’s high-altitude equatorial jet between 2004 and 2009, by 20 m s⁻¹ at tropopause level and by 60 m s⁻¹ in the stratosphere.

An influence of solar irradiance variations on Earth’s surface climate has been repeatedly suggested. Simulations with a climate model driven by satellite measurements of solar ultraviolet irradiance show an atmospheric response to the solar minimum that resembles the negative phase of the North Atlantic Oscillation.

Pronounced warming in the Arctic region is an important feature of observed and modelled climate change. Simulations with a coupled climate model show that the thermal inversion at the surface that predominates in Arctic winter amplifies Arctic warming by lowering the ability of the warming surface layer to radiate to space.

Tropical Atlantic sea surface temperatures and surface winds vary together in a pattern termed the Atlantic Meridional Mode. Simulations with an ocean general circulation model that is driven by a record of dust radiative forcing suggest that dust emissions over West Africa substantially influence the state of the tropical Atlantic Ocean on interannual to decadal scales.

Eutrophication increases the acidity of coastal waters. Model simulations suggest that the drop in pH in coastal waters of the northern Gulf of Mexico since pre-industrial times is greater than that expected from eutrophication and ocean acidification alone.

The amount of radiocarbon-depleted carbon dioxide in the atmosphere rose dramatically during the last deglaciation. Estimates of the radiocarbon content of water at 2.7 km depth in the northeast Pacific Ocean over the past 24,000 years suggest that this water mass was not a significant source of this carbon.

The early Eocene was marked by a series of abrupt warming events. Numerical modelling suggests that the events were the result of nonlinear interactions between orbital forcing, ocean circulation and the carbon cycle.

Ocean circulation patterns during the Late Cretaceous greenhouse interval remain disputed. Marine sediment geochemistry suggests that the end of the greenhouse interval coincided with the onset or intensification of deep-water formation in the North Atlantic Ocean.

Retreating ice caps overlying volcanoes are thought to relieve surface pressure, causing enhanced magma generation and volcanic activity. Analysis of crustal stress during a dyke intrusion event associated with retreat of Iceland’s largest ice cap indicates that ice retreat could instead promote storage of magma in the crust, rather than eruption at the surface.

Eddies and other mesoscale processes are thought to enhance biological production in the ocean, particularly in nutrient-limited regions. Satellite data and model simulations suggest that eddies suppress production in eastern boundary upwelling systems.

Elevated concentrations of arsenic are common in shallow groundwater in many parts of South and Southeast Asia. Field experiments and model simulations suggest that adsorption of arsenic to sediments could help to limit contamination of deep groundwater.

Boninite lavas are erupted during the early stages of subduction, however they have previously been found only in the ancient geological record. Discovery of an active boninite eruption shows that abundant volatile gases derived from the subducting slab drive this violent eruptive activity, even in the deep sea.

Noble gases from the atmosphere are carried into Earth’s mantle through subduction. Geochemical analyses of rocks that record slab dehydration during progressively deeper stages of subduction indicate that noble gases incorporated into hydrous minerals close to the sea floor are efficiently transported to mantle depths of at least 200 km.

Research into city living and its impacts is burgeoning, thanks to the fact that more than half of us now live in urban areas. In this web focus we compile a number of papers documenting some of the challenges associated with city life, and some of the less expected outcomes.