Research articles

Decadal- to centennial-scale variability has been identified in the Arctic Oscillation, but less is known about variations on the millennial scale. A record of sea-ice drift from off the Alaskan coast shows a 1,500-year cycle in the phase of the Arctic Oscillation.

Episodes of ice sheet disintegration and meltwater release over glacial–interglacial cycles are recorded in the sediments of the Labrador Sea. Analyses of sediment cores along the Labrador and Greenland margins reveal a layer of red material that was probably carried to the Labrador Sea during a glacial outburst flood through the Hudson Strait, early in the last interglacial period.

Above an altitude of about 50 km, carbon dioxide is the primary radiative cooling agent. Carbon dioxide and carbon monoxide mixing ratios derived from satellite-based solar occultation spectra document an estimated increase in global CO_x concentrations of about 23.5 ppm per decade at an altitude of 101 km.

The nearside and farside of the Moon are compositionally distinct. The detection of low-calcium pyroxene around large impact basins suggests that the huge Procellarum basin on the nearside may be an ancient impact structure and a relic scar of the violent collision that produced the lunar dichotomy.

Recent changes in the Southern Annular Mode are associated with warmer, drier conditions in the Southern Hemisphere. An analysis of tree-ring records there suggests that these changes have significantly altered tree growth.

In spring 2011, a record-breaking flood necessitated diversion of water from the lower Mississippi River to the Atchafalaya River Basin. A comparison between the dynamics in the two basins based on field-calibrated satellite observations and in situ data suggests that river-mouth dynamics and wetland sedimentation are directly linked.

Earthquake rupture is influenced by stress conditions in the crust before the quake. Analysis and modelling of surface deformation caused by the May 2011 earthquake in Lorca, Spain, indicate that groundwater extraction influenced the pattern of fault rupture.

Over the past decade, Kīlauea and Mauna Loa—adjacent volcanoes in Hawai‘i—have inflated and deflated in tandem, yet their shallow volcanic plumbing systems are separate. Numerical modelling of the volcanoes shows that dynamic stress transfer by asthenospheric pore pressure is a viable mechanism for volcano coupling in Hawai‘i.

Marine ice streams whose beds deepen inland are thought to be inherently unstable. Numerical modelling of the Maguerite Bay ice-stream retreat in West Antarctica since the Last Glacial Maximum suggests that an ice stream can stabilize on an inland-sloping bed owing to increased lateral drag where the ice stream narrows.

During the Last Glacial Maximum, the pattern of Atlantic Meridional Overturning Circulation was different from today. A combination of sediment chemistry and a scavenging model suggests that the glacial circulation was shallower and at least as vigorous as today.

Over the past few years, it has become clear that the Moon’s surface is not entirely dry. The direct identification of hydroxyl in glasses produced in lunar soils by the impact of micrometeorites supports the idea that water was delivered to the lunar surface by the solar wind.

The Atlantic Ocean has been suggested as an important driver of variability in European climate on decadal timescales. Analyses of ocean and atmosphere temperature data from observations suggest that the shift in European climate during the 1990s was a result of warming in the North Atlantic Ocean.

Subtropical high-pressure systems influence atmospheric circulation and global climate. Model simulations and reanalysis data suggest that summertime high pressure systems in the Northern Hemisphere subtropics will intensify as a result of climate change.

The last glacial period was marked by rapid reorganizations of oceanic and atmospheric circulation. Speleothem records from the Amazon Basin suggest that precipitation variability was linked to these events.

Life on land dates back at least 2.7 billion years, but the effects of this early terrestrial biosphere on biogeochemical cycling are poorly constrained. Marine sulphur data and geochemical modelling suggest that microbial pyrite weathering has transferred a substantial amount of sulphur to the oceans for at least 2.5 billion years.

The North Atlantic Oscillation influences climate in the Arctic region and northern Europe. Reconstructions of circulation patterns associated with the North Atlantic Oscillation from a 5,200-year-long lake sediment record suggest that the atmospheric circulation responded to significant transitions in Northern Hemisphere climate.

Stratospheric circulation is known to affect weather in the troposphere. Climate modelling reveals a connection between variations in the stratospheric and North Atlantic ocean circulation over the past 30 years, and demonstrates that the stratosphere is an important component of climate over multidecadal timescales.

Glaciers store and transform organic carbon, which, on release, could support downstream microbial life. An analysis of 26 glaciers in the European Alps suggests that a significant fraction of glacier organic matter is available for microbial consumption.

Seamount chains in the southeast Atlantic Ocean are thought to have formed above plumes sourced from the deep mantle. Dating of lavas erupted along the trails show that the formation and distribution of the seamount chains is also controlled by the motion and structure of the African Plate.

Precipitation extremes increase in intensity over many regions of the globe in simulations of a warming climate, but not always consistently. Observational constraints, together with a close relationship between model responses to interannual variability and climate change, suggest a high sensitivity of tropical extreme precipitation to warming.