Nature Geoscience contents: October 2013 Volume 6 Number 10 pp801-890

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Find out more about this and how you can apply for other specialist sections here TABLE OF CONTENTS October 2013 Volume 6, Issue 10 Editorial Correspondence In the press Research Highlights News and Views Review Letters Articles Subscribe   Facebook   RSS   Recommend to library   Twitter   Advertisement Nature Geoscience Insight: Marine cycles in flux In this Nature Geoscience Insight we highlight some of the most intriguing advances in the microbial biogeochemistry of the oceans, a field that is very much in flux.  Free online for a limited time   Produced with support from:     Editorial Top Déjà vu on climate change   p801 doi:10.1038/ngeo1983 The latest report on global warming brings yet another rise in confidence that human actions are altering the Earth's climate. But in contrast to its 2007 predecessor, it is unlikely to cause a stir. Correspondence Top Magma balloons or bombs?   pp802 - 803 Thomas Shea, Julia Hammer and Emily First doi:10.1038/ngeo1971 Reply to 'Magma balloons or bombs?'   p803 Melissa D. Rotella, Colin J. N. Wilson, Simon J. Barker and Ian C. Wright doi:10.1038/ngeo1970 In the press Top Deep blue planet   p804 Emily Lakdawalla doi:10.1038/ngeo1965 Research Highlights Top Climate science: El Niño and nitrous oxide | Planetary science: Wonky to the core | Palaeoclimate: Interglacial monsoon | Geochemistry: Primordial mix News and Views Top Early Mars: Without phosphate limits   pp806 - 807 Matthew Pasek doi:10.1038/ngeo1929 Phosphorus is an important element for biogeochemical development. According to a set of experiments, martian phosphate minerals dissolve more quickly than terrestrial ones, possibly providing nutrients in aqueous environments for early martian life. See also: Letter by Adcock et al. Palaeoclimate: A fresh look at Arctic ice sheets   pp807 - 808 Julie Brigham-Grette doi:10.1038/ngeo1960 During the Last Glacial Maximum, ice sheets in Eurasia terminated at the edge of the Laptev Sea. Seismic data now suggest that a separate ice sheet was repeatedly centred further east, in the East Siberian Sea, during previous glacial periods. See also: Letter by Niessen et al. Ernst Maier-Reimer: The discovery of silence   p809 Klaus Hasselmann doi:10.1038/ngeo1953 Marine biogeochemistry: Methylmercury manufacture   pp810 - 811 Daniel Cossa doi:10.1038/ngeo1967 The neurotoxin methylmercury can accumulate in marine food webs, contaminating seafood. An analysis of the isotopic composition of fish in the North Pacific suggests that much of the mercury that enters the marine food web originates from low-oxygen subsurface waters. See also: Article by Blum et al. Plate tectonics: Magma for 50,000 years   pp811 - 812 W. Roger Buck doi:10.1038/ngeo1951 Intrusions of magma into the crust help accommodate the divergence between tectonic plates. A magnetotelluric survey of the crust and mantle beneath Afar, Ethiopia, has identified enough magma to accommodate plate separation there for about 50,000 years. See also: Letter by Desissa et al. Geoscience JOBS of the week Assistant Professorship in Seismology Ludwig-Maximilans-University München Lecturers (High Temperature and Low Temperature Synchrotron Geosciences) Monash University - Faculty of Science More Science jobs from Review Top Three decades of global methane sources and sinks   pp813 - 823 Stefanie Kirschke, Philippe Bousquet, Philippe Ciais, Marielle Saunois, Josep G. Canadell et al. doi:10.1038/ngeo1955 Methane is an important greenhouse gas, responsible for about 20% of the warming induced by long-lived greenhouse gases since pre-industrial times. A compilation of observations and results from chemical transport, ecosystem and climate chemistry models suggests that a rise in wetland and fossil fuel emissions probably accounts for the renewed increase in global methane levels after 2006. Letters Top Readily available phosphate from minerals in early aqueous environments on Mars   pp824 - 827 C. T. Adcock, E. M. Hausrath and P. M. Forster doi:10.1038/ngeo1923 Phosphate is thought to be a chemical nutrient essential for life, but the low solubility of phosphate minerals means that abiogenesis on Earth had to overcome the hurdle of phosphate-limited environments. Dissolution experiments of phosphate minerals commonly found on Mars suggest that phosphate may have been more readily available in early martian environments. See also: News and Views by Pasek Similar spatial patterns of climate responses to aerosol and greenhouse gas changes   pp828 - 832 Shang-Ping Xie, Bo Lu and Baoqiang Xiang doi:10.1038/ngeo1931 Anthropogenic aerosols are highly spatially variable, whereas greenhouse gases are largely well-mixed at the global scale, but both affect climate. Nevertheless, climate simulations suggest that regional changes in sea surface temperature and precipitation to changes in greenhouse gas and aerosol forcings are similar. Diverse calving patterns linked to glacier geometry   pp833 - 836 J. N. Bassis and S. Jacobs doi:10.1038/ngeo1887 Iceberg calving—implicated in the retreat of ice shelves—is a complex process constrained by few observations. Numerical simulations suggest that the pattern of iceberg calving is controlled by the geometry of the glacier, and that regions of Greenland and Antarctica may be particularly vulnerable to catastrophic calving-driven retreat. Air–sea temperature decoupling in western Europe during the last interglacial–glacial transition   pp837 - 841 Maria Fernanda Sánchez Goñi, Edouard Bard, Amaelle Landais, Linda Rossignol and Francesco d’Errico doi:10.1038/ngeo1924 Between 80,000 and 70,000 years ago, climate cooled and ice sheets in the high northern latitudes expanded. Pollen and microfossil data from marine sediments indicate that an increasing thermal gradient between cold air and warmer oceans could have supported continental ice growth. Repeated Pleistocene glaciation of the East Siberian continental margin   pp842 - 846 Frank Niessen, Jong Kuk Hong, Anne Hegewald, Jens Matthiessen, Rüdiger Stein et al. doi:10.1038/ngeo1904 During glacial periods, ice sheets covered continental margins through much of Arctic North America, Greenland and western Eurasia. Marine structures suggest that an ice sheet up to a kilometre in depth periodically covered the East Siberian continental shelf as well. See also: News and Views by Brigham-Grette Subduction-zone earthquake complexity related to frictional anisotropy in antigorite   pp847 - 851 Marcello Campione and Gian Carlo Capitani doi:10.1038/ngeo1905 Mantle minerals in faults above a subducting slab can become aligned. Laboratory analyses show that this mineral alignment can also generate direction-dependent friction that can cause faults to slip both seismically and aseismically, depending on the direction of movement. Hydrologic control of forearc strength and seismicity in the Costa Rican subduction zone   pp852 - 855 Pascal Audet and Susan Y. Schwartz doi:10.1038/ngeo1927 The subduction zone beneath Costa Rica experiences infrequent large earthquakes in its northwestern part, whereas slow slip dominates in the southeast. Seismic data reveal a disparity in fluid accumulation in the overriding continental crust that correlates with this change in seismic behaviour, implying that spatial gradients in fluid content may control subduction-zone seismicity. Eruption cyclicity at silicic volcanoes potentially caused by magmatic gas waves   pp856 - 860 Chloé Michaut, Yanick Ricard, David Bercovici and R. Steve J. Sparks doi:10.1038/ngeo1928 Volcanic eruptions can be cyclical, alternating between intense activity and repose over periods of hours to days. Numerical simulations of a viscous, gas-rich magma show that ascent through the volcanic conduit naturally induces a periodic pulse of pressurized gas to travel through the magma, which, on reaching the surface, can trigger the cyclical eruptions. A mantle magma reservoir beneath an incipient mid-ocean ridge in Afar, Ethiopia   pp861 - 865 M. Desissa, N. E. Johnson, K. A. Whaler, S. Hautot, S. Fisseha et al. doi:10.1038/ngeo1925 The buoyancy of magma should cause it to rise into the crust, preventing it from ponding in the uppermost mantle. Magnetotelluric data from the Dabbahu rift segment, Ethiopia, identify a magma reservoir that extends well into the mantle beneath the rift, and is so large that it should persist for thousands of years. See also: News and Views by Buck Fine-scale segmentation of the crustal magma reservoir beneath the East Pacific Rise   pp866 - 870 Suzanne M. Carbotte, Milena Marjanović, Helene Carton, John C. Mutter, Juan Pablo Canales et al. doi:10.1038/ngeo1933 Mid-ocean ridges are composed of segmented faults and magma reservoirs. Seismic images from the East Pacific Rise show that the magma reservoirs are segmented on the same fine scale as the surface faults, and that distinct lava eruptions are sourced from largely isolated magma lenses. Hadean mantle melting recorded by southwest Greenland chromitite 186Os signatures   pp871 - 874 Judith A. Coggon, Ambre Luguet, Geoffrey M. Nowell and Peter W. U. Appel doi:10.1038/ngeo1911 Earth’s crust formed from melted mantle, yet the earliest record of this process is recorded only in crustal rocks. Isotopic dating of mantle rocks in the Ujaragssuit Nunãt intrusion, southwest Greenland, identify melting events that occurred up to 4.36 Gyr ago, providing a mantle record of ancient melting to complement the crustal record. Carbon storage at defect sites in mantle mineral analogues   pp875 - 878 Jun Wu and Peter R. Buseck doi:10.1038/ngeo1903 The mode of carbon storage in Earth’s mantle is unclear. High-pressure laboratory experiments on mantle analogue materials reveal that significant quantities of carbon can be stored in tiny defects within the minerals, providing an efficient mechanism for carbon storage in the mantle. Articles Top Methylmercury production below the mixed layer in the North Pacific Ocean   pp879 - 884 Joel D. Blum, Brian N. Popp, Jeffrey C. Drazen, C. Anela Choy and Marcus W. Johnson doi:10.1038/ngeo1918 Mercury enters marine food webs in the form of microbially generated monomethylmercury. An analysis of the mercury isotopic composition of nine species of North Pacific fish suggests that microbial production of monomethylmercury below the surface mixed layer contributes significantly to the mercury contamination of marine food webs. See also: News and Views by Cossa Independent variations of CH4 emissions and isotopic composition over the past 160,000 years   pp885 - 890 Lars Möller, Todd Sowers, Michael Bock, Renato Spahni, Melanie Behrens et al. doi:10.1038/ngeo1922 Atmospheric methane concentrations varied substantially over the last glacial cycle. An analysis of the δ13C of the methane suggests that the relative strength of various methane sources and sinks varied independently of overall changes in methane concentrations. Top   Natureevents is a fully searchable, multi-disciplinary database designed to maximise exposure for events organisers. The contents of the Natureevents Directory are now live. The digital version is available here. Find the latest scientific conferences, courses, meetings and symposia on natureevents.com. For event advertising opportunities across the Nature Publishing Group portfolio please contact natureevents@nature.com More Nature Events

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