Volume 9 Issue 9, September 2016

Climate change is causing widespread permafrost thaw in the Arctic. Measurements at 33 Arctic lakes show that old carbon from thawing permafrost is being emitted as methane, though emission rates have not changed during the past 60 years.

The sources contributing to the deglacial rise in atmospheric CO₂ concentrations are unclear. Climate model simulations suggest thawing permafrost soils were the initial source, highlighting the vulnerability of modern permafrost carbon stores.

The Himalaya grow as India and Eurasia collide. Analyses of deformation during the 2015 Gorkha earthquake suggest that slip on small-scale splay faults, as well as motion during the interseismic period, help to create Earth's highest mountains.

Volcanic eruptions can release large amounts of climatically active gases. An emerging view stresses the role of the size and chemical composition of the plume, including its water content, in controlling the climatic effects of an eruption.

Extratropical storms contribute to precipitation, wind and temperature extremes. A synthesis of the influences of a changing climate on storm tracks reveals competing effects on meridional temperature gradients, which make projections difficult.

The Moon has a tenuous exosphere and dust-sized particles have been detected. Analysis of spectral observations by the LADEE spacecraft suggests that the Moon also has a spatially and temporally variable exosphere of nanodust particles.

Global mean surface temperature change over the past 120 years resembles a rising staircase. Simulations with a coupled ocean–atmosphere model reveal that the tropical Pacific Ocean is the pacemaker of variable warming rates.

Biomass turnover time is a key parameter in the global carbon cycle. An analysis of global land-use data reveals that biomass turnover is almost twice as fast when the land is used to enhance terrestrial ecosystem services.

Warming thaws permafrost, releasing carbon that can cause more warming. Radiocarbon, soil carbon, and remote sensing data suggest that 0.2–2.5 Pg of carbon has been emitted from permafrost as CO₂ and CH₄ around Arctic lakes since the 1950s.

Atmospheric CO₂ concentrations rose during the last deglaciation, but the carbon sources are unclear. Climate and carbon cycle simulations suggest that permafrost melting was the main source of carbon between 17,500 and 15,000 years ago.

Rivers transport terrestrial organic carbon. Ancient molecular markers of methanogens and radiocarbon data from offshore sediments suggest that much of this carbon in the Congo River is aged, and that hydrology controls the amount transported.

Land carbon uptake reduced atmospheric CO₂ levels during the Little Ice Age. Numerical simulations of atmospheric carbonyl sulfide levels and ice-core carbon isotope data reveal that temperature change, not land-cover change, was responsible.

Whether fast and slow earthquakes nucleate in the same way is unclear. Laboratory simulations of fast and slow slip reveal similar precursor seismic signals for both modes, suggesting the same physical mechanisms may govern both types of slip.

Most oceanic crust is subducted back into Earth’s mantle within 200 million years of formation. Analysis of magnetic data from the eastern Mediterranean reveals oceanic crust formed up to 340 million years ago, as part of an ancient ocean basin.

Rivers crossing zones of active uplift can bevel broad alluvial platforms. Experiments suggest that competition between lateral channel mobility and uplift rate controls the ability of a river to flatten the landscape.

The Himalaya grow as the Indian Plate is thrust beneath Tibet. Analysis of surface deformation caused by the 2015 Gorkha earthquake suggests slip on smaller-scale faults at the foot of the high Himalaya help build Earth’s highest peaks.

Subduction zones consume seafloor carbonates. Laboratory experiments on carbonate fault gouge from the Costa Rican subduction zone show that carbonates weaken with increasing temperature and pore-fluid pressure, and may nucleate earthquakes.

The origin of large-scale mantle heterogeneities remains enigmatic. Experiments show that different oxygen fugacities lead to density differences in lower-mantle materials, which lead to a heterogeneously oxidized mantle in simulations.