Volume 1
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No. 12 December 2008
Global warming is likely to increase soil organic carbon decomposition, and thus CO2 release to the atmosphere, creating a positive feedback cycle. Inclusion of realistic estimates of soil black carbon in prediction models results in a decrease in soil CO2 emission in Australia by up to 24.4% following a 3 °C warming over 100 years, suggesting that black carbon reduces the strength of this feedback. The image shows a high-fuel-load, high-intensity savanna fire near Darwin, Northern Territory, Australia. (Image credit: R. D. Graetz.)
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No. 11 November 2008
A three-dimensional evaluation of earthquake hypocentres beneath the Kanto basin in Japan reveals the presence of a distinct, 25-km-thick and 100-km-wide body. Its fast seismic velocity and the presence of a double seismic zone suggest that it is a fragment of the Pacific slab, rather than an extension of the Philippine Sea slab. The image is a digital elevation model showing the tectonic triple junction between the Pacific, Philippine Sea and Eurasian plates, with the Kanto plain just left of the centre. Chains of extinct seamounts descend into the Japan trench at the right hand side.
Cover design by Serkan B. Bozkurt (AMEC Geomatrix)
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No. 10 October 2008
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 of 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. The image shows Jakobshavn Isbræ, photographed in May 2005 by Konrad Steffen.
Cover design by Karen Moore
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No. 9 September 2008
The Arctic soil organic carbon pool is poorly constrained. Measurements of soil organic carbon in the North American Arctic reveal that the carbon store in this region is larger than previous estimates suggest, and highly dependent upon landscape type. The image shows a cryogenic structure, exposed at 45-50 cm depth in a tundra soil profile in Isachsen, Ellef Ringes Island, Nunavut, Canada.
Cover design by Karen Moore
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No. 8 August 2008
Cratons are ancient continental nuclei that have resisted significant fragmentation for almost two billion years. Yet, many cratons also experience phases of instability in the form of erosion and rejuvenation of their thick lithospheric mantle keels. Melting governed by redox processes, as well as small-scale convection, play a key role in triggering such instability. The image is an artistically enhanced photo of an outcrop of Archaean gneiss, a type of rock that is typical of the crust of Archaean cratons,at Turnavik Island in Labrador.
Cover design by Karen Moore
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No. 7 July 2008
Eclogites have been suggested as reservoirs with high niobium/tantalum ratios that complement the low niobium/tantalum ratios of the silicate Earth. However, the hafnium isotopic composition of eclogite fragments suggests that they did not possess high niobium/tantalum ratios to begin with. Instead, the high ratios probably reflect chemical modification during residence in the subcontinental lithospheric mantle. The image shows a photomicrograph of a rutile-bearing eclogite fragment entrained in the Lac de Gras kimberlites from the central Slave Craton, Canada.
Letter p468
Cover design by Karen Moore
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No. 6 June 2008
Using projected boundary conditions for the end of the twenty-first century, the frequency of Atlantic tropical cyclones and hurricanes in a regional climate model of the Atlantic basin is reduced compared with observed boundary conditions at the end of the twentieth century. This is inconsistent with the idea that higher levels of atmospheric greenhouse gases will result in increased Atlantic hurricane activity. The image shows a visualization of high clouds from the regional climate model. A well-developed model-hurricane can be seen making landfall on the US Gulf Coast. Land visualization is based on observed surface topography and NASA satellite-derived land albedo.
Visualization by Remik Ziemlinski (NOAA/GFDL).
Cover design by Karen Moore
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No. 5 May 2008
On geological timescales, carbon dioxide enters the atmosphere through volcanism and oxidation of organic matter, and is removed through mineral weathering and carbonate burial. An analysis of ice-core CO2 records and marine carbonate chemistry indicates a tight coupling between these processes during the past 610,000 years, which suggests that a weathering feedback driven by atmospheric CO2 leads to a mass balance between carbon sources and sinks on long timescales. The cover image shows an eruption of Augustine Volcano, Alaska on 26 March 2006. Volcanic eruptions and outgassing release CO2, as well as ash and other gases, to the atmosphere.
Image credit: Cyrus Read.
Cover design by Karen Moore
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No. 4 April 2008
Blue jets, gigantic jets, cloud-to-cloud discharges and cloud-to-ground lightning are all electrical discharges from thunderclouds. An analysis of numerical simulations and observations of these phenomena places them all in a unifying framework. The image shows a cloud-enshrouded 'bolt-from-the-blue' lightning discharge in a storm near Langmuir Laboratory in central New Mexico, that produced an incipient upward jet above the top of the storm before turning downward to ground.
Image credit: Harald Edens.
Cover design by Karen Moore
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No. 3 March 2008
Despite Titan's cold temperatures (about 93.7 K at the equator), fluvial and atmospheric processes are active on this moon of Saturn, with methane playing a similar role to water on Earth. However, Titan lacks a global methane ocean, and rainfall appears to be episodic. The image shows a fish-eye projection of Titan's surface from a distance of about 5 km, taken with the descent imager/spectral radiometer onboard the European Space Agency's Huygens probe, on 14 January 2005. Copyright ESA/NASA/JPL/University of Arizona.
Cover design by Karen Moore
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No. 2 February 2008
A significant fraction of the anthropogenic nitrogen input into the coastal oceans from fertilizers is transferred back to land by commercial fisheries. This fraction has decreased over the past few decades, because fertiliser loads have increased at a faster rate than harvests from fisheries. The photo was taken on the beach at St Louis in Senegal where women were drying and smoking fish. (Image credit: Kieran Kelleher/Marine Photobank.)
Cover design by Karen Moore
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No. 1 January 2008
Water is stored within glaciers in linked cavities and at the glacier bed, where it can affect glacier motion. But neither water pressure nor the volume of water stored provides a satisfactory explanation for short-term variations of glacier velocity. Studying Kennicott Glacier, Alaska, Timothy Bartholomaus and colleagues find that short pulses of water, for example due to an outburst flood from a lake upstream, affect glacier velocity the most. The cover image shows Gates Glacier, one of the main tributaries to the Kennicott Glacier.
Cover design by Karen Moore
Letter by Bartholomaus et al.