Research articles

Tidal dissipation in the Moon depends on the lunar tidal period. Numerical modelling of the Moon’s response to tidal forces suggests that tidal dissipation is localized in an ultralow-viscosity zone at the core–mantle boundary.

The geochemical variability of lavas erupted at mid-ocean ridges is lowest where plate spreading rates are high, implying that large-scale plate motions mix the mantle—yet lavas erupted at slow-spreading ridges are also quite homogeneous. Numerical simulations suggest that small-scale convection in the mantle mixes and homogenizes the lavas erupted at slow-spreading ridges.

The formation and preservation of sandstone landforms such as pillars and arches is enigmatic. Experiments and numerical modelling show that load-bearing material weathers more slowly, and thus the internal stress field can shape and stabilize sandstone landforms.

Despite the role that calving plays in Greenland mass loss, the mechanisms of calving are poorly constrained. Observations of Greenland’s Helheim Glacier suggest that buoyant flexure at the glacier terminus leads to the propagation of basal crevasses and iceberg calving.

Precipitation in austral autumn and winter has declined over parts of southern and southwestern Australia. Simulations with a high-resolution climate model reproduce many aspects of the observed rainfall decline as a response to anthropogenic changes in atmospheric levels of greenhouse gases and ozone, and project significant further drying for southwest Australia over the twenty-first century.

In the Southern Ocean, deep-water masses of the world ocean upwell to the surface and subsequently sink to intermediate and abyssal depths in two overturning cells. Observational evidence relates changes in abyssal mixing—a key influence on the lower cell—to oceanic eddy variability.

Whether a precipitation event leads to flooding depends on the watershed’s wetness. A case study of the 2011 Missouri River floods demonstrates that the predisposition of a river basin to flooding can be inferred from satellite-based gravity data months in advance.

Unlike the other terrestrial planets, Mercury has a relatively thin silicate mantle. Numerical and statistical models suggest that Mercury and other metallic planetary bodies could be survivors of accretion that had their mantles stripped in collisions with larger impactors.

Sea surface temperatures in the tropical oceans were thought to have remained stable during a period of warmth about five million years ago. Reconstructions of the sea surface temperature from the Caribbean and Pacific suggest that tropical temperatures have in fact changed in concert with global mean temperatures over the past five million years.

The ratio of the refractory lithophile elements niobium and tantalum in the silicate Earth is anomalously low. Partitioning experiments suggest that the ratio of these elements is controlled by oxygen fugacity, and thus can be used to constrain the redox conditions of planetary accretion and core formation.

The factors that control the submarine melt rate at Greenland’s glaciers are uncertain and largely inferred from brief summer surveys in the fjords where glaciers terminate. Continuous records of water properties and velocity for the months September to May from two large Greenland fjords reveal strong variability on 3- to 10-day timescales as a result of pulses of water that are propagated from the shelf ocean.

As northern summer solstice nears on Saturn’s moon Titan, dynamic processes on its surface are expected. Recent observations by the Cassini spacecraft reveal transient bright features in or on a Titan sea that are consistent with an ephemeral phenomenon such as waves.

When basal meltwater refreezes, the resulting warm ice can influence the flow dynamics of the ice sheet above. An analysis of airborne gravity and radar data identifies extensive basal-ice units across the northern Greenland ice sheet that coincide with areas of deformed ice and fast ice flow.

Topographic relief continued to develop in the Appalachian Mountains, eastern USA, long after the tectonic forces that created the range had become inactive. Numerical modelling and reconstructions of sediment deposition in the Gulf of Mexico suggest that the topographic relief was rejuvenated by subsidence-induced differential erosion caused by sinking of the subducted Farallon slab in the underlying mantle.

The albedo of the Greenland ice sheet has declined in recent years. Analyses of satellite data, combined with numerical simulations, suggest that Greenland’s darkening is tied to an increase in the impurity content of snow.

Marine sediments deposited beneath the eastern Pacific upwelling margin are a substantial sink for silica. The geochemistry of these sediments suggests that periods of intense upwelling result in iron limitation, which enhances the export of silica from the surface to the deep ocean and sediments.

Giant volcanic eruptions occur when large volumes of magma accumulate in crustal reservoirs and do not cool and crystallize to form a solid pluton of rock within the crust. Geochronological dating of a pluton from Elba, Italy, shows that the magma solidified in the crust within just 10–40 thousand years of being injected into the crust, implying that the time window for an eruption was short.

The hydrological response to climate forcing during the past 25,000 years varied throughout the Indo-Pacific warm pool region. Marine sediment records suggest that during the Last Glacial Maximum, drying in northeast Borneo did not result in a vegetation shift, whereas the development of a severe dry season on Sumba led to water stress and the expansion of herby vegetation.

The high elevation in Earth’s topography of hard rocks, such as granites and basalts, was thought to be caused by their inherent resistance to erosion. Numerical modelling now demonstrates, counterintuitively, that erosion-induced isostatic rebound of rocks, which is density dependent, causes granites and basalts to occupy high elevations because they are more dense than surrounding rocks.

The Brady soil body was buried by loess deposits as a result of early Holocene climate change. Geochemical analyses suggest that large amounts of organic carbon were trapped in this soil as a result of fire activity and slow decomposition resulting from rapid burial.