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In our trial of a double-blind procedure for peer review, authors' awareness of their peer-review choices in the early stages of writing a paper is key for their decision to opt in or out.
Large quantities of methane lie trapped beneath the floor of the Arctic Ocean. Measurements in the southern Laptev Sea around the Lena River delta suggest that bubbles and storms facilitate the flux of some of this submarine methane to the atmosphere.
Runoff estimates from the Greenland ice sheet carry uncertainty because the fate of surface melt in permanently snow-covered regions is unconstrained. In situ and airborne observations reveal large-scale liquid water storage in buried layers of aged and compacted snow.
Relatively little is known about the dynamics of the Antarctic Circumpolar Current during the last glacial period. Estimates of current speeds over the past 20,000 years based on sediment grain size suggest that average flow speeds during the last glacial were comparable to modern speeds, but not in the areas with overlying winter sea ice.
Surface melt water from the Greenland ice sheet can become trapped in firn, delaying its journey to the sea. Radar and ice-core observations provide direct evidence of a perennial aquifer in the firn layer in southern Greenland that represents a potentially significant contribution to the Greenland mass budget.
Climate variations over the past 1,000 years correspond to solar fluctuations, but the magnitude of the solar variability is unclear. An analysis of numerical simulations and climate reconstructions suggests that the amplitude of solar forcing was small over this interval, with the main climate forcing derived from volcanic eruptions and greenhouse gas concentrations.
Part of the subduction zone plate interface beneath Costa Rica was previously locked, which allowed strain to accumulate. Analyses using GPS and geomorphic data show that almost the entire locked region ruptured during a megathrust quake in 2012, implying that plate-interface mapping towards the end of the earthquake cycle can aid seismic hazard assessments.
The metal content of magmas erupted at subduction zone arcs is thought to be derived from the mantle. A correlation between crustal thickness and copper content in arc magmas worldwide, however, reveals an important role for the crust in the upper plate.
Volcanic eruptions are often preceded by long-period seismic events that were thought to be generated by the resonance of cracks filled with magmatic fluid. Analysis and modelling of long-period seismicity at volcanoes in Italy, Costa Rica and Peru shows that it could instead be caused by slow rupture along faults in the upper volcanic edifice.
The characteristics of magmas typically associated with porphyry copper deposits are thought to be imparted in the mantle. Statistical assessment of over 40,000 geochemical analyses of magmatic rocks formed in subduction zones worldwide, however, shows that the characteristics of these magmatic rocks are systematically controlled by the thickness of the arc crust.
