Volume 9 Issue 7, July 2016

After more than a decade exploring Saturn and its moons, the Cassini mission is in its closing act. Cassini's last year is an encore performance stuffed with science, including a final plunge into Saturn's atmosphere.

Ethane emissions can lead to ozone pollution. Measurements at 49 sites show that long-declining atmospheric ethane concentrations started rising in 2010 in the Northern Hemisphere, largely due to greater oil and gas production in the USA.

Anomalously bright spots are seen on the dark cratered surface of the dwarf planet Ceres. The Dawn spacecraft's detection of sodium carbonates in bright areas is consistent with aqueous activity in an ice-poor and salty regolith.

Soil carbon stocks depend on inputs from decomposing vegetation and return to the atmosphere as CO₂. Monitoring of carbon stocks in German alpine soils has shown large losses linked to climate change and a possible positive feedback loop.

A weakening of the Atlantic meridional overturning circulation has emerged from noise after years of painstaking measurements. Three independent lines of evidence suggest that an anthropogenic influence on this overturning is not yet detectable.

Two large zones through which seismic waves travel unusually slowly are found at the base of Earth's mantle. These zones are thermally and chemically distinct from the surrounding mantle and may be a source for mantle plumes.

Atmospheric non-methane hydrocarbon concentrations began declining in the 1970s. Surface and column measurements show that Northern Hemisphere ethane concentrations are now rising, probably due to North American oil and natural gas emissions.

Sulfur dioxide is a key air contaminant. A satellite-based emissions inventory reveals a number of hitherto unknown sources, with a cluster around the Persian Gulf, and identifies large discrepancies with conventional inventories in some regions.

Organic carbon decays as it travels through inland waters from soils to the sea. Analysis of data from across the continuum of inland and marine aquatic systems reveals that the rate of organic carbon decay depends on water retention time.

Eastern boundary coastal upwelling systems are locations of high ocean productivity. Numerical simulations reveal that wind alters current- and eddy-driven nutrient supply, which affects net primary productivity in the California Current system.

The North Atlantic Oscillation has varied markedly on multidecadal timescales. Analyses of climate simulations show that these variations have contributed to Arctic sea ice loss, Northern Hemisphere warming and tropical storm activity.

The mid-1990s’ warming of the North Atlantic subpolar gyre was probably related to strengthened overturning. Observations and numerical models suggest that a climate reversal to a cooling trend occurred around 2005.

The Atlantic meridional overturning circulation has weakened over the past decade. Examination of a global reanalysis that matches independent observations shows that the decline is consistent with recovery from an earlier invigoration.

Freshwater release from melting polar ice could weaken the Atlantic overturning circulation. Eddy-resolving ocean simulations reveal that the freshening has not yet significantly affected meridional overturning, but an effect may emerge soon.

Meltwater runoff from the Greenland ice sheet alters ocean surface salinity. Numerical simulations show that meltwater from southeastern Greenland is transported to the Labrador Sea more efficiently than that from southwestern Greenland.

Great Himalayan earthquakes are rare. Analysis of surface motions in the months after the 2015 Gorkha earthquake reveals negligible aseismic slip, implying that stress may be stored in the crust to be tapped during future great earthquakes.

The dwarf planet Ceres is thought to have an ice-rich layer in its shallow subsurface. The morphologies of craters, however, suggest little relaxation by viscous flow has occurred and instead indicate a subsurface that is less than 40% ice.

Soil carbon concentrations are sensitive to climate warming. Pairs of measurements of forest soil carbon stocks in the German Alps reveal that topsoil carbon concentrations declined as air temperatures rose between 1976 and 2011.

Unlike the Arctic, the Southern Ocean has shown little warming. An analysis of observations and numerical simulations suggests that Southern Ocean warming patterns are shaped by meridional overturning more than surface heating.

The fate of the Indian plate during collision with Asia is debated. Seismic images of the western Himalaya reveal large-scale thrust faults that transfer Indian crust upwards, into the overriding Asian plate.