Press releases
The first papers of the May 2008 issue of Nature Geoscience are now available online as advance online publication.
Please quote Nature Geoscience as the source of these items.
April 2008
Long-term carbon cycle finely balanced
Over the last 610,000 years, the input of carbon to the atmosphere has been closely balanced by its removal. A paper online this week in Nature Geoscience provides the first direct observational support for long term carbon-cycle feedbacks that provide an effective thermostat for the Earth's temperatures.
Richard Zeebe and a colleague compared the levels of atmospheric carbon dioxide as recorded in ice cores with records of carbonate saturation in the deep sea for the last six glacial cycles. They found that although carbon dioxide levels varied between glacial and interglacial states, the long-term average atmospheric carbon dioxide concentrations changed by no more than 22 parts per million by volume. This is suggestive of a feedback mechanism in which the carbon dioxide released into the atmosphere, primarily through volcanoes, is balanced by the removal of atmospheric carbon dioxide through the weathering of mountains, usually within a few hundred thousand years.
Close mass balance of long-term carbon fluxes from ice-core CO2 and ocean chemistry records
Richard Zeebe (University of Hawaii, Honolulu, HI, USA)
Published online: 27 April 2008 | doi 10.1038/ngeo185
Fast ice flow on water?
In the coming decades, significant changes in the polar regions will increase the contribution of ice sheets to global sea-level rise. The degree of influence that water beneath the ice sheets exerts on fast ice flow in Greenland and Antarctica will depend on the geometry and capacity of the subglacial hydrologic system, concludes a review article published online this week in Nature Geoscience.
Ice sheets and glaciers are underlain by complex systems of meltwater streams and ponds. Robin Bell's overview of recent work suggests that in Greenland, the influence of meltwater on ice loss will depend on the subglacial hydrologic system met by water transferred down from surface meltwater ponds. In Antarctica, subglacial lakes can modulate the speed of ice streams and act as nucleation points for new fast-flowing tributaries.
The role of subglacial water in ice-sheet mass balance
Robin Bell (Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, USA)
Published online: 27 April 2008 | doi 10.1038/ngeo186
Greenhouse effect from tropospheric ozone
The greenhouse effect from tropospheric ozone measured between 45° S and 45° N is about 0.48 Watts per square metre for the year 2006, according to a paper published online this week in Nature Geoscience. The new data provide a critical observational constraint for radiative forcing used in climate model predictions.
Helen Worden and colleagues analysed infrared radiance measurements from NASA's Aura satellite for clear-sky conditions over land and the oceans, along with estimates of atmospheric ozone and water vapour concentrations. They were thereby able to quantify the greenhouse effect from tropospheric ozone observationally. Earlier model results reported by the Intergovernmental Panel for Climate Change range from 0.25 to 0.65 Watts per square metre for the radiative forcing from anthropogenic changes to tropospheric ozone.
Satellite measurements of the clear-sky greenhouse effect from tropospheric ozone
Helen Worden (National Center for Atmospheric Research, Boulder, CO, USA)
Published online: 20 April 2008 | doi 10.1038/ngeo182
Other papers from Nature Geoscience to be published online at the same time and with the same embargo:
Submarine groundwater discharge revealed by 228Ra distribution in the upper Atlantic Ocean
Willard S. Moore (University of South Carolina, Columbia, South Carolina, USA)
Published online: 20 April 2008 | doi 10.1038/ngeo183
Freezing the Eocene greenhouse
About 34 million years ago, the Earth's climate abruptly cooled from warm greenhouse conditions to an icehouse climate – a time known as the Eocene-Oligocene transition. A study published online this week in Nature Geoscience suggests that this transition happened in three geologically rapid steps, each lasting for only several thousand years, culminating in a two degree cooling of the deep oceans and producing Antarctic ice sheets that were 25& larger than exist today.
Miriam Katz used marine sediments to reconstruct ocean temperature and sea level changes for the Eocene-Oligocene transition. Shell records indicated two intervals of bottom water cooling, providing previously elusive evidence that the deep oceans followed suit when the climate became cooler. Sea level decreased by up to 100 metres during the transition because water was stored in the Antarctic Ice Sheet.
Stepwise transition from the Eocene greenhouse to the Oligocene icehouse
Miriam Katz (Rensselaer Polytechnic Institute, Troy, NY, USA)
Published online: 13 April 2008 | doi 10.1038/ngeo179
Other papers from Nature Geoscience to be published online at the same time and with the same embargo:
Partitioning of palladium at high pressures and temperatures during core formation
K. Righter (Mailcode KT, NASA Johnson Space Center, 2101 NASA Parkway, Houston, Texas 77058, USA)
Published online: 13 April 2008 | doi 10.1038/ngeo180
Coastal pollution could produce an unhealthy chemical cocktail
The reaction of chemical compounds in the pollution from cities and ships with sea salt aerosols from the ocean could affect air quality in coastal areas where the two meet, according to research online this week in Nature Geoscience. A team measured high levels of nitryl chloride, an active halogen implicated in ground-level ozone production, in industrially polluted air along the southeast coast of the US, implying that ozone pollution could be particularly high where industrial combustion products meet the ocean, as in many megacities around the world.
James Roberts and colleagues measured unexpectedly high levels of nitryl chloride in ship exhaust plumes along the southeast coast of the US. They show that this chemical compound is produced during the night by the reaction of the nitrogen oxides in polluted air from ships or cities with the chlorine from sea salt. With the help of the morning sunlight, nitryl oxide is rapidly split into a reactive radical that can produce ozone in combination with suitable atmospheric compounds, and nitrogen oxides.
High levels of nitryl chloride in the polluted subtropical marine boundary layer
James Roberts (National Oceanic and Atmospheric Administration, Boulder, CO, USA)
Published online: 6 April 2008 | doi 10.1038/ngeo177
Related Backstory
'Hunting for halogen chemistry' by James Roberts describes the field work and the background to the work.
James M. Roberts (National Oceanic and Atmospheric Administration, Boulder, CO, USA)
Published online: 6 April 2008 | doi 10.1038/ngeo184
Other papers from Nature Geoscience to be published online at the same time and with the same embargo:
Slow slip and frictional transition at low temperature at the Hikurangi subduction zone
Robert McCaffrey (GNS Science, PO Box 30368, Lower Hutt, New Zealand)
Published online: 6 April 2008 | doi 10.1038/ngeo178