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Role of biogenic silica in the removal of iron from the Antarctic seas
Iron plays a key role in controlling biological production in the Southern Ocean, yet mechanisms regulating iron availability are not completely understood. Here, Ingall et al.show that structural incorporation of reduced, organic iron into biogenic silica represents a new and substantial removal pathway.
- Ellery D. Ingall
- , Julia M. Diaz
- & Jay A. Brandes
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| Open AccessHuman deforestation outweighs future climate change impacts of sedimentation on coral reefs
Forest cover up-river influences the sediments reaching coral reefs, but how this relationship is affected by future climate change is not clear. In a study of the Malagasy coral reefs, Maina et al.find that regional land-use management is more important than mediating climate change for reducing reef sedimentation.
- Joseph Maina
- , Hans de Moel
- & Jan E. Vermaat
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Inferred time- and temperature-dependent cation ordering in natural titanomagnetites
Cation ordering in cubic-structured oxides can strongly affect magnetic properties. Here, the authors show that in some natural titanomagnetites, large and reversible changes in Curie temperature result from annealing at moderate temperatures (350–400 °C), most likely arising from changes in cation ordering.
- Julie A. Bowles
- , Mike J. Jackson
- & Jeffrey S. Gee
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A new Late Triasssic phytogeographical scenario in westernmost Gondwana
In the Late Triassic, southern Gondwanan flora is thought to have been dominated by endemic species mainly restricted to eastern areas with some mixing with northern species. In this study, pollen and spore assemblages from Argentina reveal the presence of these mixed flora in the westernmost Gondwana as well.
- Silvia N Césari
- & Carina E Colombi
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| Open AccessDevelopment of Middle Stone Age innovation linked to rapid climate change
The South African archaeological record contains evidence of the early flourishing of the human mind. Ziegler et al. provide new paleoclimate reconstructions, which suggest that rapid fluctuations in global climate have played a key role in the evolution of these early human cultures.
- Martin Ziegler
- , Margit H. Simon
- & Rainer Zahn
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Pyroclastic passage zones in glaciovolcanic sequences
Subglacial volcanoes host passage zones that can be used to define high stands of englacial lakes and paleo-ice thickness. This study identifies a pyroclastic passage zone in a subglacial volcano, which may help calculate transient paleolake levels and improve estimates of paleo-ice thickness.
- James K. Russell
- , Benjamin R. Edwards
- & Lucy A. Porritt
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Discovery of seifertite in a shocked lunar meteorite
Few high-pressure polymorphs have been found from lunar meteorites even though the moon has experienced heavy meteorite bombardment. This study presents evidence of a high-pressure polymorph of silica—seifertite—from a lunar meteorite; a record of an intense planetary collision on the moon ~2.7 Ga ago.
- Masaaki Miyahara
- , Shohei Kaneko
- & Naohisa Hirao
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Biological carbon precursor to diagenetic siderite with spherical structures in iron formations
The role of bacteria in the origin of iron formations (IF) remains unclear because no direct evidence for their involvement exists. This study shows that spherical siderite in deep-water IF represents a biosignature for photoferrotrophy, whereas massive siderite reflects high cyanobacterial biomass in shallow-water.
- Inga Köhler
- , Kurt O Konhauser
- & Andreas Kappler
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Another rapid event in the carbon-14 content of tree rings
A strong increase in atmospheric 14C was measured in tree rings at AD 774 to 775, providing potential evidence of large cosmic ray fluxes to Earth, but the cause of this event is unclear. Here, Miyake et al. report a second 14C event in AD 993, which suggests that the most likely cause was a large solar proton event.
- Fusa Miyake
- , Kimiaki Masuda
- & Toshio Nakamura
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Louisville seamount subduction and its implication on mantle flow beneath the central Tonga–Kermadec arc
Seamounts that have subducted beneath a mantle wedge allow the study of trace element recycling and mantle flow in subduction zones. Here, a geochemical analysis of central Tonga–Kermadec arc lavas suggests primarily trench-normal mantle flow in the mantle wedge beneath the central Tonga–Kermadec arc.
- Christian Timm
- , Daniel Bassett
- & Anthony B. Watts
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| Open AccessInitialized near-term regional climate change prediction
Near-term climate prediction is an information tool used in climate adaptation services. This study analyses the quality of the predictions, showing that near-term climate forecasts have good skill in predicting temperature at regional scales, where most of the skill is attributed to atmospheric composition changes.
- F. J. Doblas-Reyes
- , I. Andreu-Burillo
- & G. J. van Oldenborgh
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| Open AccessOcean lead at the termination of the Younger Dryas cold spell
The abrupt ending of the Younger Dryas cooling episode marked the onset of the present interglacial and was the most prominent climate change in the Earth’s recent history. This study shows evidence for a sequence of events with a leading role of the ocean at the transition into the present day warm Holocene epoch.
- Christof Pearce
- , Marit-Solveig Seidenkrantz
- & Søren M. Kristiansen
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Early Cretaceous chalks from the North Sea giving evidence for global change
Calcareous nannofossils were important marine primary producers in Jurassic and Cretaceous oceans at low latitudes. Here, North Sea sediment records reveal that favourable conditions for nannoconids existed also at high latitudes, and nannoconids faced global decline at the onset of greenhouse conditions.
- Jörg Mutterlose
- & Cinzia Bottini
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Seismic detection of increased degassing before Kīlauea's 2008 summit explosion
The onset of the ongoing summit eruption at Kilauea Volcano was associated with changes in seismic anisotropy and increased gas flux. This study shows that seismic anisotropy variations are also a function of alterations in stress conditions, and provides a new method for tracking gas flux using seismic observations.
- Jessica H. Johnson
- & Michael P. Poland
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Reconciliation of marine and terrestrial carbon isotope excursions based on changing atmospheric CO2 levels
Carbon isotope excursions (CIEs) measured in marine and terrestrial substrates indicate large-scale changes in the global carbon cycle. Schubert and Jahren show that larger-amplitude CIEs measured in terrestrial substrates reflect increased carbon isotope fractionation by land plants under elevated atmospheric CO2.
- Brian A. Schubert
- & A. Hope Jahren
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| Open AccessObservations from old forests underestimate climate change effects on tree mortality
It is thought that only climate change drives temporal tree mortality increases in old forests. Here, Luo and Chen show that both forest dynamics and climate change drive temporal tree mortality increases in young and old forests, and that climate change-associated mortality increases are higher in the young forests.
- Yong Luo
- & Han Y. H. Chen
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Nitrogen cycle feedbacks as a control on euxinia in the mid-Proterozoic ocean
Clear evidence between sulphidic conditions and denitrification in the Proterozoic ocean should be observable in the rock record. Here, minimalistic biogeochemical modelling shows how periods of extensive sulphate reduction must have gone hand-in-hand with low denitrification and available nitrate.
- R.A. Boyle
- , J.R. Clark
- & T.M. Lenton
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| Open AccessIncreased ventilation of Antarctic deep water during the warm mid-Pliocene
It is thought that during the mid-Pliocene warm period the Atlantic Meridional Overturning Circulation (AMOC) must have been stronger than today. Here, using proxy data compilation and simulation, Zhang et al.show that the two observations used to support stronger AMOC may not necessitate its increased strength.
- Zhongshi Zhang
- , Kerim H. Nisancioglu
- & Ulysses S. Ninnemann
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| Open AccessSolar wind entry into the high-latitude terrestrial magnetosphere during geomagnetically quiet times
A full understanding of the penetration of solar wind plasma into the Earth’s magnetosphere, during geomagnetically quiet times, remains elusive. Using multi-spacecraft data, Shi et al.find unexpected entry of the solar wind into the high-latitude magnetosphere and suggest a probable entry mechanism.
- Q.Q. Shi
- , Q.-G. Zong
- & E. Lucek
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| Open AccessOne mechanism contributing to co-variability of the Atlantic inflow branches to the Arctic
The branched inflow of warm Atlantic Water to the Arctic has been known for more than a hundred years, yet what controls the relative strengths of the two pathways remains poorly understood. Here, the authors identify the role of atmospheric circulation over the northern Barents Sea in controlling inflow.
- Vidar S. Lien
- , Frode B. Vikebø
- & Øystein Skagseth
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Effect of iron oxidation state on the electrical conductivity of the Earth’s lower mantle
In the Earth’s lower mantle, pressure changes can cause spin transitions of iron, in turn influencing mantle properties. Here a new Mössbauer spectroscopy method is applied to show that Fe3+remains in the high-spin state at pressure–temperature conditions relevant for the lower mantle.
- V. Potapkin
- , C. McCammon
- & L. Dubrovinsky
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Climate change patterns in Amazonia and biodiversity
The long-term hydroclimate variability in Amazonia and its influence on biodiversity remain poorly understood. Here, new speleothem oxygen isotope records characterize spatial–temporal changes in precipitation and provide new insights to understanding the west–east contrasting pattern of biodiversity in Amazonia.
- Hai Cheng
- , Ashish Sinha
- & Augusto S. Auler
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Constraining timescales of focused magmatic accretion and extension in the Afar crust using lava geochronology
In mature continental rifts, magma intrusion appears to accommodate significant crustal extension. Here, radiometric ages for lavas suggest that this style of focused magmatic accretion and rifting remained stable in the Ethiopian crust for at least ~200 kyr, prior to the onset of true oceanic spreading.
- David J. Ferguson
- , Andrew T. Calvert
- & Tim J. Wright
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The Tissint Martian meteorite as evidence for the largest impact excavation
High-pressure minerals in meteorites reflect the conditions prevailing when they were excavated and launched from their parent bodies. Tissint—a recent Martian meteorite—contains an unusual number of large high-pressure minerals, suggesting excavation from an impact of larger magnitude than for previous Martian samples.
- Ioannis P. Baziotis
- , Yang Liu
- & Lawrence A. Taylor
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| Open AccessCaribbean-wide decline in carbonate production threatens coral reef growth
Coral reef health is declining globally and is projected to lead to net loss of reef structure. This study shows that ecological change across the Caribbean has reduced reef growth rates to levels lower than those measured over the last ~8,000 years, threatening the ability of reefs to keep pace with future sea-level rise.
- Chris T. Perry
- , Gary N. Murphy
- & Peter J. Mumby
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| Open AccessHigh heat flow and ocean acidification at a nascent rift in the northern Gulf of California
Active seafloor spreading has been documented in some of the tectonically active basins of the Gulf of California. This work presents new geophysical and geochemical data as evidence that active seafloor spreading is also occurring in the northernmost Wagner and Consag basins of the Gulf.
- Rosa Ma Prol-Ledesma
- , Marco-Antonio Torres-Vera
- & Carlos Robinson
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Mechanisms of carbon storage in mountainous headwater rivers
Rivers receive more terrestrial carbon than they transport to the ocean, leaving carbon stored along the way. Here, with an estimate of carbon storage in the headwater rivers of the Rocky Mountains, the authors show that broad valley bottoms with old-growth forest store most of the above- and below-ground carbon.
- Ellen Wohl
- , Kathleen Dwire
- & Roberto Bazan
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Warming and nitrogen deposition lessen microbial residue contribution to soil carbon pool
Microbes appear to play an important role in carbon sequestration. Here, the composition of microbial residues in a California grassland with elevated carbon dioxide, warming and nitrogen deposition reveals that warming and nitrogen deposition can both alter the fraction of carbon derived from microbes in soils.
- Chao Liang
- & Teri C. Balser
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Holocene winter climate variability in mid-latitude western North America
Mineral cave deposits—speleothems—provide a record of past rainfall changes. This study presents a speleothem data-set from southwestern Oregon, revealing winter climate change over the past 13,000 years with abrupt transitions between warm-dry and cold-wet regimes influenced by solar forcing.
- Vasile Ersek
- , Peter U. Clark
- & R. Lawrence Edwards
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A four-dimensional X-ray tomographic microscopy study of bubble growth in basaltic foam
Changes in bubble foam structure influence magma strength. Here, Bakeret al. measure bubble size and wall thickness of basaltic foams and find that basaltic magmas are most likely to fail immediately upon vesiculation, but a permeability increase within a few seconds may reduce the risk of explosive eruptions.
- Don R. Baker
- , Francesco Brun
- & Mark Rivers
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Atmospheric phosphorus deposition may cause lakes to revert from phosphorus limitation back to nitrogen limitation
Increased atmospheric input of nitrogen has shifted planktonic lake nutrient systems from natural nitrogen to human-induced phosphorus limitation. This study proposes that decades of increased atmospheric phosphorus in the Pyrenean lake district may have reverted the system from phosphorus back to nitrogen-limited.
- L. Camarero
- & J. Catalan
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Reconstructing plate-motion changes in the presence of finite-rotations noise
Reconstructing short-term plate-motion changes through time provides important geodynamical information, but data noise is a problem at fine temporal resolution. This study presents a trans-dimensional hierarchical Bayesian framework that eliminates noise without loss of temporal resolution.
- Giampiero Iaffaldano
- , Thomas Bodin
- & Malcolm Sambridge
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| Open AccessPronounced interannual variability in tropical South Pacific temperatures during Heinrich Stadial 1
During the last glacial termination, the North Atlantic experienced a cold interval, but its impact on tropical climate variability is not clear. Here, a fossil Tahiti coral record shows that tropical sea surface temperature varied actively during this event, consistent with climate model simulations.
- Thomas Felis
- , Ute Merkel
- & Miriam Pfeiffer
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| Open AccessSurface changes in the North Atlantic meridional overturning circulation during the last millennium
Palaeoclimate proxies, such as shells, record past ocean changes. A radiocarbon study based on a shell chronology from the Icelandic shelf is used to track changes in ocean circulation and climate for the past 1,350 years, suggesting a declining influence of North Atlantic surface waters on the Icelandic shelf over the last millennium.
- Alan D. Wanamaker Jr
- , Paul G. Butler
- & Christopher A. Richardson
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The oceanic biological pump modulates the atmospheric transport of persistent organic pollutants to the Arctic
Persistent organic pollutants can reach and pollute pristine environments, such as the Arctic Ocean, through atmospheric transport. This study shows that the oceanic biological pump can sequester atmospheric polychlorinated biphenyls, reducing the transport of pollutants to the Arctic Ocean.
- Cristóbal Galbán-Malagón
- , Naiara Berrojalbiz
- & Jordi Dachs
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Abyssal undular vortices in the Eastern Mediterranean basin
Small-scale ocean dynamics can have wide reaching impacts on the larger-scale ocean circulation. Using temperature and velocity data, this study shows the presence of abyssal vortices in the Eastern Mediterranean basin, adding complexity to the structure and evolution of water masses in this region.
- A. Rubino
- , F. Falcini
- & A. Capone
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The origin of pelletal lapilli in explosive kimberlite eruptions
Kimberlites are volatile-rich magmas that form diverging pipes containing pelletal lapilli - well rounded clasts that consist of an inner seed particle. Gernonet al. suggest that pelletal lapilli are formed when fluid volatile-rich melts intrude into earlier volcaniclastic infill close to the diatreme root zone.
- T.M. Gernon
- , R.J. Brown
- & T.K. Hincks
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Environmental noise exposure degrades normal listening processes
The damaging effects of loud noise on auditory function are well established, but the effects of low-level noise are not so well understood. Zhou and Merzenich chronically expose adult rats to structured low-level noise and find that it causes auditory cortex damage and sound discrimination impairment.
- Xiaoming Zhou
- & Michael M. Merzenich
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| Open AccessPotential regime shift in decreased sea ice production after the Mertz Glacier calving
The calving of the Mertz Glacier occurred in 2010 in East Antarctica, brought on by the re-positioning of a large iceberg. Using satellite data, this study shows a reduction in sea ice production following the calving, interpreted as a potential regime shift towards reduced sea ice production for the coming decades.
- T. Tamura
- , G.D. Williams
- & K.I. Ohshima
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| Open AccessTwo centuries of limited variability in subtropical North Atlantic thermocline ventilation
Ocean circulation moves heat and gases between the ocean and atmosphere, impacting the carbon cycle at decadal timescales. Here, a radiocarbon coral record of ocean mixing from Bermuda suggests that the formation of mode water, and thus carbon uptake, have been more stable over the past 200 years than previously thought.
- Nathalie F. Goodkin
- , Ellen R. M. Druffel
- & Scott C. Doney
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Past daily light cycle recorded in the strontium/calcium ratios of giant clam shells
A record of the daily light cycle in tropical regions is difficult to extract from biogenic marine carbonates such as shells. Here, the precise analysis of Sr/Ca ratios is shown in a cultivated giant clam shell, revealing variations that reflect the daily light cycle and the potential for future development of a proxy.
- Yuji Sano
- , Sayumi Kobayashi
- & Kenji Iwai
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Power laws reveal phase transitions in landscape controls of fire regimes
Understanding the environmental controls of past wildfires is difficult due to the lack of records of weather or vegetation. This study shows, using cross-scale analysis, how power laws associated with fire-event time series can identify critical thresholds in landscape dynamics in a rapidly changing climate.
- Donald McKenzie
- & Maureen C. Kennedy
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Three decades of high-resolution coastal sea surface temperatures reveal more than warming
A detailed assessment of near-shore temperature changes is needed for improved forecasts of the consequences of coastal warming. Here, changes in coastal sea surface temperature are estimated, showing that although 71% of the world's coastlines are warming, the rates of change have varied spatially.
- Fernando P. Lima
- & David S. Wethey
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Stress-induced chemical waves in sediment burial diagenesis
Dolomite sedimentary rock has lateral metre-scale periodic variations in porosity and composition, which may provide information on formation and transformation. This study suggests that such variations are fossilized chemical waves emerging from stress-mediated mineral-water interaction during sediment burial diagenesis.
- Yifeng Wang
- & David A. Budd
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Rapid microbial response to the presence of an ancient relic in the Antarctic Dry Valleys
It is thought that turnover in soil microbiota occurs very slowly in the Antarctic Dry Valleys due to the extreme cold and aridity. Now, Tiaoet al. show that a transformation of microbial communities can happen in a matter of years in soils altered by the presence of a mummified seal.
- Grace Tiao
- , Charles K. Lee
- & S. Craig Cary
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Enhanced sea-ice export from the Arctic during the Younger Dryas
The Younger Dryas cold period is thought to have occurred mainly due to the release of fresh water into the North Atlantic from the glacial Lake Agassiz. Here, sedimentary and geochemical data from the central Arctic Ocean support the hypothesis of a northward route drainage event from Lake Agassiz during the Younger Dryas.
- Christelle Not
- & Claude Hillaire-Marcel
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| Open AccessHydrothermal vent fields and chemosynthetic biota on the world's deepest seafloor spreading centre
The Mid-Cayman Spreading Centre is an ultraslow-spreading mid-ocean ridge in the Caribbean. This study reveals two hydrothermal vent fields on the ridge, including high-temperature vents on an off-axis oceanic core complex where, similar to Mid-Atlantic vents, an alvinocaridid shrimp is common at both vent fields.
- Douglas P. Connelly
- , Jonathan T. Copley
- & Sally Wilcox
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River-margin habitat of Ardipithecus ramidus at Aramis, Ethiopia 4.4 million years ago
The habitat where early humans, hominins, lived provides information about the early part of human evolution. In this study, sedimentological and stable carbon and oxygen isotope data suggest homininArdipithecus ramiduslived in a river-margin forest in a wooded grassland landscape at Aramis, Ethiopia.
- M. Royhan Gani
- & Nahid D. Gani
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Migrating deformation in the Central Andes from enhanced orographic rainfall
Active shortening in the Central Andes shifted from the western to the eastern margin between 10-7 Myr ago, but the mechanism of formation is still unclear. Here, using critical wedge theory and local-scale fault friction calculations, this shift is proposed to have been controlled by changes in erosion patterns.
- Kevin Norton
- & Fritz Schlunegger