bluuebunny/crossref_metadata_2025 huggingface dataset:
Methane flux from the Amazon River floodplain: Emissions during rising water
Authors: Bartlett Karen B. , Crill Patrick M. , Bonassi Jose A. , Richey Jeffrey E. , Harriss Robert C.
Published: February 2008

During April and May of 1987, an extensive methane flux data set from Amazonian wetland habitats was collected during the wet season as river water levels were high and rising. This work extends measurements made in the dry season of 1985, when water levels were falling. Comparison of these two data sets allows estimation of the amount of seasonal variability in this globally significant source of tropospheric methane. A total of 284 flux measurements were made in the three primary floodplain environments of open‐water lakes and channels, floating grass mats, and flooded forests, along approximately 1500 km of the central floodplain. Emissions (means and standard errors) were 74±14 mg CH4/m2/d (open water), 201±35 mg CH4/m2/d (grass mats), and 126±20 mg CH4/m2/d (flooded forests). These values were not significantly different from the majority of those from 1985, in part due to the high variability in flux seen at both times. Although ebullition was a significant component of methane emissions at both periods, the frequency of bubbling and its contribution to total flux was lower during the period of rising water than during falling water. A prominent diurnal pattern in atmospheric methane concentrations was observed, with minimum levels of about 1.75 ppm at midday and a maximum of 2.12 ppm at about midnight. Given the relatively small seasonal changes observed in flux at the two stages of the river's hydrographic curve, our earlier estimates of regional methane flux remain largely unchanged. Revision of global estimates of wetland methane sources based on these tropical data and recently published figures for northern peatlands indicated that tropical wetlands may be more important than previously suggested, but that wetland sources overall remain at approximately 110 Tg/yr.
A case study of the nocturnal air flow around an isolated hill using tetroons and numerical simulation
Authors: Möllmann‐Goers M. , Vogt S.
Published: February 2008

In 1987, dispersion experiments and extensive meteorological measurements were carried out at an overburden tip called “Sophienhoehe” near the Research Centre Jülich. In addition to classical instruments like radiosondes, a tethered balloon, towers, and sonic detection and ranging, free‐flying balloons, so‐called tetroons, were used. Three tetroons were launched during nighttime and six tetroons during daytime conditions. Measurements from a selected field experiment formed the basis for a simulation of a tetroon flight using the flow over terrain with natural and anthropogenic heat sources (FITNAH) mesoscale model. Our verification study showed that the tetroon trajectory was well simulated. Some differences can be explained by the model results. This case study showed that FITNAH is a model which can simulate stable air flow in a very realistic way, and it further showed that tetroon flights have the potential to be a valuable tool to evaluate flow simulations. It is planned to do similar comparisons for the daytime flights.
Joint distribution of size and infrared optical thickness in cumulus cloud fields
Authors: O'Brien D. M. , Davis T. J.
Published: February 2008

This paper presents a parameterization of the joint distribution of size and infrared optical thickness in cumulus cloud. The model involves only two parameters, each of which has a clear physical interpretation, it is shown how knowledge of the size distribution and the mean infrared radiance transmitted by a cloud field can be used to deduce the thickness distribution of the field. One implication of this result is that the conjunction of Advanced Very High Resolution Radiometer data with size statistics, gathered for example in real time by processing high resolution images on board a satellite, can be used to predict the transfer of infrared flux by broken cloud.
The rate coefficient for the reaction NO2 + NO3 → NO + NO2 + O2 From 273 to 313 K
Authors: Cantrell Chris A. , Shetter Richard E. , McDaniel Anthony. H. , Calvert Jack G.
Published: February 2008

Laboratory experiments were performed to measure the ratio of rate constants for reactions (R3): NO3 + NO → 2 NO2 and (R4): NO2 + NO3 → NO + NO2 + O2. This was accomplished through direct measurement of the nitric oxide and nitrogen dioxide concentrations in an N2O5/NO2/N2 mixture over the temperature range from 273 to 313 K. The measured ratio is represented by the expression, k3/k4 = 387 exp(−1375/T). The result, when combined with measurements of k3 in order to determine k4, is in reasonable agreement with other recent results from this laboratory; however, it is approximately a factor of 2 smaller than earlier reports. The experimental details are reported along with possible atmospheric implications of this result.
Radiation balance at the sea surface in the Atlantic Ocean region between 40°S and 40°N
Authors: Behr H. D.
Published: February 2008

A 4‐week continuous record from March 21 to April 15, 1987, of solar and terrestrial downward and upward radiation flux densities (1 data set per minute) obtained during the Atlantic Ocean cruise of the R/V Polarstern (ANT V/5) along 30°W between 40°S and 40°N is evaluated. Meridional and frequency distributions of radiation balance components are calculated for the range of climatological zones traversed. Interhemispherical differences are shown. The variation of the sea‐surface albedo with solar elevation angle and weather conditions is also shown. The results are in good agreement with the parameterization reported by Coakley (1979).
Are there interactions of iodine and sulfur species in marine air photochemistry?
Authors: Chatfield Robert B. , Crutzen Paul J.
Published: February 2008

Portions of the global cycles of sulfur and iodine could be intertwined in reactions resulting from the emissions of dimethyl sulfide (DMS) and methyl iodide. A two‐dimensional photochemical model of a marine tropical tropospheric synoptic system is used to analyze the consequences of these emissions through their atmospheric transformation cycles to aerosols. Following one line of analysis, the reaction of IO+DMS → DMSO+I could play a significant role, ∼30–50%, in destroying DMS, if the reaction proceeds at the published fast rate. Under these assumptions, the concentrations of DMSO (dimethyl sulfoxide), dimethyl sulfone (DMSO2), and sulfate appear to set rather strict upper limits on the extent of the reaction over the global oceans, and hence, on [IO], which is < 2×105 molecule cm−3. DMS plays an important role in the iodine cycle by converting IO into I. The formation of a reservoir species HOI, following H abstraction by IO, may help explain the high concentrations and apparent strong diurnal variation of filter‐sampled inorganic iodine gases and help to explain low [IO] values. In an alternate, preferred, line of analysis, the rate of reaction of IO+DMS may be much slower, < 10−12 cm3 molecule−1s−1 and the I and S cycles remain decoupled: in this case, it appears that the OH+DMS addition reaction could proceed ∼30% to form DMSO. The mean concentration and variations of gaseous and particulate iodine species are also better simulated. A simple aerosol model describing fine and coarse particles is used to close the S budget, and, if only a minor role is played by DMSO, the budget compares well with data. Simulated SO2 concentrations for the upper troposphere are highly dependent on upper tropospheric [OH]. The paper concentrates on remote tropical ocean regions and includes simulations of the spatial and diurnal variation of iodine species I, IO, HI, HOI, IONO2, I2O2 and Itot(particulate) the sulfur species DMS, DMSO, DMSO2, MSA (methane sulfonic acid), SO2, and SO4=(particulate), as well as the species OH, HO2, and H2O2.
Chemical analysis of rain samples collected over the Pacific Ocean
Authors: Nagamoto C. , Parungo F. , Kopcewicz B. , Zhou M. Y.
Published: February 2008

During seven research cruises in the Pacific Ocean from 1984 to 1989 we collected rain samples for chemical analyses. The geographical and temporal variations of rain chemistry were studied in relation to natural and anthropogenic sources and transport of the constituents. The pH values of rain samples ranged from 3.9 to 7.2, with a mean of 5.6 (n = 104, σ = 0.5). The most acidic rain was found near the big ports, where SO4= and NO3− concentrations in rain were also the highest. The data indicated that wet deposition transports anthropogenic pollution from continents to oceans. Enrichments of Ca++ and K+, which are compared to Na+ in seawater, were observed in all rain samples throughout the ocean. However, their enrichment factors (EF) decrease with distance from land, signifying the extent of transport of crustal elements through cloud process and wet deposition. The EFs of Mg++ were close to unity, indicating its common origin with Na+. The EFs of Cl− in most rain samples were less than l, indicating loss of Cl− in aerosols, cloud droplets, or rain drops. High EFs of SO4= were also observed at the equatorial regions, where biogenic production of dimethyl sulfide is well known. During the 1987 El Niño anomaly the sulfate aerosol distribution and rainfall patterns altered with air trajectories. The effects of sulfate aerosol on cloud condensation and rainfall amount in various regions during normal years and the El Niño anomaly are discussed.
Diurnal variation of nitric oxide in the upper stratosphere
Authors: Kondo Y. , Aimedieu P. , Pirre M. , Matthews W. A. , Ramaroson R. , Sheldon W. R. , Benbrook J. R. , Iwata A.
Published: February 2008

Two recent measurements of the temporal variation of nitric oxide at constant altitude near 40 km are reported. The observations were made at float altitude with a balloon‐borne chemiluminescence detector together with in situ ozone measurements. The first measurement was made at 44°N on September 17, 1987, at an altitude of 40 km from before sunrise until 1000 LT. The second observation was made at the same latitude on June 18, 1988 at 39 km from 0800 to 1230 LT. The precision of the NO measurements is about 10% at these altitudes, obtained through a more accurate determination of the sample flow rate at pressures down to 2 mbar with a reduced ozone/oxygen flow rate. At an altitude of 40 km, nitric oxide was observed to start increasing very rapidly at sunrise when the solar zenith angle reached about 95°. After the rapid initial buildup, the rate of NO increase stabilized for 3 hours at about 1.2 ppbv/hour. Near 1100 LT at 39 km in summer the NO mixing ratio was observed to become nearly constant. These features of the diurnal variation of NO are in accord with the temporal variation expected from a time‐dependent zero‐dimensional photochemical model. Mixing ratios of NOy and N2O5 have been determined from the measured temporal variation of NO at 39.5±0.5 km, using the photochemical model of Pirre et al. (1989). These derived values of the NOy and N2O5 mixing ratios, 15.5±5.0 ppbv and 1.4±0.6 ppbv, respectively, are in good agreement with other recent measurements by balloon‐borne and space‐borne infrared experiments.
Taxonomic evolution of Neogene planktonic foraminifera and paleoceanographic relations
Authors: Wei Kuo‐Yen , Kennett James P.
Published: February 2008

The taxonomic evolution of Neogene (24 Ma to present day) planktonic foraminiferal species are described using four indices: rate of speciation, rate of extinction, rate of diversification, and rate of turnover. The evolution of Neogene planktonic foraminifera is marked by three principal stages: (1) a diversification stage (24 to 16 Ma, early Miocene), (2) an equilibrium stage (16 to 5 Ma, middle and late Miocene), and (3) a declining stage (5 Ma to Recent, Pliocene and Quaternary). The early Miocene diversification was in response to an increase in polar to equatorial thermal gradients and related subdivision of surface water masses. During the middle and late Miocene, the assemblages remained close to their equilibria, with relatively low diversification rates. The decline in diversity during the Pliocene and Quaternary probably resulted from adverse effects imposed by both large‐scale paleoceanographic fluctuations that began about 6 Ma and high‐frequency climatic oscillations related to northern hemisphere glaciations and deglaciations that began at about 2.5 Ma. Bursts of evolutionary activity marked by higher rates of turnover coincided with major paleoceanographic changes. Average evolutionary rates appear to be similar for tropical, transitional, and temperate assemblages, although the actual numbers of extinctions and speciations are higher in tropical assemblages because of higher standing diversity. Contemporaneity of turnover peaks in the three climatic regimes indicates global control of paleoceanographic perturbations upon planktonic foraminiferal evolution. The observed evolutionary pattern supports the stationary model of Stenseth and Maynard Smith (1984).
Possible significance of Early Paleozoic fluctuations in bottom current intensity, northwest Iapetus Ocean
Authors: Lash Gary G.
Published: February 2008

Sedimentologic and geochemical characteristics of red and green deep water mudstone exposed in the central Appalachian orogen define climatically‐induced fluctuations in bottom current intensity along the northwest flank of the Iapetus Ocean in Early and Middle Ordovician time. Red mudstone accumulated under the influence of moderate to vigorous bottom current velocities in oxygenated bottom water produced during climatically cool periods. Interbedded green mudstone accumulated at greater sedimentation rates, probably from turbidity currents, under the influence of reduced thermohaline circulation during global warming periods. The close association of green mudstone and carbonate turbidites of Early Ordovician (late Tremadocian to early Arenigian) age suggests that a major warming phase occurred at this time. Increasing temperatures reduced bottom current velocities and resulted in increased production of carbonate sediment and organic carbon on the carbonate platform of eastern North America. Much of the excess carbonate sediment and organic carbon was transported into deep water by turbidity currents. Although conclusive evidence is lacking, this eustatic event may reflect a climatic warming phase that followed the postulated glacio‐eustatic Black Mountain event. Subsequent Middle Ordovician fluctuations in bottom current intensity recorded by thin red‐green mudstone couplets probably reflect periodic growth and shrinkage of an ice cap rather than major glacial episodes.
Comparison of albedo changes due to shelf exposure and ice during the Late Ordovician glacioeustatic regression
Authors: Gildner Raymond F. , Cisne John L.
Published: February 2008

In a glacioeustatic regression the amount of exposure of the continental shelves and the size of the ice cap are intimately related. We use a numerical model to compare the effects on planetary albedo of the formation of ice caps and the exposure of continental shelves due to an eustatic regression such as was the known case in the Late Ordovician. To compare the two effects in a meaningful way, we link them by relating the size of the ice sheet to the change in volume of the ocean and thus to the exposure of the shelves. For the conditions of the Late Ordovician (Caradocian and Ashgillian) the change in albedo from the exposure of continental shelves and epeiric seafloor is many times greater than that due to the formation of ice (up to Δαs = 0.0233 versus Δαs = 0.0009, 25% versus 1% of the global mean surface albedo; Δαp = 0.0079 versus Δαp = 0.0001, 2.6% versus less than 0.1%). The change in planetary albedo is enough to lower the earth's effective temperature by up to three quarters of a degree Kelvin. We extend the hypothesis that the Ashgillian ice age was intensified and possibly even triggered by the exposure of extensive areas of epeiric floor during the Caradocian. The effect is more pronounced for the Ordovician than more recent times due to the differences in continental positions, today's lack of epeiric seas, differences in atmospheric composition, and the absence of land plants.
Isopollen maps for 18,000 years B.P. of the Atlantic offshore of northwest Africa: Evidence for paleowind circulation
Authors: Hooghiemstra Henry , Bechler Andreas , Beug H. ‐J.
Published: February 2008

Distribution patterns of the most important pollen types from southern European and northwest African source areas for the 18,000 years B.P. time slice are reconstructed from pollen records of 14 well‐dated deep‐sea cores located between 37° and 9°N and compared with the modern pollen distribution in this area. It is concluded that the belt with maximum African Easterly Jet transport did not shift latitudinally during the last glacial‐interglacial transition but remained at about 20°N. Furthermore, it is substantiated that the trade winds did not shift latitudinally during the last glacial‐interglacial transition. This evidence is not compatible with an atmospheric circulation model that assumes a zone of surface westerlies in the northern part of northwest Africa. Trade winds during glacial episodes did, however, intensify, especially from about 36° to 24° N.
Cenozoic paleoceanography 1986: An introduction
Authors: Berger W. H. , Mayer L. A.
Published: February 2008

New developments in Cenozoic paleoceanography include the application of climate models and atmospheric general circulation models to questions of climate reconstruction, the refinement of conceptual models for interpretation of the carbon isotope record in terms of carbon mass balance, paleocirculation, paleoproductivity, and the regional mapping of paleoceanographic events by acoustic stratigraphy. Sea level change emerges as a master variable to which changes in the ocean environment must be traced in many cases, and tests of the onlap‐offlap paradigm therefore are of crucial importance.
Diachrony of Late Neogene microfossils in the southwest Pacific Ocean: Application of the graphic correlation method
Authors: Dowsett Harry J.
Published: February 2008

The assumption of synchrony of first and last occurrences of fossil taxa can be tested using graphic correlation procedures which, by allowing measured stratigraphic sections to be compared on a common depth scale, make it possible to develop a correlation model which integrates information from a number of cores. The strategy of the test presented here is to use a graphic correlation model that is based on data from the Atlantic (Deep Sea Drilling Project (DSDP) sites 502, 516A) and north Pacific (DSDP site 577A) as a basis for determining to what extent fossil datums in the southwest Pacific are synchronous.

First and last occurrences of Pliocene calcareous nannofossils and planktonic foraminifers have been compared in five DSDP cores from the southwest Pacific ocean (sites 586, 587, 588, 590A, and 592). All cores were recovered using hydraulic piston coring technology, which assures the best recovery and minimal disturbance. Most of these cores contain abundant, well‐preserved foraminifers and nannofossils, as well as a partial record of many of the expected magnetic polarity reversals in this part of the section. To assure taxonomic consistency, all taxonomic identifications were made by the author.

Graphic correlation of this data set suggests that several important biostratigraphic markers are highly diachronous. For example, this study confirms thatGloborotalia truncatulinoidesfirst occurs at approximately 2.4 Ma between 20° and 35° south latitude in the southwest Pacific, approximately 0.5 m.y. earlier than it is found elsewhere in the Atlantic and Pacific. Other datums, such as the last occurrence ofDiscoaster brouweri, are essentially synchronous. These findings suggest that biostratigraphic models based on the assumption of synchrony of first and last occurrences of fossil taxa may be incorrect. Biostratigraphic models created with the Graphic Correlation method offer an opportunity to examine the biogeographic dimensions of origination, migration, and extinction of planktonic taxa.
Distribution of thorium 232 in manganese nodules and crusts: Paleoceanographic implications
Authors: Huh C. ‐A. , Ku T. ‐L.
Published: February 2008

Detailed depth profiles of 232Th in deep‐sea ferromanganese nodules and encrustations often show a subsurface maximum followed by a drastic inward decrease to a certain depth before levelling out. Length scales of this feature vary among the profiles but are proportional to growth rates of the specimens, suggesting that the profiles record changes in oceanic 232Th flux with time. Consideration of the nodule chronology, the history of eolian accumulation recorded in sediment cores, and the marine geochemical behavior and budget of 232Th leads us to propose that 232Th in nodules/crusts is of eolian origin. The drastic inward decrease of 232Th is a reflection of increase in the wind borne dust flux induced by the Northern Hemisphere glaciation beginning 2–3 Ma. The subsurface 232Th peak may indicate the decline of eolian flux since 0.1–0.3 Ma.
A bimodal climate response controlled by water vapor transport in a coupled ocean‐atmosphere box model
Authors: Birchfield G. Edward , Wang Huaxiao , Wyant Matthew
Published: February 2008

The importance of the hydrological cycle as a controlling factor on the magnitude of the thermohaline circulation is illustrated in a simple one‐hemisphere coupled ocean‐atmosphere box model. The ocean model includes differential surface heating and evaporation, horizontal and vertical exchange of heat and salt between boxes, and a simply parameterized thermohaline circulation. Surface heat fluxes and evaporation are determined through the coupled ocean and energy balance atmosphere models which treat fluxes of long‐ and short‐wave radiation and sensible and latent heat. Two parameters represent the most important physics: µ controls the magnitude of the thermohaline circulation; ε controls the strength of the hydrological cycle. For fixed µ, two regimes are distinguished. One, associated with small values of ε, has weak latitudinal water vapor transport in the atmosphere, a strong thermohaline circulation with sinking in high latitudes, upwelling in low latitudes, and strong latitudinal transport of heat by the ocean. The second regime for larger ε is characterized by strong latitudinal water vapor transport which, by reducing the surface salinity in high latitudes, shuts down the thermohaline circulation and has reduced ocean and net latitudinal heat transport. The bimodal response in the model is shown to be the consequence of a shift in the mechanism of supply of salt to the high‐latitude surface ocean from predominantly thermohaline transport, a nonlinear process, to or from predominantly eddy mixing transport, a linear process. In climatological terms, the bimodality represents two distinct climate regimes, one with an active ocean meridional circulation and relatively warm ocean and atmosphere temperatures in high latitudes, and the other with a less active ocean circulation and an increased latitudinal temperature gradient in atmosphere and ocean. The regime with an active thermohaline circulation tends to be less stable than the other, exhibiting over a range of ε a “halocline catastrophe” to perturbations in surface salinity. In many respects the model supports current concepts concerning the role of bimodal ocean physics and atmospheric water vapor transport in glacial to interglacial climate changes and in the more rapid events such as the Younger Dryas.
Solution of inverse problems by statistical optimization methods
Authors: Rastrigin L. A.
Published: February 2008

Inverse problems of seismology can be formulated as matrix inversion problems. If there are constraints on the system, such as the requirement that the parameters take positive values, and if the number of variables is large, statistical search methods become useful. A random search method is proposed which is superior to the usual gradient methods of search and which approaches the ‘ravine’ method if the interval of search is not changed by a ‘learning’ process during the search.
Algorithm for automatic recognition of a seismic signal by a computer
Authors: Naimark B. M.
Published: February 2008

Four criteria are supplied to a computer for deciding whether a seismic signal is present amid background noise. These criteria are those of (1) high energy, (2) rapid rate of change of amplitude, (3) short periods, and (4) a combination of short period and large amplitude. If a certain threshold is exceeded in any one of the four tests, an identification is made. For real signals artificially added to real noise, positive identification was made in every one of 27 tests for signals having peak amplitudes as low as one‐half the peak noise amplitude.
Stratospheric tidal circulations
Authors: Webb Willis L.
Published: February 2008

Diurnal heating of the ozonosphere near the stratopause level results in a diurnal temperature variation of approximately 15°C and development of a tidal circulation in the stratospheric wind field. This tidal circulation is hemispherically separated over the equator by earth rotational effects and rises into the mesosphere at high latitudes as a result of oblique incidence of solar radiation. Winds of the tidal circulation are principally meridional in middle latitudes—poleward ahead of the crest of the heat wave and equatorward in the afternoon and evening. At high latitudes the circulation is zonal around the poleward end of the heated ridge—westerly as the turn is made short of the pole in the winter situation and easterly in summer when the heated ridge includes the polar region. It is postulated that solar input energy to the general stratospheric circulation is redistributed by this tidal circulation, and that vertical winds of this tidal circulation are responsible for the support of noctilucent cloud particles and special ionospheric electrical phenomena such as the equatorial electrojet.
Exploring the atmosphere with nuclear explosions
Authors: Donn William L. , Shaw David M.
Published: February 2008

Pressure waves from large nuclear explosions have been recorded at many stations over the earth by instruments installed by the Lamont Geological Observatory. The propagation of these waves is controlled primarily by gravity and the acoustic properties of the atmosphere in a manner that produces group velocity dispersion of the acoustic‐gravity modes making up the signal. The nature of the wave dispersion depends on both the thermal and the wind stratification of the atmosphere. The casual relationships have been studied both experimentally and theoretically. To provide more data for air‐wave investigations, the 208 Lamont records made at 15 stations from 45 nuclear explosions are presented here together with related data on source, times, and distances.
Microseisms: Coastal and pelagic sources
Authors: Haubrich Richard A. , McCamy Keith
Published: February 2008

Wave‐number frequency spectra of seismic background recordings from the large aperture seismic array (LASA) in eastern Montana have been used to study the source locations of different wave types in the frequency band from 40 to 500 mHz. Microseisms in this band consist of surface waves of the Rayleigh and Love type and compressional body, waves. The peak power band near 140 mHz (7‐sec microseisms) and the lower frequency band near 70 mHz consist of fundamental Rayleigh waves, which often come from the same direction. This is especially true for directions from coasts in the vicinity of large storms. The average directional properties of the two bands are similar, indicating coastal sources for both. Love waves and higher mode Rayleigh waves in some instances come from the same coastal directions as the fundamental mode. Compressional body wave sources, pinpointed by using horizontal phase velocity to measure range, occur near storms both in coastal and pelagic regions. Pelagic storm sources were found only at frequencies that were high compared with double the frequency of ocean waves having a group velocity equal to the storm velocity. Located in the wake of a moving storm, such sources appear to be due to the oppositely traveling waves set up when a storm moves faster than its waves.
Strategy for scientific exploration of the terrestrial planets
Authors: Adams John B. , Conel James E. , Dunne James A. , Fanale Fraser , Holstrom Geoffrey B. , Loomis Alden A.
Published: February 2008

A strategy is presented for exploration of the inner solar system that will lead to knowledge of its origin and history. Several critical points in the evolution of the solar system are identified at which alternate evolutionary paths might have been possible. Experiments are suggested to help reveal the actual course of events at these critical points. The result is a framework relating experiments to be performed on the terrestrial planets and satellites to the major goal of determining the origin and history of the solar system. From this background, the lunar‐exploration portion of the suggested over‐all program is discussed in further detail. It is concluded that the moon offers a unique opportunity for investigating certain problems of the solar system.
Relativity experiments in space vehicles
Authors: Schiff L. I.
Published: February 2008

This paper reviews experiments under way or contemplated that make use of space vehicles for the quantitative study of gravitation. Several experiments are discussed briefly, some which can be performed in earth orbit, and others which require deep space probes. It is anticipated that the decade of the 1970's will place the relativistic theory of gravitation on a firm experimental basis.
General theory of water flow at the base of a glacier or ice sheet
Authors: Weertman J.
Published: February 2008

The theory of the flow of water at the base of a glacier is reviewed and extended. A detailed analysis is made of flow through Röthlisberger channels. (Röthlisberger channels are channels at the base of a glacier that are incised upward into the ice mass.) It is shown that, in general, a pressure gradient drives water melted from the bottom surface of a glacier away from Röthlisberger channels. Thus these channels are not good collectors of the water produced at the bottom surface of a glacier or ice sheet. If Nye channels exist (Nye channels are incised downward into the bedrock of a glacier bed), they should be important in the discharge of water at the base of a glacier. Nye tributary channels are expected to be spaced over several hundred meters apart. The analysis indicates that sheet flow is the main mechanism by which water melted from the bottom ice surface flows out of a glacier or ice sheet. The sheet flow described in this paper is a modification of that considered in our earlier papers. The thickness of the present sheets is not roughly uniform, but rather squeezes to negligible values at high‐pressure zones, where ice moves over the upstream side of obstacles and irregularities in the bed. The pressure of the water in the sheets is lower than the ice overburden pressure. The difference between the pressure in the sheets and the ice overburden pressure is estimated with the aid of the recent major refinements to glacier sliding theory made by J. F. Nye and by B. Kamb. (L. Lliboutry made the original suggestion that the pressure of the water at the base of a glacier is smaller than the ice overburden pressure.) Analysis indicates that a single Röthlisberger channel runs down the center of a glacier over a major fraction of its length. Pressure gradients, produced by the concave shape of the transverse bed profile, exist that drive water in the sheet toward this channel. However, in the upper parts of a glacier, this channel may take the form of a thick water layer of finite breadth.
Propagation and application of waves in the ionosphere
Authors: Yeh K. C. , Liu C. H.
Published: February 2008

This review deals with the propagation of waves, especially radio waves in the ionosphere. In the macroscopic electromagnetic theory, the mathematical structure of wave propagation problems depends entirely on the properties of the dielectric operator in a magnetically nonpermeable medium. These properties can be deduced from general discussions of symmetry and considerations of physical principles. When the medium is specifically the ionosphere, various physical phenomena may occur. Because of a large number of parameters, it is desirable to define a parameter space. A point in the parameter space corresponds to a specific plasma. The parameter space is subdivided into regions whose boundaries correspond to conditions of resonance and cutoff. As the point crosses these boundaries, the refractive index surface transforms continuously. The medium in which the propagation takes place may influence the wave in many different ways. Specific experiments can be designed to probe the medium to learn its properties.
Brief history of the Martian ‘violet haze’ problem
Authors: Thompson Don T.
Published: February 2008

A brief but thorough survey of the literature on the Martian ‘Violet haze’ problem is presented. It is evident that both the normal lack of contrast of the surface features in violet light and their occasional appearance are phenomena intrinsic to Mars. Models involving simple uniform layers of scattering or absorbing materials are inadequate to account for the observations.

We suggest that the role of haze has historically been misinterpreted. The blank disk of Mars in violet light occurs when the atmosphere is relatively free of haze. The formation of optically thin white hazes over the bright areas increases the contrast and produces ‘blue clearing.’
Horizontal variations in thermospheric composition
Authors: Johnson Francis S.
Published: February 2008

Constant boundary conditions at 120 km have been so widely and successfully used in atmospheric modeling and in fitting atmospheric density data obtained from satellite drag to models that attention has been diverted from the variations that occur at 120 km, especially in composition. Atomic oxygen concentrations vary by factors as large as 4, with highest concentrations occurring in the winter hemisphere but at mid‐latitudes rather than over the polar region. A substantial additional degree of variability occurs that is especially associated with geomagnetic activity. The helium concentration varies by about an order of magnitude between poles, with the maximum concentration occurring at high winter latitudes and a secondary minimum occurring over the winter pole.
Irregularities in the equatorial ionosphere: The Berkner Symposium
Authors: Farley D. T.
Published: February 2008

The main results of the symposium, which dealt with both E and F region irregularities, are summarized and discussed. The basic processes generating the E region (electrojet) irregularities now seem to be understood, but the details are not. Linear plasma instability theory appears to account for the presence or absence of irregularities. However, the irregularity amplitudes, the wavelength distribution, the propagation velocities, etc., all of which depend on nonlinear effects, are not well explained. The question of nonlinear mechanisms is controversial and is being attacked from a number of directions. The F region irregularities are still poorly understood; the basic driving mechanisms are not yet established. Two new ideas that seem promising involve (1) a gravitational interchange instability involving entire magnetic tubes of force and (2) irregular ‘fingers’ of metallic ions extending into the lower ionosphere that alter the E × B drift patterns.
Internal tides in the ocean
Authors: Wunsch Carl
Published: February 2008

Theory and observations of internal tides in the oceans are reviewed. Internal tides are simply a form of internal wave with quasi‐tidal periodicity, though north of their inertial latitudes they should be trapped to bottom topographic features, including continental shelves. In oceans of constant depth, their theory is reducible to that of ordinary (surface) tides in very shallow equivalent oceans. The short wavelengths appropriate to internal tides, however, mean that localized nonglobal solutions are most useful. Theory and observation both support the notion that internal tides are generated by the passage of the surface tide over topographic features, though it is not yet possible to say with certainty that any of several mechanisms dominates. A tabulation of worldwide observations suggests that internal semidiurnal tides contain 10–50% of the energy of the surface tide. Consideration of both the rate of input of energy into the internal tides and the rate of loss from them leads to the conclusion that the internal tides are probably not a significant sink for energy extracted from the surface tide. The energy does appear significant compared with the rates of input of energy to the general circulation by wind and thermal forcing. Unlike other internal waves the tides are dominated by the lowest vertical modes.
Petrology and plate tectonics
Authors: Miyashiro Akiho
Published: February 2008

Petrology played an important role in the formulation of plate tectonics and early plate tectonic interpretations of the geologic past. In the last few years widespread interest in plate tectonics and progress in plate tectonic interpretations have begun to give petrology various feedback effects.

In the period 1971–1974 there were two symposiums intended particularly to connect petrology with plate tectonics [Wyllie, 1973; Yoder, 1971]. Some other symposiums in plate tectonics involved the reading of a paper or papers dealing with petrologic problems.
Meteorite research
Authors: Wasson John T.
Published: February 2008

Although lunar samples were competing for the attention of meteorite researchers during the 4 years since the reports of Bogard [1971], Burnett [1971], Dodd [1971a], and Wasson [1971a], a number of exciting developments can be reported. Since this paper is the only survey of progress in meteoritics to appear in this quadrennial report, the bibliography is relatively long. The references regarding meteorite research in the United States are essentially complete for the period from July 1970 to June 1974. A number of important studies carried out outside the United States are also cited.

References have been assigned to the eight broad subject categories discussed in the text. In some cases any such assignment is arbitrary, and the reader is advised to search through other categories if complete references are needed.
Marine magnetic anomalies as related to plate tectonics
Authors: Herron E. M. , Pitman W. C.
Published: February 2008

During the last 4 years, preliminary or revised analyses of magnetic lineations have been published for all the major ocean basins. These results are graphically summarized in the global lineation and geologic age maps of Pitman et al. [1974] and have also been incorporated in the bibliography for this section. Using magnetic, bathymetric, and seismic data and different mathematical techniques, Chase [1972] and B. Minster et al. (personal communication, 1974) determined models of the instantaneous relative motion of major rigid crustal plates. In addition to describing the relative motion of 11 major plates, the Minster et al. model also suggests that there has been no relative movement between various hot spots during the last 10 m.y.
Recent advances in rock magnetism and their applications to paleomagnetism
Authors: Banerjee S. K.
Published: February 2008

The purpose of the present article is to review the highlights in rock magnetism research as seen from papers published (and those presently in press) during the period 1971–1974. Since this review is not meant to be comprehensive, I apologize in advance for possible omissions. Reviews dealing with the magnetic properties of lunar, meteoritic, and oceanic materials will be found elsewhere in this issue. Efforts have been made to make the bibliography at the end of this article as comprehensive as possible. Papers in rock magnetism are defined not only to include bona fide rock magnetism articles dealing with the various physicochemical aspects of the origin and stability of the natural remanent magnetization (NRM) of rocks and minerals but also to include those particular articles in paleomagnetism which do not treat (magnetic) rocks as ‘black boxes’ and to point out one interesting aspect or another of the magnetic minerals and their relevance to the measured NRM properties. In fact, it is my hope that the tenor of the present article is such that it will place rock magnetism firmly in this context, that of its applications to paleomagnetic and hence geological and geophysical problems. Also, at the outset I should refer here to four recent review articles [Dunlop, 1973c; Hargraves and Banerjee, 1973; Harrison, 1974; Fuller, 1974] and a new book [Stacey and Banerjee, 1974] in the field of rock magnetism.
Paleomagnetism, continental drift, and plate tectonics
Authors: Van der Voo Rob
Published: February 2008

The title of this chapter might induce the reader to expect rather more than what actually is being offered; this review restricts itself to those aspects of paleomagnetism that are related to continental drift, polar wandering, and plate tectonics, and vice versa. A sensu lato interpretation would not only lead to a lengthy recitation; it would also in fact be an impossible task to list all U.S. contributions for the period 1970–1974, so pervasive have the mobilistic concepts been in gaining acceptance in all subdisciplines of the earth sciences.

Below, the accomplishments and highlights of the past 4 years are reviewed. Emerging and remaining questions that still require satisfactory answers are occasionally outlined. The publications in paleomagnetism as it relates to tectonics can be classified in three major categories. The first category comprises the contributions that have provided the details for those theories that gradually gained acceptance during the period of 1960–1970. Then there are the publications that contributed in the last 4 years to the successful formulation of tectonic ideas, which previously were just emerging or not even thought of. Finally, I will mention those contributions that outlined newly emerging areas of research but that await independent confirmations and/or more concise formulations. The following sections roughly follow this trend.
Control surveys
Authors: Meade Buford K.
Published: February 2008

This report covers the national and international activities of U.S. federal agencies engaged in the establishment of geodetic control in the United States, and in other areas through international cooperation, during the period January 1, 1971, to December 31, 1974. The control established by the various agencies is summarized by agency under horizontal control, vertical control, and geodetic astronomy. These agencies are the National Ocean Survey (NOS); Defense Mapping Agency Topographic Center (DMATC); Defense Mapping Agency Aerospace Center, Geodetic Survey Squadron (DMAAC/GSS); U.S. Geological Survey (USGS); and the U.S. Naval Oceanographic Office (NAVOCEANO).

The Department of Commerce is responsible for the basic geodetic networks in the United States and for coordinating the surveying activities of all federal agencies. This primary responsibility, assigned to NOS of the National Oceanic and Atmospheric Administration, includes planning, processing, publication, and distribution of geodetic data to meet the national needs.
Earth tides
Authors: Kuo John T.
Published: February 2008

Since the last U.S. national report on earth tides to the Fifteenth General Assembly, International Union of Geodesy and Geophysics [Kuo, 1971], research activities in tidal gravity have been moving rapidly from the search for a basic understanding of the predominant influence of ocean tides on tidal gravity toward studies of interaction of the earth and ocean tides. These activities in tidal tilt and tidal strain are as yet centered around the problem of evaluation of ocean tidal and local influences.

However, all accumulated knowledge of spatial variations of earth tides points the direction of earth tidal research toward attacking the inverse problem for ocean tides by means of earth tidal measurements on the lands and islands, supplemented by ocean bottom measurements. Attempts at solving the inverse problem by means of tidal gravity measurements have already begun. Once the local influences on tidal tilt and tidal strain are understood and can be corrected, the precise tidal tilt and tidal strain measurements can also be of great value in solving the inverse problem. The prospects for satellite mapping of both earth and ocean tides are very hopeful.
Dynamic satellite geodesy
Authors: Gaposchkin E. M.
Published: February 2008

Since the last quadrennial report [Gaposchkin, 1971], dynamic satellite geodesy has been continually refined with several new and independent solutions for the gravity field [Yionoulis et al., 1972; Gaposchkin, 1973a, 1974; Lerch et al., 1972a, b, 1974; Lerch and Wagner, 1972; Rapp, 1971a, 1973a, b, 1974a; Koch, 1972, 1974; Koch and Witte, 1971; Koch and Morrison, 1970] and station coordinates [Anderle, 1974a; Gaposchkin, 1973a, 1974; Lerch et al., 1972a, b, 1974; Lerch and Wagner, 1972; Marsh et al., 1971, 1972, 1973a, b; Koch, 1972, 1974; Koch and Witte, 1971; Koch and Morrison, 1970]. The new results have led to a consolidation of the discipline and have provided general agreement for these geodetic parameters. In addition, a milestone was achieved with the completion of The National Geodetic Satellite Program (NGSP), sponsored by the National Aeronautics and Space Administration (NASA). Many of the above‐mentioned results, the product of that program, are documented by the National Aeronautics and Space Administration [1975]. The NGSP was based on what have become classical satellite methods. In addition, some new and exciting observing techniques, now coming into use under the sponsorship of the NASA Earth and Ocean Physics Applications Program (Eopap), will be complementary to the classical satellite and terrestrial methods. These techniques include the use of satellite‐to‐sea‐surface radar altimetry and satellite‐to‐satellite tracking. An important technological achievement was accomplished with the successful launch and operation of the surface force compensated satellite Triad [Black, 1973]; such force compensation allows the corrupting effects of nongravitational forces to be eliminated from future geodetic analyses. A similar objective is sought with the imminent launch of Lageos, which will be used for the dynamical determination, to centimeter accuracy, of site locations, polar motion, and crustal displacement.