bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluctuations of total ozone and their relationship to stratospheric air motions
Authors: Salby Murry L. , Callaghan Patrick F.
Published: February 2008

Satellite measurements reveal the distribution of ozone column abundance to be complex and highly dynamic, with fluctuations as large as 100% common in both hemispheres. Observations of total ozone from Nimbus 7 total ozone mapping spectrometer (TOMS) together with contemporaneous analyses of the circulation are used to investigate the origin of these fluctuations. A large component of total ozone variability is explained by quasi‐columnar motion of air along isentropic surfaces in the lower stratosphere. The vertical component of such motion introduces anomalous column abundance through compression arid expansion, which alters the ozone number density of individual bodies of air. This process leads to a high correlation between the total ozone and the elevation of isentropic surfaces in the lower stratosphere. The horizontal component of column‐averaged motion introduces anomalous total ozone by rearranging the distribution of column‐averaged ozone mixing ratio, which can be derived from TOMS measurements and contemporaneous isentropic analyses. Quasi‐conserved, column‐averaged ozone mixing ratio is well correlated with equivalent barotropic potential vorticity, which is a tracer of column‐averaged motion. In fact, anomalies of column‐averaged mixing ratio created during major warmings can be tracked intact and coincident with companion anomalies in the circulation for as long as 3 weeks. Because it follows from observations of tracer behavior, column‐averaged ozone mixing ratio may provide a more detailed picture of air motions in the lower stratosphere than is possible from potential vorticity, which must be derived largely from temperature observations. Together with contemporaneous cloud imagery, TOMS observations also reveal interactions with tropospheric convection, which result in a loss and, ultimately, the destruction of stratospheric ozone.
Measurement distortion in aircraft, space shuttle, and balloon observations of atmospheric density and temperature perturbation spectra
Authors: Gardner Chester S. , Gardner Nathan F.
Published: February 2008

Aircraft, space shuttle, and balloon observations are being used to study the density, temperature, and wind structure of the atmosphere. The horizontal and vertical wave number spectra derived from these observations are contaminated by undesired spatial and temporal variations unique to the observational geometries. We use numerical models to quantify this distortion. The results show that distortion is negligible in aircraft and space shuttle measurements of horizontal wave number spectra if the aircraft velocity is ∼100 m/s or larger and the slant angle of the shuttle reentry path is ∼0.5° or less. The distortion in balloon measurements of vertical wave number spectra is negligible provided the ascent velocity is ∼3 m/s or larger and the horizontal wind speed is not more than about 10 times the balloon ascent velocity. This latter condition can be violated during some balloon flights when horizontal winds are strong. In those circumstances the measured spectrum will be larger in magnitude and have a shallower slope than the intrinsic vertical wave number spectrum.
Cloud condensation nuclei near marine cumulus
Authors: Hudson James G.
Published: February 2008

Extensive airborne measurements of cloud condensation nucleus (CCN) spectra and condensation nuclei below, in, between, and above the cumulus clouds near Hawaii point to important aerosol‐cloud interactions. Consistent particle concentrations of 200 cm−3 were found above the marine boundary layer and within the noncloudy marine boundary layer. Lower and more variable CCN concentrations within the cloudy boundary layer, especially very close to the clouds, appear to be a result of cloud scavenging processes. Gravitational coagulation of cloud droplets may be the principal cause of this difference in the vertical distribution of CCN. The results suggest a reservoir of CCN in the free troposphere which can act as a source for the marine boundary layer.
Global NOx, HNO3, PAN, and NOy distributions from fossil fuel combustion emissions: A model study
Authors: Kasibhatla P. S. , Levy H. , Moxim W. J.
Published: February 2008

The 11‐level Geophysical Fluid Dynamics Laboratory global chemical transport model (GCTM) which explicitly treats NOx, HNO3, and PAN as transported species has been used to assess the impact of fossil fuel combustion emissions on the distribution of reactive nitrogen compounds (NOy ) in various regions of the troposphere. The GCTM is driven by 6‐hour time‐averaged wind and total precipitation fields derived from a parent general circulation model. PAN production rates are calculated using background, two‐dimensional ethane and propane fields, which are then adjusted to parameterize the effect of short‐lived hydrocarbons over continental regions. From an analysis of our model results, we conclude that (1) the model reproduces the observed spatial patterns of wet deposition near the major fossil fuel combustion source regions. Wet and dry deposition in source regions account for 30% and 40–45% of the emissions, respectively, with the remainder being exported over the adjacent ocean basins; (2) the fossil fuel source accounts for a large fraction of the observed surface concentrations and wet deposition fluxes of HNO3 in the extra tropical North Atlantic; (3) while it appears that a significant fraction of NOy observed in the marine free troposphere during the NASA Global Tropical Experiment/CITE 2 experiment in the eastern North Pacific cannot be explained in terms of the fossil fuel source, this may simply indicate that in this region subgrid‐scale transport from adjacent continental source regions is not being adequately resolved by the model; (4) at the more remote Mauna Loa, Hawaii site, less than 30% of the observed NOy during May 1988, appears to be due to distant fossil fuel sources; (5) even with the explicit treatment of PAN as a transported species, the fossil fuel source has only a minor impact on NOy, levels in the remote tropics and in the southern hemisphere; (5) model calculations indicate that the relatively high levels of NOy observed over western Alaska during the ABLE 3A experiment in July‐August 1988, cannot be explained in terms of long‐range transport of fossil fuel combustion emissions from the northern hemisphere mid‐latitude surface source regions; and (6) away from source regions, PAN is a major component of fossil fuel NOy, and is the dominant component poleward of 45°N. However, the relative impact of this sequestered PAN on regional spring time NOx levels has yet to be established.
Spectral measurements of solar UVB radiation and its relations to total ozone, SO2, and clouds
Authors: Bais Alkiviadis F. , Zerefos Christos S. , Meleti Chariklea , Ziomas Ioannis C. , Tourpali Kleareti
Published: February 2008

Spectral solar UV radiation measurements performed at Thessaloniki, Greece (40°N), are presented, and the influence of various atmospheric constituents such as total ozone, cloud cover, and columnar SO2 on these measurements is examined. By comparing UV radiation measurements at days with different total ozone amounts the magnification factor was calculated. Its values range from 1 to 20, depending on the wavelength and the total ozone. A relationship between the UV radiation and the cloud cover was established, being representative only for measurements at 50° solar zenith angle. In addition, the influence of columnar SO2 variations on UV irradiances was also studied. Finally, an attempt was made to compare the relative influence of these parameters on UV radiation, which proved that total ozone is the major factor controlling the solar UVB radiation received at the ground.
Characteristics of gravity waves in the mesosphere observed with the middle and upper atmosphere radar: 2. Propagation direction
Authors: Nakamura T. , Tsuda T. , Yamamoto M. , Fukao S. , Kato S.
Published: February 2008

We studied the characteristics of dominant component of gravity waves (λz ∼ 10 km) in the vertical profile of the wind velocities observed in the mesosphere (at around 70–75 km) with the middle and upper atmosphere (MU) radar in the four observation campaigns (June 1987, July 1990, October 1986, and January/February 1991) and the monthly mesosphere observations carried out 4–5 days a month in December 1985 to December 1988. By assuming linear dispersion relations of gravity waves, both vertical and horizontal propagation directions of gravity waves were determined. Most of the dominant waves propagated upward, except that they sometimes propagated downward mainly in summer. A typical vertical wavelength and intrinsic period of the dominant gravity waves were 4–15 km and 4–15 hours, respectively. The mean values of the vertical wavelength, horizontal wavelength, and intrinsic periods were 8.2 km, 1200 km, and 10.2 hours, respectively, which did not show significant seasonal variations. Most of the waves were found to be dissipated by the eddy diffusion of 15–100 m2/s, which does not agree with MF radar observations (10‐ to 120‐min observed periods) but is rather consistent with sodium lidar observations (36–300 m2/s). The mean horizontal phase velocity was 33 m/s. The horizontal propagation direction was generally eastward throughout a year except for the westward propagation in early winter (November to December). This suggests that the dominant gravity waves are less sensitive to a change in the mean zonal wind direction in the middle atmosphere than the short‐period gravity waves (2 hours to 5 min). Momentum flux carried by the dominant gravity waves was estimated to be 0.5–1 m2/s2, which was generally smaller than the momentum flux of gravity waves with periods ranging from 8 hours to 5 min. The amplitude of the momentum flux of the dominant gravity waves had an autumn maximum, while the momentum flux with periods of 8 hours to 5 min had equinoctial minima. Thus in September and October the momentum flux due to the dominant gravity waves became significant. We further pointed out that the possibility that
/ depends on the wave periods, and therefore the major frequency component of
is not easily determined from simple dispersion relation only.
Dynamics of the atmospheres of the outer planets: Post‐Voyager measurement objectives
Authors: Gierasch Peter J. , Conrath Barney J.
Published: February 2008

Current knowledge about dynamics and thermal structure on the outer planets is reviewed with the aim of identifying important measurements which should be made in the post‐Voyager era. The existence of jets and cloud bands is the puzzle that underlies all others. Discussion focuses on the particular case of Jupiter because documentation is most complete. Recent dynamical work has successfully reproduced much of the behavior of jets and spots with simple models that contain few parameters. It is argued that the gross dynamical parameters, such as density stratification and rotation rate, are the keys to their behaviors, rather than the particular specifics of radiative forcing, cloud distributions, thermodynamic transformations. Voyager data have shown that the jet systems decay with height in the region above the visible clouds. Therefore the highest priority must be given to establishing dynamical parameters that characterize levels within and beneath the clouds. These require determination of the deep structure of the jets, of the density stratification, and of the horizontal density contrasts. The deep regions are not easily accessible, and these measurements present challenging opportunities. Indirect inferences about the controlling processes may sometimes be possible by observing waves and other activity in the more easily accessible stratosphere, and some of these issues are also discussed.
Volcanic geology of Hadriaca Patera and the eastern Hellas region of Mars
Authors: Crown David A. , Greeley Ronald
Published: February 2008

Hadriaca Patera is a low‐relief volcano in the southern highlands of Mars northeast of the Hellas basin. Layered, friable deposits composing the extensive channeled flanks of the volcano surround a well‐defined, summit caldera containing late stage eruptive products. The morphologic characteristics of the channels suggest erosion by groundwater sapping and surface runoff. The erosional morphology of the volcano, the lack of lava flow features, and the friable nature of the flank materials indicate that Hadriaca Patera consists predominantly of pyroclastic deposits. Gravity‐driven flow models demonstrate that the distribution of flank materials can be attributed to the emplacement of pyroclastic flows. Both magmatic and hydromagmatic eruption models are viable: For the magmatic case, the necessary mass eruption rates (107–108 kg/s), ejection velocities (≥ ∼400 m/s), and volatile contents (∼1.5–3.0 wt % H2O) are consistent with parameters derived for terrestrial Plinian eruptions; for the hydromagmatic case, the required energy conversion efficiencies are comparable to those of laboratory experiments, and the inferred permeability of the Martian crust allows large amounts of groundwater to be transported rapidly (at flow rates of 103–104 m3/s) into the region. Models of cooling during emplacement indicate that welding of pyroclastic flows can occur at large distances (hundreds of kilometers) from a source vent on Mars; the layering within Hadriaca Patera could be attributed to welding of pyroclastic flows that would control its susceptibility to erosion. Morphologic similarities between Hadriaca and Tyrrhena paterae suggest a similar volcanic history, with an early pyroclastic‐dominated, shield‐building phase followed by effusive eruptions at their summit calderas and on the flank of Tyrrhena Patera. The formation of the extensive ridged plains of Hesperia Planum following the formation of the highland paterae supports the interpretation of a transition from explosive to effusive volcanism in the eastern Hellas region. A progressive depletion of volatiles on Mars is consistent with the morphologic properties of highland paterae and other central vent volcanoes. A predominance of hydrovolcanic eruptions in the development of Hadriaca and Tyrrhena paterae would imply that the transition in volcanic eruption style can be attributed to a volatile depletion of the crust, whereas magmatic eruptions at the paterae would be indicative of temporal changes in Martian magmas.
Martian global dust storms: Zonally symmetric numerical simulations including size‐dependent particle transport
Authors: Murphy James R. , Haberle Robert M. , Toon Owen B. , Pollack James B.
Published: February 2008

The size‐dependent transport of dust particles in the Martian atmosphere away from a specified surface source is numerically investigated employing a coupled system of a zonally symmetric primitive equation grid point model of the Martian atmosphere and an aerosol transport/microphysical model. The coupled model accounts for diabatic heating due to a radiatively active evolving dust field but neglects feedbacks between atmosphere‐surface interactions and surface dust lifting, which is prescribed. The differing suspension lifetimes of various sized dust particles (radius = 1–80 μm) in conjunction with spatially varying atmospheric dynamics results in latitudinal differences in several measurements of the column integrated particle concentration. The latitudinal extent of dust (opacity) transport away from a southern subtropical source is enhanced by the presence in suspension of smaller dust particles (r < 1 μm) when compared to the presence of only a single dust particle size (2.5 μm). The input particle size distribution, that inferred by Toon et al. (1977) from Mariner 9 IRIS measurements, is not preserved in suspension at subsolar latitudes for spherical particles (r = 1–10 μm), counter to Toon et al.'s interpretation of IRIS spectra. Visible to 9‐μm dust opacity ratios, which provide an indication of the relative number of large particles, are generally smaller (<1.7) than values (2–2.5) inferred from both Mariner 9 and Viking measurements. The invocation of slower falling nonspherical (disk) shaped particles results in an improved maintenance in suspension of the input particle size distribution at subtropical latitudes and visible to‐9 μm opacity ratios in better agreement with inferred values. Calculated visible opacity values at the Viking lander latitudes increase less abruptly than was observed at the onsets of the two 1977 dust storms, which has implications for both source locations and magnitudes. This work indicates the importance of considering the full range of particle sizes (and shapes) of the suspended dust during Martian global dust storms and their impact upon the spatial extent and wavelength‐dependent radiative influence of such storms.
Comparison of Phytoplankton in Sediment Trap Time Series and Surface Sediments Along a Productivity Gradient
Authors: Sancetta Constance
Published: February 2008

Three years of sediment trap data collected by the Multitracers project are compared with surface sediments for sites off the coast of southern Oregon, using phytoplankton microfossils. Sites were located to monitor a region frequently affected by plumes from coastal upwelling (Nearshore), one occasionally affected by the largest plumes (Midway) and an area outside the zone of coastal influence (Gyre). Diatoms overwhelmingly dominate the microfossils, with silicoflagellates an order of magnitude fewer and calcareous nanofossils absent. This absence suggests that the rarity of the group in the sediments may be a function of low production, rather than of deepwater dissolution. The Midway and Nearshore sites were generally similar in taxonomic composition and timing of flux maxima, while the Gyre site differed in both regards. Interannual variability in taxon composition appears to correlate with productivity; the most productive site (Nearshore) has the most consistent interannual trend and the least productive (Gyre) exhibits the greatest variability. The sediment assemblage at the Nearshore site is most similar to trap samples from the late fall and winter seasons, rather than the more productive spring and summer. This is partly a function of differential dissolution, but the relationship persists even when only resistant taxa are used. Two possible explanations are discussed: addition of material from the continental shelf, and inadequate representation of long‐term trends by the trapping experiment. At the Midway site the data are few and scattered, but once the dissolution effect is removed it appears that the sediments contain material from several seasons of production. At the Gyre site preservation bias results in a sediment assemblage most similar to late spring and summer, only partly corresponding to maximum production. Comparison between sites indicates that the Nearshore and Gyre sediments have characteristic assemblages which are similar to the corresponding trap collections. The Midway sediments are similar to trap samples from all 3 sites, implying that the assemblage lies on a gradient between the other two and lacks a unique character of its own.
Ice Sheet and Ocean Interactions, Margin of the East Greenland Ice Sheet (14 Ka to Present): Diatom Evidence
Authors: Williams Kerstin M.
Published: February 2008

Seven marine sediment cores were collected from the Kangerdlugssuaq Trough off the southeast coast of Greenland. The trough cuts across the continental shelf from the fjord mouth to the upper slope in Denmark Strait and provides a sedimentary environment sheltered from the East Greenland Current flowing along the shelf. The cores have been 14C dated (accelerator mass spectroscopy dates) and analyzed for diatom accumulation rates and changes in floral composition. It was found that the shelf probably was not glaciated by grounded ice but occupied by an ice shelf and/or permanent sea ice between 14,000 years B.P. and the present. Average retreat rates of glacial/permanent sea ice were circa 60 m/yr between circa 13,500 and 11,000 years B.P. The retreat rates increased to about 150 m/yr between 11,000 to 10,000 years B.P. The increase is unexpected because this correlates with Fairbanks' (1989) projected low glacial meltwater discharge for the same time which is coeval with the Younger Dryas. Several events of sea surface warming/cooling took place on the outer shelf from 12,000 to 9000 years B.P. followed by cooling to the present, with a possible warming between 3000–4000 years BP. On the inner shelf pulses of warm/cool surface water occurred from 9000 to 6000 years B.P., which was succeeded by surface water cooling until present.
From the International Geophysical Year to global change
Authors: Fleagle Robert G.
Published: February 2008

A series of major scientific programs carried out over the past 40 years has greatly increased understanding of our global environment and has led to the present concern over global change. Each program responded to a specific and urgent scientific need or opportunity. In each case, institutions and resources were created that provided the foundation for later programs. Increased scientific understanding has exposed threats to future welfare and has raised serious policy implications for governments. Institutions for responding to global policy issues need to be created or strengthened.
Beacon calibration with a multifrequency radiometer
Authors: Mallet C. , Lavergnat J.
Published: February 2008

The European program Olympus of slant millimeter waves propagation studies uses three beacons on board an experimental satellite, the frequency of which is 12.5, 20, and 30 GHz. The objectives of the program require an accuracy of attenuation measurement lower than 0.1 dB. It is difficult to determine the no‐attenuation level relative to which the atmospheric attenuation is measured because the transmitted signal shows daily variations caused by satellite movements and temperature changes. The problem is thus to separate the diurnal pattern of the satellite signal from propagation effects. The purpose of this paper is to analyze the calibration method of using a multifrequency radiometer. One attempt was made to deduce the absorption on the satellite‐Earth line from the apparent sky temperature. We discuss some retrieval algorithms using radiometer measurements, keeping the Olympus experiment objectives in mind, and show a new inversion method. Retrieval algorithm and calibration method performances lead to a final accuracy of the method lower than 0.1 dB.
Seismicity and tectonics in Jujuy Province, northwestern Argentina
Authors: Cahill Thomas , Isacks Bryan L. , Whitman Dean , Chatelain Jean‐Luc , Perez Alejandro , Chiu Jer Ming
Published: February 2008

The Portable Array for Numerical Digital Analysis (PANDA) network, a digitally recorded seismic array, operated for nine months in Jujuy province of northwestern Argentina. The network was deployed along the eastern edge of the Altiplano‐Puna plateau in a major N‐S thrust belt that is transitional in style between the thin‐skinned deformation of the Bolivian foreland to the north and basement‐involved deformation of the Pampean region to the south. Teleseismic locations of crustal earthquakes in the region indicate that seismicity is associated with compressional structures found near the eastern deformation front. No crustal seismicity was detected beneath the Puna plateau to the west. Peak seismicity levels beneath the foreland occurred between 20 and 25 km depth; a sharp decrease in seismicity was observed below 25 km. An estimate of 42 km for the thickness of the Jujuy foreland crust was inferred from wide‐angle Moho reflections observed on the digital seismograms. The highest concentration of crustal seismicity was located beneath Sierra de Zapla, a broad anticline immediately east of San Salvador de Jujuy. Many of the earthquakes in the 20–25 km depth range have a shallow, west dipping nodal plane as does the focal mechanism solution for a moderately large 1973 earthquake. Inversion of focal mechanism data for the orientation of principal stresses shows that maximum compression is oriented at azimuth 74°, closely paralleling both the current Nazca‐South America convergence direction and the shortening direction derived from regional Quaternary fault slip data. We interpret the earthquakes as occurring on planes of weakness first produced during Cretaceous rifting and later reactivated by Neogene compressive stresses. Crustal seismicity patterns and fault plane solutions suggest the presence of a midcrustal detachment, along which significant late Cenozoic E‐W shortening has occurred.
The Paleozoic tectonic evolution of the northern edge of North America: A structural study of Northern Ellesmere Island, Canadian Arctic Archipelago
Authors: Klaper Eva M.
Published: February 2008

On Ellesmere Island, the Clements Markham fold belt of the Franklinian mobile belt is flanked to the northwest by a Caledonian terrane, Pearya. On the basis of the Proterozoic to mid‐Ordovician stratigraphic and structural similarities with Spitsbergen and on the mid to late Silurian relationship between Pearya and Ellesmere Island, some strike‐slip displacement must have been involved in the accretion of Pearya to its present position. However, the structural style of the Clements Markham fold belt on Ellesmere Island is characterized by chevron folds with axial planar cleavage (flexural folding) and shallow plunging fold axes. The present terrane boundary faults show steeply plunging lineations indicating a vertical component of motion strongly predominating the strike‐slip component. Thus the first detailed structural study of the area has produced no positive structural evidence for late Silurian transcurrent shear or transpression. Therefore decoupling of a strike‐slip component of plate motion from a distributed compressive component is suggested for northern Ellesmere Island. Accretion of Pearya most likely occurred along one of the major fault zones to the southeast of the thrust faults marking the present terrane boundary. However, indications of strike‐slip displacement have not yet been observed along these faults possibly due to later thrust faulting. The Silurian Imina and Lands Lokk formations form an accretionary wedge of orogen‐derived turbidites which were deposited on oceanic or highly attenuated continental crust. Thus the time interval spanning the deposition and deformation of the turbidite formations dates the period of accretion and of predominantely orthogonal continental convergence. In the light of current ideas concerning the episodic and diachronous development of orogenic belts, the Silurian deformation in northwestern Ellesmere Island may be interpreted as the beginning of the orogenic cycle that culminated in the Late Devonian ‐ early Carboniferous Ellesmerian event.
Synconvergence spreading of the higher Himalaya crystalline in Ladakh
Authors: Gapais D. , Pêcher A. , Gilbert E. , Ballèvre M.
Published: February 2008

In Ladakh (Suru valley, NW Himalaya), regional fabrics of the Higher Himalaya Crystalline result from a major deformation event that (1) is restricted to the Indian crust above the Main Central Thrust (MCT), (2) postdates piling up of units above the MCT, (3) ended while thrusting was still continuing on the MCT, (4) developed under high‐temperature conditions following thickening, (5) resulted in an asymmetric gneiss dome, and (6) is associated with ENE‐WSW to EW regional extension. We suggest that extension was accommodated by spreading of the hot basement accompanied and followed by its uplift within the overlying cover along a major detachment zone. The onset of the process appears closely related to strong thermal softening of the Higher Himalaya Crystalline and is broadly synchronous with the formation of the Himalayan leucogranites, around 25 Ma. The regional pattern suggests that the MCT zone could have acted as a decoupling zone between a thickening lower part and a thinning upper part of the Indian crust during Miocene times. The extension direction is consistent with bulk Himalayan kinematics involving NW‐SE dextral wrenching along the western syntax, and eastward extrusion of Tibet. We suggest that exhumation of gneissic ridges which characterize Indian units above the MCT all along the Himalayan belt could reflect large‐scale crustal instability developed from thermally anomalous layers whose spreading ability can favor synconvergence extension.
Dip domain method applied to the Mesozoic Connecticut Valley Rift Basins
Authors: Wise Donald U.
Published: February 2008

This paper presents a new approach to structural analysis of U.S. East Coast Mesozoic basins. A contoured compilation of numerical values of dip data for the Connecticut Valley rift basins reveals distinct domains related to their broader tectonic development. Additional, more standard geologic constraints are then used to interpret the dip domain patterns. Most of the tilt deformation involved and hence postdated Early Jurassic basaltic flow units and overlying Jurassic thick alluvial deposits. Normal drag characterizes the attitude of Mesozoic strata along the Western Border fault of the main Hartford basin, whereas reverse drag is common along its larger, listric, Eastern Border fault. Strata within the basin, mostly along its eastern margin, include several subgrabens and/or strongly tilted zones associated with early subbasins marked by local changes in strike of the early border fault. The Meriden cross‐graben may be a similar structure that extended much farther southwestward across the basin. Within the Hartford basin, linear domains of steeper dips are interpreted as surface expressions of the edges of a 5 to 15 km wide, late stage, Central graben that trends N15°E diagonally across the basin, possibly a reflection of very late, strike‐slip stress systems.
Neogene tectonics and kinematics of western North America
Authors: Walcott Dick
Published: February 2008

Recent quantitative studies of deformation in western North America including Pacific and North American relative plate motion, estimates of Neogene displacement in the southern Basin and Range, and anomalous paleomagnetic declinations of the Pacific Northwest are self‐consistent and, together, determine a simple kinematic model of the deformation that is an extension of the 1970 plate tectonic model of Atwater. A large continental lithospheric block, called here the Sierra Nevada/Klamath block, was displaced about 300 km to the W‐NW relative to the North American craton during the Neogene. The southern end of the overriding plate in the subduction zone along the Pacific Northwest has been shifted the same amount, resulting in the subduction zone and overlying accretionary complex rotating clockwise about 30°. The pivot is located near Seattle and the several tens of kilometers of N‐S shortening required to accommodate the rotation is taken up in the major thrusts of the Juan de Fuca Strait and Olympic Peninsula.
Geologic evolution of Iron Mountain, central Mojave Desert, California
Authors: Boettcher Stefan S. , Walker J. Douglas
Published: February 2008

Geologic mapping, structural analysis, petrologic study, and U‐Pb geochronology at Iron Mountain, 20 km southwest of Barstow, California, place important constraints on the paleogeographic affinities of metasedimentary rocks in the area and provide new data to test Mesozoic and Cenozoic tectonic models for the central Mojave Desert. Rocks present at Iron Mountain include: Precambrian(?) and/or lower Paleozoic(?) miogeoclinal rocks, Middle Jurassic tonalite, Middle Jurassic Hodge volcanic series, Late Jurassic hornblende diorite, Cretaceous(?) peraluminous granite, and Cretaceous(?) granodiorite prophyry. Two phases of ductile deformation are present at Iron Mountain. The first phase, which penetratively deforms the miogeoclinal rocks, tonalite, and Hodge volcanic series, developed under amphibolite and greenschist facies metamorphic conditions. Fabric development in the Hodge volcanic series preceded emplacement of 151 ± 11 Ma granite. The second fabric deforms peraluminous granite and Late Jurassic hornblende diorite as well, and consists of spaced mylonitic shear zones. The shear zones predate emplacement of Late Cretaceous dikes (83 ± 1 Ma). The presence of probable miogeoclinal strata indicates that the boundary between allochthonous eugeoclinal rocks and parautochthonous miogeoclinal/cratonal rocks must lie north of Iron Mountain. The older amphibolite facies metamorphism and contractile deformation at Iron Mountain are interpreted to be part of a belt of Middle to Late Jurassic age deformation that runs northeastward through the Mojave Desert and forms the southern continuation of the east Sierran contractile belt. Newly recognized subvertical mylonitic shear zones of Cretaceous age at Iron Mountain have not been documented elsewhere in the central Mojave Desert. No significant Tertiary ductile deformation fabrics are present at Iron Mountain.
Comparison of carbon dynamics in tropical and temperate soils using radiocarbon measurements
Authors: Trumbore Susan E.
Published: February 2008

The magnitude and timing of the response of the soil carbon reservoir to changes in land use or climate is a large source of uncertainty in global carbon cycle models. One method of assessing soil carbon dynamics, based on modeling the observed increase of 14C in organic matter pools during the 30 years since atmospheric weapons testing ended, is described in this paper. Differences in the inventory and residence time of carbon are observed in organic matter from soils representing tropical (Amazon Basin, Brazil) and temperate (western slope of the Sierra Nevada mountains, California) forest ecosystems. The majority of the organic carbon in the upper 22 cm of the tropical soil (7.1 kgC m−2) has residence times of 10 years or less, with a minor component of very refractory carbon. The estimated annual flux of carbon into and out of the soil organic matter in this horizon of the mineral soil, based on modeling of the 14C data, is between 1.9 and 5.5 kgC m−2 yr−1. In contrast, organic matter in the temperate soil over a similar depth interval (0‐23 cm; 5.2 kgC m−2), is made up of approximately equal amounts of carbon with residence times of 10, 100, and 1000 years. The estimated annual flux of carbon into and out of this soil is 0.22 to 0.45 kgC m−2 yr−1. Rapid turnover of organic matter with density <1.6 ‐ 2.0 g cm−3contributes a major component of the annual flux of carbon into and out of both soil types. Hydrolysis of mineral soil organic matter of density < 1.6‐2.0 g cm−3 removed 14C‐enriched components from the temperate soil but had no effect on the 14C content of the residue in 0 ‐ 22 cm layer of the tropical soil. The results presented here show that carbon cycle models which treat soil carbon dynamics as a single reservoir with a turnover rate based on radiocarbon measurements of bulk soil organic matter underestimate the annual fluxes of organic matter through the soil organic matter pool, particularly in tropical regions.
Carbon remineralization in a north Florida swamp forest: Effects of water level on the pathways and rates of soil organic matter decomposition
Authors: Happell James D. , Chanton Jeffrey P.
Published: February 2008

Water level controlled gas emissions from North Florida swamp forests. Under flooded conditions, CO2 and CH4 were the principle carbon gases transported to the atmosphere by bubble ebullition and molecular diffusion. The respective emission rates were for CO2, 29.3 ± 16.4 (13% by means of ebullition, 87% by means of diffusion, error is ± 1 standard deviation throughout) and for CH4, 2.16 ± 2.24 (45% by means of ebullition, 55% by means of diffusion) mol m−2 yr−1. Methane emissions were significantly attenuated by CH4 oxidation which occurred primarily at the sediment‐water interface. Forty‐six ± 22 % (n=19) of the belowground CH4 diffusing to this interface was oxidized before it could escape to the atmosphere. Under dry conditions, CO2 was the principle carbon gas released and atmospheric CH4 was consumed by microbes in the soil. The respective rates were 101.2 ± 26.80 and −0.015 ± 0.005 mol mr−2 yr−1. A carbon budget for the degradation of soil organic matter was developed for a swamp forest site under flooded and dry conditions. Assuming that live root respiration accounted for 67% (value determined in a swamp forest and is at the upper range of literature values) of the total CO2 emissions (given above), we calculate that under flooded conditions carbon remineralization proceeded at a total rate of 11.9 mol C m−2 yr−1. Forty‐nine percent of the remineralization was by means of nonmethanogenic processes which produce CO2; the balance was by means of methanogenic processes, which produce both CH4 and CO2. Under dry conditions, remineralization was dominated by aerobic processes at a rate of 33.7 mol C m−2 yr−1. Carbon inputs to the soil occurred by aboveground and belowground production. Aboveground litter production contributed 25.6 mol C m−2 yr−1. If belowground production contributed an equal amount, then over the course of this study organic carbon accumulated in the soils at rates of 39.3 and 17.5 mol C m−2 yr−1 under flooded and dry conditions, respectively. If root respiration accounted for only 6% (lowest value in literature) of the total CO2 emissions, organic carbon would accumulate in the soil at a rate of 21.6 mol C m−2 d−1 under flooded conditions and be lost from the soil at a rate of 43.8 mol C m−2 d−1 under dry conditions.
Wide‐angle reflection studies of the crust and moho beneath the Archean Gneiss Terrane of southern Minnesota
Authors: Gohl Karsten , Hawman Robert B. , Smithson Scott B.
Published: February 2008

Densely spaced wide‐angle reflection data from oldest Archean crust in southern Minnesota were processed and modeled to place constraints on average crustal structure and the nature of the Moho. A preliminary 1‐D extremal inversion of τ(p) arrivals extracted from vibroseis and quarry blast recordings covering offsets betweeen 70 and 108 km suggests a crustal thickness between 45 and 51 km. Slowness‐depth models corresponding to extremal depths have average velocities ranging from 6.5 to 7.0 km/s, with velocities at the base of the crust ranging from 6.8 to 7.5 km/s. Estimates of Vp/Vs based on travel time ratios of P‐ and S‐wave arrivals show an increase from 1.71 ± 0.02 in the near‐surface to an average of 1.76 ± 0.03 for the whole crust, which is consistent with an increasingly mafic or plagioclase‐rich composition with depth. Although the data are sparse, the occurrence of broad‐band PmP, SmS, and PmS/SmP, arrivals at slightly precritical offsets combined with sporadic multicyclic reflections observed in coincident normal‐incidence CDP sections suggests that the Moho beneath this terrane is not a simple velocity gradient, but rather a layered zone involving small velocity contrasts.
Sea surface temperature estimation from the DMSP operational linescan system Using a SSM/I‐derived water vapor correction
Authors: May Douglas A.
Published: February 2008

Atmospheric correction algorithms for Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) single channel infrared (IR) estimation of sea surface temperature (SST) have been derived based on Special Sensor Microwave/Imager (SSM/I) water vapor (WV) content retrievals. It is demonstrated that the OLS single IR channel atmospheric correction can be correlated to WV and that the SSM/I‐derived correction algorithms provide significant improvement over uncorrected single IR channel SST estimation. Best results are obtained from a correction algorithm that incorporates a quadratic WV term. Use of the quadratic SSM/I‐derived WV correction on properly cloud screened OLS IR data produces SST retrievals accurate to within 1.0°C RMS when compared to moored buoy in situ SST measurements.
Submarine basalts from the Red Sea: New Pb, Sr, and Nd isotopic data
Authors: Volker Frank , McCulloch Malcolm T. , Altherr Rainer
Published: February 2008

High‐precision Pb isotope analyses are reported for Holocene basalts from the axial trough of the Red Sea in order to resolve the discrepancy between Pb isotope data published in two recent papers [Dupré et al., 1988; Altherr et al., 1990]. Carefully handpicked glassy rock chips were leached in strong acid prior to dissolution to minimize contamination and alteration effects. In addition, Sr and Nd isotopes were analysed from the same sample solution to obtain a complete isotopic profile along this nascent oceanic basin.

Red Sea basalts show a wide range in Pb isotopes with 206Pb/204Pb ratios extending from 18.1 to 19.6. In a plot of 207Pb/204Pb versus 206Pb/204Pb, the basalts lie next to, or slightly above, the Northern Hemisphere Reference Line with Δ7/4 values between −1.5 and +3.1, in accord with the data from Dupré et al. [1988]. High Δ7/4 values (up to +12) reported by Altherr et al. [1990] are most probably due to severe sample contamination.

Basalts with chemical and isotopic signatures typical for N‐type MORBs (206Pb/204Pb = 18.1–18.3; 87Sr/86Sr ≈ 0.70269; 143Nd/144 Nd ≈0.51315) occur in the central region of the Red Sea at about 21.4°N. To the North and South of this central region, Pb and Sr isotope ratios show a systematic increase accompanied by a decrease in Nd isotope ratios. N‐type MORBs from the central part of the Red Sea display Pb, Sr, and Nd isotopic signatures indistinguishable from basalts from the Carlsberg Ridge of the Indian Ocean. Thus there is no evidence that these two oceanic spreading centres tap chemically different convective systems in the asthenosphere as has been suggested previously.
OH(ν,N) column densities from high‐resolution Earthlimb spectra
Authors: Dodd J. A. , Blumberg W. A. M. , Lipson S. J. , Lowell J. R. , Armstrong P. S. , Smith D. R. , Nadile R. M. , Wheeler N. B. , Huppi E. R.
Published: February 2008

Individual OH(ν,N) rotational state population column densities have been derived from spectral analysis of CIRRIS 1A nighttime earthlimb airglow data. Both pure rotation and vibration‐rotation fundamental spectra have been examined, providing unique information on highly excited rotational states of OH(ν=0‐6). The relative populations of the four spin sublevels have also been determined. These findings provide important insights into OH dynamics at the mesopause.
Adiabatic vs. non‐adiabatic particle distributions during convection surges
Authors: Sánchez Ennio R. , Mauk Barry H. , Meng Ching‐ I.
Published: February 2008

The convection surge is a mechanism whereby a temporary intensification and subsequent relaxation of the east‐west electric field coexists with an earthward displacement of the nightside curved magnetospheric field lines. Calculations of single particle trajectories for H+ and O+ during convection surges have found that the first adiabatic invariant µ = E⟂/B (where E⟂ is the energy contributed by the motion of the particle perpendicular to the magnetic field and B is the magnitude of the ambient magnetic field) may break down, depending on the particle's species and location. Applying this property to a collection of single particle trajectories, it has been suggested that the boundary between the adiabatic and non‐adiabatic regimes could be interpreted as the injection boundary formed in the middle magnetosphere during substorm expansions. Under this interpretation, the non‐adiabatic conditions establish the character of the populations tailward of the injection boundary. To investigate the behavior of the full particle distributions, we have modified the convection surge numerical code of Mauk [1986] to approximate the breakdown of the adiabaticity. In this report we present simulated results for various parameter conditions. Contrary to the adiabatic results, the non‐adiabatic conditions do not yield the magnetic‐field‐aligned distributions that are commonly observed tailward of the injection boundary.
OH reaction kinetics and atmospheric lifetimes of CF3CFHCF3 and CF3CH2Br
Authors: Nelson D. D. , Zahniser M. S. , Kolb C. E.
Published: February 2008

The rate constants for the reaction of the OH radical with CF3CFHCF3 and with CF3CH2Br have been measured as a function of temperature using the discharge flow technique with laser induced fluorescence detection of the OH radicals. The temperature dependent rate coefficients are well described by a simple Arrhenius expression, k(T) = A exp[−E/(RT)]. For the reaction of OH with CF3CFHCF3 we find A = 3.7 × 10−13 cm³ molecule−1 s−1 and E/R = 1615 K; for the reaction of OH with CF3CH2Br we report A = 1.4 × 10−12 cm³ molecule−1 s−1 and E/R = 1350 K. These Arrhenius parameters imply rate coefficients at 277 K of 1.09 × 10−15 cm³ molecule−1 s−1 for CF3CFHCF3 and 1.06 × 10−14 cm³ molecule−1 s−1 for CF3CH2Br. We find atmospheric lifetimes for CF3CFHCF3 and CF3CH2Br of 42 years and 4.1 years, respectively. We also estimate the steady state ozone depletion potential (ODP) of the brominated species relative to CFCl3 as ∼0.84 using a semi‐empirical model.
Ambipolar limit of electron precipitation
Authors: Liu W. W.
Published: February 2008

In a magnetospheric condition, particles are often precipitated into the ionosphere of the host planet. When a flux tube is not interacting with those neighboring it, charge lost through its open ends to the ionosphere must vanish to ensure charge quasi‐neutrality in the flux tube as a whole. To achieve this, a parallel electric field must be present to impede the faster electron motion. Electric fields so arisen are usually referred to as ambipolar fields. In this paper, we discuss a number of specific aspects of the ambipolar coupling, including the value of the ambipolar potential drop, the effects of loss cone depletion, the outflow of ionospheric electrons extracted by the ambipolar field, and point‐to‐point distribution of the potential. Although the noninteractive assumption for the flux tube restricts the validity of the treatment to cases where field‐aligned currents are very weak, the construction of the model sheds new light on an important problem in magnetospheric physics.
The observation of a C5 alcohol emission in a North American pine forest
Authors: Goldan Paul D. , Kuster William C. , Fehsenfeld Fred C. , Montzka Stephen A.
Published: February 2008

During a recent study carried out at an isolated site in the Colorado mountains, a C5 alcohol, 2‐methyl‐3‐buten‐2‐ol, was found to be the most abundant volatile organic compound of biogenic origin present in the atmosphere. This finding, if generally characteristic of the natural chemical species present in the atmosphere in forested areas, has important implications. First, the presence in large quantities of a reactive chemical compound at these high levels can significantly influence the local atmospheric chemistry. Secondly, this compound, although previously identified as a pheromone for Ips typographus (spruce bark beetle), an insect predator responsible for major forest die‐backs in this region, is strongly correlated with isoprene. Since isoprene is known to be emitted by the local vegetation, the observed 2‐methyl‐3‐buten‐2‐ol appears also to have a vegetative rather than entomological source.