Compositional trends in aeolian dust along a transect across the southwestern United States
H.L. Goldstein, R. L. Reynolds, M.C. Reheis, J. C. Yount, J. C. Neff
2008, Journal of Geophysical Research F: Earth Surface (113)
Aeolian dust strongly influences ecology and landscape geochemistry over large areas that span several desert ecosystems of the southwestern United States. This study evaluates spatial and temporal variations and trends of the physical and chemical properties of dust in the southwestern United States by examining dust deposited in natural depressions...
Modeling the evolution of channel shape: Balancing computational efficiency with hydraulic fidelity
C.W. Wobus, J. W. Kean, G.E. Tucker, R. Scott Anderson
2008, Journal of Geophysical Research F: Earth Surface (113)
The cross-sectional shape of a natural river channel controls the capacity of the system to carry water off a landscape, to convey sediment derived from hillslopes, and to erode its bed and banks. Numerical models that describe the response of a landscape to changes in climate or tectonics therefore require...
Alaska Melilotus invasions: Distribution, origin, and susceptibility of plant communities
J.S. Conn, K.L. Beattie, M.A. Shephard, M.L. Carlson, I. Lapina, M. Hebert, R. Gronquist, R. Densmore, M. Rasy
2008, Arctic, Antarctic, and Alpine Research (40) 298-308
Melilotus alba and M. officinalis were introduced to Alaska in 1913 as potential forage crops. These species have become naturalized and are now invading large, exotic plant-free regions of Alaska. We determined distributions of M. alba and M. officinalis in Alaska from surveys conducted each summer from 2002 to 2005....
Distributed energy balance modeling of South Cascade Glacier, Washington and assessment of model uncertainty
Faron S. Anslow, S. Hostetler, W. R. Bidlake, P.U. Clark
2008, Journal of Geophysical Research F: Earth Surface (113)
We have developed a physically based, distributed surface energy balance model to simulate glacier mass balance under meteorological and climatological forcing. Here we apply the model to estimate summer ablation on South Cascade Glacier, Washington, for the 2004 and 2005 mass balance seasons. To arrive at optimal mass balance simulations,...
Surface albedo observations at Gusev Crater and Meridiani Planum, Mars
J.F. Bell III, M.S. Rice, J. R. Johnson, T.M. Hare
2008, Journal of Geophysical Research E: Planets (113)
During the Mars Exploration Rover mission, the Pancam instrument has periodically acquired large-scale panoramic images with its broadband (739??338 nm) filter in order to estimate the Lambert bolometric albedo of the surface along each rover's traverse. In this work we present the full suite of such estimated albedo values measured...
The formation conditions of chondrules and chondrites
C. M. O’D. Alexander, Jeffrey N. Grossman, D.S. Ebel, F.J. Ciesla
2008, Science (320) 1617-1619
Chondrules, which are roughly millimeter-sized silicate-rich spherules, dominate the most primitive meteorites, the chondrites. They formed as molten droplets and, judging from their abundances in chondrites, are the products of one of the most energetic processes that operated in the early inner solar system. The conditions and mechanism of chondrule...
Diurnal and vertical variability of the sensible heat and carbon dioxide budgets in the atmospheric surface layer
P. Casso-Torralba, J. V. -G. de Arellano, F. Bosveld, M.R. Soler, A. Vermeulen, C. Werner, E. Moors
2008, Journal of Geophysical Research D: Atmospheres (113)
The diurnal and vertical variability of heat and carbon dioxide (CO2) in the atmospheric surface layer are studied by analyzing measurements from a 213 in tower in Cabauw (Netherlands). Observations of thermodynamic variables and CO2 mixing ratio as well as vertical profiles of the turbulent fluxes are used to retrieve...
Oceanic loading of wildfire-derived organic compounds from a small mountainous river
G.B. Hunsinger, Siddhartha Mitra, J.A. Warrick, C. R. Alexander
2008, Journal of Geophysical Research G: Biogeosciences (113)
Small mountainous rivers (SMRs) export substantial amounts of sediment into the world's oceans. The concomitant yield of organic carbon (OC) associated with this class of rivers has also been shown to be significant and compositionally unique. We report here excessively high loadings of polycyclic aromatic hydrocarbons (PAHs), lignin, and levoglucosan,...
Iron isotope fractionation during magmatic differentiation in Kilauea Iki lava lake
F.-Z. Teng, N. Dauphas, Rosalind Tuthill Helz
2008, Science (320) 1620-1622
Magmatic differentiation helps produce the chemical and petrographic diversity of terrestrial rocks. The extent to which magmatic differentiation fractionates nonradiogenic isotopes is uncertain for some elements. We report analyses of iron isotopes in basalts from Kilauea Iki lava lake, Hawaii. The iron isotopic compositions (56Fe/54Fe) of late-stagemeltveins are 0.2 permil...
Wind-driven particle mobility on Mars: Insights from Mars Exploration Rover observations at "El Dorado" and surroundings at Gusev Crater
R. Sullivan, R. Arvidson, J.F. Bell, Ralf Gellert, M. Golombek, R. Greeley, Kenneth E. Herkenhoff, J. Johnson, S. Thompson, P. Whelley, J. Wray
2008, Journal of Geophysical Research E: Planets (113)
The ripple field known as 'El Dorado' was a unique stop on Spirit's traverse where dust-raising, active mafic sand ripples and larger inactive coarse-grained ripples interact, illuminating several long-standing issues of Martian dust mobility, sand mobility, and the origin of transverse aeolian ridges. Strong regional wind events endured by Spirit...
Deep drilling into the Chesapeake Bay impact structure
G. S. Gohn, C. Koeberl, K.G. Miller, W.U. Reimold, J.V. Browning, C.S. Cockell, J. Wright Horton Jr., T. Kenkmann, A.A. Kulpecz, D.S. Powars, W. E. Sanford, M.A. Voytek
2008, Science (320) 1740-1745
Samples from a 1.76-kilometer-deep corehole drilled near the center of the late Eocene Chesapeake Bay impact structure (Virginia, USA) reveal its geologic, hydrologic, and biologic history. We conducted stratigraphic and petrologic analyses of the cores to elucidate the timing and results of impact-melt creation and distribution, transient-cavity collapse, and ocean-water...
Mars Exploration Rover Navigation Camera in-flight calibration
J.M. Soderblom, J.F. Bell III, J. R. Johnson, J. Joseph, M.J. Wolff
2008, Journal of Geophysical Research E: Planets (113)
The Navigation Camera (Navcam) instruments on the Mars Exploration Rover (MER) spacecraft provide support for both tactical operations as well as scientific observations where color information is not necessary: large-scale morphology, atmospheric monitoring including cloud observations and dust devil movies, and context imaging for both the thermal emission spectrometer and...
Genetic characterization of Hawaiian isolates of Plasmodium relictum reveals mixed-genotype infections
S.I. Jarvi, M.E.M. Farias, C. T. Atkinson
2008, Biology Direct (3)
Background: The relatively recent introduction of a highly efficient mosquito vector and an avian pathogen (Plasmodium relictum) to an isolated island ecosystem with nai??ve, highly susceptible avian hosts provides a unique opportunity to investigate evolution of virulence in a natural system. Mixed infections can significantly contribute to the uncertainty in...
Hydrothermal processes at Gusev Crater: An evaluation of Paso Robles class soils
A. S. Yen, R.V. Morris, B. C. Clark, Ralf Gellert, A.T. Knudson, S. Squyres, D. W. Mittlefehldt, D. W. Ming, R. Arvidson, T. McCoy, M. Schmidt, J. Hurowitz, R. Li, J. R. Johnson
2008, Journal of Geophysical Research E: Planets (113)
The Mars Exploration Rover Spirit analyzed multiple occurrences of sulfur-rich, light-toned soils along its traverse within Gusev Crater. These hydrated deposits are not readily apparent in images of undisturbed soil but are present at shallow depths and were exposed by the actions of the rover wheels. Referred to as 'Paso...
MGS-TES thermal inertia study of the Arsia Mons Caldera
Glen E. Cushing, Timothy N. Titus
2008, Journal of Geophysical Research E: Planets (113)
Temperatures of the Arsia Mons caldera floor and two nearby control areas were obtained by the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES). These observations revealed that the Arsia Mons caldera floor exhibits thermal behavior different from the surrounding Tharsis region when compared with thermal models. Our technique compares...
Evaluating the potential effectiveness of compensatory mitigation strategies for marine bycatch
M. Finkelstein, V. Bakker, D.F. Doak, B. Sullivan, R. Lewison, W.H. Satterthwaite, P.B. McIntyre, S. Wolf, D. Priddel, J.M. Arnold, R.W. Henry, P. Sievert, J. Croxall
2008, PLoS ONE (3)
Conservationists are continually seeking new strategies to reverse population declines and safeguard against species extinctions. Here we evaluate the potential efficacy of a recently proposed approach to offset a major anthropogenic threat to many marine vertebrates: incidental bycatch in commercial fisheries operations. This new approach, compensatory mitigation for marine bycatch...
Sediment and nutrient delivery from thermokarst features in the foothills of the North Slope, Alaska: Potential impacts on headwater stream ecosystems
W.B. Bowden, M.N. Gooseff, A. Balser, A. Green, B. J. Peterson, J. Bradford
2008, Journal of Geophysical Research G: Biogeosciences (113)
Permafrost is a defining characteristic of the Arctic environment. However, climate warming is thawing permafrost in many areas leading to failures in soil structure called thermokarst. An extensive survey of a 600 km2 area in and around the Toolik Lake Natural Research Area (TLNRA) revealed at least 34 thermokarst features,...
Molecular sequences derived from Paleocene Fort Union Formation coals vs. associated produced waters: Implications for CBM regeneration
Donald A. Klein, Romeo M. Flores, Christophe Venot, Kendra Gabbert, Raleigh Schmidt, Gary D. Stricker, Amy Pruden, Kevin Mandernack
2008, International Journal of Coal Geology (76) 3-13
Coalbed methane regeneration is of increasing interest, and is gaining global attention with respect to enhancement of gas recovery. The objective of this study is to determine if there are differences in methanogen nucleic acid sequences associated with low rank coals from the Powder River Basin, Wyoming, in comparison with...
Microbial and chemical factors influencing methane production in laboratory incubations of low-rank subsurface coals
Stephen H. Harris, Richard L. Smith, Charles E. Barker
2008, International Journal of Coal Geology (76) 46-51
Lignite and subbituminous coals were investigated for their ability to support microbial methane production in laboratory incubations. Results show that naturally-occurring microorganisms associated with the coals produced substantial quantities of methane, although the factors influencing this process were variable among different samples tested. Methanogenic microbes in two coals from the...
Evaluating transition-metal catalysis in gas generation from the Permian Kupferschiefer by hydrous pyrolysis
M. D. Lewan, M.J. Kotarba, D. Wieclaw, A. Piestrzynski
2008, Geochimica et Cosmochimica Acta (72) 4069-4093
Transition metals in source rocks have been advocated as catalysts in determining extent, composition, and timing of natural gas generation (Mango, F. D. (1996) Transition metal catalysis in the generation of natural gas. Org. Geochem.24, 977–984). This controversial hypothesis may have important implications concerning gas generation in unconventional shale-gas accumulations....
Susceptibility of synthetic long-chain alkylbenzenes to degradation in reducing marine sediments
Robert P. Eganhouse, James Pontolillo
2008, Environmental Science & Technology (42) 6361-6368
Long-chain alkylbenzenes (LCABs) synthesized for production of alkylbenzene sulfonate surfactants have been used as molecular markers of anthropogenic waste for 25 years. Synthetic LCABs comprise two classes, the tetrapropylene-based alkylbenzenes (TABs) and the linear alkylbenzenes (LABs). LABs supplanted TABs in the mid-1960s because of improved biodegradability of their sulfonated analogs....
Moist-soil seed abundance in managed wetlands in the Mississippi Alluvial Valley
J. Kross, R.M. Kaminski, K. J. Reinecke, E.J. Penny, A.T. Pearse
2008, Journal of Wildlife Management (72) 707-714
Managed moist-soil units support early succession herbaceous vegetation that produces seeds, tubers, and other plant parts used by waterfowl in the Mississippi Alluvial Valley (MAV), USA. We conducted a stratified multi-stage sample survey on state and federal lands in the MAV of Arkansas, Louisiana, Mississippi, and Missouri during autumns...
Exploring visitor acceptability for hardening trails to sustain visitation and minimize impacts
K.L. Cahill, J. L. Marion, S.R. Lawson
2008, Journal of Sustainable Tourism (16) 232-245
Protected natural area managers are challenged to provide high quality recreation opportunities and ensure the protection of resources from impacts associated with visitation. Development of visitor use facilities and application of site hardening practices are commonly applied tools for achieving these competing management objectives. This study applies stated...
Estimating species occurrence, abundance, and detection probability using zero-inflated distributions
S.J. Wenger, Mary C. Freeman
2008, Ecology (89) 2953-2959
Researchers have developed methods to account for imperfect detection of species with either occupancy (presence-absence) or count data using replicated sampling. We show how these approaches can be combined to simultaneously estimate occurrence, abundance, and detection probability by specifying a zero-inflated distribution for abundance. This approach may be...
Quantifying the extent of river fragmentation by hydropower dams in the Sarapiquí River Basin, Costa Rica
Elizabeth P. Anderson, Catherine M. Pringle, Mary C. Freeman
2008, Aquatic Conservation: Marine and Freshwater Ecosystems (18) 408-417
Costa Rica has recently experienced a rapid proliferation of dams for hydropower on rivers draining its northern Caribbean slope. In the Sarapiquí River Basin, eight hydropower plants were built between 1990 and 1999 and more projects are either under construction or proposed. The majority of these dams are small (<15 m...
