News & Views in 2014

In the first decades of the twentieth century, the Earth warmed rapidly. A coral-based climate proxy record of westerly winds over the equatorial Pacific suggests that wind strength and warming rate were linked, as they are today.

Soil contains aged organic carbon that can be hundreds or thousands of years old. Human disturbance in small and large watersheds is mobilizing some of this fossil carbon from soils to aquatic systems.

Carbon dioxide can stimulate photosynthesis in trees and increase their growth rates. A study of tree rings from three seasonal tropical forests shows no evidence of faster growth during 150 years of increasing atmospheric CO₂ concentrations.

A period of rapid warming about 55.5 million years ago was triggered by a massive release of carbon. The carbon isotope composition of soil nodules provides evidence for a smaller, but still important, carbon release prior to the main event.

The fate of water that enters the mantle within subducting slabs is unclear. Laboratory experiments indicate that subducted crust can transport large amounts of water into the deep Earth, and the lower mantle may become more hydrated over time.

Nitrous acid can initiate photochemical air pollution events, but it is not clear where it comes from. Laboratory experiments now suggest that surface-bound nitrite accumulated overnight can release nitrous acid during the daytime.

The ocean's biological pump transfers carbon to long-term storage in deep waters and sediments. Two inverse modelling studies describe the export of organic matter throughout the surface layer of the world's oceans in exceptional detail.

Aqueous subduction-zone fluids contain CO₂ and methane. New calculations indicate that these fluids also host a wide array of organic carbon species, in concentrations sufficient to influence the deep carbon cycle.

Elevated levels of CO₂ can stimulate photosynthesis in plants and increase their uptake of atmospheric carbon. A five-year study in Minnesota grasslands shows that increased plant uptake of CO₂ is restricted by the availability of vital nutrients and water.

Temporal variations in coarse river deposits are often attributed to climate change. Cosmogenic nuclide concentrations of river cobbles suggest that climate plays a subordinate role to earthquake-induced landslides in producing coarse sediments in arid Peru.

Some modern microorganisms derive energy from the oxidation and reduction of arsenic. The association of arsenic with organic cellular remains in 2.7-billion-year-old stromatolites hints at arsenic-based metabolisms at the dawn of life.

Shorelines are vulnerable to the destructive waves and water levels of increasingly frequent extreme storm events. Wave tank experiments demonstrate that salt marsh vegetation dissipates wave energy and withstands extreme storm conditions.

Surface salinity in the Nordic Seas dropped between 1965 and 1995, but the source of fresh water to this region is contentious. Observations and simulations suggest that the low-salinity water was derived from the North Atlantic Ocean.

Earthquake prediction is a long-sought goal. Changes in groundwater chemistry before earthquakes in Iceland highlight a potential hydrogeochemical precursor, but such signals must be evaluated in the context of long-term, multiparametric data sets.

Upwelling within the highly productive Benguela current off the Namibian coast began in, and intensified throughout, the Neogene epoch. Model simulations indicate its development was intimately connected to evolving topography and mountain uplift in Africa.

Freshwater deficits and heavy rainfall have been projected to intensify in a warming climate. An analysis of hydrological data suggests that past changes in wet and dry extremes were more complex than a simple amplification of existing patterns.