Press releases
The first papers of the August 2009 issue of Nature Geoscience are now available online as advance online publication.
Please quote Nature Geoscience as the source of these items.
July 2009
Independent support for sea-level rise projections
A new model based on past sea-level changes suggests that sea level will rise between 7 and 82 cm by the end of the twenty-first century in response to rising temperatures. This estimate, published online in Nature Geoscience, is in line with projections from the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC).
Mark Siddall and colleagues developed a sea-level model that is based on the sea-level response to global average temperature changes that occurred over the past 22,000 years. This approach is very different from the more complex models used for the IPCC reports, but both converge on similar values of sea-level rise — the IPCC's latest report gave values between 18 and 59 cm — in response to the projected 1 to 6°C warming. This independent modelling effort therefore increases confidence in the IPCC estimates.
Constraints on future sea-level rise from past sea-level change
Mark Siddall, Thomas F. Stocker and Peter U. Clark
Published online: 26 July 2009 | doi 10.1038/ngeo587
Noble clues to interaction between carbon and groundwater
Groundwater is key to the storage of carbon dioxide in aquifers and gas fields, and to the formation of many hydrocarbon deposits like crude oil, according to an overview published online in Nature Geoscience. Societies are generally dependent on fossil-fuel energy sources, but their use has also resulted in the rise of climate-altering atmospheric carbon dioxide concentrations.
Barbara Sherwood Lollar and Christopher Ballentine reviewed the use of noble gases — including neon and argon — as tracers for the movement and cycling of carbon dioxide in groundwater systems. Their review showed that groundwater stores much of the carbon dioxide that enters the aquifer. Groundwater was also seen to transport hydrocarbons to underground 'traps', where they can be more easily recovered by drilling. However, groundwater can also degrade existing reservoirs.
They conclude that noble gases could be used to monitor any leakage of human-created carbon dioxide that has been removed from the atmosphere and stored in aquifers or oil and gas fields.
Insights into deep carbon derived from noble gases
B. Sherwood Lollar and C. J. Ballentine
Published online: 26 July 2009 | doi 10.1038/ngeo588
Full circle
Dust clouds from China were transported more than one full circle around the globe in 13 days, according to a study published online in Nature Geoscience. The findings illustrate that dust clouds generated in one region could have effects on many parts of the world.
Itsushi Uno and colleagues used satellite and model data to show that a storm in China's Taklimakan Desert in May 2007 generated dust clouds that were lifted 8–10 km above the Earth's surface, and transported more than one full circle around the Earth. When the dust reached the northwestern Pacific Ocean for a second time, the subsidence of a high-pressure system caused the dust-laden clouds to descend into the lower atmosphere and some of the dust was then deposited in the ocean.
The analysis also suggests that the dust particles may have triggered ice formation in the high-altitude clouds.
Asian dust transported one full circuit around the globe
Itsushi Uno, Kenta Eguchi, Keiya Yumimoto, Toshihiko Takemura, Atsushi Shimizu, Mitsuo Uematsu, Zhaoyang Liu, Zifa Wang, Yukari Hara & Nobuo Sugimoto
Published online: 20 July 2009 | doi 10.1038/ngeo583
Fast-flowing ice streams mould their beds
The sediments beneath fast-flowing ice streams change dynamically within decades, reports a study published online in this week's Nature Geoscience. The work shows conclusively that elongated ridges in the sediment bed — called mega-scale glacial lineations — are characteristic of regions of fast ice flow.
Edward King and colleagues collected radar data that reveal the ice-sediment interface beneath Rutford Ice Stream, a glacier in West Antarctica. They identified mega-scale glacial lineations in the sedimentary bed that have identical characteristics to sediment beds of ancient ice sheets. Using seismic data, the researchers conclude that beneath fast-flowing ice streams the sediment bed changes relatively quickly. Most of the discharge from large ice sheets — such as the one covering Antarctica — is channelled through such fast-flowing streams, and the properties of the underlying sediments can affect the speed of ice flow.
In an accompanying Backstory, Edward King writes about his experience of camping in Antarctica to collect the data.
Formation of mega-scale glacial lineations observed beneath a West Antarctic Ice Stream
E.C. King, R.C.A. Hindmarsh & C.R. Stokes
Published online: 20 July 2009 | doi 10.1038/ngeo581
Unexplained warming during the Palaeocene–Eocene Thermal Maximum
The amount of carbon released during an abrupt warming event 55.5 million years ago was insufficient to cause the 5–9 °C temperature rise at the time, as reported online this week in Nature Geoscience. The study suggests that the greenhouse effect of the atmospheric carbon dioxide must have been amplified substantially by processes that, at present, are not understood, or taken into account in estimates of future warming.
Richard Zeebe and colleagues used analyses of marine sediments and a carbon-cycle model to estimate the amount of carbon dioxide released during the Palaeocene–Eocene Thermal Maximum, which lasted for about 100,000 years. They found that, using current estimates of climate sensitivity to increasing levels of atmospheric carbon dioxide, the carbon release could only explain up to 3.5 °C of the warming. They concluded that as yet unknown warming feedbacks must have caused the additional rise in temperature.
In the accompanying News & Views article, David Beerling writes "The upshot of the study by Zeebe and colleagues is that forecasts of future warming could be severely underestimating the extent of the problem that lies in store for humanity as greenhouse gases accumulate in the atmosphere."
Carbon dioxide forcing alone insufficient to explain Palaeocene–Eocene Thermal Maximum warming
Richard E. Zeebe, James C. Zachos & Gerald R. Dickens
Published online: 13 July 2009 | doi 10.1038/ngeo578
Palaeoclimate: Enigmatic Earth
David J. Beerling
Published online: 13 July 2009 | doi 10.1038/ngeo582
Nutrient spark
Cloud-to-ground lightning alters the chemistry of phosphorus, producing rare, but biologically usable forms of this vital nutrient, according to a study published online this week in Nature Geoscience.
Phosphorus is a key and frequently limiting nutrient in marine and terrestrial ecosystems. Matthew Pasek and colleagues examined the chemical composition of fulgurites – the glassy compounds produced by lightning strikes — retrieved from North America, Africa and Australia. They found that half of these compounds contained rare and biologically usable forms of phosphorus. The researchers suggest that lightning can provide some of the rarer forms of phosphorus used by microbes.
Lightning-induced reduction of phosphorus oxidation state
Matthew Pasek & Kristin Block
Published online: 13 July 2009 | doi 10.1038/ngeo580
Triassic–Jurassic plant extinction related to extensive volcanism
The turnover of land plants in Europe 200 million years ago was driven by environmental changes triggered by massive volcanic activity, according to a study published online this week in Nature Geoscience.
The mass extinction at the boundary of the Triassic and Jurassic periods is considered to be one of the five largest extinctions, but its causes, particularly on land, have remained elusive.
Bas van de Schootbrugge and colleagues used cores of rock to reconstruct the changing ecology and environment in what is now Germany and southern Sweden. They found that as volcanic activity increased, the lush Triassic forests were replaced by a hardier assemblage of ferns, horsetails and mosses. Geochemical analyses indicated that toxic chemicals — generated by the interaction of basalt lava and organic matter — were deposited throughout the European region.
The authors conclude that the decline of the forests was caused by these environmental toxins, combined with climate change triggered by massive release of carbon dioxide from the volcanic activity.
Floral changes across the Triassic/Jurassic boundary linked to flood basalt volcanism
B. van de Schootbrugge, T. M. Quan, S. Lindström, W. Püttmann, C. Heunisch, J. Pross, J. Fiebig, R. Petschick, H.-G. Röhling, S. Richoz, Y. Rosenthal & P. G. Falkowski
Published online: 13 July 2009 | doi 10.1038/ngeo577
Methane bubbling up
Substantial amounts of the greenhouse gas methane can reach the surface ocean from seafloor seeps as deep as 600 metres, shows a study online in Nature Geoscience this week. The results indicate that current estimates of the global flux of methane from the oceans to the atmosphere may be too low.
Using a submersible robotic vehicle, Evan Solomon and colleagues directly sampled methane concentrations in bubble plumes at several sites in the Gulf of Mexico between 500 and 600 metres depth, where the gas emanates from seafloor vents. The researchers suggest that the transfer of methane to the atmosphere from the investigated deepwater plumes is 10 to 1,000 times higher than the amounts previously estimated for shallow-water seeps. This is contrary to the idea that only methane from shallow-water seeps reaches the ocean surface in significant amounts.
The researchers suggest that seeps in similar active hydrocarbon basins, such as the Persian Gulf, Caspian Sea, West African Margin and the Alaska North Slope, should be investigated more closely to improve estimates of the global methane flux from the oceans to the atmosphere.
Considerable methane fluxes to the atmosphere from hydrocarbon seeps in the Gulf of Mexico
Evan A. Solomon, Miriam Kastner, Ian R. MacDonald and Ira Leifer
Published online: 5 July 2009 | doi 10.1038/ngeo574
