A call to outreach - p635

doi:10.1038/ngeo329

Life in the 21st century requires an understanding of science and technology. Earth Science Week is an opportunity to bring the geosciences to the wider public.

Full Text - A call to outreach | PDF (177 KB) - A call to outreach

How a century of ammonia synthesis changed the world - pp636 - 639

Jan Willem Erisman, Mark A. Sutton, James Galloway, Zbigniew Klimont & Wilfried Winiwarter

doi:10.1038/ngeo325

On 13 October 1908, Fritz Haber filed his patent on the "synthesis of ammonia from its elements" for which he was later awarded the 1918 Nobel Prize in Chemistry. A hundred years on we live in a world transformed by and highly dependent upon Haber–Bosch nitrogen.

Full Text - How a century of ammonia synthesis changed the world | PDF (366 KB) - How a century of ammonia synthesis changed the world

Rediscovering the record of humans - p640

William R. Ruddiman reviews The earth after us by Jan Zalasiewicz

doi:10.1038/ngeo317

Full Text - Rediscovering the record of humans | PDF (108 KB) - Rediscovering the record of humans

Rising volcanoes, Mississippi sinking and more - p641

doi:10.1038/ngeo330

Full Text - Rising volcanoes, Mississippi sinking and more | PDF (184 KB) - Rising volcanoes, Mississippi sinking and more

Terrestrial biosphere: The burning issue - pp643 - 644

Andrew C. Scott

doi:10.1038/ngeo321

Wildfires have been a natural part of the Earth system for millions of years. A new charcoal database for the past two millennia shows that human activity increased biomass burning after AD 1750 and suppressed it after AD 1870.

Full Text - Terrestrial biosphereThe burning issue | PDF (213 KB) - Terrestrial biosphereThe burning issue

Subject Category: Climate science

Climate change: Cool spray - p644

Heike Langenberg

doi:10.1038/ngeo326

Full Text - Climate changeCool spray | PDF (131 KB) - Climate changeCool spray

Carbon cycle: Fertilizing change - pp645 - 646

Gordon Bonan

doi:10.1038/ngeo328

Carbon cycle–climate feedbacks are expected to diminish the size of the terrestrial carbon sink over the next century. Model simulations suggest that nitrogen availability is likely to play a key role in mediating this response.

Full Text - Carbon cycleFertilizing change | PDF (208 KB) - Carbon cycleFertilizing change

Subject Category: Climate science

Palaeontology: A long-lost tundra - p646

Alicia Newton

doi:10.1038/ngeo319

Full Text - PalaeontologyA long-lost tundra | PDF (174 KB) - PalaeontologyA long-lost tundra

Climate science: The mysteries of Sahel droughts - pp647 - 648

Kerry H. Cook

doi:10.1038/ngeo320

Past variability in Sahel rainfall is closely linked to global sea surface temperature distributions in observations and models alike. Climate simulations for the 21st century suggest that additional influences may become important in the future.

Full Text - Climate scienceThe mysteries of Sahel droughts | PDF (158 KB) - Climate scienceThe mysteries of Sahel droughts

Subject Category: Climate science

Mineral physics: The spin deep within - pp648 - 650

Stephen Stackhouse

doi:10.1038/ngeo327

The electronic configuration of iron impurities in lower-mantle minerals influences their physical properties, but it is not well constrained. New studies suggest that ferrous iron in silicate phases exists mainly in an intermediate spin state.

Full Text - Mineral physicsThe spin deep within | PDF (153 KB) - Mineral physicsThe spin deep within

Subject Category: Volcanology, mineralogy and petrology

Palaeoclimate: Africa on the edge - pp650 - 651

Peter B. deMenocal

doi:10.1038/ngeo323

Saharan humidity has varied dramatically throughout the Pleistocene era. A new deep-sea sediment record reveals large and rapid hydrological shifts that are linked to the competing influences of low- and high-latitude climate processes.

Full Text - PalaeoclimateAfrica on the edge | PDF (161 KB) - PalaeoclimateAfrica on the edge

Subject Category: Palaeoclimate and palaeoceanography

The role of surface heat fluxes in tropical intraseasonal oscillations - pp653 - 657

Adam H. Sobel, Eric D. Maloney, Gilles Bellon & Dargan M. Frierson

doi:10.1038/ngeo312

The tropics sustain strong coherent variations in wind and precipitation on intraseasonal timescales of 30–60 days. These variations pace the active and break cycles of the monsoons, exerting a direct control on the livelihoods of large populations dependent on rain-fed agriculture. Emerging evidence suggests that heat fluxes from ocean to atmosphere play a fundamental role in driving these intraseasonal oscillations.

Abstract - | Full Text - The role of surface heat fluxes in tropical intraseasonal oscillations | PDF (583 KB) - The role of surface heat fluxes in tropical intraseasonal oscillations

Subject Categories: Atmospheric science | Climate science

Acceleration of Jakobshavn Isbræ triggered by warm subsurface ocean waters - pp659 - 664

David M. Holland, Robert H. Thomas, Brad de Young, Mads H. Ribergaard & Bjarne Lyberth

doi:10.1038/ngeo316

Observations over past decades show a sudden switch of Jakobshavn Isbræ—a large outlet glacier feeding a deep-ocean fjord on Greenland's west coast—from slow thickening to rapid thinning in 1997. This switch is associated with a doubling in glacier velocity. Hydrographic data show a concurrent sudden increase in subsurface ocean temperatures along the entire west coast of Greenland, suggesting that the changes in Jakobshavn Isbræ were triggered by the arrival of relatively warm water originating from the Irminger Sea.

First Paragraph - | Full Text - Acceleration of Jakobshavn Isbræ triggered by warm subsurface ocean waters | PDF (814 KB) - Acceleration of Jakobshavn Isbræ triggered by warm subsurface ocean waters | Supplementary information

Subject Categories: Cryospheric science | Oceanography | Climate science

Interdependence of groundwater dynamics and land-energy feedbacks under climate change - pp665 - 669

Reed M. Maxwell & Stefan J. Kollet

doi:10.1038/ngeo315

Climate change will have a significant impact on the hydrologic cycle, creating changes in freshwater resources, land cover and land–atmosphere feedbacks. Simulations using a groundwater flow model with integrated overland flow and land-surface model processes show that groundwater depth, which results from lateral water flow at the surface and subsurface, determines the relative susceptibility of regions to changes in temperature and precipitation.

First Paragraph - | Full Text - Interdependence of groundwater dynamics and land-energy feedbacks under climate change | PDF (812 KB) - Interdependence of groundwater dynamics and land-energy feedbacks under climate change

Subject Categories: Hydrology, hydrogeology and limnology | Climate science

Coherent high- and low-latitude control of the northwest African hydrological balance - pp670 - 675

Rik Tjallingii, Martin Claussen, Jan-Berend W. Stuut, Jens Fohlmeister, Alexandra Jahn, Torsten Bickert, Frank Lamy & Ursula Röhl

doi:10.1038/ngeo289

Variability in northwest African humidity has been documented for the Holocene period, but less is known about the development of the hydrological balance during the Pleistocene period. Sedimentary records and numerical simulations for the past 120,000 years show abrupt millennial-scale changes in humidity, which may be related to changes in the strength of the North Atlantic meridional overturning circulation.

First Paragraph - | Full Text - Coherent high- and low-latitude control of the northwest African hydrological balance | PDF (527 KB) - Coherent high- and low-latitude control of the northwest African hydrological balance | Supplementary information

Subject Category: Palaeoclimate and palaeoceanography

See also: News and Views by deMenocal

Non-volcanic tremor resulting from the combined effect of Earth tides and slow slip events - pp676 - 678

Ryoko Nakata, Naoki Suda & Hiroshi Tsuruoka

doi:10.1038/ngeo288

Swarms of non-volcanic tremor in southeastern Japan are associated with slow slip events and tend to occur with a periodicity of 12 or 24 h. This periodicity can be reproduced by a combination of stresses due to Earth tides and transient stress changes caused by slow slip events. Non-volcanic tremors may therefore be useful for understanding stress relaxation at the subduction-zone interface.

First Paragraph - | Full Text - Non-volcanic tremor resulting from the combined effect of Earth tides and slow slip events | PDF (538 KB) - Non-volcanic tremor resulting from the combined effect of Earth tides and slow slip events | Supplementary information

Subject Categories: Seismology | Structural geology, tectonics and geodynamics

Coseismic fluid–rock interactions at high temperatures in the Chelungpu fault - pp679 - 683

Tsuyoshi Ishikawa, Masaharu Tanimizu, Kazuya Nagaishi, Jun Matsuoka, Osamu Tadai, Masumi Sakaguchi, Tetsuro Hirono, Toshiaki Mishima, Wataru Tanikawa, Weiren Lin, Hiroyuki Kikuta, Wonn Soh & Sheng-Rong Song

doi:10.1038/ngeo308

Chemical and isotopic variations in crushed material along the Chelungpu fault in Taiwan are suggestive of interactions at high temperatures with coseismically generated aqueous fluids. High fluid pressures along the fault zone during the magnitude 7.6 Chi-Chi earthquake in 1999 could have reduced friction and fault strength.

First Paragraph - | Full Text - Coseismic fluid–rock interactions at high temperatures in the Chelungpu fault | PDF (532 KB) - Coseismic fluid–rock interactions at high temperatures in the Chelungpu fault | Supplementary information

Subject Categories: Geochemistry | Structural geology, tectonics and geodynamics

Stable intermediate-spin ferrous iron in lower-mantle perovskite - pp684 - 687

C. McCammon, I. Kantor, O. Narygina, J. Rouquette, U. Ponkratz, I. Sergueev, M. Mezouar, V. Prakapenka & L. Dubrovinsky

doi:10.1038/ngeo309

Iron has the ability to adopt different electronic configurations, and transitions in its spin state in the lower mantle can significantly influence mantle properties and dynamics. Experimental results for two lower-mantle perovskite compositions show that the intermediate spin state of iron is stable throughout the bulk of the lower mantle.

First Paragraph - | Full Text - Stable intermediate-spin ferrous iron in lower-mantle perovskite | PDF (563 KB) - Stable intermediate-spin ferrous iron in lower-mantle perovskite | Supplementary information

Subject Categories: Structural geology, tectonics and geodynamics | Volcanology, mineralogy and petrology

See also: News and Views by Stackhouse | related Backstory

Intermediate-spin ferrous iron in lowermost mantle post-perovskite and perovskite - pp688 - 691

Jung-Fu Lin, Heather Watson, György Vankó, Esen E. Alp, Vitali B. Prakapenka, Przemek Dera, Viktor V. Struzhkin, Atsushi Kubo, Jiyong Zhao, Catherine McCammon & William J. Evans

doi:10.1038/ngeo310

The Earth's lowermost mantle displays an important mineralogical transition from perovskite to post-perovskite but the spin state of iron in these phases remains poorly known. Experimental results suggest that iron occurs in the intermediate spin state in both of these phases, which implies that changes in physical properties of the lower mantle must be governed by factors other than spin transitions in iron.

First Paragraph - | Full Text - Intermediate-spin ferrous iron in lowermost mantle post-perovskite and perovskite | PDF (329 KB) - Intermediate-spin ferrous iron in lowermost mantle post-perovskite and perovskite | Supplementary information

Subject Categories: Structural geology, tectonics and geodynamics | Volcanology, mineralogy and petrology

Seismic evidence for distinct anisotropy in the innermost inner core - pp692 - 696

Fenglin Niu & Qi-Fu Chen

doi:10.1038/ngeo314

To understand the evolution of the inner core it is important to constrain the structure of its innermost part. Analysis of two types of seismic waves that traverse the inner core reveals seismic anisotropy of the innermost region and is consistent with the slowest direction of anisotropy being tilted away from the equatorial plane.

First Paragraph - | Full Text - Seismic evidence for distinct anisotropy in the innermost inner core | PDF (2,463 KB) - Seismic evidence for distinct anisotropy in the innermost inner core

Subject Categories: Geomagnetism, palaeomagnetism and core processes | Seismology | Structural geology, tectonics and geodynamics

Climate and human influences on global biomass burning over the past two millennia - pp697 - 702

J. R. Marlon, P. J. Bartlein, C. Carcaillet, D. G. Gavin, S. P. Harrison, P. E. Higuera, F. Joos, M. J. Power & I. C. Prentice

doi:10.1038/ngeo313

A compilation of wildfire records spanning six continents and 2,000 years reveals global patterns in biomass burning to be temporally linked with changes in climate, population and land use. An abrupt decline in biomass burning beginning about 150 years ago may be related to the expansion of intensive grazing, agriculture and fire management activities.

Abstract - | Full Text - Climate and human influences on global biomass burning over the past two millennia | PDF (1,327 KB) - Climate and human influences on global biomass burning over the past two millennia | Supplementary information

Subject Categories: Climate science | Palaeoclimate and palaeoceanography

See also: News and Views by Scott

Alternating Si and Fe deposition caused by temperature fluctuations in Precambrian oceans - pp703 - 708

Nicole R. Posth, Florian Hegler, Kurt O. Konhauser & Andreas Kappler

doi:10.1038/ngeo306

Precambrian banded iron formations contain thin alternating layers of iron- and silica-rich minerals. Microbial culture experiments show that these alternations could be caused by changes in the relative dominance of microbial iron oxidation and abiotic silica precipitation driven by fluctuating ocean temperature.

Abstract - | Full Text - Alternating Si and Fe deposition caused by temperature fluctuations in Precambrian oceans | PDF (314 KB) - Alternating Si and Fe deposition caused by temperature fluctuations in Precambrian oceans | Supplementary information

Subject Categories: Biogeochemistry | Oceanography | Palaeoclimate and palaeoceanography

See also: related Backstory

Changes in ocean denitrification during Late Carboniferous glacial–interglacial cycles - pp709 - 714

Thomas Algeo, Harry Rowe, James C. Hower, Lorenz Schwark, Achim Herrmann & Phil Heckel

doi:10.1038/ngeo307

Rates of denitrification below some oceanic upwelling zones reach a maximum during periods when sea level rise was fastest throughout the Pleistocene glacial cycles. Nitrogen isotope data from North American shales deposited 300 million years ago during Palaeozoic glaciations are indicative of a similar pattern.

Abstract - | Full Text - Changes in ocean denitrification during Late Carboniferous glacial–interglacial cycles | PDF (579 KB) - Changes in ocean denitrification during Late Carboniferous glacial–interglacial cycles | Supplementary information

Subject Categories: Biogeochemistry | Palaeoclimate and palaeoceanography

Chasing light beams - p718

doi:10.1038/ngeo324

Catherine McCammon and colleagues surmounted experimental obstacles at the European Synchrotron Radiation Facility in France to unlock the secrets of iron in the Earth's lower mantle.

Full Text - Chasing light beams | PDF (217 KB) - Chasing light beams

Recreating rocks - pE17

doi:10.1038/ngeo322

Nicole Posth and colleagues spent a month touring South African rock formations in their quest to understand the origin of ancient iron and silicate layers.

Full Text - Recreating rocks | PDF (184 KB) - Recreating rocks