ALBERT

Description: Presented here is the complete genome sequence of Thiomicrospira crunogena XCL-2, representative of ubiquitous chemolithoautotrophic sulfur-oxidizing bacteria isolated from deep-sea hydrothermal vents. This gammaproteobacterium has a single chromosome (2,427,734 base pairs), and its genome illustrates many of the adaptations that have enabled it to thrive at vents globally. It has 14 methyl-accepting chemotaxis protein genes, including four that may assist in positioning it in the redoxcline. A relative abundance of coding sequences (CDSs) encoding regulatory proteins likely control the expression of genes encoding carboxysomes, multiple dissolved inorganic nitrogen and phosphate transporters, as well as a phosphonate operon, which provide this species with a variety of options for acquiring these substrates from the environment. Thiom. crunogena XCL-2 is unusual among obligate sulfur-oxidizing bacteria in relying on the Sox system for the oxidation of reduced sulfur compounds. The genome has characteristics consistent with an obligately chemolithoautotrophic lifestyle, including few transporters predicted to have organic allocrits, and Calvin-Benson-Bassham cycle CDSs scattered throughout the genome.

Description: The interaction of clouds with solar and terrestrial radiation is one of the most important topics of climate research. In recent years it has been recognized that only a full three-dimensional (3D) treatment of this interaction can provide answers to many climate and remote sensing problems, leading to the worldwide development of numerous 3D radiative transfer (RT) codes. The international Intercomparison of 3D Radiation Codes (I3RC), described in this paper, sprung from the natural need to compare the performance of these 3D RT codes used in a variety of current scientific work in the atmospheric sciences. I3RC supports intercomparison and development of both exact and approximate 3D methods in its effort to 1) understand and document the errors/limits of 3D algorithms and their sources; 2) provide “baseline” cases for future code development for 3D radiation; 3) promote sharing and production of 3D radiative tools; 4) derive guidelines for 3D radiative tool selection; and 5) improve atmospheric science education in 3D RT. Results from the two completed phases of I3RC have been presented in two workshops and are expected to guide improvements in both remote sensing and radiative energy budget calculations in cloudy atmospheres.

Description: Atmospheric radiative transfer plays a central role in understanding global climate change and anthropogenic climate forcing, and in the remote sensing of surface and atmospheric properties. Because of their opacity and highly scattering nature, clouds (covering more than half the planet at any time) pose unique challenges in atmospheric radiative transfer calculations. Some widely-used assumptions regarding clouds—such as having a flat top and base, horizontal uniformity, and infinite extent—are amenable to simple one-dimensional (1-D) radiative transfer and are therefore attractive from a computational point of view. However, these assumptions are completely unrealistic and yield errors. The ever-increasing need to realistically simulate cloud radiative processes in remote sensing and energy budget applications has contributed to the recent rapid growth of the three-dimensional (3-D) radiative transfer (RT) community [e.g., Marshak and Davis, 2005].

Description: The LaRonde Penna Au-rich volcanogenic massive sulfide (VMS) deposit is the largest Au deposit currently mined in Canada (58.8 Mt at 4.31 g/t, containing 8.1 Moz of Au). It is part of the Doyon-Bousquet-LaRonde mining camp located in the eastern part of the Blake River Group of the Abitibi greenstone belt which is host to several of the world’s most important, present and past, Au-rich VMS deposits (e.g., Horne, Quemont, Bousquet, Bousquet 2-Dumagami). The LaRonde Penna deposit consists of massive to semimassive sulfide lenses (Au-Zn-Ag-Cu-Pb), stacked in the upper part of a steeply dipping, south-facing homoclinal volcanic sequence composed of extensive tholeiitic basaltic flows (Hébécourt Formation) overlain by tholeiitic to transitional, mafic to intermediate, effusive and volcaniclastic units at the base (lower member of the Bousquet Formation) and transitional to calc-alkaline, intermediate to felsic, effusive and intrusive rocks on top (upper member of the Bousquet Formation). The mafic to felsic volcanism of the Hébécourt Formation and of the lower member of the Bousquet Formation formed an extensive submarine basement or platform on which the intermediate to felsic rocks of the upper member of the Bousquet Formation were emplaced at restricted submarine eruptive centers or as shallow composite intrusive complexes. The submarine felsic volcanic rocks of the upper member of the Bousquet Formation are characterized by dacitic to rhyodacitic autoclastic (flow breccia) deposits that are cut and overlain by rhyodacitic and rhyolitic domes and/or partly extrusive cryptodomes and by intermediate to mafic sills and dikes. This volcanic architecture is thought to have been responsible for internal variations in ore and alteration styles, not only from one lens to another, but also along a single mineralized horizon or lens. In the upper part of the mine, the 20 North lens comprises a transposed pyrite-chalcopyrite (Au-Cu) stockwork (20N Au zone) overlain by a pyrite-sphalerite-galena-chalcopyrite-pyrrhotite (Zn-Ag-Pb) massive sulfide lens (20N Zn zone). The latter was formed, at least in part, by replacement of footwall rhyodacitic autoclastic deposits emplaced within a subbasin located between two rhyolite domes or cryptodomes. The 20N Zn zone tapers with depth in the mine and gives way to the 20N Au zone. At depth in the mine, the 20N Au zone consists of semimassive sulfides (Au-rich pyrite and chalcopyrite) enclosed by a large aluminous alteration halo on the margin of a large rhyolitic dome or cryptodome. U-Pb zircon geochronology gives ages of 2698.3 ± 0.8 and 2697.8 ± 1 Ma for the footwall and hanging-wall units of the 20 North lens, respectively. Thus, the formation of the 20 North lens was coeval with other VMS deposits in the Bousquet Formation and in the uppermost units of the Blake River Group. Although deformation and metamorphism have affected the primary mineral assemblages and the original geometry of the deposit, these events were not responsible for the different auriferous ore zones and alteration at LaRonde Penna. Studies of the LaRonde Penna deposit show that the hydrothermal system evolved in time and space from near-neutral seawater-dominated hydrothermal fluids, responsible for Au-Cu-Zn-Ag-Pb mineralization, to highly acidic fluids with possible direct magmatic contributions, responsible for Au ± Cu-rich ore and aluminous alteration. The different ore types and alteration reflect the evolving local volcanic setting described in this study.

Description: Large uncertainties remain in the current and future contribution to sea level rise from Antarctica. Climate warming may increase snowfall in the continent’s interior1,2,3, but enhance glacier discharge at the coast where warmer air and ocean temperatures erode the buttressing ice shelves4,5,6,7,8,9,10,11. Here, we use satellite interferometric synthetic-aperture radar observations from 1992 to 2006 covering 85% of Antarctica’s coastline to estimate the total mass flux into the ocean. We compare the mass fluxes from large drainage basin units with interior snow accumulation calculated from a regional atmospheric climate model for 1980 to 2004. In East Antarctica, small glacier losses in Wilkes Land and glacier gains at the mouths of the Filchner and Ross ice shelves combine to a near-zero loss of 4±61 Gt yr−1. In West Antarctica, widespread losses along the Bellingshausen and Amundsen seas increased the ice sheet loss by 59% in 10 years to reach 132±60 Gt yr−1 in 2006. In the Peninsula, losses increased by 140% to reach 60±46 Gt yr−1 in 2006. Losses are concentrated along narrow channels occupied by outlet glaciers and are caused by ongoing and past glacier acceleration. Changes in glacier flow therefore have a significant, if not dominant impact on ice sheet mass balance.