Back to basics - p407

doi:10.1038/ngeo246

The discovery that biogenic methane production may not be limited to oxygen-free environments throws conventional thinking into turmoil, and calls into question basic assumptions regarding the global methane budget.

Full Text - Back to basics | PDF (162 KB) - Back to basics

Listening to glaciers - p408

M. Schulz, W. H. Berger & E. Jansen

doi:10.1038/ngeo235

Full Text - Listening to glaciers | PDF (91 KB) - Listening to glaciers

Farming pollution - pp409 - 411

Viney P. Aneja, William H. Schlesinger & Jan Willem Erisman

doi:10.1038/ngeo236

Modern farms produce particulate matter and gases that affect the environment and human health and add to rising atmospheric greenhouse-gas levels. European policymakers have made progress in controlling these emissions, but US regulations remain inadequate.

Full Text - Farming pollution | PDF (311 KB) - Farming pollution

Did an impact blast away half of the martian crust? - pp412 - 414

H. J. Melosh

doi:10.1038/ngeo237

The northern and southern hemispheres of Mars are topographically distinct. Crustal thickness analyses and numerical simulations suggest a giant impact just after the crust differentiated 4.4 billion years ago as a plausible cause for this dichotomy.

Full Text - Did an impact blast away half of the martian crust? | PDF (407 KB) - Did an impact blast away half of the martian crust?

Uncovering Titan's secrets - pp415 - 416

Dominic Fortes reviews Titan: Exploring an Earthlike World by Athena Coustenis & Fredrick W. Taylor

doi:10.1038/ngeo238

Full Text - Uncovering Titan's secrets | PDF (120 KB) - Uncovering Titan's secrets

Shaken volcanoes, cloud albedo and more - p417

doi:10.1038/ngeo239

Full Text - Shaken volcanoes, cloud albedo and more | PDF (143 KB) - Shaken volcanoes, cloud albedo and more

Oceanography: Making methane - pp419 - 420

Ellery D. Ingall

doi:10.1038/ngeo242

Most of the world's surface oceans are oversaturated with respect to atmospheric methane and emit large quantities of this greenhouse gas. Aerobic decomposition of phosphorus-containing organic compounds may be responsible.

Full Text - OceanographyMaking methane | PDF (231 KB) - OceanographyMaking methane

Subject Category: Oceanography

Climate science: Of sun and ice - p420

Heike Langenberg

doi:10.1038/ngeo241

Full Text - Climate scienceOf sun and ice | PDF (164 KB) - Climate scienceOf sun and ice

Biogeochemistry: Fixing forests - pp421 - 422

Eric A. Davidson

doi:10.1038/ngeo244

The uneven distribution of biological nitrogen fixation in terrestrial ecosystems has yet to be explained. Latitudinal gradients in temperature and phosphorus may hold the answer.

Full Text - BiogeochemistryFixing forests | PDF (316 KB) - BiogeochemistryFixing forests

Subject Category: Biogeochemistry

Geomorphology: Sculpted by a megaflood - p422

Ninad Bondre

doi:10.1038/ngeo240

Full Text - GeomorphologySculpted by a megaflood | PDF (234 KB) - GeomorphologySculpted by a megaflood

Palaeoceanography: Saline water sinking - pp423 - 424

Silke Voigt

doi:10.1038/ngeo243

Ninety-five million years ago, ocean bottom waters were much warmer than at present. Some of this warmth could have come from the proto-North Atlantic's continental shelves after the balmy surface waters became increasingly salty through evaporation.

Full Text - PalaeoceanographySaline water sinking | PDF (251 KB) - PalaeoceanographySaline water sinking

Subject Category: Palaeoclimate and palaeoceanography

Carbon accumulation in European forests - pp425 - 429

P. Ciais, M. J. Schelhaas, S. Zaehle, S. L. Piao, A. Cescatti, J. Liski, S. Luyssaert, G. Le-Maire, E.-D. Schulze, O. Bouriaud, A. Freibauer, R. Valentini & G. J. Nabuurs

doi:10.1038/ngeo233

European forests are intensively exploited for wood products, yet they are also a potential sink for carbon. European forest inventories combined with timber harvest statistics from sixteen European countries show that between 1950 and 2000 forest biomass increased faster than the amount of timber harvests. Silviculture, which has developed over the past 50 years, can efficiently sequester carbon on timescales of decades, while maintaining forests that meet the demand for wood.

Abstract - | Full Text - Carbon accumulation in European forests | PDF (226 KB) - Carbon accumulation in European forests | Supplementary information

Subject Categories: Biogeochemistry | Climate science

Global nitrogen deposition and carbon sinks - pp430 - 437

Dave S. Reay, Frank Dentener, Pete Smith, John Grace & Richard A. Feely

doi:10.1038/ngeo230

Land and ocean carbon sinks play a critical role in determining atmospheric carbon dioxide levels. Nitrogen-induced increases in land and ocean sink strength are unlikely to keep pace with future increases in carbon dioxide.

Abstract - | Full Text - Global nitrogen deposition and carbon sinks | PDF (716 KB) - Global nitrogen deposition and carbon sinks | Supplementary information

Subject Categories: Biogeochemistry | Climate science

Phosphorus cycling in the North and South Atlantic Ocean subtropical gyres - pp439 - 443

Rhiannon L. Mather, Sarah E. Reynolds, George A. Wolff, Richard G. Williams, Sinhue Torres-Valdes, E. Malcolm S. Woodward, Angela Landolfi, Xi Pan, Richard Sanders & Eric P. Achterberg

doi:10.1038/ngeo232

The surface waters of the North Atlantic subtropical gyre are depleted in phosphate, relative to the South Atlantic gyre. Despite this nutrient limitation, the two gyres have comparable rates of carbon fixation. Measurements of enzyme activity suggest that dissolved organic phosphorus may be fuelling northern productivity.

First Paragraph - | Full Text - Phosphorus cycling in the North and South Atlantic Ocean subtropical gyres | PDF (476 KB) - Phosphorus cycling in the North and South Atlantic Ocean subtropical gyres | Supplementary information

Subject Category: Oceanography

See also: related Backstory

Oceanic link between abrupt changes in the North Atlantic Ocean and the African monsoon - pp444 - 448

Ping Chang, Rong Zhang, Wilco Hazeleger, Caihong Wen, Xiuquan Wan, Link Ji, Reindert J. Haarsma, Wim-Paul Breugem & Howard Seidel

doi:10.1038/ngeo218

Abrupt changes in the African Monsoon, which have been recorded throughout the late Pleistocene and early Holocene epochs, tend to coincide with changes in North Atlantic thermohaline circulation. A numerical simulation shows that the interaction between thermohaline circulation in the North Atlantic Ocean and wind-driven currents in the topical Atlantic Ocean contributes to the rapidity of African Monsoon transitions during abrupt climate change events.

First Paragraph - | Full Text - Oceanic link between abrupt changes in the North Atlantic Ocean and the African monsoon | PDF (459 KB) - Oceanic link between abrupt changes in the North Atlantic Ocean and the African monsoon | Supplementary information

Subject Categories: Climate science | Palaeoclimate and palaeoceanography

Episodic reductions in bottom-water currents since the last ice age - pp449 - 452

Summer K. Praetorius, Jerry F. McManus, Delia W. Oppo & William B. Curry

doi:10.1038/ngeo227

Although North Atlantic deep-water formation was greatly reduced during the last glacial maximum, bottom-water currents were as vigorous as at present. However, they were weakened during periods of North Atlantic surface freshening. A strong correlation can be seen between bottom-water-current strength and Greenland air-temperature records, thus confirming a close connection between ocean circulation and abrupt climate change.

First Paragraph - | Full Text - Episodic reductions in bottom-water currents since the last ice age | PDF (521 KB) - Episodic reductions in bottom-water currents since the last ice age | Supplementary information

Subject Category: Palaeoclimate and palaeoceanography

Warm saline intermediate waters in the Cretaceous tropical Atlantic Ocean - pp453 - 457

Oliver Friedrich, Jochen Erbacher, Kazuyoshi Moriya, Paul A. Wilson & Henning Kuhnert

doi:10.1038/ngeo217

During the Cretaceous period, warm deep and intermediate waters filled the oceans. Evidence from benthic foraminferal ¹⁸O and Mg/Ca ratios suggests that the intermediate water masses in the proto-Atlantic Ocean formed from high salinity waters sinking from shallow shelf seas.

First Paragraph - | Full Text - Warm saline intermediate waters in the Cretaceous tropical Atlantic Ocean | PDF (615 KB) - Warm saline intermediate waters in the Cretaceous tropical Atlantic Ocean | Supplementary information

Subject Category: Palaeoclimate and palaeoceanography

See also: News and Views by Voigt

Two-stage subduction history under North America inferred from multiple-frequency tomography - pp458 - 462

Karin Sigloch, Nadine McQuarrie & Guust Nolet

doi:10.1038/ngeo231

The ancient Farallon plate subducted under North America in two distinct stages. High-resolution tomographic images show large pieces of the plate, including the currently active piece, which descends from the Pacific Northwest coast to 1,500 km depth, and its stalled predecessor, which now occupies the transition zone and lower mantle beneath the eastern half of the continent.

First Paragraph - | Full Text - Two-stage subduction history under North America inferred from multiple-frequency tomography | PDF (1,093 KB) - Two-stage subduction history under North America inferred from multiple-frequency tomography | Supplementary information

Subject Category: Structural geology, tectonics and geodynamics

The relationship between rifting and magmatism in the northeastern Arabian Sea - pp463 - 467

Timothy A. Minshull, Christine I. Lane, Jenny S. Collier & Robert B. Whitmarsh

doi:10.1038/ngeo228

The rifting of the Seychelles microcontinent from India involved two phases of extensional activity. The initial separation of the Laxmi Ridge from India was accompanied by extensive magmatism but the later separation of the Seychelles from the Laxmi Ridge was only weakly magmatic.

First Paragraph - | Full Text - The relationship between rifting and magmatism in the northeastern Arabian Sea | PDF (859 KB) - The relationship between rifting and magmatism in the northeastern Arabian Sea | Supplementary information

Subject Categories: Seismology | Structural geology, tectonics and geodynamics

See also: related Backstory

Subcontinental lithospheric mantle origin of high niobium/tantalum ratios in eclogites - pp468 - 472

Sonja Aulbach, Suzanne Y. O'Reilly, William. L. Griffin & Norman J. Pearson

doi:10.1038/ngeo226

Eclogites have been suggested as high niobium/tantalum reservoirs that complement the low niobium/tantalum ratios of the silicate Earth. However, the hafnium isotopic composition of eclogite fragments suggest that the high niobium/tantalum signature of eclogites is unlikely to be primary. Instead, it probably reflects chemical modification during residence in the subcontinental lithospheric mantle.

First Paragraph - | Full Text - Subcontinental lithospheric mantle origin of high niobium/tantalum ratios in eclogites | PDF (256 KB) - Subcontinental lithospheric mantle origin of high niobium/tantalum ratios in eclogites | Supplementary information

Subject Category: Geochemistry

Aerobic production of methane in the sea - pp473 - 478

David M. Karl, Lucas Beversdorf, Karin M. Björkman, Matthew J. Church, Asuncion Martinez & Edward F. Delong

doi:10.1038/ngeo234

Surface waters of most of the world's oceans are supersaturated with respect to atmospheric methane. Measurements in seawater samples suggest that an aerobic methane production pathway, which involves the decomposition of phosphorus-containing organic compounds, may be responsible.

Abstract - | Full Text - Aerobic production of methane in the sea | PDF (287 KB) - Aerobic production of methane in the sea

Subject Categories: Biogeochemistry | Climate science | Oceanography

See also: News and Views by Ingall

Simulated reduction in Atlantic hurricane frequency under twenty-first-century warming conditions - p479

Thomas Knutson, Joseph Sirutis, Stephen Garner, Gabriel Vecchi & Isaac Held

doi:10.1038/ngeo229

Full Text - Simulated reduction in Atlantic hurricane frequency under twenty-first-century warming conditions | PDF (73 KB) - Simulated reduction in Atlantic hurricane frequency under twenty-first-century warming conditions

Sailing for stretched lithosphere - p482

doi:10.1038/ngeo245

Having managed to get themselves and all their instruments on board a ship not too far away from an imminent war zone, Jenny Collier and colleagues enjoyed the serenity of life at sea as they investigated the rifted continental margin of India.

Full Text - Sailing for stretched lithosphere | PDF (261 KB) - Sailing for stretched lithosphere

Nourishing the ocean deserts - pE11

doi:10.1038/ngeo247

Rhiannon Mather, Sarah Reynolds and colleagues criss-crossed the Atlantic Ocean armed with pumps and plastic bottles in search of the nutrients that feed open-ocean productivity.

Full Text - Nourishing the ocean deserts | PDF (198 KB) - Nourishing the ocean deserts