Volume 8 Issue 5, May 2015

Subduction zone faults can slip slowly, generating tremor. The varying correlation between tidal stresses and tremor occurring deep in the Cascadia subduction zone suggests that the fault is inherently weak, and gets weaker as it slips.

Mountain glaciers around the world are in decay. According to a modelling study that — unusually — includes full ice flow physics, those in Western Canada will largely be restricted to the coastal region by the year 2100.

Titan's equatorial dunes seem to move in the opposite direction to the prevailing easterly winds. Infrequent methane storms at Titan's low latitudes may briefly couple surface winds to fast westerlies above, dominating the net movement of sand.

Analyses of ice-core carbon isotopes show that variations in atmospheric CO₂ levels during the past millennium are controlled by changes in land reservoirs. But whether climate variations or human activity were mainly responsible is uncertain.

El Niño diversity and its genesis are debated. An overview of existing work along with a fuzzy clustering analysis and simulations suggest that the asymmetry, irregularity and extremes of El Niño result from westerly wind bursts.

An iris effect in tropical cloud-cover was controversially proposed as a negative climate change feedback that is not represented in climate models. If such an effect exists, it could go some way to reconciling climate models and observations.

Mercury’s surface is darker than expected given its low iron content. The delivery of cometary carbon to Mercury in micrometeorite impacts may explain the planet’s globally low reflectance.

Liquid water on equatorial Mars is inconsistent with large-scale climatic conditions. Humidity and temperature measurements by the Curiosity rover support the formation of subsurface liquid brines by hydration of perchlorates during the night.

Titan’s equatorial dunes propagate eastwards, whereas Titan’s surface winds blow towards the West. Atmospheric simulations suggest that tropical methane storms generate strong eastward gusts that may dominate sand transport on Titan’s surface.

Forests may be vulnerable to future droughts. A tree mortality threshold based on plant hydraulics suggests that increased drought may trigger widespread dieback in the southwestern United States by mid-century.

The glaciers in western Canada are experiencing rapid mass loss. Projections of their fate with a model that couples physics-based ice dynamics with a surface mass balance model suggest that glacier volume will shrink by 70% by 2100.

Methanotrophic bacteria can consume methane emitted from the ocean floor before it reaches the atmosphere. Variations in coastal currents can reduce methane oxidation in the ocean by limiting methanotroph residence time above methane seeps.

Atmospheric CO₂ concentrations varied on multidecadal timescales over the past millennium. Measurements of the carbon isotope composition of ice core CO₂ suggest climate-driven changes in land carbon stores caused these fluctuations.

Continental breakup can occur with or without extensive magmatic activity. Numerical simulations show that magmatic and amagmatic rifts can develop in the same tectonic setting, if a rising mantle plume is deflected to one side of the continent.

The Hawaiian–Emperor volcanic chain has a distinctive bend. Geochemical analyses show that lavas erupted on the ocean floor close to the bend formed during deformation of the Pacific Plate, implying the bend was caused by changes in plate motion.

Over the past 140 years, planet-encircling storms have occurred on Saturn about every 30 years. A sufficiently wet troposphere can explain the suppression of moist convection and storm recurrence interval on Saturn.

Fluid transport in subduction zones is complex. Geochemical analysis of lavas from the Cascade Arc shows that dehydration of the deep slab interior can trigger melting in the outer part of the subducting slab in young, hot subduction zones.

At subduction zones, deep parts of the fault can slip slowly, generating tremor. Analysis of tremor in Cascadia reveals increasing sensitivity of slip to tidal stresses over several days, implying that the fault is weak, and weakens as it slips.