The exchange of water across the Antarctic continental shelf break brings warm waters towards ice shelves and glacier grounding lines. Ocean glider observations reveal that eddy-induced transport contributes significantly to this exchange. The image shows the deployment of a Seaglider in the northwestern Weddell Sea in January 2012.

Letter p879

IMAGE: ANDREW THOMPSON

COVER DESIGN: DAVID SHAND

Solar dimming from aerosols has the potential to reduce surface evaporation. A detection analysis suggests that through this effect, river flow increased by up to 25% in the most heavily polluted regions of Europe around 1980. The image shows air pollution over the river Rhine near Duisburg, Germany on 20 October 2007.

Letter p796

IMAGE: © IMAGEBROKER/ALAMY

COVER DESIGN: DAVID SHAND

Plants may enhance sedimentation and help deltas to keep up with rising sea levels. Numerical simulations show that intermediate vegetation height and density are optimal, whereas too much vegetation inhibits sediment deposition in deltaic marshes. The image shows freshwater marsh vegetation in Wax Lake Delta, Louisiana, in June 2014.

Letter p722

IMAGE: ELIZABETH OLLIVER

COVER DESIGN: DAVID SHAND

Narrow river gorges are often shortlived features. Images of a bedrock gorge in Taiwan, which was carved after 1999,reveal rapid widening where the upstream floodplain meets the gorge, an erosional front that propagates downstream as the gorge is erased. The image shows the upper section of the Daan River gorge in March 2009, when this reach was still actively incising.

Article p682; News & Views p624

IMAGE: KRISTEN L. COOK

COVER DESIGN: DAVID SHAND

The formation and preservation of sandstone landforms such as pillars and arches are enigmatic. Experiments and numerical modelling show that load-bearing material weathers more slowly, and thus the internal stress field can shape and stabilize sandstone landforms. The image shows Double Arch at Arches National Park in Utah, USA at night.

Letter p597; News & Views p552

IMAGE: MARSEL VAN OOSTEN

COVER DESIGN: DAVID SHAND

The factors that control the submarine melt rate at Greenland's glaciers are uncertain and largely inferred from brief summer surveys in the fjords where glaciers terminate. Continuous records of water properties and velocity for the months September to May from two large Greenland fjords reveal strong variability on 3- to 10-day timescales as a result of pulses of water that are propagated from the shelf ocean. The image shows an iceberg in Sermilik Fjord on Greenland's southeast coast, in August 2013. The iceberg is a fragment of Helheim Glacier that has calved into the ocean.

Letter p503

IMAGE: MAGDALENA ANDRES

COVER DESIGN: DAVID SHAND

Ethanol-based vehicles are thought to generate less pollution than gasoline-based vehicles. An analysis of pollutant concentrations in the subtropical megacity of São Paulo, Brazil, reveals that levels of ozone pollution fell, but levels of nitric oxide and carbon monoxide rose, during periods of prevailing gasoline use relative to ethanol use. The image shows part of the São Paulo cityscape.

Article p450; News & Views p395

IMAGE: © LAZYLLAMA / ALAMY

COVER DESIGN: DAVID SHAND

The balance between carbonate subduction into the deep Earth and CO2 release through degassing at volcanoes is critical for the carbon cycle. Geochemical analyses of an exhumed subduction zone complex in Greece show that fluidmediated reactions could liberate significant amounts of carbon from the subducting slab for later release at arc volcanoes. The image shows crystals of epidote, several millimetres in length, in crosspolarized light. The crystals are from a quartz vein on Tinos island, Greece, that facilitated fluid infiltration and carbonate mineral dissolution.

Letter p355; News & Views p333

IMAGE: JAY J. AGUE

COVER DESIGN: DAVID SHAND

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. The image shows a 270-km-long lobate scarp named Carnegie Rupes, looking southeast. The scarp cross-cuts Duccio crater on Mercury. High elevation is shown in red, low elevations are blue.

Article p301; News & Views p251

IMAGE: NASA / JOHNS HOPKINS UNIV. APPLIED PHYSICS LAB. / CARNEGIE INST. WASHINGTON

COVER DESIGN: DAVID SHAND

The 2011 eruption of a 20-km-high volcanic plume from Grímsvötn Volcano, Iceland, led to the closure of northern European airspace. Geodeticmeasurements from the volcano reveal a correlation between plume height, surface deformation and magma-chamber pressure, implying that volcanic plume behaviour can be predicted before eruption onset. The image shows the Grímsvötn volcanic plume on 21 May 2011, at an altitude of about 10,000 feet and within an hour of the start of the eruption. The aircraft is a 4-seat Piper Cherokee Warrior.

Article p214; News & Views p168

IMAGE: OLAFUR SIGURJONSSON

COVER DESIGN: DAVID SHAND

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. The image shows lava and spatter issued on 27 October 2005 from two separate vents at Sierra Negra, one of the most active and voluminous volcanoes that overlie the Galápagos mantle plume.

Article p151

IMAGE: DENNIS GEIST

COVER DESIGN: DAVID SHAND

Dark streaks that appear on the surface of Mars during warm seasons have been observed at the mid-latitudes and tentatively attributed to the flow of briny water. Imagery from the Mars Reconnaissance Orbiter over multiple Mars years suggests that these seasonally active features are also present in equatorial regions, where liquid surface water is not expected. The image shows dark, narrow flows called recurring slope lineae that are more than 1 km long in this portion of Eos and Capri Chasma in eastern Valles Marineris, Mars. The image is in enhanced infrared-shifted colour, and downhill is to the right or the bottom.

Article p53

IMAGE: NASA/JPL/UNIVERSITY OF ARIZONA

COVER DESIGN: DAVID SHAND