bluuebunny/crossref_metadata_2025 huggingface dataset:
Pore fluid constraints on deep ocean temperature and salinity during the Last Glacial Maximum
Authors: Adkins J. F. , Schrag D. P.
Published: February 2004

Pore water records of δ18O and [Cl] from ODP Site 1063A on the Bermuda Rise constrain the change in seawater δ18O and salinity from the Last Glacial Maximum (LGM) to the Holocene to be 0.75±0.05‰ and 2.5±0.1% respectively. Coupled with a measured benthic foraminiferal δ18O change, this result means that bottom waters were 4.6±0.8°C cooler than the Holocene at the LGM and therefore at or near the seawater freezing point. Coupled δ18O and chlorinity results give an extrapolated mean ocean LGM to Holocene change in δ18O of 0.95±0.09‰. These data also constrain the past southern source deep‐water salinity to be 35.76±0.04 psu, which is within error of the mean deep ocean value for this time.
Error spectrum for the global M2 ocean tide
Authors: Ray R. D. , Eanes R. J. , Egbert G. D. , Pavlis N. K.
Published: February 2004

The most accurate determinations of the global ocean tides are currently based on altimeter measurements made by the Topex/Poseidon satellite. The error spectrum corresponding to the M2 tidal solution is here estimated, primarily by inverse methods and secondarily by simple differencing of several of the best tidal models. The tidal error spectrum is flatter than the tidal signal spectrum, and it exceeds 10% of the signal at spherical harmonic degree 15 and above. The tide errors also exceed the anticipated sensitivity of the upcoming Grace satellite gravity mission for all degrees below 40, and possibly below 50.
Possible causes of stratospheric NO2 trends observed at Lauder, New Zealand
Authors: Fish D. J. , Roscoe H. K. , Johnston P. V.
Published: February 2004

A recently published analysis of slant columns of NO2 observed at twilight at 45°S has identified trends of about 5%/decade between 1980 and 1998. This is twice the trend in tropospheric N2O, which is the source of stratospheric NO2. By means of a column photochemical model, we explore the sensitivity of NO2 to the observed trends in stratospheric temperature, O3 and H2O. The resulting calculated trends in NO2 are smaller than observed, and we cannot force agreement by varying the ozone or temperature trends. The calculated sensitivity of NO2 to stratospheric aerosol is large, and a 20% per decade decrease in aerosol surface area creates agreement. We conclude that a small residual in the statistical fit of aerosol to the NO2 measurements may remain, and is a likely cause of the trends found in the NO2 measurements.
Application of Mwp to tsunami earthquake
Authors: Tsuboi Seiji
Published: February 2004

Tsunami earthquake produces anomalously strong tsunamis for their surface wave magnitude. To issue accurate early tsunami warnings for tsunami earthquakes, it is critical to identify them as tsunamigenic events as early as possible. Here we show that a pulse width of P‐wave, which we use to calculate broadband moment magnitude Mwp, gives accurate estimates of source duration time. We find that we may identify 1992 Nicaragua earthquake as a possible tsunamigenic earthquake by using a combination of both Mwp and the source duration. Our result suggests that the combination of Mwp and the source duration will provide an effective tool to issue early tsunami warnings even for tsunami earthquakes which have anomalously long source duration.
Hypersensitive decadal oscillations in the Arctic/Subarctic climate
Authors: Ikeda M. , Wang J. , Zhao J.‐P.
Published: February 2004

A conceptual model of the Arctic climate system is generated by taking two key components in the coupled atmosphere‐ice‐ocean system, having a basis on a box model with water exchanges among the Arctic Basin, the Greenland‐Iceland‐Norwegian (GIN) Seas and the North Atlantic. One of the key components is deep water formation in the GIN Seas induced by the saline Atlantic inflow to the area. The second key component is a positive feedback between a more intense (or weaker) Polar Vortex and less (or more) ice cover in the Arctic Basin. The system possesses a decadal oscillation in a limited range of the combination of the key component intensities. This oscillatory state is potentially relevant to the decadal oscillations remarkable in the Arctic climate only for last three decades. The present study promotes an attempt to examine responses of the Arctic atmospheric circulation to decadal variability in the surface heat flux, as these responses are the most uncertain.
Mass independent oxygen isotopic composition of atmospheric sulfate: Origin and implications for the present and past atmosphere of Earth and Mars
Authors: Lee Charles C.‐W. , Savarino Joel , Thiemens Mark H.
Published: February 2004

It is reported that atmospheric (aerosol and rainwater) sulfate possesses a mass independent isotopic composition, with excess 17O. Laboratory experiments indicate that the oxidants, H2O2 and O3, are the source of anomalous 17O enrichments in atmospheric sulfate via aqueous phase S(IV) oxidation. The discovery of the oxygen anomaly in atmospheric sulfate, with definition of its origin, provides a new way to investigate atmospheric and general planetary processes. The observations provide new insight into atmospheric chemistry with application in studies of the evolution of the atmosphere, and surface‐atmosphere interactions, both on Earth and Mars.
The oxygen to carbon dioxide ratios observed in emissions from a wildfire in northern California
Authors: Lueker Timothy J. , Keeling Ralph F. , Dubey Manvendra K.
Published: February 2004

At Trinidad, California we observed elevated CO2concentrations and concomitant lowered O2levels coincident with forest fires 70 km distant (from 10/8/99 to 10/21/99). The precision of our O2data, ±1 µmol O2/mol dry air, revealed the reduction of atmospheric oxygen resulting from the combustion of biomass, and the stoichiometric ratios (−O2/CO2) of the wildfire emissions. Estimates of daily −O2/CO2ratios were obtained by regression of CO2against corresponding O2data (R² 0.86 to 0.96). Daily −O2/CO2ratios changed from 1.15 to 1.41 on a particularly smoky day that coincided with elevated levels of CH4and increased CH4/CO2ratios. The change to a higher ratio during smoky conditions illustrates the association between changing emissions and −O2/CO2ratios, possibly due to changing wildfire dynamics.
Identifying global climate change using simple indices
Authors: Karoly David J. , Braganza Karl
Published: February 2004

Several simple indices of surface air temperature patterns are used to describe global climate variability and change. The indices include the land‐ocean temperature contrast, the hemispheric contrast, the meridional gradient, and the magnitude of the seasonal cycle, as well as the global‐mean temperature. The behaviour of the indices is investigated using global observational data for the period 1881–1994 and long control and anthropogenic climate change simulations with two different climate models. The indices represent the key features of the “fingerprint” of greenhouse climate change. For natural climate variations, they contain information independent of the global‐mean temperature. The observed trends over the last 40 years in all the indices, except for the hemispheric contrast, are unlikely to have occurred due to natural climate variations and all are consistent with model simulations of anthropogenic climate change.
Soil freeze/thaw cycles over snow‐free land detected by passive microwave remote sensing
Authors: Zhang T. , Armstrong R. L.
Published: February 2004

The timing, duration, and areal extent of the near‐surface soil freeze/thaw status were investigated using passive microwave satellite remote sensing data for the 1997/98 winter over the contiguous United States. A frozen soil algorithm was validated using soil temperature data at 0 cm and 5 cm depths from more than 20 sites over the study area. Results indicated that a negative spectral gradient and a cut‐off 37‐GHz vertical polarized brightness temperature of 258.2K can be used to determine near‐surface soil freeze/thaw status with confidence. The microwave freeze/thaw boundary generally agreed with −5.0°C isotherm of air temperature although frozen soils occurred sporadically between 0°C and −5.0°C isotherms. The maximum frozen soil area over snow‐free land surface was about 3.75 × 106 km² or about 37% of the total study area during the 1997/98 winter. The near‐surface soils often froze before snow covered the land surface, but soil freeze/thaw status under snow cover cannot be detected using this microwave technique. The onset of soil freeze mainly occurred in October and November, while the last days of soil freeze occurred in March and April, resulting in the duration of soil freezing varying from five to seven months over the majority of the study areas. The number of days of surface soil freezing varied from several days to longer than five months.
Regional moment tensor inversion for strong aftershocks of the August 17, 1999 Izmit Earthquake (Mw=7.4)
Authors: Örgülü Gonca , Aktar Mustafa
Published: February 2004

We analyzed the source mechanisms of the thirty largest aftershocks (4.0 ≤ML ≤ 6.2) of the August 17, 1999 Izmit earthquake (Mw=7.4) by applying the Regional Moment Tensor inversion method using data from near‐regional broadband stations. The inversion solutions were compared to 17 well‐constrained first motion solutions, and were seen to be in good agreement. We found that the dominance of strike‐slip motion is the main characteristic of the Izmit earthquake sequence. Significant aftershock activity was recorded to the west and east of the un‐ruptured extremities. In the east the aftershocks located near the town of Düzce represent an early replica of the November 12, 1999 Düzce earthquake (Mw=7.2) in terms of locations and source mechanisms. In the Marmara Sea, where the fault geometry is still very poorly resolved, most aftershocks have right lateral strike slip solutions with strike direction parallel to the submerged branches of the North Anatolian Fault.
Retrieval of coccolithophore calcite concentration from SeaWiFS Imagery
Authors: Gordon Howard R. , Boynton G. Chris , Balch William M. , Groom Stephen B. , Harbour Derek S. , Smyth Tim J.
Published: February 2004

We examined blooms of the coccolithophoridE. huxleyi, observed in SeaWiFS imagery, with a new algorithm for the retrieval of detached coccolith concentration. The algorithm uses only SeaWiFS bands in the red and near infrared (NIR) to minimize the influence of the absorption by chlorophyll and dissolved organic material. We used published experimental determinations of the calcite specific backscattering and its spectral dependence, and assumed that the absorption coefficient of the medium was that of pure water, to estimate the marine contribution to the SeaWiFS radiance. The aerosol (and Rayleigh‐aerosol interaction) contribution to the radiance was modeled as an exponential function of wavelength. These allow derivation of the coccolith concentration on a pixel‐by‐pixel basis from SeaWiFS imagery. Application to a July 30, 1999 SeaWiFS image of a bloom south of Plymouth, UK indicates that the SeaWiFS estimates are in good agreement with surface measurements of coccolith concentration.
Slab melting: Its role in continental crust formation and mantle evolution
Authors: Tatsumi Yoshiyuki
Published: February 2004

A possible mechanism for continental crust formation, slab‐melting and subsequent melt‐mantle interaction, was examined by geochemical formulation of partial melting and melt‐solid reactions. The modeling results suggest that such a process can reasonably explain the major and trace element compositions of the andesitic bulk continental crust. However, the Sr‐Nd‐Pb isotopic compositions of melting residues in the subducting slab, which may have foundered and been stored in the deep mantle, do not match those of any proposed geochemical reservoir. This may lead to the conclusion that the slab melting did not play the major role in the continental crust formation during the Archean.
Mantle flow at a slab edge: Seismic anisotropy in the Kamchatka Region
Authors: Peyton Valerie , Levin Vadim , Park Jeffrey , Brandon Mark , Lees Jonathan , Gordeev Evgenii , Ozerov Alexei
Published: February 2004

The junction of the Aleutian Island and the Kamchatka peninsula defines a sharp turn in the boundary of the Pacific and North American plates, terminating the subduction zones of the northwest Pacific. The regional pattern of shear‐wave birefringence near the junction indicates that trench‐parallel strain follows the seismogenic Benioff zone, but rotates to trench‐normal beyond the slab edge. Asthenospheric mantle is inferred to flow around and beneath the disrupted slab edge, and may influence the shallowing dip of the Benioff zone at the Aleutian junction.
A new 27 ky high resolution East Antarctic climate record
Authors: Jouzel J. , Masson V. , Cattani O. , Falourd S. , Stievenard M. , Stenni B. , Longinelli A. , Johnsen S. J. , Steffenssen J. P. , Petit J. R. , Schwander J. , Souchez R. , Barkov N. I.
Published: February 2004

The ice core recently drilled at the Dome Concordia site on the East Antarctic plateau provides a new high resolution isotope record covering part of the last glacial, the last transition and the Holocene. The two step shape of the deglaciation is remarkably similar for all the ice cores now available on the East Antarctic plateau. The first warming trend ends about 14000 years ago and is followed by the well marked Antarctic Cold Reversal (ACR) with a secondary peak common to all records. During the deglaciation, there are more similarities between the near coastal site of Taylor Dome and inland East Antarctica than between Taylor Dome and central Greenland. However, the results for EPICA do appear to confirm the Taylor Dome timescale after about 14 ka, showing cooling into the ACR roughly in phase between Greenland and Antarctica. While the overall deglacial pattern is asynchronous, this suggests that the now classical picture of a temperature seesaw between Antarctica and Greenland may be too simplistic.
The origin of the anomalous or “mass‐independent” oxygen isotope fractionation in tropospheric N2O
Authors: Röckmann Thomas , Kaiser Jan , Crowley John N. , Brenninkmeijer Carl A. M. , Crutzen Paul J.
Published: February 2004

Analysis of the complete oxygen isotopic composition (16O, 17O, 18O) of tropospheric N2O from various northern hemispheric locations reveals a mass independent anomaly with a 17O excess of Δ17O = 1.0±0.2‰ at δ18O = 20.7±0.3‰. So far, the origin of this intriguing isotope signature has remained elusive. New laboratory experiments demonstrate that the fractionation during UV photolysis of N2O, which causes 15N and 18O enrichments in the stratosphere, is strictly mass dependent (Δ17O = 0). To explain the isotope anomaly in atmospheric N2O, we propose a chemical mechanism for heavy oxygen transfer from O3 to N2O. In a first step, the NOx‐O3 photochemical interaction leads to the formation of NO2 with significant excess 17O. In a second step, the heavy oxygen anomaly is transferred to N2O via the reaction , as part of the gas phase degradation of ammonia. This small but significant N2O source is of the right magnitude to explain the tropospheric observations.
On the development of highly‐viscous skins of liquid around bubbles during magmatic degassing
Authors: Mourtada‐Bonnefoi Catherine C. , Mader Heidy M.
Published: February 2004

We report experiments which show that the development of high‐viscosity volatile‐depleted skins of liquid around bubbles has a major effect on bubble growth rates and thus on volcanic conduit flow dynamics. Decompression experiments were performed at room temperature in a cylindrical shock‐tube using viscous solutions of gum rosin and acetone (GRA). After an initial transient, the propagation of the flow front follows an empirical exponential law covering most of the final expansion. Theories of magma flow dynamics that rely on a constant liquid viscosity conclude that most of the degassing takes place in a diffusion‐limited, decelerating bubble growth regime. By contrast, we assume that viscous resistance to bubble growth is controlled by the high viscosity of the liquid skins around bubbles, and find that, in both explosive GRA and magma flows, bubble growth lies mostly in a diffusion‐driven but viscosity‐limited, accelerating regime. We infer that in explosive events, diffusion‐limited degassing is unlikely to occur before fragmentation.
Post‐drought growth responses of western Juniper (Juniperus occidentals var. occidentalis) in central Oregon
Authors: Knapp Paul A. , Soulé Peter T. , Grissino‐Mayer Henri D.
Published: February 2004

Increased atmospheric CO2 may affect the physiological response of natural trees to drought. We examined radial growth rates developed from five western juniper chronologies to determine if post‐drought growth responses have changed. Using prior year October to current year June precipitation from 1896–1998, we identified drought recovery years as having standardized scores (z‐scores) >0 and preceded by a year with a z‐score <−0.6. We defined our analysis by an early period, 1896–1930, when atmospheric CO2 concentrations were close to preindustrial levels, and a late period, 1964–1998, when concentrations were substantially higher. Mean growth index values of recovery years between early and late periods were significantly greater (p<0.05) for four of the five sites, and for all sites combined. These results are consistent with the drought‐ameliorating effects of CO2 shown by controlled laboratory studies and suggest that rising levels of atmospheric CO2 may impact western juniper growth rates.
Imaging two geomagnetic storms in energetic neutral atoms
Authors: Mitchell D. G. , Hsieh K. C. , Curtis C. C. , Hamilton D. C. , Voss H. D. , Roelof E. C. , C:son‐Brandt P.
Published: February 2004

The IMAGE mission is the first of its kind. It is designed to comprehensively image a variety of emissions from the Earth's magnetosphere with sufficient time resolution to follow the dynamics associated with the development of magnetospheric storms. This paper describes initial observations of two qualitatively different geomagnetic storms by the IMAGE High Energy Neutral Atom imager (HENA). HENA images formed at energies between 10 and 60 keV/nucleon reveal the distribution and the evolution of energetic ion distributions as they are injected into the ring current during geomagnetic storms, drift about the Earth on both open and closed drift paths, and decay through charge exchange to pre‐storm levels. Substorm ion injections are also imaged, as are regions of low altitude, high latitude ion precipitation into the upper atmosphere. Two events are discussed: one a major magnetic storm (the “Bastille Day” storm of July 15 and 16, 2000, Dst=−300nT), and the other, a minor storm (June 10, 2000, Dst=−55nT). The larger storm is characterized by ion injection deep into the magnetosphere (L∼3 RE), while the images from the minor storm are consistent with injection to L∼7 RE.
Estimates of internal tide energy fluxes from Topex/Poseidon Altimetry: Central North Pacific
Authors: Ray Richard D. , Cartwright David E.
Published: February 2004

Energy fluxes for first‐mode M2 internal tides are deduced throughout the central North Pacific Ocean from Topex/Poseidon satellite altimeter data. Temporally coherent internal tide signals in the altimetry, combined with climatological hydrographic data, determine the tidal displacements, pressures, and currents at depth, which yield power transmission rates. For a variety of reasons the deduced rates should be considered lower bounds. Internal tides are found to emanate from several large bathymetric structures, especially the Hawaiian Ridge, where the integrated flux amounts to about 6 gigawatts. Internal tides are generated at the Aleutian Trench near 172°W and propagate southwards nearly 2000 km.
Effects of continents on Earth cooling: Thermal blanketing and depletion in radioactive elements
Authors: Grigné Cécile , Labrosse Stéphane
Published: February 2004

Estimate of mantle heat flow under continental shields are very low, indicating a strong insulating effect of continents on mantle heat loss. This effect is investigated with a simple approach: continents are introduced in an Earth cooling model as perfect thermal insulators. Continental growth rate has then a strong influence on mantle cooling. Various continental growth models are tested and are used to compute the mantle depletion in radioactive elements as a function of continental crust extraction. Results show that the thermal blanketing effect of continents strongly affects mantle cooling, and that mantle depletion must be taken into account in order not to overestimate mantle heat loss. In order to obtain correct oceanic heat flow for present time, continental growth must begin at least 3 Gy ago and steady‐state for continental area must be reached for at least 1.5 Gy in our cooling model.
Non‐conservative mixing behavior of colored dissolved organic matter in a humic‐rich, turbid estuary
Authors: Uher Günther , Hughes Claire , Henry Gordon , Upstill‐Goddard Robert C.
Published: February 2004

The estuarine mixing behavior of colored dissolved organic matter (CDOM) absorbance was investigated in combined field and laboratory studies. From February to October 1998, surface water samples were collected along 9 transects in the Tyne estuary, Northeast England, from the tidal limit into the coastal North Sea. In 8 of these transects, mixing plots of absorbance vs. salinity indicated substantial removal of CDOM absorbance (average: 32%) in the upper estuary. Results from laboratory studies under simulated estuarine conditions suggest that an average of 21% (range: 9–39%) of riverine CDOM may be removed by adsorption onto suspended sediment, while CDOM flocculation accounted for an average removal of only 6% (range: 0–18%). We propose that adsorptive removal exerts a major control on CDOM in estuaries with elevated turbidity levels.
Rayleigh lidar observations of mesospheric inversion layers at Poker Flat, Alaska (65 °N, 147°W)
Authors: Cutler Laura J. , Collins Richard L. , Mizutani Kohei , Itabe Toshikazu
Published: February 2004

Rayleigh lidar measurements of the stratosphere and mesosphere have been made on an ongoing basis over a three‐year period at Poker Flat, Alaska (65°N, 147°W). These observations have yielded 27 nightly measurements of the middle atmosphere temperature profile (∼ 40–80 km). These nighttime measurements are distributed between August and April. Mesospheric inversion layers have been observed on five occasions. The average altitude of the inversion layer peak is 60 km, with average amplitude of 18 K. The temperature gradients on the topside of the inversion layers approach the adiabatic lapse rate. The inversion layers do not exhibit the apparent downward phase velocities that are commonly observed at lower latitudes. Furthermore, the inversion layers appear significantly less frequently than at lower latitudes. The observations are discussed in terms of current models and observations at other sites.
Segregation of NaBr in NaBr/NaCl crystals grown from aqueous solutions: Implications for sea salt surface chemistry
Authors: Zangmeister Christopher D. , Turner Jessica A. , Pemberton Jeanne E.
Published: February 2004

Surface segregation of NaBr in mixed NaBr/NaCl crystals precipitated from aqueous solutions containing Br is investigated. Crystals were grown from solutions of a wide range of Br:Cl values and studied using x‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy‐dispersive x‐ray fluorescence (EDX), and atomic force microscopy (AFM). Results indicate that NaBr surface‐segregates to cover 4–5% of the surface at the Br:Cl value found in sea water (1:660). The surface NaBr:NaCl values are ∼35 times higher those of the bulk crystals. The surface NaBr forms domains of average size 635 nm × 635 nm × 53 nm. Large areas of the surface contain NaCl with no detectable NaBr. Complete surface segregation of all Br found in sea salt particles is likely to occur, thereby making a greater amount of Br available for surface reactions with gas‐phase constituents than would be predicted based on bulk composition.
Earthshine observations of the Earth's reflectance
Authors: Goode P. R. , Qiu J. , Yurchyshyn V. , Hickey J. , Chu M.‐C. , Kolbe E. , Brown C. T. , Koonin S. E.
Published: February 2004

Regular photometric observations of the moon's “ashen light” (earthshine) from the Big Bear Solar Observatory (BBSO) since December 1998 have quantified the earth's optical reflectance. We find large (∼5%) daily variations in the reflectance due to large‐scale weather changes on the other side of the globe. Separately, we find comparable hourly variations during the course of many nights as the earth's rotation changes that portion of the earth in view. Our data imply an average terrestrial albedo of 0.297±0.005, which agrees with that from simulations based upon both changing snow and ice cover and satellite‐derived cloud cover (0.296±0.002). However, we find seasonal variations roughly twice those of the simulation, with the earth being brightest in the spring. Our results suggest that long‐term earthshine observations are a useful monitor of the earth's albedo. Comparison with more limited earthshine observations during 1994–1995 show a marginally higher albedo then.
Generation mechanism for magnetic holes in the solar wind
Authors: Buti B. , Tsurutani B. T. , Neugebauer M. , Goldstein B. E.
Published: February 2004

A new mechanism for generation of magnetic holes in the solar wind is presented. In the high speed solar wind, large‐amplitude right‐hand polarized Alfvénic wave packets propagating at large angles to the ambient magnetic field are shown to generate magnetic holes (MHs). Characteristics of these holes crucially depend on plasma β (β being the ratio of kinetic pressure to magnetic pressure) and the ratio of electron temperature Te to proton temperature Ti. Proton temperature anisotropy is found to be favorable but not essential for the development of MHs. From our simulations we observe MHs with microstructures bounded by sharp gradients (magnetic decreases) in some cases. The holes generated by this process have thicknesses of hundreds of ion Larmor radii, typical of many of the solar wind hole observations, the depths of the holes are also comparable. The theory can explain the presence of MHs seen in the solar wind for those cases when anisotropies are not favorable for the development of the mirror mode instability.
Cascading of water down the sloping sides of a deep lake in winter
Authors: Fer Ilker , Lemmin Ulrich , Thorpe S. A.
Published: February 2004

During winter, the temperature of the water over‐lying the shallow, typically 2–5 m deep, ‘shelf‧ region around the edge of the 310 m deep Lake Geneva falls more rapidly than that over deeper areas. This causes the spilling or ‘cascading‧ of relatively dense water from the shallows down the sloping sides of the lake in the form of gravity currents, 2–15 m thick and typically 0.1 °C cooler than the ambient. The flow is intermittent with ‘slugs‧ of cold water lasting, on average, for 8 hrs with mean downslope speeds of 5.2 cms−1. The temperature and thickness of the slugs is however variable, with pulses of colder water lasting for 1–3 hrs, each preceded by a ‘front‧ in which thickness increases and temperature falls by about 0.01 °C per min. The net volume flux carried by the ‘slugs‧ is 18.5 times the mean winter flow into the lake from rivers.
Atmospheric torques during the winter of 1989: Impact of ENSO and NAO positive phases
Authors: de Viron O. , Marcus S. L. , Dickey J. O.
Published: February 2004

The axial component of atmospheric angular momentum (AAM) reached a decadal minimum during the winter of 1989, when the cool (La Niña) phase of the ENSO cycle and the positive phases of the North Atlantic Oscillation (NAO) and the related Arctic Oscillation (AO) were active. Here, we examine the global atmospheric dynamics associated with this event from the torque point of view. It will be shown how mountain torques on North America, South America and Europe related to these oscillations led to the AAM minimum, partly compensated by a positive ENSO‐related mountain torque over Asia. The friction torque had more nearly equal positive and negative anomalies associated with ENSO and NAO forcing, respectively, and made a smaller, offsetting contribution to the global AAM anomaly during this episode.
Deep‐sea, high‐resolution, hydrography and current measurements using an autonomous underwater vehicle: The overflow from the Strait of Sicily
Authors: Stansfield Kate , Smeed David A. , Gasparini Gian Pietro , McPhail Stephen , Millard Nick , Stevenson Peter , Webb Andy , Vetrano Anna , Rabe Benjamin
Published: February 2004

AUTOSUB‐2, an autonomous underwater vehicle (AUV) developed by the Southampton Oceanography Centre, was used for high resolution hydrographic surveys in the Sicily Strait. A combination of “seasoar” type profiling and terrain following missions were undertaken and velocity and hydrographic measurements taken from AUTOSUB‐2 were compared with concurrent shipboard hydrographic and velocity profiles. Even though shipboard stations were separated by just 5 to 8 km along the mission path, data from the AUV showed small scale variability that was missed by the shipboard sampling. In this paper we present the example of an intense jet, with maximum speed greater than 0.50 m s−1, less than 4 km wide.
Transfer of mass‐independent fractionation in ozone to other oxygen‐containing radicals in the atmosphere
Authors: Lyons James R.
Published: February 2004

Mass‐independent fractionation (MIF) of ozone has been observed in both the troposphere and stratosphere. Because ozone is a photochemically active species, its MIF signature can be imparted to other atmospheric molecules. Using a photochemical equilibrium model for short‐lived radical species, I have computed the expected MIF for typical mid‐latitude conditions. The model accounts for about ∼70% of recent measurements of Δ177O for H2O2 in rainwater, and predicts large MIF for NOx and ClO species (∼40–70‰), and their products (ClONO2 and HNO3). Furthermore, in the stratosphere oxygen exchange reactions between OH and NOx yield OH with Δ17O from 2 to 45‰. Stratospheric water produced during H abstraction by OH would be similarly mass‐independently fractionated. In the troposphere rapid exchange between OH and H2O erases any MIF signature in OH. These model results depend on several O exchange reactions with unknown activation energies or with rate coefficients known only as upper limits.
Self‐similarity and multifractality of fluvial erosion topography: 2. Scaling properties
Authors: Veneziano Daniele , Niemann Jeffrey D.
Published: February 2004

In a companion paper [Veneziano and Niemann, this issue] the authors have proposed self‐similarity and multifractality conditions for fluvial erosion topography within basins and have shown that topographic surfaces with this property can evolve from a broad class of dynamic models. Here we use the same self‐similarity and multifractality conditions to derive geomorphological scaling laws of hydrologic interest. We find that several existing relations should be modified, as they were obtained using definitions of the quantities involved or measurement techniques that are inappropriate under self‐similarity. These relations include Hack's law, the power law decay of the distributions of contributing area and main channel length, the scaling of channel slope with contributing area, and the self‐similarity condition for river courses. Most results are further generalized by replacing main stream flow length and drainage area with generic measures of basin size. The relations we obtain among properly measured topographic variables have simple universal exponents. For example, the exponent of Hack's law is 0.5, the exponent of the distribution of contributing area is −0.5, and the exponent of the distribution of main stream length is −1.0. We also suggest a stochastic condition of drainage network self‐similarity that incorporates topological as well as geometric and hydrologic features and a reformulation of Horton's laws using drained area rather than stream order.
Identifying fracture‐zone geometry using simulated annealing and hydraulic‐connection data
Authors: Day‐Lewis Frederick D. , Hsieh Paul A. , Gorelick Steven M.
Published: February 2004

A new approach is presented to condition geostatistical simulation of high‐permeability zones in fractured rock to hydraulic‐connection data. A simulated‐annealing algorithm generates three‐dimensional (3‐D) realizations conditioned to borehole data, inferred hydraulic connections between packer‐isolated borehole intervals, and an indicator (fracture zone or background‐Kbedrock) variogram model of spatial variability. We apply the method to data from the U.S. Geological Survey Mirror Lake Site in New Hampshire, where connected high‐permeability fracture zones exert a strong control on fluid flow at the hundred‐meter scale. Single‐well hydraulic‐packer tests indicate where permeable fracture zones intersect boreholes, and multiple‐well pumping tests indicate the degree of hydraulic connection between boreholes. Borehole intervals connected by a fracture zone exhibit similar hydraulic responses, whereas intervals not connected by a fracture zone exhibit different responses. Our approach yields valuable insights into the 3‐D geometry of fracture zones at Mirror Lake. Statistical analysis of the realizations yields maps of the probabilities of intersecting specific fracture zones with additional wells. Inverse flow modeling based on the assumption of equivalent porous media is used to estimate hydraulic conductivity and specific storage and to identify those fracture‐zone geometries that are consistent with hydraulic test data.
Evaporation from a tropical rain forest, Luquillo Experimental Forest, eastern Puerto Rico
Authors: Schellekens J. , Bruijnzeel L. A. , Scatena F. N. , Bink N. J. , Holwerda F.
Published: February 2004

Evaporation losses from a watertight 6.34 ha rain forest catchment under wet maritime tropical conditions in the Luquillo Experimental Forest, Puerto Rico, were determined using complementary hydrological and micrometeorological techniques during 1996 and 1997. At 6.6 mm d−1 for 1996 and 6.0 mm d−1 for 1997, the average evapotranspiration (ET) of the forest is exceptionally high. Rainfall interception (Ei), as evaluated from weekly throughfall measurements and an average stemflow fraction of 2.3%, accounted for much (62–74%) of the ET at 4.9 mm d−1 in 1996 and 3.7 mm d−1 in 1997. Average transpiration rates (Et) according to a combination of the temperature fluctuation method and the Penman‐Monteith equation were modest at 2.2 mm d−1 and 2.4 mm d−1 in 1996 and 1997, respectively. Both estimates compared reasonably well with the water‐budget‐based estimates (ET − Ei) of 1.7 mm d−1 and 2.2 mm d−1. Inferred rates of wet canopy evaporation were roughly 4 to 5 times those predicted by the Penman‐Monteith equation, with nighttime rates very similar to daytime rates, suggesting radiant energy is not the dominant controlling factor. A combination of advected energy from the nearby Atlantic Ocean, low aerodynamic resistance, plus frequent low‐intensity rain is thought to be the most likely explanation of the observed discrepancy between measured and estimated Ei.
Analytical solutions for the transport of volatile organic chemicals in unsaturated layered systems
Authors: Yates S. R. , Papiernik S. K. , Gao F. , Gan J.
Published: February 2004

Several analytical solutions were developed that describe the transport of volatile organic chemicals or other gases in layered porous media. Solutions are presented for a one‐dimensional system consisting of either two finite soil layers or a finite layer adjacent to an infinite soil layer. The proposed solutions may be useful for studying the movement of volatile chemicals or other gases in layered soils, as well as for gas movement from soils into passive flux chambers, which are commonly used for measuring the surface volatilization rate. The behavior of the solutions is illustrated by several examples showing the soil gas concentration and the flux density as a function of time. At early times it was found that the flux density into a chamber is relatively constant when the mass transfer coefficient h is small. However, the concentration at the soil‐chamber interface changes rapidly. For large h the flux density at the interface changes rapidly, and the concentration is relatively constant.
Flux of nutrients from Russian rivers to the Arctic Ocean: Can we establish a baseline against which to judge future changes?
Authors: Holmes R. M. , Peterson B. J. , Gordeev V. V. , Zhulidov A. V. , Meybeck M. , Lammers R. B. , Vörösmarty C. J.
Published: February 2004

Climate models predict significant warming in the Arctic in the 21st century, which will impact the functioning of terrestrial and aquatic ecosystems as well as alter land‐ocean interactions in the Arctic. Because river discharge and nutrient flux integrate large‐scale processes, they should be sensitive indicators of change, but detection of future changes requires knowledge of current conditions. Our objective in this paper is to evaluate the current state of affairs with respect to estimating nutrient flux to the Arctic Ocean from Russian rivers. To this end we provide estimates of contemporary (1970s–1990s) nitrate, ammonium, and phosphate fluxes to the Arctic Ocean for 15 large Russian rivers. We rely primarily on the extensive data archives of the former Soviet Union and current Russian Federation and compare these values to other estimates and to model predictions. Large discrepancies exist among the various estimates. These uncertainties must be resolved so that the scientific community will have reliable data with which to calibrate Arctic biogeochemical models and so that we will have a baseline against which to judge future changes (either natural or anthropogenic) in the Arctic watershed.
Field evaluation of passive capillary samplers for estimating groundwater recharge
Authors: Louie Michael J. , Shelby Patrick M. , Smesrud Jason S. , Gatchell Lance O. , Selker John S.
Published: February 2004

Passive capillary samplers (PCAPS), which sample water from the vadose zone via a hanging water column in a fiberglass wick, have shown potential to provide superior estimates of soil water flux compared to alternative methods. The objectives of this study were to evaluate the performance of PCAPS under natural rain‐fed conditions concerning (1) their operational characteristics and (2) their ability to estimate soil water flux. Forty‐two PCAPS were installed in 21 commercial agricultural fields in Lane County, Oregon. Monthly measurements of soil water flux and precipitation were recorded at each site for the 4‐year project duration. Of the 42 installed PCAPS, 12 samplers at six sites were inoperable or did not operate efficiently: 10 samplers were consistently below the water table, which overflowed the collection vessels rendering the samplers inoperable. Only two of the PCAPS exhibited technical failure resulting in unusually low collection efficiencies, thought to be due to a collapse of the collection vessel from oversuction during sample retrieval. On average, the 30 remaining PCAPS measured soil water flux 25% greater than that obtained from a water balance estimate. This discrepancy represents ∼8% of the total annual precipitation and irrigation each site received. PCAPS collection efficiency was found to be significantly correlated (R2 = 0.75) to the water balance yearly estimated recharge. The difference between PCAPS measured and water balance estimated percolation could be the result of inaccuracy in water balance evapotranspiration estimates and/or oversampling in the presence of high water tables. To estimate the mean yearly recharge at each site with a 30% bound on the mean at the 0.05 confidence level, eight PCAPS are required. This number corresponds closely to the results of Brandi‐Dohrn et al. [1996a] and is thought to be due to intrinsic variability of percolation.
Determination of finger shape using the dynamic capillary pressure
Authors: DiCarlo D. A. , Blunt M. J.
Published: February 2004

Descriptions of fingered flow typically are based on linear instability theory, which becomes inappropriate once a finger has formed. In contrast, we obtain a self‐similar solution to a moving finger with a curved interface by using the dynamic capillary pressure, where the capillary pressure depends on the velocity of the moving interface. From this solution we find analytical expressions for the shape and width of gravitationally driven fingers when they are fully developed. The solution has an unphysical limit of zero width at the limit of zero velocity owing to the simple dependence of capillary pressure on velocity. We discuss modifications to this dependence and compare the results to previous observations of fingering by Glass et al. [1989].
Spatial analysis of water characteristic functions in a sandy podzol under pine forest
Authors: Deurer M. , Duijnisveld W. H. M. , Böttcher J.
Published: February 2004

Water characteristic functions of 351 undisturbed soil cores taken at three profiles on a two‐dimensional regular grid with a spacing of 0.15 m are shown to vary linearly and nonlinearly in space. To describe their heterogeneity, linear and nonlinear scaling factors are independently derived with soil horizons as separate similarity classes. Their estimated empirical distributions are different, and the spatial statistics show a comparable integral scale only in the horizontal direction (∼0.15 m). In the vertical direction, nonlinear scaling factors exhibit an integral scale of ∼0.2 m, and linear scaling factors exhibit a pure nugget effect. On a small sample subset, other soil material properties (e.g., texture) were also analyzed. In a multiple linear regression between those material properties and scaling factors the organic carbon content is a significant deterministic factor at the site.
On the late‐time behavior of tracer test breakthrough curves
Authors: Haggerty Roy , McKenna Sean A. , Meigs Lucy C.
Published: February 2004

We investigated the late‐time (asymptotic) behavior of tracer test breakthrough curves (BTCs) with rate‐limited mass transfer (e.g., in dual‐porosity or multiporosity systems) and found that the late‐time concentration c is given by the simple expression c = tad{c0g − [m0(∂g/∂t)]}, for t ≫ tad and tα ≫ tad, where tad is the advection time, c0 is the initial concentration in the medium, m0 is the zeroth moment of the injection pulse, and tα is the mean residence time in the immobile domain (i.e., the characteristic mass transfer time). The function g is proportional to the residence time distribution in the immobile domain; we tabulate g for many geometries, including several distributed (multirate) models of mass transfer. Using this expression, we examine the behavior of late‐time concentration for a number of mass transfer models. One key result is that if rate‐limited mass transfer causes the BTC to behave as a power law at late time (i.e., C ∼ t−k), then the underlying density function of rate coefficients must also be a power law with the form αk−3 as a α → 0. This is true for both density functions of first‐order and diffusion rate coefficients. BTCs with k < 3 persisting to the end of the experiment indicate a mean residence time longer than the experiment, and possibly an infinite residence time, and also suggest an effective rate coefficient that is either undefined or changes as a function of observation time. We apply our analysis to breakthrough curves from single‐well injection‐withdrawal tests at the Waste Isolation Pilot Plant, New Mexico.
Ocean tide‐induced head fluctuations in wells
Authors: Depner Joe
Published: February 2004

Wells in coastal aquifers can attenuate and delay aquifer hydraulic head fluctuations induced by ocean tides. To infer how the attenuation/delay depend on system dimensions and hydraulic properties, I solved a boundary value problem in which a well with storage fully penetrates a confined, coastal aquifer. The well‐induced attenuation and delay are (1) maximum at the well and decrease to zero at the aquifer's horizontal periphery; (2) generally increasing functions of well radius, distance from seaward boundary, and tidal frequency; (3) decreasing functions of transmissivity; and (4) nearly independent of storativity for lesser radii and generally decreasing functions of storativity for greater radii. Approximations were developed for (1) a point in the aquifer, valid when the distance from the point to the well greatly exceeds the well radius, and (2) at the well, valid when the distance from the well to the seaward boundary greatly exceeds the radius.
Relationship between the sea ice cover in the retreat and advance seasons in the Antarctic Ocean
Authors: Nihashi Sohey , Ohshima Kay I.
Published: February 2004

Relationship between ice concentrations in the retreat (December) and advance (April) seasons is investigated in the Antarctic Ocean using SMMR and SSM/I data. For most years, the negative (positive) anomalies in ice concentration in the retreat season lead to the negative (positive) anomalies in the next advance season with strong correlation. This positive feedback can be regarded as ice‐albedo feedback in a coupled ice‐ocean system. In the retreat season, net heat input into the upper ocean from the atmosphere becomes maximum and is mostly determined by ice concentration. Because of large interannual variation of ice concentration in the retreat season, the anomaly in the heat input becomes tremendous. It is inferred that this anomaly is memorized in the ocean, and then affects the next advance of sea ice, skipping over the open ocean period (February–March). This process can partly explain the interannual variation of the sea ice cover.
A central tropical Pacific coral demonstrates Pacific, Indian, and Atlantic decadal climate connections
Authors: Cobb Kim M. , Charles Christopher D. , Hunter David E.
Published: February 2004

While instrumental and proxy‐based climate records describe significant decadal‐scale climate variability throughout the tropical Pacific, Indian, and Atlantic Oceans, the processes responsible for these variations and their interactions are not readily apparent from the observations. A new 112‐yr coral‐based sea surface temperature (SST) reconstruction from Palmyra Island in the central tropical Pacific (CTP) exhibits strong decadal variability with an amplitude of roughly 0.3°C. A 12–13yr‐period signal in this coral record is highly coherent with long equatorial Atlantic and Indian Ocean climate records, implying a unified phenomenon. The Atlantic pattern suggests that it may fall under direct influence of anomalous SST in the CTP, as it does over inter annual timescales, while the Indian Ocean pattern exhibits maximum response during the switch between warm/cold states in the tropical Pacific. The results demonstrate that the CTP has played a significant role in determining the expression of global decadal climate variability over the twentieth century.
40Ar‐39Ar ages of Bombay trachytes: Evidence for a Palaeocene phase of Deccan volcanism
Authors: Sheth Hetu C. , Pande Kanchan , Bhutani Rajneesh
Published: February 2004

We present40Ar‐39Ar ages of 60.4±0.6 Ma and 61.8±0.6 Ma (2σ) for Deccan Trap trachytes from Manori and Saki Naka, Bombay, situated in the tectonized Panvel flexure zone along the western Indian rifted continental margin. These ages provide clear evidence that (i) these trachytes are of Palaeocene age and therefore substantially younger than the lower part of the main flood basalt sequence exposed in the Western Ghats, which precedes the K‐T Boundary in age and (ii) the formation of the Panvel flexure along the west coast must have been subsequent to ∼60 Ma. Considering early alkaline Deccan rocks previously dated at ∼68.5 Ma, the total duration of Deccan volcanism was at least ∼8 MY.