bluuebunny/crossref_metadata_2025 huggingface dataset:
Coastal carbonate aquifer sensitivity to tides
Authors: Loper David E. , Werner Christopher L. , Chicken Eric , Davies Gareth , Kincaid Todd
Published: October 2006

Regional groundwater flow in karstified carbonate aquifers typically occurs via a connected system of conduits, rather than in a porous matrix. This feature makes such aquifers difficult to characterize and quantify and they are among the most poorly modeled of all physical systems. Current models drastically overpredict travel times of pollutants, and current statistical methods cannot reliably determine the salient properties of these aquifers using surface‐flow data.

Better understanding of such aquifers is needed, since they are widespread [Veni, 2002], typically more productive than other types of aquifers, and vulnerable to contamination.
Developing quantitative skills activities for geoscience students
Authors: Hancock Gregory , Manduca Cathy
Published: October 2006

Teaching quantitative skills is one of the most challenging and important aspects of teaching geoscience. Quantitative skills are essential for Earth science students and citizens alike, and these skills have been deemed a critical goal for U.S. undergraduate education [National Science Foundation, 1996].

Public policy decisions increasingly are made and explained to the public based on data presentation, numerical models, statistics, and numbers. Introductory Earth sciences are among the primary courses chosen by nonscience students to fulfill science requirements and thus provide an important vehicle for teaching these essential skills. Courses in the geoscience major are equally important in introducing students to the quantitative analysis that is increasingly central to the discipline. It is therefore essential that adequate training be provided to Earth science majors and nonmajors in quantitative techniques ranging from simple graph and data interpretation to more sophisticated techniques such as numerical modeling.
Testing the Lake Agassiz meltwater trigger for the Younger Dryas
Authors: Lowell Thomas , Waterson Nicholas , Fisher Timothy , Loope Henry , Glover Katherine , Comer Gary , Hajdas Irka , Denton George , Schaefer Joerg , Rinterknecht Vincent , Broecker Wallace , Teller James
Published: October 2006

Meltwater drainage from glacial Lake Agassiz has been implicated for nearly 15 years as a trigger for thermohaline circulation changes producing the abrupt cold period known as the Younger Dryas. On the basis of initial field reconnaissance to the lake's proposed outlets, regional geomorphic mapping, and preliminary chronological data, an alternative hypothesis may be warranted.

Should ongoing data collection continue to support preliminary results, it could be concluded that Lake Agassiz did not flood catastrophically into the Lake Superior basin preceding the Younger Dryas (Figure 1). All preliminary findings imply a retreating ice sheet margin approximately 1000 years younger than previously thought, which would have blocked key meltwater corridors at the start of the Younger Dryas.
Arctic ocean study: Synthesis of model results and observations
Authors: Proshutinsky A. , Yang J. , Krishfield R. , Gerdes R. , Karcher M. , Kauker F. , Koeberle C. , Hakkinen S. , Hibler W. , Holland D. , Maqueda M. , Holloway G. , Hunke E. , Maslowski W. , Steele M. , Zhang J.
Published: October 2006

Model development and simulations represent a comprehensive synthesis of observations with advances in numerous disciplines (physics; mathematics; and atmospheric, oceanic, cryospheric, and related sciences), enabling hypothesis testing via numerical experiments. For the Arctic Ocean, modeling has become one of the major instruments for understanding past conditions and explaining recently observed changes.

In this context, the international Arctic Ocean Model Intercomparison Project (AOMiphttp://fish.cims.nyu.edu/project_aomip/overview. html) has investigated various aspects of ocean and sea ice changes for the time period 1948 to present. Among the major AOMIP themes are investigations of the origin and variability of Atlantic water (AW) circulation, mechanisms of accumulation and release of fresh water (FW), causes of sea level rise, and the role of tides in shaping climate.
Urban heat islands developing in coastal tropical cities
Authors: González Jorge E. , Luvall Jeffrey C. , Rickman Douglas , Comarazamy Daniel , Picón Ana , Harmsen Eric , Parsiani Hamed , Vásquez Ramón E. , Ramírez Nazario , Williams Robin , Waide Robert W. , Tepley Craig A.
Published: October 2006

Beautiful and breezy cities on small tropical islands, it turns out, may not be exempt from the same local climate change effects and urban heat island effects seen in large continental cities such as Los Angeles or Mexico City. A surprising, recent discovery indicates that this is the case for San Juan, Puerto Rico, a relatively affluent coastal tropical city of about two million inhabitants that is spreading rapidly into the once‐rural areas around it.

A recent climatological analysis of the surface temperature of the city has revealed that the local temperature has been increasing over the neighboring vegetated areas at a rate of 0.06°C per year for the past 30 years. This is a trend that may be comparable to climate changes induced by global warming.
Katrina and Rita were lit up with lightning
Authors: Shao X.‐M. , Harlin J. , Stock M. , Stanley M. , Regan A. , Wiens K. , Hamlin T. , Pongratz M. , Suszcynsky D. , Light T.
Published: October 2006

Hurricanes generally produce very little lightning activity compared to other noncyclonic storms, and lightning is especially sparse in the eye wall and inner regions within tens of kilometers surrounding the eye [Molinari et al., 1994, 1999]. (The eye wall is the wall of clouds that encircles the eye of the hurricane.) Lightning can sometimes be detected in the outer, spiral rainbands, but the lightning occurrence rate varies significantly from hurricane to hurricane as well as within an individual hurricane's lifetime.

Hurricanes Katrina and Rita hit the U.S. Gulf coasts of Louisiana, Mississippi, and Texas, and their distinctions were not just limited to their tremendous intensity and damage caused. They also differed from typical hurricanes in their lightning production rate.
Glacier shrinkage and water resources in the Andes
Authors: Francou Bernard , Coudrain Anne
Published: October 2006

For more than a century glaciers around the world have been melting as air temperatures rise due to a combination of natural processes and human activity. The disappearance of these glaciers can have wide‐ranging effects, such as the creation of new natural hazards or changes in stream flow that could threaten water supplies

Some of the most dramatic melting has occurred in the Andes mountain range in South America. To highlight the climatic and glacial change in the Andes and to encourage the scientific community to strengthen the glacier observation network that stretches from Colombia to the Patagonian ice fields, the Instituto Nacional de Recursos Naturales (INRENA), Perú, and the Institute of Research and Development (IRD), France, recently organized the second Symposium on Mass Balance of Andean Glaciers in Huaráz,Perú.
The role of volatiles and atmospheres on Martian impact craters
Authors: Barlow Nadine , Stewart Sarah , Barnouin‐Jha Olivier
Published: October 2006

Many questions remain about what Martian impact craters reveal about the planet's environment at the time of the impact and about the subsequent processes that have modified these craters. In particular, questions remain about the role of near‐surface or “target” volatiles (volatiles within the upper few kilometers of the surface) and the planets variable carbon dioxide (CO2) atmosphere on ejecta formation and modification.

A recent meeting, “Workshop on the Role of Volatiles and Atmospheres on Martian Impact Craters,” helped to better define these questions and review current understandings. The workshop was sponsored by the Lunar and Planetary Institute, Mars Crater Consortium, NASA, Johns Hopkins University's Applied Physics Laboratory, and the Mars Exploration Program Analysis Group.
Seafloor margin map helps in understanding subduction earthquakes
Authors: Collot J.‐Y. , Migeon S. , Spence G. , Legonidec Y. , Marcaillou B. , Schneider J.‐L. , Michaud F. , Alvarado A. , Lebrun J.‐F. , Sosson M. , Pazmino A.
Published: October 2006

Ecuador and southwest (SW) Colombia suffered widespread damage during the twentieth century as a result of some of the greatest subduction earthquakes and associated tsunamis ever recorded. In 1906, the Ecuador‐SW Columbia margin, located at the transition between the continent and deep ocean, ruptured over a 500‐kilometer length as a single great (Mw = 8.8) subduction earthquake (Figure 1a) [Kelleher, 1972]. The 1906 rupture zone was partially reactivated in 1942, 1958, and 1979 by earthquakes of Mw 7.7 to 8.2 (Figure 1b), with 100‐200 kilometerlong rupture zones [Beck and Ruff, 1984].

Such considerable variation in earthquake rupture length and magnitude in this area's seismic cycles during the last century has raised questions about the nature and enduring significance of the boundaries that exist between rupture zones and about the long‐term recurrence interval between earthquakes.
Mars atmospheric surface interactions and the CO2 cycle
Authors: Titus Timothy N. , Colaprete Anthony
Published: October 2006

Mars' northern and southern seasonal polar caps are formed during their respective autumn and winter seasons both by condensation of atmospheric carbon dioxide (CO2) directly onto the surface, and through atmospheric precipitation in the form of CO2 snow. During the polar spring and summer, the seasonal ice sublimes, returning CO2 to the atmosphere.

Roughly 25% of the atmosphere, which is 95% CO2 by volume, is cycled through the seasonal caps annually. This CO2 cycle dominates atmospheric circulation on Mars and must be thoroughly understood before the fundamental questions about Mars' climate history and the global distribution of near‐surface water can be addressed.
Sumatra earthquake research indicates why rupture propagated northward
Authors: Singh Satish C.
Published: October 2006

The Sumatra earthquake of 26 December 2004 (Mw = 9.3) was one of the largest megathrust earthquakes ever recorded using a modern seismic network. The rupture initiated around 3°N near Simeulue Island and propagated northward for about 1250 kilometers up to the Andaman Islands. Nearly three months later, on 28 March 2005, a second large earthquake occurred (Mw = 8.6) about 150 kilometers farther southeast.

The aftershocks of these two events (Figure 1) do not overlap, with one lying east and the other west of Simeulue Island. This observation, along with modeling studies [Lay et al., 2005; Ammon et al., 2005] of the earthquake ruptures suggest that there should be a lithosphere‐scale boundary around Simeulue, which could be either in the lower plate or in the upper plate. Such a boundary will act as a barrier for rupture propagation from an earthquake initiated on the other side of the boundary.
Using magnetograms for earthquake magnitude evaluation
Authors: Batlló J. , Arrazola D. , Ugalde A.
Published: October 2006

Recent research into the feasibility of calculating past earthquake magnitudes from old geomagnetic records on photographic paper has yielded promising results. Such a tool will help to complete seismic catalogues and thus more accurately assess seismic hazards.
Paleoelevation measurement: Combining proxies and approaches
Authors: Sahagian Dork
Published: October 2006

Determining paleoelevation, the past elevation of the Earth's surface, is a key problem facing Earth science. This is in part because it bears on and links together tectonics, climate, and geomorphological issues, and also in part because the prospect of reliable solutions to specific paleoelevation histories has now brought the problem to the verge of being tractable.

The geodynamic evolution of large‐scale mountain belts and plateaus such as Tibet, the Altiplano (in Bolivia and Chile), or the interior of western North America has long been contested. Nevertheless, these areas have served as the focus for the development of fundamental tectonic models that attempt to elucidate lithospheric processes. Reconstruction of paleotopography and its influence on global atmospheric circulation is a critical element for reconstructing past climate and understanding the distribution of precipitation controlled by orographic barriers.
First sighting of active fluid venting in the Gulf of Cadiz
Authors: Van Rooij David , Depreiter Davy , Bouimetarhan Ilham , De Boever Eva , De Rycker Koen , Foubert Anneleen , Huvenne Veerle , Réveillaud Julie , Staelens Peter , Vercruysse Jeroen , Versteeg Willem , Henriet Jean‐Pierre
Published: October 2006

The Mercator mud volcano, located in the Gulf of Cadiz off the coasts of Spain, Portugal, and Morocco (Figure 1), may provide an accessible field laboratory for studying local active venting and its possible internal and external controls. The recent discovery of the first active deep ocean ‘brown smoker’ chimney in this area can possibly be linked with the disintegration of a gas hydrate layer between the seafloor and a subsurface level that is dependent on pressure and temperature.

For more than a decade, the international marine scientific community has deployed considerable efforts in exploring the Gulf of Cadiz. Since the discovery of the Gulf's first mud volcano in 1999, research cruises have steadily unveiled one mud volcano after another [Gardner, 2001; Pinheiro et al., 2003; Somoza et al., 2003]. These mud volcanoes are clustered in several fields on the Portuguese, Spanish, and Moroccan margins (Figure 1). Extensive geophysical evidence of shallow gas and subsurface fluid flow has been reported in the Gulf of Cadiz [Baraza and Ercilla 1996; Pinheiro et al., 2003].
Crater glaciers on active volcanoes: Hydrological anomalies
Authors: Walder Joseph S. , LaHusen Richard G. , Vallance James W. , Schilling Steve P.
Published: October 2006

Mount St. Helens is an active volcano that hosts glacier ice within its crater. Although the common picture of volcano/glacier interactions is one of rapid meltwater generation when hot material is brought into contact with snow and ice [e.g.,Major and Newhall, 1989], there have been practically no observable hydrological consequences of the ongoing episode of silicic lava dome emplacement at Mount St. Helens.

The glaciological consequences have nonetheless been dramatic: The crater glacier has been cut in half since the dome growth began in September 2004, and the resulting ice bodies have in succession been squeezed between the growing lava dome and the crater wall.
Implementing a U.S. National Phenology Network
Authors: Betancourt Julio L. , Schwartz Mark D. , Breshears David D. , Cayan Daniel R. , Dettinger Michael D. , Inouye David W. , Post Eric , Reed Bradley C.
Published: October 2006

The passing of seasons, as gauged by annual events or phenophases in organisms' life cycles, is arguably one of the most pervasive environmental variations on Earth. Shifts in seasonal timing, or phenology, are observed in flowering and other stages of plant development, animal migration and reproduction, hibernation, and the seasonal activity of cold‐blooded animals [e.g., Schwartz, 2003; Root et al., 2005]. As an important life history trait, phenology is an object of natural selection; depending on timescales, shifts in phenology can lead to evolutionary change. Thus, phenology is not only an indicator of pattern in environmental science, but also its variation has fitness consequences for individuals, and these can scale up to broader ecological dynamics.
Along‐strike variation of orogenic wedges associated with vertical axis rotations
Authors: Soto Ruth , Casas‐Sainz Antonio M. , Pueyo Emilio L.
Published: October 2006

Analogue experiments with variable along‐strike shortening were performed by pushing a rotating rigid backstop against constant thickness one‐layer (sand) and two‐layer (sand‐silicone) cakes. Along‐strike shortening differences were introduced by the vertical axis rotation of the backstop and caused lateral variations in the deformational style of the accretionary wedge. Deformational fronts were diachronous and oblique with respect to the backstop direction. Numerous oblique ramps developed in order to accommodate the structural differences between sectors with different amounts of shortening, individual thrust sheets rotated significantly less than the backstop, and older thrust sheets presented higher vertical axis rotations than younger ones. Analogue models show the importance of strike‐slip motions during thrusting and significant vertical axis rotations in frictional and ductile basal conditions, respectively. Our modeling results are compared with natural examples from the southern Pyrenees, the Idaho‐Wyoming thrust belt, and the Transverse Ranges, where external axis rotations are linked to oblique ramps, differential shortening, and thrust propagation in orogenic wedges.
Predicting the frequency of storm surges and extreme sea levels in the northwest Atlantic
Authors: Bernier N. B. , Thompson K. R.
Published: October 2006

A 40 year hindcast of storm surges in the northwest Atlantic and adjacent shelf seas is performed using a 2‐D nonlinear barotropic ocean model forced by realistic 6 hourly winds and air pressures. This hindcast is used to generate spatial maps of the return level of storm surges and also to estimate the return period of extreme total sea levels. The accuracy of the hindcast is assessed in two ways. First, the standard deviation of the difference between the observed residuals (total sea level minus tide) and the hindcast is calculated at 24 tide gauge locations. A typical error standard deviation is 8 cm. Second, the 40 year return level of observed residuals is compared to that of the hindcast surges. The predicted 40 year return levels are typically within 10 cm of observed return levels at the 24 observation locations. A spatial map of the 40 year return level of surges is presented for the northwest Atlantic. It identifies the regions exposed to the largest surges. Total sea levels are reconstructed using (1) the hindcast surges and (2) tides and higher‐frequency variability predicted from short, observed sea level records. An extremal analysis of the reconstructed total sea levels shows that their 40 year return levels are in good agreement (within about 10 cm) with the levels calculated from multidecadal observed sea level records. This means that given a short record anywhere within the model domain, or results from a good tidal model, 40 year return levels can be estimated.
Modeling the 1998–2003 summer circulation and thermal structure in Lake Michigan
Authors: Beletsky Dmitry , Schwab David , McCormick Michael
Published: October 2006

A three‐dimensional primitive equation numerical model was applied to Lake Michigan on a 2 km grid for 6 consecutive years to study interannual variability of summer circulation and thermal structure in 1998–2003. The model results were compared to long‐term observations of currents and temperature at seven moorings and two NOAA buoys. The accuracy of modeled currents improved considerably relative to previous summer circulation modeling done on a 5 km grid, while the accuracy of temperature simulations remained the same. Particle trajectory model results were also compared with satellite‐tracked surface drifter observations. Large‐scale circulation patterns tend to be more cyclonic (counterclockwise) toward the end of summer as the thermocline deepens and density effects become more important. Circulation in southern Lake Michigan appears to be more variable than circulation in northern Lake Michigan. An important new feature not previously seen in observations was found in southern Lake Michigan: an anticyclonic gyre extending northward from the southern shore of Lake Michigan, sometimes occupying the entire southern basin.
Radar imaging mechanism of marine sand waves at very low grazing angle illumination caused by unique hydrodynamic interactions
Authors: Hennings Ingo , Herbers Dagmar
Published: October 2006

The investigations carried out between 2002 and 2004 during six field experiments within the Operational Radar and Optical Mapping in monitoring hydrodynamic, morphodynamic and environmental parameters for coastal management (OROMA) project aimed to improve the effectiveness of new remote sensing monitoring technologies such as shipborne imaging radars in coastal waters. The coastal monitoring radar of the GKSS Research Center, Geesthacht, Germany, is based on a Kelvin Hughes RSR 1000 X band (9.42 GHz) vertical (VV) polarized river radar and was mounted on board the research vessel Ludwig Prandtl during the experiments in the Lister Tief, a tidal inlet of the German Bight in the North Sea. The important progress realized in this investigation is the availability of calibrated X band radar data. Another central point of the study is to demonstrate the applicability of the quasi‐specular scattering theory in combination with the weak hydrodynamic interaction theory for the radar imaging mechanism of the seabed. Radar data have been taken at very low grazing angles ≤2.6° of flood and ebb tide–oriented sand wave signatures at the sea surface during ebb tidal current phases. Current speeds perpendicular to the sand wave crest ≤0.6 m s−1 have been measured at wind speeds ≤4.5 m s−1 and water depths ≤25 m. The difference between the maximum measured and simulated normalized radar cross section (NRCS) modulation of the ebb tide–oriented sand wave is 27%. For the flood tide–oriented sand wave, a difference of 21% has been calculated. The difference between the minimum measured and simulated NRCS modulation of the ebb tide–oriented sand wave is 10%, and for the flood tide–oriented sand wave, a value of 43% has been derived. Phases of measured and simulated NRCS modulations correspond to asymmetric sand wave slopes. The results of the simulated NRCS modulation show the qualitative trend but do not always quantitatively match the measured NRCS modulation profiles because the quasi‐specular scattering theory at very low grazing angle is a first‐order theory.
Reconstructing depositional processes and history from reservoir stratigraphy: Englebright Lake, Yuba River, northern California
Authors: Snyder Noah P. , Wright Scott A. , Alpers Charles N. , Flint Lorraine E. , Holmes Charles W. , Rubin David M.
Published: October 2006

Reservoirs provide the opportunity to link watershed history with its stratigraphic record. We analyze sediment cores from a northern California reservoir in the context of hydrologic history, watershed management, and depositional processes. Observations of recent depositional patterns, sediment‐transport calculations, and 137Cs geochronology support a conceptual model in which the reservoir delta progrades during floods of short duration (days) and is modified during prolonged (weeks to months) drawdowns that rework topset beds and transport sand from topsets to foresets. Sediment coarser than 0.25–0.5 mm deposits in foresets and topsets, and finer material falls out of suspension as bottomset beds. Simple hydraulic calculations indicate that fine sand (0.063–0.5 mm) is transported into the distal bottomset area only during floods. The overall stratigraphy suggests that two phases of delta building occurred in the reservoir. The first, from dam construction in 1940 to 1970, was heavily influenced by annual, prolonged >20 m drawdowns of the water level. The second, built on top of the first, reflects sedimentation from 1970 to 2002 when the influence of drawdowns was less. Sedimentation rates in the central part of the reservoir have declined ∼25% since 1970, likely reflecting a combination of fewer large floods, changes in watershed management, and winnowing of stored hydraulic mining sediment.
Numerical computation of sand dune migration with free surface flow
Authors: Giri Sanjay , Shimizu Yasuyuki
Published: October 2006

This paper presents a morphodynamic model for free surface flows over bed forms. The model reproduces bed form evolution and migration in a physically based manner. The flow model component of the coupled morphodynamic model, which is two‐dimensional in the streamwise and vertical directions, explicitly treats unsteadiness and nonhydrostatic effects. Comparison with measurements shows that the flow model accurately simulates both mean flow and turbulence structure induced by bed forms under free surface flow. The flow model performance is enhanced by the use of a high‐order Godunov scheme known as the cubic interpolated pseudoparticle (CIP) technique to compute the advection phase of the Navier‐Stokes equation. In addition, an enhanced k‐ɛ turbulence closure with nonlinear terms is incorporated in the present model in order to allow better predictions of Reynolds stress anisotropy in regions with flow separation. Performance of the nonlinear k‐ɛ model is compared with standard k‐ɛ closure in the context of the flow as well as morphodynamic simulation. Nonequilibrium bed load sediment transport is treated using a Eulerian stochastic formulation of the sediment exchange process in terms of pickup and deposition functions. The proposed approach for sediment transport explicitly considers the local flow variability during morphodynamic computation. Model results show that the vertical grid distribution pattern affects the simulation result, particularly for bed form morphodymics. The model successfully simulates some important physical features of bed form evolution, such as amalgamation and asymmetric geometry. The simulation results are in agreement with laboratory experiments as well as some commonly used prediction methods for geometric characteristics of bed forms.
Pore‐scale visualization of colloid straining and filtration in saturated porous media using micromodels
Authors: Auset Maria , Keller Arturo A.
Published: October 2006

Colloid transport was studied at the pore scale in order to gain insight into the microscale processes governing particle removal. Monodisperse suspensions of colloids and water‐saturated micromodels were employed. Experiments were carried out for different particle sizes, grain surface roughness, solution ionic strength, and flow rates. Straining and attachment were observed and measured by tracking the trajectory and fate of individual colloids using optical microscopy. Classical filtration theory proved appropriate for throat to colloid ratios (T/C) larger than 2.5 but did not take into account the possibility of straining that becomes an important capture mechanism for smaller T/C ratios. Spatially within the porous medium, straining occurred within the first 1–2 pore throats, while interception and attachment was seen from the inlet to the first 6–10 pore spaces, depending on particle size. Once a particle passed the initial region, the probability of attachment was very small. Colloid attachment increased with increasing solution ionic strength or decreasing flow rate, whereas straining was mainly independent of flow rate. Surface roughness of the grains also played a significant role in colloid capture, increasing collision efficiency by a factor of 2–3. The mechanisms of removal and the spatial distribution of colloid retention differed noticeably as a function of the T/C ratio. Micromodel visualizations clearly showed that physical straining and the effect of surface roughness should be taken into account when predicting the transport of colloids in saturated porous media.
Finite element transport modeling using analytic element flow solutions
Authors: Craig J. R. , Rabideau A. J.
Published: October 2006

Finite element methods for solute transport simulation typically use a discrete representation of the flow domain obtained from a finite element solution of the associated groundwater flow problem. Velocity, saturated thickness, and components of the dispersion coefficient tensor are represented as a set of nodal and/or element‐averaged values. In contrast, the analytic element method (AEM) provides continuous mesh‐independent solutions for these variables. In this paper, a set of techniques for using two‐dimensional AEM flow solutions as the basis of finite element solute transport models is introduced. First, a general AEM‐based discretization approach is presented that addresses the existence of curved boundaries, singularities, and discontinuities in vertically averaged concentration. Second, residual integration methods that handle continuous parameters with internal and boundary singularities are developed and evaluated. Third, an approach is introduced for handling internal discontinuities in concentration across certain analytic elements. This new approach uses a nonstandard mesh topology and a new formulation for internal coupled boundary conditions. The AEM‐based transport simulation methods introduced in this paper are demonstrated to be robust and accurate for a variety of test problems.
Sensor web enables rapid response to volcanic activity
Authors: Davies Ashley Gerard , Chien Steve , Wright Robert , Miklius Asta , Kyle Philip R. , Welsh Matt , Johnson Jeffrey B. , Tran Daniel , Schaffer Steven R. , Sherwood Robert
Published: October 2006

Rapid response to the onset of volcanic activity allows for the early assessment of hazard and risk [Tilling, 1989]. Data from remote volcanoes and volcanoes in countries with poor communication infrastructure can only be obtained via remote sensing [Harris et al., 2000]. By linking notifications of activity from ground‐based and spacebased systems, these volcanoes can be monitored when they erupt.

Over the last 18 months, NASA's Jet Propulsion Laboratory (JPL) has implemented a Volcano Sensor Web (VSW) in which data from ground‐based and space‐based sensors that detect current volcanic activity are used to automatically trigger the NASA Earth Observing 1 (EO‐1) spacecraft to make highspatial‐resolution observations of these volcanoes.
Time to replace the Saffir‐Simpson hurricane scale?
Authors: Kantha Lakshmi
Published: October 2006

The 2005 hurricane season set many new records, including the most named storms (26) and the most hurricanes in a season (14). Of the four hurricanes that made landfall in the U.S., three (Katrina, Rita, and Wilma) reached Category 5, struck the Gulf Coast, and inflicted severe damage and loss of life. Hurricane Wilma had an observed sealevel center pressure of 882 millibar (mbar) at its peak and is the strongest hurricane ever recorded in the Atlantic Ocean. Katrina damaged vast areas along the Mississippi coast, flooded large parts of New Orleans, and is the most destructive hurricane on record
Hydrology's efforts toward the cyberfrontier
Authors: Bandaragoda Christina , Tarboton David , Maidment David
Published: October 2006

As part of its ‘cyberinfrastructure’ initiative, the U.S. National Science Foundation is supporting the Hydrologic Information System (HIS) project of the Consortium of Universities for the Advancement of Hydrologic Sciences, Inc. (CUAHSI). Cyberinfrastructure is the use of high‐speed telecommunications to integrate networks of computers and provide advanced data access and computational resources beyond what an individual scientist would normally have available.

The integration of multiple data sets—which can have inconsistent metadata styles over a wide variety of spatial and time scales—into formats that can be easily used by researchers with varied software and operating system preferences is a challenging task. No such information system presently exists, and a central task of the HIS program is to design and develop this system.
Can Earth's albedo and surface temperatures increase together?
Authors: Pallé Enric , Goode Philip R. , Montañés‐Rodriguez Pilar , Koonin Steven E.
Published: October 2006

Changes in climate depend essentially on three basic parameters, the amount of incident sunlight, the fraction of this sunlight that is reflected by the Earth, and the trapping of the Earth's infrared radiation by greenhouse gases.The Earth's reflectance of the Sun's radiation back to space—or albedo—is the least well studied of the three.

The albedo depends primarily on cloud properties, and ground‐based and satellite studies published within the past 3–4 years have shown a surprisingly significant interannual and decadal variability in this parameter. The variability in reflectance is tied to changes in cloud location, amount, and thickness. However, clouds are very poorly parameterized in climate models. Thus,the scale of these variations presents a fundamental, and as yet unmet, challenge to understanding and predicting the Earth's climate.
True color earth data set includes seasonal dynamics
Authors: Stöckli Reto , Vermote Eric , Saleous Nazmi , Simmon Robert , Herring David
Published: October 2006

Space exploration has changed our visual perception of planet Earth. In the 1950s,satellites revolutionized weather forecasting. Astronaut photography in the early 1970s showed us the Earth in color, the so‐called ‘Blue Marble’ (Figure 1, left). Since 1972,satellite sensors have been acquiring atmosphere, land, ice, and ocean data with increasing spectral and spatial resolution. Satellite remote sensing systems such as the NASA Earth Observing System (EOS) help us to understand and monitor Earth's physical, chemical, and biological processes [Running et al., 1999].
New directions in the radiative transfer of cloudy atmospheres
Authors: Oreopoulos Lazaros , Marshak Alexander , Cahalan Robert F. , Várnai Tamás , Davis Anthony B. , Macke Andreas
Published: October 2006

Atmospheric radiative transfer plays a central role in understanding global climate change and anthropogenic climate forcing, and in the remote sensing of surface and atmospheric properties. Because of their opacity and highly scattering nature, clouds (covering more than half the planet at any time) pose unique challenges in atmospheric radiative transfer calculations.

Some widely‐used assumptions regarding clouds—such as having a flat top and base, horizontal uniformity, and infinite extent—are amenable to simple one‐dimensional (1‐D) radiative transfer and are therefore attractive from a computational point of view. However, these assumptions are completely unrealistic and yield errors. The ever‐increasing need to realistically simulate cloud radiative processes in remote sensing and energy budget applications has contributed to the recent rapid growth of the three‐dimensional (3‐D) radiative transfer (RT) community [e.g., Marshak and Davis, 2005].
Monitoring the reawakening of Canary Islands' Teide Volcano
Authors: García Alicia , Ortiz Ramon , Marrero Jose M. , S´nchez Nieves , Vila Josep , Correig Antoni M. , Marcià Ramon , Sleeman Reinoud , Tárraga Marta
Published: October 2006

Following more than 30 years of seismic and volcanic quiescence, the Canary Islands region located off the northwestern coast of Africa started to show signs of seismovolcanic activity at the end of 2003 (Figure 1). In spring 2004, there was a significant increase in the number of seismic events (a mixture of volcano‐tectonic events and regional earthquakes with pure volcanic events such as tremors and long‐period signals) located inland on Tenerife Island.

The increase ofactivity in 2004 coincided with an increase of fumarolic activity at the Teide volcano on Tenerife Island, an increase in the emission of carbon dioxide in the northwestern part of the island, and changes in the gravimetric field on the northern flank of the volcano. After several seismic events had been felt by the population, the first alert level was declared by the civil protection division of the local government.This apparent reawakening of Teide, which last erupted in 1909, provides an opportunity to study from the initial stages the reactivation of this volcanic area and its related phenomena.
Satellite data gives snapshot of the 2005 Pakistan earthquake
Authors: Fujiwara Satoshi , Tobita Mikio , Sato Hiroshi P. , Ozawa Shinzaburo , Une Hiroshi , Koarai Mamoru , Nakai Hiroyuki , Fujiwara Midori , Yarai Hiroshi , Nishimura Takuya , Hayashi Fumi
Published: October 2006

While it is well‐known that the collision of the Indian subcontinent with the Eurasian continent forms the Himalayas, the real‐time spatial crustal movement of these plates is difficult to observe. However, scientists can witness a part of this process of the formation of the Himalayas through an eye in space: synthetic aperture radar (SAR).

From the European Space Agency's Envisat, a satellite with SAR, the details of crustal deformation resulting from a major earthquake—a chance snapshot of the growth of the Himalayas—has been captured. Envisat's SAR has provided important data about the northern Pakistan earthquake (M7.6) of 8 October 2005, which occurred in the Kashmir region in the northwestern part of the Himalayas.
Energy in the dark: Fuel for life in the deep ocean and beyond
Authors: Bach Wolfgang , Edwards Katrina J. , Hayes John M. , Sievert Stefan , Huber Julie A. , Sogin Mitchell L.
Published: October 2006

To most people, the ‘biosphere’ begins with green plants and ends with bacteria. Everything in it is part of a food chain that depends on organic carbon initially captured and packaged by photosynthesis. Most geoscientists, though, are aware that this view is too restrictive, as it does not include carbon fixation that is fuelled by chemical energy.

It is becoming increasingly obvious that energy and carbon cycling in the deep ocean and subseafloor are potentially important issues in solving redox and carbon budgets. Yet, quantification of the magnitude and activity of this dark and deep biosphere and its organic versus inorganic energy and carbon sources is difficult. Photosynthesis and its products are pervasive, and it is hard to identify environments that are unaffected by their presence to at least some degree.
Estimating carbon budgets for U.S. ecosystems
Authors: Potter Christopher , Klooster Steven , Nemani Ramakrishna , Genovese Vanessa , Hiatt Seth , Fladeland Matthew , Gross Peggy
Published: October 2006

On a global basis, plants and soils may hold more than twice the amount of carbon present in the atmosphere [Geider et al., 2001]. Under increasing atmospheric carbon dioxide (CO2) concentrations and subsequently warming temperatures, these large biogenic pools may change in size [Cox et al., 2000]. Due to a lack of long‐term field studies, there is uncertainty as to whether vegetation and soils will act as a net sink or a source of atmospheric CO2 in coming years. It is certain, however, that no retrospective analysis of the U.S. carbon balance will be possible without a comprehensive historical baseline of the sizes of various ecosystem carbon pools and the variability in their net annual increments.
North Atlantic paleoceanography: The last five million years
Authors: Stein Ruediger , Kanamatsu Toshiya , Alvarez‐Zarikian Carlos , Higgins, Sean M. , Channell Jim E. T. , Aboud Essam , Ohno Masao , Acton Gary D. , Akimoto Kazumi , Bailey Ian , Bjørklund Kjell R. , Evans Helen , Nielsen Simon H. H. , Fang Nianqiao , Ferretti Patrizia , Gruetzner Jens , Guyodo Yohan J.B. , Hagino Kentaro , Harris Robert , Hatakeda Kentaro , Hefter Jens , Judge Shelley A. , Kulbanek Denise K. , Nanayama Futoshi , Rashid Harunur , Sierro Sanchez Francisco J. , Voelker Antje , Zhai Quimin
Published: October 2006

In the North Atlantic, cold, relatively salty water sinks in the icy Labrador and Greenland seas, forming North Atlantic Deep Water (NADW).This circulates through the global ocean, driving ocean overturning and global heat transport and, thus, impacting global climate. As one of the most climatically sensitive regions on Earth, the North Atlantic has experienced abrupt changes to its oceanatmosphere‐cryosphere system, triggered by fluctuations in meltwater delivery to source areas of NADW formation.

For about the past 100 thousand years, these abrupt jumps in climate state have manifested as ‘Dansgaard/Oeschger’ (D/O) oscillations (millennial‐scale warm‐cold oscillations) and 'Heinrich' events in ice and marine sediment cores, respectively [e.g., Dansgaard et al., 1993; Bond and Lotti, 1995]. These Heinrich events are characterized as huge input of ice‐rafted debris (IRD) and meltwater pulses, documenting episodes of sudden instability and collapse of the current Greenland ice sheets and the Laurentide ice sheet, the latter of which covered northern North America several times during the Pleistocene Epoch.
Multiple spaceborne water cycle observations would aid modeling
Authors: Crow Wade T. , Entekhabi Dara , Koster Randal D. , Reichle Rolf H.
Published: October 2006

A land data assimilation system (LDAS) is designed to provide continental‐scale estimates of surface moisture and temperature states—and water and energy flux exchanges with the atmosphere—by integrating micrometeorological forcing data (such as surface precipitation, incoming radiation, wind, air temperature, and humidity) with a land surface model. When measurements of land system states are available, data assimilation approaches can be used to optimally update model states based on the assumed magnitude of modeling and observational errors [e.g., Reichle and Koster, 2005].

LDAS estimates have value for water, energy, and biogeochemical studies as well as for the initialization of land surface states, such as soil moisture and temperature, in numerical weather prediction or seasonal climate forecasts. To improve forecast performance, collaborative LDAS projects are currently under way for the North American (NLDAS; http://ldas.gsfc.nasa.gov), European (ELDAS; http://www.knmi.nl/samenw/eldas), and global (GLDAS; http://ldas.gsfc.nasa.gov) domains. Preliminary results demonstrate that the incorporation of LDAS approaches into subseasonal forecast initialization can lead to statistically significant improvements in precipitation predictability [Koster et al., 2004].
Mapping supports potential submission to U.N. Law of the Sea
Authors: Gardner James V. , Mayer Larry A. , Armstrong Andrew
Published: October 2006

Multibeam bathymetric data from selected U.S. continental margins are being collected for use in the future development of potential submissions that the United States may make to the United Nations Commission on the Law of the Sea (UNCLOS) to extend the nation's sovereign rights over the resources of the seafloor and the subsurface.

However, the new data also represent a valuable resource for the next generation of marine geologists to study the complexity of surficial processes of several U.S. continental margins. For example, the details of the morphology of large sediment slides on the U.S.Atlantic continental slope and rise have been mapped, and enigmatic features such as a meandering channel on a channel levee on the U.S.Alaskan Pacific margin have been discovered.
New products from the shuttle radar topography mission
Authors: Gesch Dean , Farr Tom , Slater James , Muller Jan‐Peter , Cook Sally
Published: October 2006

New data products with broad applicability to the Earth sciences are now available from the Shuttle Radar Topography Mission (SRTM). SRTM, a joint project of the National Geospatial‐Intelligence Agency (NGA) and NASA, flew aboard the Space Shuttle Endeavour on an 11‐day mission in February 2000 with the goal of collecting a near‐global data set of high‐resolution elevation data [Fan and Kobrick, 2000]. Data from the mission have been available to researchers for several years, but newly available products offer enhanced usability and applicability.

Final products include elevation data resulting from a substantial editing effort by the NGA in which water bodies and coastlines were well defined and data artifacts known as spikes and wells (single pixel errors) were removed. This second version of the SRTM data set, also referred to as ‘finished’ data, represents a significant improvement over earlier versions that had nonflat water bodies, poorly defined coastlines, and numerous noise artifacts. The edited data are available at a one‐arc‐second resolution (approximately 30 meters) for the United States and its territories, and at a three‐arc‐second resolution (approximately 90 meters) for non‐U.S. areas.
Yangtze sediment decline partly from Three Gorges Dam
Authors: Xu Kehui , Milliman John D. , Yang Zuosheng , Wang Houjie
Published: October 2006

It could be argued that nowhere has the impact of dams on rivers been more important than in China, where since 1950 almost half of the world's large dams (higher than 15 meters) have been built ]Fuggle and Smith, 2000]. China's Yangtze River (Changjiang)—the largest river in south Asia (1.8 million square kilometers) and whose basin is home to more than 400 million inhabitants—alone has more than 50,000 dams within its watershed, including the world's largest, the Three Gorges Dam (TGD) (Figure 1a ).

Water and sediment began being impounded behind the TGD in June 2003, and two years after impoundment, river sediment discharge downstream (at Datong Station) had decreased by nearly half of its 2002 load (Figure 1c). However, the decrease in Yangtze sediment load did not begin with TGD impoundment. Rather, the sediment load at Datong has declined continually since 1987 despite a slight increase in river discharge (Figure 1c ). The change in pre‐TGD loads atYichang, just downstream from the TGD, has been even more extreme, decreasing by approximately 300 million tons in 1986–2002, before declining another 130 million tons after 2002 (Figure 1b). All of this suggests that collective changes on the Yangtze upstream (above Yichang) have been more important in decreasing the river's sediment load than the TGD.
Coupled Climate Model appraisal: A benchmark for future studies
Authors: Phillips Thomas J. , AchutaRao Krishna , Bader David , Convey Curtis , Doutriaux Charles M. , Fiorino Michael , Glecker Peter J. , Sperber Kenneth R. , Taylor Karl E.
Published: October 2006

Studies of future climate scenarios, such as those conducted in support of the Intergovernmental Panel on Climate Change (IPCC, http://www.ipcc.ch/), rely heavily on numerical experiments performed with coupled ocean‐atmosphere general circulation models (OAGCMs). In order to assess the results of such climate change experiments, a benchmark for evaluating model performance is required.To provide this benchmark, Lawrence Livermore National Laboratory's Program for Climate Model Diagnosis and Intercomparison (PCMDI) conducted an extensive appraisal of multidecadal climate simulations by 11 coupled OAGCMs that were developed during the period of 1995–2002 [Bader etal., 2004].

While diverse representations of atmosphere, ocean, sea ice, land, and of their respective couplings were employed (see Table 1), all of these climate models were run with current values of solar and greenhouse gas radiative forcings. Thus, by comparing details of the OAGCM simulations with analogous facets of climate observations, the needed model‐performance benchmark can be obtained. If, for instance, a model simulation closely replicates the salient features of the present climate, a necessary (though not sufficient) condition is met for placing some confidence in the model's projections of the climate of the next several decades.