Volume 9 Issue 5, May 2016

The Paris Agreement introduced three mitigation targets. In the future, the main focus should not be on temperature targets such as 2 or 1.5 °C, but on the target with the greatest potential to effectively guide policy: net zero emissions.

Phosphorus is essential for food production, but it is also a key cause of eutrophication. Estimates of phosphorus flux for the past 40–70 years reveal that large river basins can experience phases of phosphorus accumulation and depletion.

Rockfall often seems to occur spontaneously without an obvious cause. Monitoring of a granitic cliff reveals that cyclical temperature variations can subtly act to slowly and incrementally damage hard rock until failure is inevitable.

Coastlines above subduction zones slowly emerge from the sea despite repeated drowning by great, shallow earthquakes. Analysis of the Chilean coast suggests that moderate-to-large, deeper earthquakes may be responsible for the net uplift.

Volatile organic compounds can affect air quality and climate. Experimental warming of vegetated tundra plots in Greenland increased biogenic volatile organic compound emissions from vegetation and soils by 260%, as a direct effect.

Phosphorus fertilizer use has roughly quadrupled in the past century. Budgets constructed from historical data show that phosphorus rapidly accumulates in river basins during periods of high inputs and continues to mobilize after inputs decline.

Anammox, an important N₂ loss pathway in marine waters, is not well understood in rivers. In situ measurements of N₂ production in UK rivers reveal that anammox can be the dominant N₂ loss pathway in permeable but not in impermeable riverbeds.

Uptake of atmospheric CO₂ contributes to ocean acidification. Measurements of seawater chemistry reveal that the extreme acidity of the East Siberian Arctic Shelf is driven by terrestrial organic matter and freshwater inputs.

Basal melting is widespread in the north-central Greenland ice sheet. Geophysical data and numerical modelling suggest a geothermal anomaly in this region resulting from the earlier passage of Greenland over the Iceland mantle plume.

Localized subglacial zones of high traction help to regulate ice sheet flow. Geophysical data from a palaeo-ice-stream suggest that methane gas accumulation and hydrate formation beneath ice sheets can produce such high-traction sticky spots.

Northern Hemisphere ice sheets expanded 2.7 million years ago. Sediment geochemistry suggests that at this time, the North Atlantic began to experience incursions of southern-sourced water during glacials, similar to the last glacial period.

Megathrust earthquakes rupture the shallow plate boundary in subduction zones. Analysis of seismic activity preceding megathrust quakes in Japan and Chile reveals deep seismicity that may mark plunging of the slabs prior to main fault rupture.

The mechanisms for mantle hydration are unclear. Seismic images offshore from Spain reveal a correlation between the amount of seawater-altered rocks and the extent of fault slip, suggesting that faults control water flux into the Earth.

Extreme summer temperatures are difficult to forecast. A statistical analysis reveals a pattern of Pacific sea surface temperature anomalies that provides skilful predictions of hot weather in the eastern US.

Some rockfalls occur without obvious triggers such as seismicity or freeze–thaw conditions. Temperature and deformation patterns on a granite cliff suggest that cyclical thermal forcing can progressively open fractures and trigger rockfalls.

Coastlines above subduction zones often uplift over geological timescales. Analysis of landscape evolution and seismicity at the central Andean margin suggests that earthquakes on the deep plate interface help build up coastal topography.