Articles in 2013

Earth’s crust is thought to eventually rebound following an earthquake so that deformation is not permanent. Field analysis in the Atacama Desert, northern Chile, however, identifies numerous large cracks in the crust, implying that the crust here has been permanently deformed by thousands of earthquakes that have occurred over the past million years.

The Antarctic Peninsula is one of the most rapidly warming regions on Earth. A reconstruction of ice melt from an ice core taken near the northeastern tip of the peninsula over the past 2,000 years shows that surface melt has accelerated during the twentieth century.

The sea floor at the easternmost Southwest Indian mid-ocean ridge is smooth, unlike that at other mid-ocean ridges. Sonar imaging and analysis of rock samples show that the sea floor here is composed almost entirely of sea-water-altered mantle rocks that have been brought to the surface by large faults on both sides of the ridge axis over the past 11 million years.

Lunar samples suggest that the inner Solar System was bombarded by asteroids about 4 Gyr ago. Radiometric ages of meteorites suggest an unusual number of high-velocity asteroids at this time, consistent with a dynamical origin of the bombardment in which the asteroids were pushed by outer planet migration onto highly eccentric orbits.

Nitrite, a central intermediate in the marine nitrogen cycle, accumulates at the base of the sunlit surface ocean. Isotopic measurements suggest that ammonia oxidation is the primary source of nitrite in the primary nitrite maximum in the Arabian Sea.

Antarctic Bottom Water fills much of the global abyssal ocean, and is known to form in three main sites in the Southern Ocean. Data from instrumented elephant seals and moorings suggest an additional source of bottom-water formation in the Cape Darnley polynya that is driven by sea-ice production.

Oxygen minimum zones account for a significant fraction of oceanic nitrogen loss. Observational and experimental data suggest that marine nitrogen loss is strongly tied to organic matter export in the South Pacific oxygen minimum zone.

The subsurface of Mars could potentially have contained a vast microbial biosphere. An evaluation of the possibility of groundwater upwelling, which might provide clues to subsurface habitability, reveals evidence in the deep McLaughlin crater for clays and carbonates that probably formed in an alkaline, groundwater-fed lacustrine setting.

Uptake of atmospheric carbon dioxide in the subpolar North Atlantic Ocean declined rapidly between 1990 and 2006. An analysis of oceanographic data suggests that the slowdown of the meridional overturning circulation was largely responsible.