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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.
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.
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.
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.
The release of carbon dioxide during biological carbonate production counters carbon uptake by phytoplankton. The carbon chemistry of sinking particles in the Southern Ocean suggests that iron availability stimulates this carbonate counter pump.
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.
Proposed engineering projects in the Amazon Basin would disrupt sediment supplies to lowland rivers. Landsat imagery of Amazonian tributaries reveals that lower sediment loads are associated with lower meander migration and cutoff rates.
Some of the most devastating earthquakes are generated in subduction zones. Analysis of the stress state of subduction zones worldwide suggests that large earthquakes are generated more frequently where a young, buoyant plate subducts.
Today, arsenic metabolism occurs in some anoxic aquatic systems. Geochemical analyses of 2.7-billion-year-old stromatolites show evidence of microbial arsenic cycling in a saline, shallow marine system.