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The composition of mid-ocean ridge basalts varies with the properties of the mantle that feeds the ridges. Thermodynamic calculations of melt evolution suggest that most of the mantle melting occurs by an overlooked mechanism, focused melting.
Most dissolved organic carbon in rivers originates from young carbon in soils and vegetation. A global radiocarbon data set suggests that human disturbance is also introducing aged carbon to rivers and to active carbon cycling.
Global temperatures rose quickly between 1910 and 1940. A reconstruction based on corals suggests that the Pacific trade winds were weak during this period of rapid warming, but strengthened as warming slowed in the following decades.
The release of massive amounts of carbon led to abrupt warming 55.5 million years ago. An analysis of soil carbonates shows two distinct carbon injections at the event onset, each releasing over 0.9 petagrams of carbon per year over hundreds to thousands of years.
Increasing CO2 concentrations are expected to increase plant growth and water efficiency. Tree-ring data covering 150 years from tropical forests show that water-use efficiency has increased with CO2 concentrations but tree growth has not.
Some of the glacial CO2 drawdown has been attributed to CO2 storage in the deep Pacific and Southern oceans. Reconstruction of apparent oxygen utilization suggests that respired CO2 storage was also enhanced in the deep northeast Atlantic.
Atmospheric phosphorus contributes to terrestrial biogeochemical cycles. Estimates of phosphorus emissions from combustion suggest that anthropogenic emissions represent more than 50% of atmospheric sources of phosphorus.
High Arctic soils can act as sources or sinks of methane. Scaled-up field measurements suggest that northeast Greenland’s ice-free soils currently act as a net sink for methane, and may take up more methane with rising temperatures.
Linear sand dunes on equatorial Titan are shaped by winds. The morphologies of smaller dunes that have been reoriented with respect to the linear dune crests suggest that winds shift with long-term orbitally driven climate cycles on Titan.
Plumes are thought to transport water-rich material from the deep mantle to Earth’s surface. High-pressure experiments identify a hydrous mineral phase that is stable under lower-mantle conditions and could provide a source for this water.
Nitrous acid cycling contributes significantly to the atmospheric oxidation capacity. Flow tube experiments and field monitoring reveal a night-time nitrous acid sink in soils, and subsequent release during the day.
Helium-4 is produced in the Earth’s crust and degassed to the atmosphere. Measurements of 4He and 81Kr dating in an aquifer in Brazil suggest that most crustal 4He reaches the atmosphere by the discharge of deep groundwater at the surface.
Transient global warming is nearly proportional to cumulative carbon emissions. A theoretically derived equation shows that this relationship stems from the partially opposing climate effects of oceanic uptake of heat and carbon.
The ratio of carbon to phosphorus in marine phytoplankton biomass varies by ecosystem. Biogeochemical modelling suggests that organic carbon exported to depth shows similar variations in stoichiometry.
The elemental composition of marine organic matter varies systematically at large scales. Simulations of the ocean circulation and observations of ocean chemistry reveal close links between light and nutrient availability and stoichiometry.
In situ measurements of sea-ice thickness off Antarctica have limited spatial coverage. Surveys of ten floes by autonomous underwater vehicles suggest that Antarctic sea ice is thicker and more deformed than previously thought.
Earth’s deep carbon cycle is poorly constrained. Theoretical calculations suggest that large amounts of carbon are returned to Earth’s surface as organic and inorganic carbon ions dissolved in subduction-zone fluids.
Evidence for liquid water on the ancient Martian surface is at odds with a presumably cold climate. Aerosol modelling shows that warming by sulphur-bearing gases during episodes of volcanism could have supported liquid water for decades.
Calving margins are highly sensitive to changes in climate and glacier terminus geometry. Numerical modelling suggests that calving glacier termini are self-organized critical systems that are fluctuating between states of advance and retreat.
Ridges on the seafloor near Iceland form when hot mantle pulses through an underlying plume. Seismic data show that the frequency of ridge formation decreased about 35 million years ago implying a change in the thermal state of the plume source.