Nature Geoscience 1, E19 (2008). doi:10.1038/ngeo375

Nathalie Goodkin and colleagues dug deep into coral geochemistry and wrestled with waves for a 200-year record of the North Atlantic Oscillation.

Nature Geoscience 1, E20 (2008). doi:10.1038/ngeo377

Deep-sea drilling was the order of the day for Peter Clift and colleagues on their expedition to the South China Sea.

Nature Geoscience 1, 803 (2008). doi:10.1038/ngeo368

Destruction from earthquakes continues to threaten poor and wealthy nations alike. The Global Earthquake Model is a potentially important step towards providing risk information on a worldwide basis, using a unified standard.

Nature Geoscience 1, 805 (2008). doi:10.1038/ngeo365

Authors: Torbjörn E. Törnqvist & Douglas J. Meffert

The 2008 Atlantic hurricane season once again highlighted the challenges awaiting low-lying population centres close to the ocean. In the face of global sea-level rise, unconventional thinking is required to make urban coasts more resilient.

Nature Geoscience 1, 809 (2008). doi:10.1038/ngeo367

Author: Helen Amanda Fricker

Glaciologists have speculated that subglacial floods might lead to increased ice flow rates, altering Antarctica's mass balance and contribution to sea-level rise. Now, observations from Byrd Glacier in East Antarctica firmly link a subglacial flood to a 10% speed up of the glacier.

Nature Geoscience 1, 811 (2008). doi:10.1038/ngeo370

Author: Oliver Timm

The North Atlantic Oscillation has shown high variability over the past few decades. A two-hundred-year-long temperature reconstruction from a Bermuda coral suggests a link to recent climate warming.

Nature Geoscience 1, 812 (2008). doi:10.1038/ngeo372

Author: Albrecht W. Hofmann

The Earth's known rock reservoirs contain more radiogenic lead than expected on average. Mantle-derived rocks with highly unradiogenic lead — as discovered in the Horoman massif — may bear witness to a previously unsampled, complementary reservoir.

Nature Geoscience 1, 814 (2008). doi:10.1038/ngeo369

Author: A. Joshua West

The influence of climate on mountain building has long been debated. A reconstruction for the past 25 million years suggests coincidence of Himalayan erosion and monsoon intensification, hinting at a causal relationship.

Nature Geoscience 1, 815 (2008). doi:10.1038/ngeo371

Author: Cindy Prescott

Two-thirds of terrestrial carbon is stored as organic matter in soils, but its response to warming has yet to be resolved. A soil warming experiment in a Canadian forest has revealed that the leaf-derived compound cutin is resistant to decomposition under elevated temperatures.

Nature Geoscience 1, 827 (2008). doi:10.1038/ngeo356

Authors: Leigh A. Stearns, Benjamin E. Smith & Gordon S. Hamilton

Changes in the velocity of large outlet glaciers and ice streams in Greenland and Antarctica are important for ice-sheet mass balance and hence sea level. Mass loss in large parts of both ice sheets is being driven by the recent accelerations of outlet glaciers in response to unknown or poorly constrained climatic or internal perturbations in their boundary conditions. Surprisingly active networks of subglacial lake drainage have recently been found beneath the Antarctic ice sheet and tentatively linked to the onset of fast ice flow. Here we report an observed acceleration of ice velocity on Byrd Glacier, East Antarctica, of about 10% of the original speed between December 2005 and February 2007. The acceleration extended along the entire 75 km glacier trunk and its onset coincided with the discharge of about 1.7 km3 of water from two large subglacial lakes located about 200 km upstream of the grounding line. Deceleration coincided with the termination of the flood. Our findings provide direct evidence that an active lake drainage system can cause large and rapid changes in glacier dynamics.

Nature Geoscience 1, 832 (2008). doi:10.1038/ngeo358

Authors: Johannes Lehmann, Jan Skjemstad, Saran Sohi, John Carter, Michele Barson, Pete Falloon, Kevin Coleman, Peter Woodbury & Evelyn Krull

Annual emissions of carbon dioxide from soil organic carbon are an order of magnitude greater than all anthropogenic carbon dioxide emissions taken together. Global warming is likely to increase the decomposition of soil organic carbon, and thus the release of carbon dioxide from soils, creating a positive feedback. Current models of global climate change that recognize this soil carbon feedback are inaccurate if a larger fraction of soil organic carbon than postulated has a very slow decomposition rate. Here we show that by including realistic stocks of black carbon in prediction models, carbon dioxide emissions are reduced by 18.3 and 24.4% in two Australian savannah regions in response to a warming of 3 ∘C over 100 years. This reduction in temperature sensitivity, and thus the magnitude of the positive feedback, results from the long mean residence time of black carbon, which we estimate to be approximately 1,300 and 2,600 years, respectively. The inclusion of black carbon in climate models is likely to require spatially explicit information about its distribution, given that the black carbon content of soils ranged from 0 to 82% of soil organic carbon in a continental-scale analysis of Australia. We conclude that accurate information about the distribution of black carbon in soils is important for projections of future climate change.

Nature Geoscience 1, 836 (2008). doi:10.1038/ngeo361

Authors: Xiaojuan Feng, André J. Simpson, Kevin P. Wilson, D. Dudley Williams & Myrna J. Simpson

Rising temperatures are predicted to accelerate the decomposition of labile soil organic compounds such as proteins and carbohydrates, whereas biochemically resistant compounds, such as lipids from leaf cuticles and roots and lignin from woody tissues, are expected to remain stable on decadal to centennial timescales. However, the extent to which soil warming changes the molecular composition of soil organic matter is poorly understood. Here we examine the impact of soil warming in a mixed temperate forest on the molecular make-up of soil organic matter. We show that the abundance of leaf-cuticle-derived compounds is increased following 14 months of soil warming; we confirm this with nuclear magnetic resonance spectra of soil organic matter extracts. In contrast, we find that the abundance of lignin-derived compounds is decreased after the same treatment, while soil fungi, the primary decomposers of lignin in soil, increase in abundance. We conclude that future warming could alter the composition of soil organic matter at the molecular level, accelerating lignin degradation and increasing leaf-cuticle-derived carbon sequestration. With annual litterfall predicted to increase in the world’s major forests with a 3 ∘C warming, we suggest that future warming may enhance the sequestration of cuticular carbon in soil.

Nature Geoscience 1, 840 (2008). doi:10.1038/ngeo364

Authors: John F. Rex & Ellen L. Petticrew

Marine fish that migrate to freshwater rivers to spawn deliver substantial quantities of marine-derived nutrients to terrestrial and freshwater environments. These nutrients support riparian vegetation, terrestrial organisms, benthic macroinvertebrates, algae and other fish populations. Although it is known that the quantity of nutrients delivered to these environments is influenced by the number of spawning salmon, little is known about the mechanisms of nutrient delivery. Here, we present a pathway for nutrient delivery and retention in a Pacific salmon stream, which depends on the aggregation of inorganic and organic particulate matter. We verify the existence of this pathway in the controlled environment conditions of a recirculating flume, replicating the hydrologic conditions of a stream environment. We show that the addition of salmon organic matter and clay to the flume increases the formation of organic–inorganic aggregates in the water column, and the transfer of these aggregates to the stream bed. We find that the formation of these aggregates is associated with an increase in the concentration of bacteria in the stream bed. We suggest that bacterial aggregation of salmon organic matter and inorganic particulate matter delivers nutrients to streambeds, and thus plays an integral role in nutrient cycling in Pacific salmon streams.

Nature Geoscience 1, 844 (2008). doi:10.1038/ngeo352

Authors: Nathalie F. Goodkin, Konrad A. Hughen, Scott C. Doney & William B. Curry

The North Atlantic Oscillation is a meridional oscillation of atmospheric mass measured between Iceland and the Açores, which drives winter climate variability in eastern North America and Europe. A prolonged period of the positive phase during the 1990s led to the suggestion that anthropogenic warming was affecting the behaviour of the North Atlantic Oscillation. However, instrumental records are too short to compare observations during periods of extended warm and cold hemispheric temperatures, and existing palaeoclimate reconstructions primarily capture terrestrial variability. Here we present a record of Sr/Ca, a sea surface temperature proxy, from a Bermuda coral from 1781 to 1999. We use this monthly resolved record to reconstruct past variability of the North Atlantic Oscillation at multiple frequencies. Our record shows enhanced multidecadal scale variability during the late twentieth century compared with the end of the Little Ice Age (1800–1850). We suggest that variability within the North Atlantic Oscillation is linked to the mean temperature of the Northern Hemisphere, which must be considered in any long-term predictions.

Nature Geoscience 1, 849 (2008). doi:10.1038/ngeo357

Authors: Nerilie J. Abram, Michael K. Gagan, Julia E. Cole, Wahyoe S. Hantoro & Manfred Mudelsee

The interplay of the El Niño Southern Oscillation, Asian monsoon and Indian Ocean Dipole (IOD) drives climatic extremes in and around the Indian Ocean. Historical and proxy records reveal changes in the behaviour of the El Niño Southern Oscillation and the Asian monsoon over recent decades. However, reliable instrumental records of the IOD cover only the past 50 years, and there is no consensus on long-term variability of the IOD or its possible response to greenhouse gas forcing. Here we use a suite of coral oxygen-isotope records to reconstruct a basin-wide index of IOD behaviour since AD 1846. Our record reveals an increase in the frequency and strength of IOD events during the twentieth century, which is associated with enhanced seasonal upwelling in the eastern Indian Ocean. Although the El Niño Southern Oscillation has historically influenced the variability of both the IOD and the Asian monsoon, we find that the recent intensification of the IOD coincides with the development of direct, positive IOD–monsoon feedbacks. We suggest that projected greenhouse warming may lead to a redistribution of rainfall across the Indian Ocean and a growing interdependence between the IOD and Asian monsoon precipitation variability.

Nature Geoscience 1, 854 (2008). doi:10.1038/ngeo359

Authors: Francis Lucazeau, Sylvie Leroy, Alain Bonneville, Bruno Goutorbe, Frédérique Rolandone, Elia d’Acremont, Louise Watremez, Doga Düsünur, Patrick Tuchais, Philippe Huchon, Nicolas Bellahsen & Khalfan Al-Toubi

During the early stages in the formation of divergent margins, the lithosphere experiences large changes in temperature that can determine its strength and influence magma generation. This, in turn, may play a key role in continental rifting, break-up, and subsequent subsidence. Here we present surface heat-flow data from the Eastern Gulf of Aden, which is a recently formed divergent margin between Africa and Arabia. In the deeper parts of the margin the heat flow is high and constant, but it decreases abruptly near the shelf-slope. Our numerical models, in conjunction with geophysical and geological constraints, suggest that the data are best explained by a thermal anomaly in the upper mantle that has persisted after continental break-up. We suggest that this anomaly is related to small-scale convection that occurred during and after rifting. Similar anomalies could have characterized other divergent margins: for example, the presence of shallow-water sediments deposited after the opening of the Atlantic Ocean hints at lower subsidence than would have occurred in the absence of persistent thermal anomalies.

Nature Geoscience 1, 859 (2008). doi:10.1038/ngeo363

Authors: Sanjeewa P. K. Malaviarachchi, Akio Makishima, Masaaki Tanimoto, Takeshi Kuritani & Eizo Nakamura

Basalts at mid-ocean ridges are generated by partial melting of the Earth’s upper mantle. As a result of this process, the upper mantle has become depleted over time in elements that are preferentially removed by melting. Although mid-ocean-ridge basalts have traditionally been thought to reflect the chemical composition of such depleted mantle, recent work has revealed the existence of domains in the upper mantle that are apparently not sampled by the basalts. Here we present the lead (Pb), neodymium (Nd) and hafnium (Hf) isotope compositions of peridotites from the Horoman orogenic massif in Japan, which is considered to represent the residues of melting of the upper mantle. These peridotites exhibit the lowest Pb isotope ratios reported from any known mantle material, along with high Nd and Hf isotope ratios. These data suggest that chemical depletion of the peridotites occurred around a billion years ago, and that they represent ancient mantle domains that have escaped convective stirring and homogenization. We suggest that such domains—if abundant in the mantle—may constitute a hitherto unrecognized reservoir with highly unradiogenic lead.

Nature Geoscience 1, 884 (2008). doi:10.1038/ngeo376

Stephen Rintoul and an international team of oceanographers headed south on the Australian icebreaker, Aurora Australis, to discover how Southern Ocean currents influence climate and biodiversity.