bluuebunny/crossref_metadata_2025 huggingface dataset:
An investigation of short‐range climate predictability in the tropical Pacific
Authors: Latif Mojib , Flügel Moritz
Published: February 2008

The predictability of the El Niño/Southern Oscillation (ENSO) phenomenon was investigated by analyzing observed sea levels, surface stresses, and subsurface temperatures simulated with an oceanic general circulation model forced by observed winds. In addition, a large ensemble of prediction experiments has been conducted with a simplified coupled ocean‐atmosphere model consisting of an oceanic general circulation model coupled to a simple atmospheric feedback model. Our analysis supports the hypothesis that the ENSO‐related interannual variability in the tropical Pacific can be understood as a cycle within the coupled ocean‐atmosphere system which is inherently predictable. This cycle consists of an accumulation of warm water in the western Pacific during the cold phases of ENSO and a loss of this heat during its warm phases. The results of the prediction experiments with our simplified coupled ocean‐atmosphere model indicate that the phase of tropical Pacific sea surface temperatures is predictable two to three seasons in advance with our simplified coupled system, whose dynamics is governed by the ocean. We found a strong dependence of the skills on season, with spring SSTs being least predictable.
Differences in drift behavior between drogued and undrogued satellite‐tracked drifting buoys
Authors: Brügge B. , Dengg J.
Published: February 2008

Drift behavior of drogued and undrogued Hermes‐type buoys is studied. After drogue loss, an increase in drift speed and acceleration is observed as well as improved correlations between drift and wind in both speed and direction. With these criteria, a method for the separation of large data sets into a drogued and an undrogued part has been developed. In most areas of the North Atlantic this works very well; problems arise in regions with strong surface currents and/or light winds. A statistical analysis is performed in a selected area to demonstrate the errors that can be caused by indiscriminate use of drogued and undrogued drifters. Mean and rms velocities as well as kinetic energies change significantly when undrogued buoys are considered. Therefore caution is essential when using surface drifters without drogues.
On the net radiative effectiveness of clouds
Authors: Hartmann Dennis L. , Doelling David
Published: February 2008

The net effect of clouds on the energy balance at the top of the atmosphere is investigated using data from the Earth Radiation Budget Experiment. A regional analysis is made of the relative magnitudes of the effects of clouds on outgoing longwave radiation and on reflected solar radiation. The ratio of these two effects is expressed in terms of a cloud factor angle defined in coordinates of reflected solar versus outgoing longwave radiation. This parameter is a measure of the net radiative effectiveness of clouds, which is insensitive to the average amount of cloud present. It is calculated in two independent ways. One method uses monthly averaged clear‐sky and average values, and the other uses regression between daily values of solar and longwave exitance. Because the effect of cloud amount variations is minimized by the analysis procedure used here, the spatial pattern of cloud radiative effectiveness is simpler than that of cloud radiative forcing and corresponds to the pattern of circulation and cloud type regimes. The two methods of estimating the effectiveness give essentially the same spatial pattern. Both estimates of the cloud radiative effectiveness indicate that the global average net radiative effect of today's clouds is cooling, with the decrease in absorbed solar greater than the decrease in outgoing longwave radiation. The ratio of the solar to the longwave effect of cloud is about 1.85 based on the regression method and 1.55 based on the comparison of clear‐sky and average radiation budget climatologies. The differences between the two methods arise primarily from regions of stratus cloud, tropical cumulonimbus cloud and clouds over snow. In each of these regions the regression method indicates a more strongly cooling effect. The difference between the global mean estimates is within their uncertainty. Investigation of the areas of disagreement between the two methods reveals remaining problems. Significant improvement in our understanding of the effect of clouds on the radiation balance will require that the analysis procedure incorporate simultaneous measurements of temperature, humidity, and cloud structure, with particular importance attached to humidity in the deep tropics and temperature over land surfaces. Additional spectral information will be necessary to discriminate the role of clouds over snow and ice.
Seasonal cycle and secular trend of the total and tropospheric column abundance of ethane above the Jungfraujoch
Authors: Ehhalt D. H. , Schmidt U. , Zander R. , Demoulin P. , Rinsland C. P.
Published: February 2008

Total column abundances of ethane (C2H6) above the Jungfraujoch Station, Switzerland, 3.58‐km altitude, have been deduced from infrared solar spectra recorded in 1951 and from 1984 to 1988. The results were derived from the spectroscopic analysis of the ν7 band PQ3, PQ1, and RQ0 subbranches of C2H6 near 2976.8, 2983.4, and 2986.7 cm−1, respectively. The 1984–1988 results obtained from more than 300 observations at 0.005 cm−1 resolution show a definite seasonal variation in the total vertical column abundance of that gas, with a maximum of (1.43±0.03)×1016 molecules/cm2 during March and April and a minimum in the fall. The corresponding C2H6 mixing ratio in the free troposphere was derived to 1.53±0.14 ppb in early April; the ratio of maximum to minimum C2H6 concentration in the troposphere was found to be 1.88±0.12. From the analysis of the same spectral features observed in March and April 1951, we have deduced a total vertical column abundance of (1.09±0.10)×1016 molecules/cm2. Assuming an exponential increase with time and correcting for a small decrease in the stratospheric amount of C2H6 due to the man‐induced increase in stratospheric chlorine, we obtain a secular trend in the tropospheric burden above the Jungfraujoch equal to (0.85±0.3)% yr−1. It is argued that this trend is valid for the entire northern hemisphere.
Stratospheric profiles of heavy water vapor isotopes and CH3D from analysis of the ATMOS Spacelab 3 infrared solar spectra
Authors: Rinsland C. P. , Gunson M. R. , Foster J. C. , Toth R. A. , Farmer C. B. , Zander R.
Published: February 2008

Stratospheric volume mixing ratio profiles of H218O, H217O, HDO, and CH3D near latitudes of 30°N and 47°S have been retrieved from ∼0.01‐cm−1 resolution infrared solar occultation spectra recorded by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer during the Spacelab 3 shuttle mission (April 29 to May 6, 1985). Improved heavy isotope water vapor and CH3D spectroscopic parameters determined from ∼0.005‐ to 0.01‐cm−1 resolution room temperature laboratory spectra have been used in the retrievals. The profiles of the three water vapor isotopes show an increase in the volume mixing ratio with altitude over the range of measurements (20 to 54 km for H218O, 20 to 46 km for H217O, and 20 to 34 km for HDO). Deuterium‐to‐hydrogen and heavy‐to‐normal oxygen isotope ratio profiles have been calculated by dividing the retrieved isotopic profiles by the previously reported profiles of H216O and CH4 obtained from the same spectral data and then referencing these results to the isotopic composition of standard mean ocean water (SMOW). At 20 km the 18O/16O ratio in H2O is slightly (∼8%) depleted relative to SMOW; this ratio increases with altitude and is slightly positive above ∼36 km. No evidence has been found for the large 18O enhancements reported previously. The 17O/16O water vapor results are similar to those for 18O/16O. The ATMOS measurements show depletions of ∼63% in the D/H content of water vapor near 20 km and an increase in this ratio with altitude up to 34 km. The D/H ratio in stratospheric methane is close to the isotopic ratio in SMOW over the 18 to 28 km altitude range. No differences between the water vapor or methane isotopic compositions at 30°N and 47°S were detected. The results are compared with previously reported measurements and calculations.
The iron catalyzed oxidation of sulfur(IV) in aqueous solution: Differing effects of organics at high and low pH
Authors: Martin L. R. , Hill M. W. , Tai A. F. , Good T. W.
Published: February 2008

We have studied the oxidation of sulfur dioxide by dissolved oxygen in highly dilute solutions with a new differential optical absorption technique. We measured the rate of oxidation catalyzed by iron(III) over a wide range of pH, ionic strength, and in the presence of various organic materials. The studies indicate that noncomplexing organic molecules are highly inhibiting at “high” pH values of 5 and above and are not inhibiting at “low” pH values of 3 and below. Furthermore, the order of the reaction with respect to iron is different in the two pH regimes. This suggests that the mechanism of this reaction differs in the two pH regimes and is probably a free radical chain at high pH and a nonradical mechanism at low pH. Some of the mechanisms proposed in the literature are discussed in the light of these new data. None of the proposed mechanisms give completely satisfactory agreement with the data. We propose a modified free radical chain mechanism for the high pH regime, which correctly predicts the organic inhibitions. For the low pH regime, mechanisms proposed by Conklin and Hoffmann (1988) and by Hoffmann and Jacob (1984) give fair agreement with the pH data and correctly predict the self‐inhibition, the sulfate inhibition, and the ionic strength inhibition. In view of the new data we believe that the iron(III) catalyzed reaction in tropospheric clouds can be a major contributor to the rate of sulfate formation, but there will be significant inhibition of this process by formic acid in some situations.
Stratospheric Aerosol and Gas Experiment II and ROCOZ‐A ozone profiles at Natal, Brazil: A basis for comparison with other satellite instruments
Authors: Barnes Robert A. , McMaster Leonard R. , Chu William P. , McCormick M. Patrick , Gelman Melvyn E.
Published: February 2008

We present the results of comparisons of satellite measurements of ozone from the Stratospheric Aerosol and Gas Experiment II (SAGE II) with in situ measurements from ROCOZ‐A and electrochemical concentration cell (ECC) ozonesondes at Natal, Brazil (5.9°S, 35.2°W), during the southern hemisphere autumn of 1985. Since data were collected over a region of low ozone variability, comparisons were made of the mean values of 14 SAGE II profiles with the mean values of 7 ROCOZ‐A and 7 ECC profiles, rather than of a more limited set of paired comparisons. The basic comparison presented here is ozone number density versus geometric altitude, the fundamental ozone measurement from SAGE II. Over the altitude region from 20 to 52 km SAGE II ozone densities averaged 0.4% lower than ROCOZ‐A. The average of the absolute values of the ozone density differences for the two instruments was 2.4% over these altitudes. Owing in large part to the number of profiles in the data sets, the 95% confidence limits for the ozone density differences in these comparisons averaged 3.5% from 20 to 52 km, a significant improvement over previous results. In terms of ozone mixing ratio versus geometric altitude from 20 to 52 km, SAGE II values had a difference of 3.4% from ROCOZ‐A (SAGE II higher), an average absolute difference of 3.8%, and an average of 4.7% for the 95% confidence limits. Differences between the ozone density and mixing ratio results are due to the auxiliary temperature and pressure values for the satellite and in situ instruments. The effects of pressure differences on the vertical positioning of the ozone profiles are not important for the altitude‐based comparisons of SAGE II and ROCOZ‐A. However, they become an important consideration in the comparisons of SAGE II with pressure‐based ozone measurements from other satellite instruments. The composite sets of ozone, temperature, and pressure values presented here form an excellent basis for comparisons with other satellite ozone measurements.
Satellite ozone comparisons: Effects of pressure and temperature
Authors: Olivero John J. , Barnes Robert A.
Published: February 2008

We examine the direct effects of errors in determining temperature, pressure, and density in the background atmosphere on the comparison of ozone measurements by two different satellite sensors. Such comparisons, particularly between satellite instruments with different fundamental measurement techniques, provide an important method for checking the performance of these sensors. For example, ozone abundance profiles from the solar backscattered ultraviolet (SBUV) spectrometer on the Nimbus 7 satellite are being reanalyzed to remove the effects of long‐term instrument drift. Measurements from other ozone instruments are vital to this reanalysis; a primary comparison is that between SBUV observations and those from the Stratospheric Aerosol and Gas Experiment II (SAGE II) instrument on the Earth Radiation Budget satellite (ERBS). SAGE II observes ozone by solar occultation, giving values of ozone concentration versus geometric altitude. SBUV provides ozone overburden and its derivatives versus pressure. The conversion between geometric altitude and pressure requires accurate information on the vertical structure of the background atmosphere. In this study we compare atmospheric structure measurements routinely available from the National Meteorological Center with a special set of in situ measurements by radiosondes and meteorological rocketsondes. Furthermore, we demonstrate the manner in which the differences in these background atmosphere measurements propagate through the direct comparisons of stratospheric ozone profiles by SBUV and SAGE II sensors. Modest differences in vertical positioning can propagate into significant ozone differences in regions with strong vertical ozone gradients, particularly at 70 mbar in the tropics. We find apparent ozone differences of 5–10% or more due solely to these background atmosphere effects within an analysis for which the ozone observations themselves are treated as error‐free.
An important current reversal (influx) in the Rifian Corridor (Morocco) at the Tortonian‐Messinian boundary: The end of Tethys Ocean
Authors: Benson Richard H. , Rakic‐El Bied Kruna , Bonaduce Gioacchino
Published: February 2008

Atlantic psychrospheric and temperate mesopelagic faunas found in the lower Messinian marls in Morocco indicate that a strong, eastward flowing, bottom current was present in the Rifian Corridor before the Salinity Crisis. This influx began just before diatomite deposition in the Paleo‐Mediterranean, continued during a decrease in species diversity in coral reef formation, and diminished with the initial stages of “brine” concentration in the deep‐water phase of the Crisis. The influx is most readily studied in a condensed section of marl in the Bou Regreg valley near Rabat. The beginning of this “siphon event” coincides with the Tortonian/Messinian boundary (6.4 Ma, subchron 6N1). It is identified by (1) a change in the planktonic foraminifera from dominance of warm, tropical, epipelagic Globorotalia menardii with Globigerinoides to the temperate, mesopelagic Gl. miotumida plexus with conomiozea; (2) the sudden appearance of an upper psychrospheric ostracode fauna with Agrenocythere pliocenica and Oblitacythereis ruggierii, (3) a change in nannoflora; and (4) beginning of the 6.3 Ma Global Carbon Shift. The initial strong influx stage of the siphon lasted at least 0.7 m.y., decreasing after the middle of Chron 5, ca. 5.7, to be lost ca. 5.3 Ma. Conditions for the siphon formed when the continental climate created a deficit in the water budget of the Paleo‐ Mediterranean Sea. The reversal took place when tectonic movement in the foredeeps of the Betic‐ Rif Orogene changed the thresholds of the twin straits, the Rifian Corridor and the Iberian Portal. Inflow increased rapidly in the southern Corridor to draw in waters from beneath the rising Atlantic pycnocline, while Paleo‐Mediterranean Overflow Water (PMOW) continued out of the northern Iberian Portal. The invasion of “nappes” or olistoliths, first into the portal and then into the corridor, led to the end of the outflow of the PMOW terminating the need for the siphon, and then to the isolation of the Paleo‐Mediterranean.
An overview of the post‐Messinian paleoenvironmental history of the western Mediterranean
Authors: Thunell R. , Rio D. , Sprovieri R. , Vergnaud‐Grazzini C.
Published: February 2008

A review of the Pliocene‐Pleistocene paleoenvironmental history of the western Mediterranean is presented based on micropaleontological and geochemical studies of Ocean Drilling Program (ODP) leg 107 material and marine outcrops in southern Italy. The calcareous plankton biochronology proposed for the Mediterranean by Rio et al. (1990 and 1991a) provides the necessary age control for determining the timing of major climatic and oceanographic changes in the region. The early Pliocene period in the Mediterranean was not a time of warm, stable climate; rather, it was marked by relatively high‐amplitude climatic oscillations. In marginal areas, these climatic oscillations resulted in the rhythmic deposition of limestone‐marl couplets which have an average duration of approximately 19,000 years. It is proposed that these sedimentary couplets are the result of precessionally induced changes in monsoon intensity which in turn cause variability in coastal divergence and upwelling. The δ18O and the calcareous plankton (foraminifera and coccoliths) records for Tyrrhenian Sea ODP site 653 reveal a cooling of surface waters at ∼3.1 Ma. Coincident with this cooling is an increase in the frequency of diatomite formation in southern Italy (Bianco section). The global cooling at ∼2.4 Ma and the associated expansion of northern hemisphere glaciation resulted in a shift to more arid conditions in the Mediterranean region. This climate change may have altered the Mediterranean water balance, resulting in the establishment of antiestuarine water exchange with the Atlantic at this time.

The δ18O record for site 653 is also marked by a sharp cooling across the Pliocene/Pleistocene boundary. In the boundary stratotype section at Vrica, this cooling is manifested as an increase in the abundance of the planktonic foraminifer Neogloboquadrina pachyderma.
Pliocene Paleoceanography: Circulation and Oceanographic Changes Associated with the 2.4 Ma Glacial Event
Authors: Sikes E. L. , Keigwin L. D. , Curry W. B.
Published: February 2008

High‐resolution δ18O records from the equatorial Pacific (site 503B), equatorial Atlantic (site 665A), and North Atlantic (site 606A) based on the benthic foraminifera Cibicidoides wuellerstorfi show the 2.4 Ma onset of major northern hemispheric glaciation to be a package of three events occurring at 2.39, 2.35, and 2.31 Ma in which a periodicity of about 40 kyr is evident. The amplitude of the signals at the three sites indicates that these events were 1/2 to 2/3 the size of the latest Quaternary glaciation and also indicates cooling of northern source bottom water by 2.7°–4.1°C relative to southern source water during glaciations. Carbon isotopes indicate that southern source waters were less oxygenated than in the Quaternary and that there was reduced production of northern source water during glacial intervals. The dominant presence of southern source water in the eastern basin of the equatorial Atlantic, regardless of climatic cycles, throughout the late Pliocene indicates a greater influence of these waters relative to northern source waters in the late Pliocene ocean.
Deep‐Sea Benthic Foraminiferal Assemblage Response to a Surface Ocean Productivity Gradient: A Test
Authors: Loubere Paul
Published: February 2008

A transect of samples from the eastern equatorial Pacific, where surface ocean productivity is the only changing environmental variable, was used to test the response of benthic foraminiferal assemblages to an open‐ocean productivity gradient. The transect runs along the East Pacific Rise from the highly productive waters near the equator to the oligotrophic South Pacific subtropical gyre. Surface sediment benthic assemblages show progressive change along the transect with strong compositional shifts corresponding to the rapid productivity gradient near the equator and to the position of the southern convergence, near 18°–19°S. The relationship of the assemblages to surface ocean productivity was tested by statistical regression of quantitative estimates of productivity on the assemblage principal component scores calculated for each sampling location. The regression yielded an r‐squared of 0.87, demonstrating a clear relationship between surface ocean productivity and deep‐sea benthic foraminiferal assemblage composition. The species most important to this relationship display a consistent response to oceanic productivity for long stretches of geologic time. This conservative behavior and the results of the regression analysis indicate that benthic foraminiferal assemblages can be used to estimate surface ocean productivity for the geologic past.
The surface magnetic charge induced by a high‐frequency whispering gallery wave on a spherical cap with nonvanishing face impedances
Authors: Şengör T.
Published: February 2008

We obtained the explicit expressions related to the scattering of the normal magnetic component of whispering gallery (WG) modes by a spherically curved sheet with different face impedances. For nonvanishing face impedances we have equivalent surface magnetic charge induced by the modes on the sheet. The results explain the influence of certain impedance properties of the diffraction of WG modes in a quite simple form. The analysis is based on one of the basic postulates of the Geometrical Theory of Diffraction, which describes high‐frequency diffraction as a local phenomenon. When the radius of the sphere becomes infinitely large, the expressions are reduced to those of the classical half plane problems.
is there an Archean Crust beneath Chesapeake Bay?
Authors: Lefort J. P. , Max M. D.
Published: February 2008

A crescent‐shaped terrane of continental crust centered on Chesapeake Bay is interpreted as being a collisional relic of Archean crust that was probably accreted during late Hercynian times. Arcuate gravity and magnetic anomalies, which represent the possible suture, separate Avalonian‐Carolinian terranes from what seems to be African‐like rocks seen in boreholes in the east Chesapeake Bay region. Seismic and heat flow data also suggest an important lithological variation in basement type across the suture.
Cenozoic extension and evolution of the Sevier Desert Basin, Utah, from seismic reflection, gravity, and well log data
Authors: Planke Sverre , Smith Robert B.
Published: February 2008

Seismic reflection profiles (∼550 km), gravity data, and well log information from west central Utah, have been interpreted to reveal an asymmetric west‐dipping Cenozoic basin beneath the Sevier Desert. The basin is underlain by a 10°–12° westward dipping, slightly undulatory, detachment surface, the Sevier Desert detachment. Finite difference synthetic seismograms were used to constrain the geometry of the interpreted reflectors in the basin. A two‐dimensional, one‐layer gravity inversion of three gravity profiles in the basin, using a 0.35 g/cm³ density contrast, corroborated the structure determined from the seismic interpretations. Physical properties and lithological data from eight wells were interpreted to acquire velocity‐depth and density‐depth functions and to obtain stratigraphic control. A minimum width of the Sevier Desert detachment of 80 km to 130 km and an area of 5600 km² to 9100 km² was estimated primarily from the reflection data. On the basis of geological and geometrical information, we estimated a minimum post‐middle Pliocene extension of 2.5 km to 3.5 km at a rate of 0.6 mm/yr to 0.8 mm/yr, corresponding to a strain rate of 2.7 10−16 s−1 to 3.5 10−16 s−1. Up to 4.0±0.6 km of predominantly post Eocene lacustrine and fluvial sediments overlie the Sevier Desert detachment including a well‐defined reflection that is interpreted as a middle Pliocene 4.2 m.y. basaltic flow that is present throughout the central and western part of the basin. The geometry of the middle Pliocene reflector, a variable ∼300 to ∼1500 m post‐middle Pliocene offset of a ∼40° eastward dipping western basin‐bounding fault, and up to ∼6 km east and west stepping of the generally north‐trending western basin‐bounding fault, suggests a complex late Tertiary deformational history. The varying deformational pattern may be a response to a changing geometry of the underlying detachment surface.
On the tectonic significance of retrograde P‐T‐t paths in eclogites of the French Massif Central
Authors: Mercier Laurence , Lardeaux Jean‐Marc , Davy Philippe
Published: February 2008

The retrograde pressure‐temperature‐time (P‐T‐t) paths in eclogites of the French Massif Central constitute a record of evolutionary thermal structures (geotherms) of the internal Variscan zones during uplift. Crystallization of all eclogitic assemblages occurred in the same range of P, T conditions: 700°–750°C for a minimal pressure of 15 kbar. In contrast the retrograde P‐T‐t paths of eclogites in the western and eastern parts of the Massif Central are clearly different. The eclogitic assemblages are retromorphosed at low temperatures in the western Massif Central, under amphibolite facies conditions in the central domain (middle temperature), and under granulite facies conditions in the eastern Massif Central (high temperature). A simple analytical thermal model, well constrained by geological features, allows us to simulate the evolution of this temperature difference during uplift. This study shows that different initial conditions of burial (depth of burial), or differences in tectonic processes during uplift (number of units involved in nappe piling, occurrence of a delay before the emplacement of a last unit) can produce such contrasting P‐T‐t paths. These cannot be explained by variations in erosion rates. In the case of different histories during uplift the P‐T‐t paths can simply be related to an efficient screen effect of a third nappe.
Earthquakes and ophiolite emplacement in the Molucca Sea Collision Zone, Indonesia
Authors: McCaffrey Robert
Published: February 2008

The Molucca Sea in eastern Indonesia is the site of an active arc‐arc collision, and among its interesting features is the exposure of ophiolitic rocks on islands of the Talaud‐Mayu Ridge (TMR), a largely submarine ridge formed of highly deformed rocks that bisects the collision zone. To explore the relationship between earthquakes and uplift of the ophiolite, the centroid depths and fault plane solutions of 18 large earthquakes occurring in the past 20 years beneath the TMR are constrained by inversion of their teleseismic, long‐period P and SH waveforms. Centroid depths range from 16 to 36 km, but uncertainties allow a range of 10 to 45 km. All events show thrust faulting; nodal planes strike parallel to the NNE trending TMR and dip 40±9° to the ESE and 53±9° to the WNW. Published seismic refraction and gravity data support the inference that the WNW dipping, steeper nodal planes are the fault planes. Dips do not change with depth, indicating either that the fault flattens below 40 km depth or that the steeply dipping fault penetrates the entire thickness of the lithosphere. I conclude that the Molucca Sea ophiolite is being lifted by high‐angle thrust faults (45° to 60°) that extend at least 15 km into the upper mantle. Summing seismic moment tensors and assuming uniformly distributed deformation suggest that the closure across the Molucca Sea collision zone may account for 14% to 59% of the Pacific‐Eurasia convergence vector or 15% to 63% of the Philippine‐Eurasia convergence. Moment tensor sums provide estimates of crustal thickening rates beneath the TMR of 7 to 20 mm/yr and these imply uplift rates of 2 to 6 mm/yr if the increase in crustal thickness is isostatically compensated. Hence the ophiolite and an enormous volume of mélange are being lifted higher than the flanks of the island arcs and will be emplaced on them by gravity. I suggest that ophiolites occur in this tectonic setting because the concave down shape of the subducted oceanic lithosphere beneath the Molucca Sea increases its effective buoyancy, preventing it from sinking out of the way of the encroaching island arcs. This case suggests a family of convergent margin settings in which normal oceanic lithosphere is buoyed up so that ophiolites can be stripped from it and emplaced on a continental margin or island arc. These settings include those where (1) slab geometry restricts asthenospheric flow away from the convergent margin, (2) subduction of younger, less dense lithosphere decreases its negative buoyancy, (3) a passive continental margin resists subduction, or (4) the presence of a thick thermal boundary layer beneath a passive continental margin inhibits asthenospheric flow necessary to accommodate the sinking oceanic lithosphere.
Lateral extrusion in the eastern Alps, Part 1: Boundary conditions and experiments scaled for gravity
Authors: Ratschbacher Lothar , Merle Olivier , Davy Philippe , Cobbold Peter
Published: February 2008

Lateral extrusion encompasses extensional collapse (gravitational spreading away from a topographic high in an orogenic belt) and tectonic escape (plane strain horizontal motion of wedges driven by forces applied to their boundaries). In the Eastern Alps it resulted from (1) an overall northerly compression (Apulia against Eurasia), (2) a strong foreland (Bohemian massif), (3) lack of constraint along a lateral boundary (Carpathian region), and (4) a previously thickened, gravitationally unstable, thermally weakened crust (Eastern Alpine orogenic belt). Six indentation experiments reproduce lateral extrusion at lithospheric scale. The models have two to four lithospheric layers, with a Mohr/Coulomb rheology for the upper and a viscous rheology for the lower crust. The lithosphere rests upon a low‐viscosity asthenosphere. A broad indenter, a narrow deformable area, and a weakly constrained eastern margin fullfill as closely as possible conditions in the Eastern Alps. Indentation produces both thickening in front of the indenter and escape of triangular wedges. Lateral variations in crustal thickness become attenuated by gravitational spreading. The overall fault pattern includes domains of reverse, strike‐slip, oblique normal, and pure normal faults. Strike‐slip faults in conjugate sets develop serially. The narrow width of the deformable area and the strength of the foreland determine the angles between the sets. Gravitational spreading produces a rhombohedral pattern of oblique and pure normal faults along the unconstrained margin. Opposite the unconstrained margin, the indenter front shows thrusts and folds intersecting with the conjugate strike‐slip sets. A triangular indenter favors spreading. High velocity of indentation favors escape. High confinement limits lateral motion, inhibits spreading, and favors thickening. Lateral extrusion in the Eastern Alps is best modeled by (1) a weak lateral confinement, (2) a broad and straight indenter, (3) a narrow width of the deformable area, and (4) a rigid foreland. Crustal thickening, lateral escape, and gravitational spreading all contribute to the overall deformation.
Geometry, evolution, and tectonic framework of the Skeena Fold Belt, north central British Columbia
Authors: Evenchick Carol A.
Published: February 2008

The Intermontane Belt of the Canadian Cordillera has long been viewed as a passive, relatively rigid block between two metamorphic‐plutonic belts, the Coast Plutonic Complex and the Omineca Belt. However, the Skeena Fold Belt, which spans most of the width of the northern Intermontane Belt, exhibits shortening comparable with that in the Rocky Mountain Fold and Thrust Belt. The Skeena Fold Belt has many features of thin‐skinned fold and thrust belts, such as thrust faults which sole into a detachment, a wide variety of structural styles which depend on rock type, a foreland basin which was cannibalized by continued deformation, a frontal triangle zone, and a hinterland of metamorphic and plutonic rocks (Coast Plutonic Complex). The Skeena Fold Belt thus is comparable with the Rocky Mountain Fold and Thrust Belt, but rather than deforming a continental terrace wedge, it developed in a terrane (Stikinia) which had accreted to North America in the early Mesozoic, and in Jurassic and Cretaceous clastic successions (Bowser Lake and Sustut groups) which overlie Stikinia. Structural and stratigraphic relationships show that the earliest deformation occurred between Oxfordian and Albian time and that the last folds developed in latest Cretaceous or early Tertiary time. As much as 160 km of northeastward shortening in the Skeena Fold Belt was broadly contemporaneous with crustal thickening in the Coast Plutonic Complex and Omineca Belt, with dextral strike‐slip faulting east of the Skeena Fold Belt, and with shortening in the Rocky Mountain Fold and Thrust Belt. Therefore, between latest Jurassic and early Tertiary times, horizontal shortening occured across most of the width of the northern Canadian Cordillera. Concurrent shortening across the Cordillera suggests that a common detachment (or detachments) fed all of these zones as far east as the Rocky Mountain Fold and Thrust Belt.
Thin‐skinned thrusting in the northern New England Orogen, central Queensland, Australia
Authors: Fergusson Christopher L.
Published: February 2008

Regional cross sections of the northern New England Orogen and eastern Bowen Basin in eastern Queensland indicate that the climactic Permian‐Triassic deformation involved thin‐skinned tectonics with the development of a mountain front represented by a syncline formed by crustal delamination with wedging of a thrust sheet from the east. The thrust sheet is exposed in the Folded Zone of the Bowen Basin and is characterized by upright NNW trending folds in Late Permian sediments. The folds have a chevron to flattened chevron style and formed mainly by flexural slip at about 60% shortening with detachment from an underlying basement of Paleozoic rocks. Farther east the basement is overlain by pervasively cleaved rocks of the Gogango Overfolded Zone in which structures show a consistent westerly vergence. These rocks overlie an inferred passive‐roof duplex in the underlying basement. Together, the Folded Zone of the Bowen Basin and the Gogango Overfolded Zone constitute a foreland fold‐thrust zone with a shortening of 50–90 km. This implies that the New England Orogen has been thrust west along a major east dipping detachment.
Satellite and ground observations of HIPAS VLF modulation
Authors: Kimura I. , Wong A. , Chouinard B. , Okada T. , Mccarrick M. , Nagano I. , Hashimoto K. , Wuerker R. , Yamamoto M. , Ishida K.
Published: February 2008

Joint experiments between the new Japanese satellite EXOS‐D (Akebono) and the HIPAS (High Power Active stimulation) facility located at Fairbanks, Alaska were made in 1989. The HF radiation was modulated in amplitude by 2.5 kHz signal. On November 28, 1989, EXOS‐D detected the VLF signal at an altitude of 2300 km with an E field of 15 μV/m and a B field of 0.25 pT. The angle between the wave normal and the geomagnetic field was found to be less than 20°.

Simultaneous ground observations were made using loop antennas at a distance about 35 km from HIPAS. The 2.5 kHz signal amplitude there at the time of the satellite observation was 1.3 pT. If this wave magnetic field is assumed to be due to an ionospheric AC current of 0.65 A, the signal strength at the satellite is roughly consistent within a factor of 3, which is much better consistency than those observed by James et al. (1984).
Antenna vector impedance measurement by the EXOS‐D (Akebono) very low frequency plasma wave instrument (VLF)
Authors: Hashimoto Kozo , Nagano Isamu , Okada Toshimi , Yamamoto Masayuki , Kimura Iwane
Published: February 2008

Antenna impedance has been measured on board the EXOS‐D (Akebono) satellite by imposing a constant current at VLF. The impedance is obtained in a complex form, i.e., as a resistance and a capacitance. This is essential to obtain the absolute electric field intensities of tbe VLF waves. A critical frequency below which the resistive part becomes important is also obtained.
Quasi‐parallel shocks: A patchwork of three‐dimensional structures
Authors: Schwartz Steven J. , Burgess David
Published: February 2008

Collisionless shocks at quasi‐parallel geometries, i.e., for which the average magnetic field direction upstream of the shock is close to the shock normal, reveal temporally varying quantities, a variety of boundary crossing and kinetic signatures, and magnetic structures, often convecting, of finite extent. These results can be put together by a framework in which the shock can be viewed as an extended region containing three‐dimensional Short Large Amplitude Magnetic Structures (SLAMS) which represent individual semi‐cycles of the ambient upstream low frequency waves associated with diffuse ions in the ULF foreshock. As SLAMS convect with the flow they grow to large amplitudes and entrain inter‐SLAMS regions to form an inhornogeneous downstream state. Their finite transverse extent is probably related to, and interacts with, ion beams, to produce a patchy transition zone which accounts for the variety of spacecraft signatures observed.
40AR/39AR age and duration of tholeiitic magmatism related to the early opening of the Red Sea rift
Authors: Féraud Gilbert , Zumbo Vilma , Sebai Amar , Bertrand Hervé
Published: February 2008

The early opening of the Red Sea rift is accompanied by tholeiitic magmatism stretching at least 1700 km along the western coast of Saudi Arabia, and consisting of thick gabbroic dykes, dense dyke swarms, plutons and discrete lava flows. Whereas the conventional K‐Ar measurements have furnished a wide variety of ages, the 40Ar/39Ar analyses presented here (giving 17 plateau‐ages) display a pronounced cluster of ages from 24 to 21 Ma. Such a short‐lived magmatic event has been suggested for other continental rifts.
Geophysical logs from the Toa Baja Scientific Drillhole, Puerto Rico
Authors: Anderson Roger N.
Published: February 2008

Geophysical logs from the Toa Baja drillhole on the north central coast of Puerto Rico are used to distinguish the variation in physical properties with depth in this non‐volcanic island arc massif. A marked unconformity separates shallow Oligocene to Miocene limestones with considerable permeability contrast from a deeper sequence of volcaniclastic rocks with decreasing shaliness. A volcanic sill or flow overlying a strongly mineralized zone is found to cause the impedance contrast responsible for the strong seismic reflection anomaly (bright spot) that was the exploration target.
Stratigraphy, geochemistry and mineralogy of Eocene rocks from the Toa Baja Drillhole
Authors: Smith Alan L. , Severin K. , Larue D. K.
Published: February 2008

The stratigraphy of the Eocene rocks of the Toa BaJa drillhole is dominated by volcaniclastic sediments which are interbedded with marly pelagic limestones, especially in the lower part of the hole, and lava flows. Petrological, geochemical and paleontological evidence suggest that the site of deposition was a deep marine basin and the source of the volcanics were subaerial or shallow submarine island arc volcanoes.
Cross section through the Toa Baja Drillsite: Evidence for northward change in Late Eocene deformation intensity
Authors: Larue D. K. , Berrong B.
Published: February 2008

A 55 km geologic cross section through the Toa Baja Drillsite, generated by integrating geologic mapping data from the foothills of the Central Mountains of Puerto Rico with onshore and offshore multichannel seismic reflection data, provides an opportunity to examine in profile from the arc interior northward to within 40 km of the current trench slope break. Three structural divisions are recognized. In the foothills of Puerto Rico, Cretaceous and Eocene rocks are separated by transpressional strike‐slip faults. In the vicinity of the Toa Baja drillsite where both seismic reflection and borehole data are available, Eocene rocks, deformed by thrust faults, lie above a lower unit, interpreted to be of Cretaceous age. Offshore, north of the drilling site, seismic reflections suggest Eocene rocks onlap structural basement, thought to be Cretaceous rocks, and both units appear only slightly deformed. All Eocene and Eocene (?) rocks are overlain by little deformed Oligocene to Recent rocks. From south to north, or from the arc massif interior toward the present‐day trench, there is an apparent decrease in amount of Late Eocene to Middle Oligocene strike‐slip and shortening deformation. Deformation events occurred mostly in the arc‐interior and were not directly associated with the plate boundary which was probably near the Puerto Rico Trench.
Discordant mid‐Cretaceous paleomagnetic pole from the Zaza Terrane of central Cuba
Authors: Renne Paul R. , Scott Gary R. , Doppelhammer Sheila K. , Cala Evelio Linares , Hargraves Robert B.
Published: February 2008

Thermal demagnetization of samples from five sites in mid‐Cretaceous volcaniclastic and carbonate rocks of south‐central Cuba reveals two or more components of magnetization. A pre‐folding magnetite borne component is recognized in all, but was difficult to isolate from secondary components in many specimens. Remagnetization circle analysis, using data for 42 specimens from all five sites, yields a pole at 30.7°N Lat., 193.3°E Long. This pole is discordant with respect to the North American APWP, indicating 43°±16° of anticlockwise rotation and 8°±6° of northward displacement since the mid‐Cretaceous. This result suggests that part or all of Cuba was transported on the Caribbean plate before accretion to North America in the Eocene.
Collisionless reconnection in Jupiter's magnetotail
Authors: Zimbardo Gaetano
Published: February 2008

We present the first quantitative study of collisionless reconnection in Jupiter's magnetotail. Recently it has been shown that collisionless reconnection can occur in the Earth's magnetotail quasi‐neutral sheet when the electrons are subject to chaotic pitch angle diffusion. This happens when the magnetic field is very taillike, i.e., when the curvature parameter κe = Bz/B0(Lz/ρe0)1/2 decreases to ≈ 1.6. For Jupiter's magnetotail, a self‐consistent axisymmetric equilibrium model is used to compute the magnetic field and κe, and it is found that the condition for electron chaotization is satisfied in a region large enough to allow the growth of a tearing instability. The favourite site for reconnection is situated at about 60 RJ, and the growth time is estimated to be about 370 s, i.e., much shorter than the plasma transit time through the chaotization region. The inductive e.m.f. along a 20 RJ X line is estimated to be of order 100kV – 1 MV, and should accelerate the ions dawnward and the electrons duskward.
Identification of polar stratospheric clouds from the ground by visible spectrometry
Authors: Sarkissian A. , Pommereau J. P. , Goutail F.
Published: February 2008

When sighted from the ground in clear weather, stratospheric clouds make large changes in the sky color during twilight. Spectrometric measurements performed from the ground during CHEOPS show that the color changes can be either large reddenings or blueings. A radiative transfer model demonstrates that the first are caused by thin hazes above 22 km while the second are related to thick clouds below, and that the color change during twilight is little sensitive to tropospheric clouds. Statistics of presence of PSC's above Kiruna during CHEOPS which shows that reddenings are correlated with temperature below NAT condensation at high altitude (30 hPa, 21.5 km) and blueings at low altitude (50 hPa, 18.5km), support this interpretation, as also the consistency with PSC measurements with in‐situ aerosol counters, balloon radiometer and from satellite observations. Spectrometric observations of the zenith sky at twilight is therefore thought to be a powerful method for identifying the presence and the altitude of PSCs above a station in all tropospheric weather conditions.
The case for accretion of the tectosphere by buoyant subduction
Authors: Abbott Dallas
Published: February 2008

This paper tests three hypotheses for the origin of the tectosphere. Continental collision cannot explain the low metamorphic grade of crust that predates the tectosphere. Halfspace cooling and buoyant underlating can both fit the diamond age data, although underplating by buoyant subduction is the favored model. Thermal models provide a further test. If half space cooling formed the tectosphere, diamonds from 150km depth will be at least 200 m.y. younger than diamonds from 190km. If buoyant subduction formed the tectosphere, diamonds from 150km depth will be the same age or older than diamonds from 190km.
Nonlinear Alfven waves in inhomogeneous plasmas
Authors: Buti B.
Published: February 2008

Nonlinear Alfvén waves, in inhomogeneous plasmas, are shown to be governed by the MDNLS (Modified Derivative Nonlinear Schrödinger) equation. The inhomogeneity leads to acceleration (deceleration) of the Alfvén solitons depending upon plasma β (kinetic pressure/magnetic pressure) and on density gradients vis‐a‐vis direction of wave propagation. Potential applications, of the model, to space and astrophysical plasmas are pointed out.
Temperature dependence of the infrared absorption cross sections of carbon tetrachloride
Authors: Orlando John J. , Tyndall Geoffrey S. , Huang Alvin , Calvert Jack G.
Published: February 2008

Infrared absorption cross sections for carbon tetrachloride are reported over the range 730 to 825 cm−1 at four different temperatures (298, 273, 248, and 223 K). The absorption cross sections were measured using Fourier transform spectroscopy at a spectral resolution of 0.05 cm−1. The integrated band intensity for this spectral region was found to be (5.75±0.30) × 10−17 cm2 molecule−1 cm−1, independent of temperature. The absorption cross sections were found to be essentially independent of spectral resolution (between 0.05 and 0.25 cm−1) and foreign gas pressure (0–1 atm at 298 K, 0–200 torr at 223 K), although changes of about 5 to 10 % were noted in the structured regions of the spectrum. Our measured band intensity appears to be about 15 % higher than recently published data. These differences are discussed in terms of their effect on previously reported stratospheric CCl4 altitude profiles.
Structural trends and back‐arc extension in the Havre Trough
Authors: Caress David W.
Published: February 2008

The Havre Trough is an active back‐arc ocean btsin located to the west of the Kermadec trench‐arc system in the southwest Pacific. Two recent cruises have provided reconnaissance swaths of Sea Beam bathymetry and GLORIA side‐scan sonar data through much of the Havre Trough as well as a detailed survey at 33.5°S, allowing the overall structural character of the trough and the nature of crustal extension within the detailed survey area to be assessed. The orientation of the tectonic fabric within the Havre Trough is consistently oblique to the basin as a whole, trending 045° to 060° while the bounding Kermadec and Colville Ridges trend 015° to 025°. The oblique internal structure indicates that the Havre Trough has not opened perpendicular to its own trend. Within the detailed survey area a series of short (15–35 km long) en echelon basins are interpreted as an active spreading center; a lack of sediment cover and the dredging of fresh basalt from one of the 3500–4000 m deep basins confirms the youth of these features. No recent extensional features are observed in a GLORIA crossing of the trough at 31.5°S, suggesting that this part of the Havre Trough may currently be inactive.