Articles in 2014

Globally increased temperatures and a perturbation of the carbon cycle and biosphere characterized the Palaeocene–Eocene Thermal Maximum about 55.9 million years ago, but its effect on ocean productivity is controversial. Records of marine barite accumulation rates suggest that carbon sequestration during the event could have been enhanced by an efficient biological pump.

During the expansion of the Antarctic ice sheet about 14 million years ago, sea surface temperatures in the Southern Ocean rose. Climate model simulations suggest that this short-lived warming was related to changes in ocean–atmosphere circulation induced by the growth of the ice sheet.

The Indian summer monsoon is influenced by numerous factors, including aerosol-induced changes to clouds, surface and atmospheric heating, and atmospheric circulation. An analysis of satellite data and global climate model simulations suggests that dust aerosol levels over the Arabian Sea, West Asia and the Arabian Peninsula are positively correlated with the intensity of the Indian summer monsoon.

Observations of compressional structures on Mercury have fallen short of accommodating the global contraction that is required owing to cooling of the planet's interior. Mapping of folds and faults across Mercury's surface using MESSENGER spacecraft images reveals deformation consistent with a planet that has contracted radially as much as seven kilometres over its history.

Low levels of iron limit primary productivity across much of the Southern Ocean. Measurements of dissolved iron levels combined with hydrographic data suggest that much of the iron in the surface waters of the Southern Ocean is supplied by deep mixing during winter.

Breaking waves on the ocean surface generate air bubbles that yield sea spray aerosols when released to the atmosphere. Measurements of sea spray aerosols in the North Atlantic Ocean and the coastal waters of California suggest that the surface water organic carbon reservoir is responsible for the organic carbon enrichment of freshly emitted sea spray aerosol.

At least two-thirds of marine genera died out during the end-Permian mass extinction about 252 million years ago. An analysis of extinct and surviving taxa shows no substantial loss in global functional diversity, although there were significant losses in some settings such as tropical reefs.

Tropospheric ozone is a potent greenhouse gas, biological irritant and significant source of highly reactive hydroxyl radicals. Simulations with a chemistry climate model suggest that shifts in atmospheric circulation can account for the seasonally dependent trends in tropospheric ozone levels observed at Mauna Loa, Hawaii, over the past three decades.

The age of the Grand Canyon is fervently debated. Thermochronological reconstructions of canyon incision show that although parts of the canyon were carved more than 50 million years ago, two key segments formed less than 6 million years ago, implying that the canyon is a young feature.

Upwelling mantle plumes are thought to be sheared by the motions of the overlying tectonic plates. Seismic imaging of a hotspot beneath the Galápagos Islands, however, identifies a plume that is not deflected in the direction of plate motion and whose characteristics are instead controlled by multistage melting processes.

Several periods of massive iceberg discharge into the North Atlantic and widespread cooling marked the last glacial period. Reconstructions of northward flow along the Florida margin suggest that not all cold events were associated with a change in the strength of the Atlantic meridional overturning circulation.