bluuebunny/crossref_metadata_2025 huggingface dataset:
Return of the cold halocline layer to the Amundsen Basin of the Arctic Ocean: Implications for the sea ice mass balance
Authors: Björk G. , Söderkvist J. , Winsor P. , Nikolopoulos A. , Steele M.
Published: October 2002

CTD measurements from the Arctic Ocean 2001 expedition reveal that the cold halocline layer (CHL) has returned to the Amundsen Basin at a position close to that found during the Oden'91 expedition. River water from the Siberian shelves formed a strong freshwater front in the Amundsen Basin, extending from the Gakkel Ridge to the Lomonosov Ridge. Furthermore, we show from model computations that the presence of a CHL may increase winter sea ice growth by 0.25 m over one season compared to a case with a non‐existing CHL due to increased vertical heat flux from the warm Atlantic water. The difference in sea ice growth is due to a much shallower winter convection with a CHL present, which is not able to reach into the warm Atlantic layer, resulting in a considerably smaller oceanic heat flux.
Determining leader potential in cloud‐to‐ground flashes
Authors: Mazur Vladislav , Ruhnke Lothar H.
Published: October 2002

A new method for estimating lightning leader potential is proposed, based on multi‐station measurements of electric field changes during the first return stroke process in cloud‐to‐ground flashes. In negative stepped leaders, this method may be used to estimate step length, which is strongly dependent on leader potential; this capability is particularly important in the evaluation of the so‐called “striking distance” in lightning protection practice.
Ecological impact of a large Antarctic iceberg
Authors: Arrigo Kevin R. , van Dijken Gert L. , Ainley David G. , Fahnestock Mark A. , Markus Thorsten
Published: October 2002

Satellite imagery has been used to document for the first time the potential for large icebergs to substantially alter the dynamics of a marine ecosystem. The B‐15 iceberg (∼10,000 km2), which calved off the Ross Ice Shelf in the biologically productive southwestern Ross Sea, Antarctica, restricted the normal drift of pack ice, resulting in heavier spring/summer pack ice cover than previously recorded. Extensive ice cover reduced both the area suitable for phytoplankton growth and the length of the algal growing season. Consequently, primary productivity throughout the region was >40% below normal, which changed both the abundance and behavior of upper trophic level organisms.
Comparison between the Au and MgO pressure calibration standards at high temperature
Authors: Matsui Masanori , Nishiyama Norimasa
Published: October 2002

We compare the MgO pressure scales previously developed using molecular dynamics simulations based on empirical and non‐empirical interatomic potentials, to check the accuracy of the reported pressure scales at high temperatures. We find excellent agreement between the two independent pressure scales over wide temperature and pressure ranges, with simulated pressure discrepancies between the two for specified relative volumes being within 0.5 GPa in the temperature and pressure ranges up to 2000 K and 30 GPa. Based on recent simultaneous pressure measurements using both the MgO and Au scales with a multi‐anvil apparatus at 1873 K, we then compare the resulting pressures based on the MgO scale with those based on the Anderson's Au scale, which is recently widely used to estimate pressures in high temperature and high pressure experiments. We find the Andrerson's Au scale underestimates pressures by 1.4 ± 0.3 GPa relative to the MgO scale at 1873 K.
High‐resolution measurements and simulation of stratospheric and tropospheric intrusions in the vicinity of the polar jet stream
Authors: Beuermann Jürgen , Konopka Paul , Brunner Dominik , Bujok Oliver , Günther Gebhard , McKenna Daniel S. , Lelieveld Jos , Müller Rolf , Schiller Cornelius
Published: October 2002

Pronounced filamentation of tropospheric and stratospheric air masses was observed on a flight in the vicinity of the polar jet stream during the STREAM 1998 campaign in Timmins, Canada. High‐spatial resolution O3 and H2O measurements showed highly variable structures for the investigated region. Reconstructing high‐resolution potential vorticity (PV) fields using the reverse‐domain‐filling (RDF) technique reproduce the in‐situ O3 measurements qualitatively. Measurements and RDF results show the intrusion of stratospheric air penetrating deep into the troposphere. The observed intrusions occur on smaller horizontal scales than generally assumed for tropopause folding events. Moreover, fine‐scale structures of tropospheric air masses being lifted up into the stratosphere could be reconstructed by the RDF technique using the tropospheric tracer specific humidity in addition to the more conventional calculations for the stratospheric tracer PV.
Ulysses' second fast‐latitude scan: Complexity near solar maximum and the reformation of polar coronal holes
Authors: McComas D. J. , Elliott H. A. , Gosling J. T. , Reisenfeld D. B. , Skoug R. M. , Goldstein B. E. , Neugebauer M. , Balogh A.
Published: October 2002

Ulysses' second fast latitude scan, near solar maximum, comprises a complicated mixture of solar wind flows from a variety of sources at high southern as well as low heliolatitudes. In contrast, observations northward of ∼40° N show the reformation of relatively steady fast solar wind flows, which are virtually indistinguishable from the polar coronal hole winds observed at high latitudes over Ulysses' first orbit. These high‐speed flows predominantly display the opposite magnetic polarity from that observed in the northern hemisphere during the previous orbit, indicating that the Sun's dipole has reversed. The recent restructuring of the high‐latitude solar wind, so soon after solar maximum, suggests that the heliospheric chaos around maximum occupies a unique and relatively shorter‐lived portion of the solar cycle with the majority of the cycle maintaining the simple bimodal solar wind structure associated with large, persistent polar coronal holes.
Water mobility in Calico Hills tuff measured by quasielastic neutron scattering
Authors: Maddox S. A. , Gomez P. , McCall K. R. , Eckert J.
Published: October 2002

Quasielastic neutron scattering (QNS) was used to measure the mobility of water in tuff at low saturation. The tuff sample is from a surface outcrop of the Calico Hills formation, which lies below the proposed location for a high‐level nuclear waste repository, at Yucca Mountain, NV. The sample is a devitrified tuff composed mainly of zeolites and having clinoptilolite (approximately 70%), mordenite, and opal‐CT as major constituents. The sample is an air dry, intact core sample. QNS measurements were made in the range 200 K to 423 K. Rotational motion of adsorbed water is easily observable and translational motion is observable at higher temperatures. The tuff data are analyzed to determine the rotational diffusion coefficient and the translational diffusion coefficient. The results yield a translational diffusion coefficient in the tuff that is significantly lower than that of bulk water but higher than for water in montmorillonite or vermiculite clays.
Geotail observations of magnetospheric midtail during an extended period of strongly northward interplanetary magnetic field
Authors: Huang Chao‐Song , Foster J. C. , Song P. , Sofko G. J. , Frank L. A. , Paterson W. R.
Published: October 2002

A number of simulations have predicted a closed magnetosphere after several hours of northward interplanetary magnetic field (IMF). During January 7–8, 1998, the IMF was strongly northward for ∼21 hours without any southward excursion. The Geotail spacecraft was located at −21 > Xgsm > −28 RE and very close to the magnetospheric equatorial plane and midnight, and detected two distinct regions. In the inner region close to the equatorial plane, the geomagnetic field is weak, the plasma pressure and plasma beta are high, and plasma flow is sunward. The outer region is characterized by lower plasma pressure and antisunward plasma flow. The observations are consistent with a closed magnetosphere and may represent the ground state of the magnetosphere.
Estimates of ocean heat flux at SHEBA
Authors: Perovich Donald K. , Elder Bruce
Published: October 2002

Observations of sea ice mass balance and temperature made during the year‐long Surface HEat Budget of the Arctic Ocean (SHEBA) field experiment were used to calculate monthly estimates of the ocean heat flux for a variety of ice types. The ocean heat flux displayed a strong seasonal cycle, with values of a few W m−2 from October through June followed by a steady increase in June and July. By the end of July the the ocean heat flux for undeformed ice reached a peak value of about 33 W m−2 during a period of substantial ice motion. The annual average ocean heat flux for multiyear ice ranged from 7.5 W m−2 for undeformed ice to 10.4 W m−2 for a melt pond to 12.4 W m−2 for an old ridge. Annual averages measured at SHEBA were more than twice as large as values observed in 1975 during AIDJEX.
Stress determination in multianvil deformation experiments based on dislocation curvatures measurements: Application to wadsleyite and ringwoodite
Authors: Cordier P. , Thurel E. , Rabier J.
Published: October 2002

The curvature of dislocation lines can serve as a probe for the resolved shear stress in multianvil deformation experiments. This method is very well adapted to deformation experiments in the multianvil apparatus where the microstructure (and in particular the dislocation density) can be largely determined by early deformation stages. On the contrary, individual dislocation movements can adjust more rapidly to stress level changes and can thus record the last stress level borne by the specimen before it is quenched. The method has been applied to dense specimens of wadsleyite and ringwoodite deformed at 15 to 22 GPa and 1000 to 1500–1600°C. The resolved shear stress is very similar in wadsleyite (400 MPa) and ringwoodite (350 MPa) deformed at 1000°C showing that these minerals exhibit very similar rheological properties under these conditions.
A practical method for long‐range forecasting of ice severity in the Beaufort Sea
Authors: Drobot Sheldon D. , Maslanik James A.
Published: October 2002

A linear regression model is used to forecast end of summer ice conditions in the Beaufort Sea with a few months lead‐time. The model retains four sea ice and atmospheric parameters, where decreased spring total and winter multiyear ice concentrations, negative October East Atlantic phases, and positive March North Atlantic Oscillation phases are associated with lighter sea ice conditions. Monte Carlo simulations suggest that the results are not adversely affected by artificial skill, while Durbin‐Watson and Variance Inflation Factor statistics imply the final model is statistically valid. Cross validation diagnostics indicate that variations in the four predictors are related to 85% of the variation in sea ice conditions, suggesting that a relatively simple ice‐atmosphere statistical model can be used to forecast end of summer ice conditions in the Beaufort Sea.
Tides on Filchner‐Ronne Ice Shelf from ERS radar altimetry
Authors: Fricker Helen Amanda , Padman Laurie
Published: October 2002

We use harmonic analysis of 8 years of ERS satellite radar altimeter (RA) data at orbital crossovers to retrieve complex amplitude (amplitude and phase) coefficients for several major tidal harmonics over the Filchner‐Ronne Ice Shelf (FRIS), Antarctica. We describe a method for estimating the accuracy of this method, which ranges from ∼2 to 8 cm per harmonic. A comparison between M2 complex amplitude from a recent ocean model and from our ERS RA analyses identifies two regions of the FRIS where the RA data are inconsistent with the model. In both regions the differences can be attributed to incorrect specification of the grounding line location in the model. Our study demonstrates the value of ERS RA data in Antarctic ice shelf tide modeling, and the potential for future altimeter satellites with high polar orbits to contribute to the definition of global tide height variations.
Pn anisotropy and distributed upper mantle deformation associated with a continental transform fault
Authors: Scherwath Martin , Melhuish Anne , Stern Tim , Molnar Peter
Published: October 2002

Differences in Pn speeds within continental lithosphere off the west coast of South Island, New Zealand, require anisotropy of at least 10 ± 3%. These data concur with SKS splitting and are inferred to show high strain of mantle lithosphere over a zone >200 km wide. An active source seismic experiment yields Pn speeds of 8.6 and 7.7 km/s along nearly perpendicular lines. The higher speed is sub‐parallel to the polarization of the faster quasi‐S wave measured from SKS splitting. Most of the observed ∼2 s of splitting in South Island can be accommodated in mantle lithosphere 150 km thick, if we assume a P to S anisotropy ratio of 1.4. The large magnitude of Pn anisotropy shows that anisotropy must occur in the relatively cold uppermost part of the mantle lithosphere and raises the possibility that dynamic recrystallization occurs in cold (∼500–600°C) olivine at geologic strain rates.
Earthquake scaling and the strength of seismogenic faults
Authors: Miller S. A.
Published: October 2002

Two important and unresolved issues in tectonics and earthquake mechanics are the strength of seismogenic faults, and scaling relationships between the seismic moment of an earthquake and the area or length of the rupture. These two issues, usually treated separately, are shown here to be fundamentally related. It is shown that the reported scatter in moment‐area and moment‐length data of strike‐slip and dip‐slip earthquakes is not scatter, but instead reflects the strength of the fault that failed. Relationships that exhibit continuous scaling between small and large earthquakes are derived, and demonstrate that fault zone pore pressure is the scaling parameter that collapses the combined catalogs of strike‐slip and dip‐slip earthquakes to a single function. It is shown that for large earthquakes overpressures vary continuously between hydrostatic and near‐lithostatic above about 15 km, with evidence for a clear transition to near‐lithostatic pore pressures below this depth. These results have significant implications for plate tectonics, earthquake source physics, and mechanistic seismic hazard assessment.
Midday sub‐auroral patches (MSPs) associated with interplanetary shocks
Authors: Liou K. , Wu C.‐C. , Lepping R. P. , Newell P. T. , Meng C.‐I
Published: October 2002

We report a new category of dayside auroral transients using auroral image data from the Polar spacecraft Ultraviolet Imager. The transients are characterized by a sudden brightening of the auroral patch in the midday sub‐auroral zone, and thus are named midday sub‐auroral patches (MSPs). MSPs were found to occur concurrently with storm sudden commencements in response to the compression of the magnetosphere by interplanetary (IP) shocks. After brightening, the MSP widened and/or moved equatorward. The latitudinal location of an MSP depends on the solar wind dynamic pressure in the shock downstream: a larger dynamic pressure corresponds to a lower latitude. The lifetime of an MSP is short (∼5–6 min). The magnetospheric source region for the MSPs, as determined with the Defense Meteorological Satellite Program particle data from one fortuitous event, is the central plasma sheet (CPS). Sudden compression of the Earth's magnetic field due to the IP shock impact may change the pitch angles of a pre‐existing population of CPS particles, which consequently fall into the loss cone and produce auroral emission.
Inland thinning of the Amundsen Sea sector, West Antarctica
Authors: Shepherd Andrew , Wingham Duncan J. , Mansley Justin A. D.
Published: October 2002

Together with the Pine Island glacier (PIG), the Thwaites (TG) and Smith (SG) glaciers are the principal drainage systems of the Amundsen Sea (AS) sector of Western Antarctica. Here we use satellite radar altimetry and interferometry to show that a rapid thinning of ice has occurred within the fastest flowing sections of all AS outlet glaciers. The pattern of thinning extends to distances greater than 150 km inland. Between 1991 and 2001, the TG and SG thinned by more than 25 and 45 m at their grounding lines, and a total of 154 ± 16 km3 of ice (or 0.43 mm of eustatic sea level rise) was lost from the AS sector glaciers to the ocean. We show that the thickness changes may have caused the PIG, TG, and SG to retreat inland by over 8, 4, and 7 km respectively, in line with independent estimates of grounding line migration.
Coincidence of the ion precipitation boundary with the HF E region backscatter boundary in the dusk‐midnight sector of the auroral oval
Authors: Jayachandran P. T. , MacDougall J. W. , St‐Maurice J.‐P. , Moorcroft D. R. , Newell P. T. , Prikryl P.
Published: October 2002

We have examined the location of the SuperDARN E region ionospheric backscatter boundary in the dusk‐midnight sector and compared it with the equatorward boundary of the hard ion precipitation (b2i) determined from the DMSP satellite particle spectrograms in the dusk‐midnight sector of the auroral oval. The locations of these two boundaries were found to be nearly coincident. This study evinces the capability of the SuperDARN radars to monitor the equatorward ion precipitation boundary (diffuse auroral boundary) and its dynamics irrespective of magnetic activity.
Flake tectonics in the Sulu orogen in eastern China as revealed by seismic tomography
Authors: Xu Peifen , Liu Futian , Ye Kai , Wang Qingchen , Cong Bolin , Chen Hui
Published: October 2002

Seismic tomographic image reveals a crocodile‐like P‐waves velocity structure beneath the Sulu orogenic belt, which marks the subduction/collision zone between the Sino‐Korean block (SK) and Yangtze block (YZ) in eastern China. It may imply that the upper crust of the YZ was detached from its lower crust and thrust over the SK for a maximum of ∼400 km in the Sulu region, whereas the remnant of the subducted Yangtze lithosphere was lay beneath the SK. This crustal detached structure (flake tectonics) might have occurred after the Triassic subduction/collision.
Sunphotometric observations of the 2001 Asian dust storm over Canada and the U.S.
Authors: Thulasiraman S. , O'Neill N. T. , Royer A. , Holben B. N. , Westphal D. L. , McArthur L. J. B.
Published: October 2002

Sunphotometry, supported by TOMS imagery and the NRL‐NAAPS global aerosol model, was used to monitor the 2001 springtime Asian dust plume across Canada and the U.S. Comparative analysis between these data sets indicated that the dust plume was remarkable in its extent and persistence and that its evolution could be inferred at western, mid‐western and eastern sunphotometer stations for a period of about a week. The dust influence on sunphotmeter monthly statistics is shown to be weak, but systematic.
Highly deformed basal ice in the Vostok core, Antarctica
Authors: Souchez R. , Petit J.‐R. , Jouzel J. , Simões J. , de Angelis M. , Barkov N. , Stiévenard M. , Vimeux F. , Sleewaegen S. , Lorrain R.
Published: October 2002

Our paper documents the build‐up of a highly deformed basal ice layer in the basal part of the Vostok ice core. This is done mainly on the basis of an isotopic composition investigation of the ice. Complex deformation in the lower 228 m of the ice sheet has resulted in folding and intermixing of ice at a submetric scale and, for the upper part of this basal sequence, in interbedding of ice layers from distinct origins at a larger scale. This complex deformation occurred at a temperature largely below the pressure‐melting point. The basal ice layer has built upwards and size‐selective incorporation of bed material into the ice has taken place. The documentation of this complex basal deformation has implications for the maximum age of ice that will be useful in paleoclimate studies and for ice sheet dynamics.
Dynamics of the elevated land plume over the Arabian Sea and the Northern Indian Ocean during northeasterly monsoons and during the Indian Ocean experiment (INDOEX)
Authors: Raman Sethu , Niyogi Dev dutta S. , Simpson Matthew , Pelon Jacques
Published: October 2002

We describe the dynamics of the formation of an elevated land plume over the Arabian Sea and northern Indian Ocean observed during the 1999 Indian Ocean Experiment (INDOEX). The presence of the elevated plume above the marine boundary layer for a depth of about 2000 m could be inferred from the thermodynamic profiles of the lower troposphere obtained from research vessels in 1997, 1998, and 1999, and in the lidar data obtained from aircraft during the INDOEX. Formation of the elevated plume was investigated further using a three‐dimensional high‐resolution mesoscale modeling system. The plume extends for hundreds of kilometers and its strength and coherence is influenced by the diurnal variation of the upwind continental boundary layer.
Low‐temperature remanence in stable single domain magnetite
Authors: Carter‐Stiglitz Brian , Jackson Mike , Moskowitz Bruce
Published: October 2002

A numerical model is developed in order to simulate the loss of low‐temperature remanence while warming through the Verwey transition. We concentrate on the amount of remanence lost (δfc and δzfc) during field cooled and zero field cooled low temperature demagnetization curves for stable single domain (SSD) particles of (1) inorganic magnetite and (2) biogenic magnetite in the form of magnetosome chains. The model predicts that delta ratios (δfc/δzfc) for inorganic SSD magnetite increase from 1 to 1.6 with increasing aspect ratio and that magnetosome chains have elevated delta ratios of at least 2.0. Disaggregated magnetosomes are predicted to behave similarly to inorganic acicular SSD magnetite. The numerical results agree with experimental results.
Processes influencing the non‐linear interaction between inertial oscillations, near inertial internal waves and internal tides
Authors: Xing Jiuxing , Davies Alan M.
Published: October 2002

A numerical model of the Hebrides shelf edge (represented by a cross section) is used to examine the non‐linear interactions producing energy at the fM2 frequency. Calculations show that in the near coastal ocean this is primarily due to coupling between wind induced inertial oscillations (although near inertial internal waves are present) and the M2 internal tide. The major non‐linear interaction, and hence largest fM2 currents, occurs in the region of the thermocline and is associated with shear in the inertial oscillation and the vertical velocity due to the internal tide. This non‐linear process represents an important contribution to the energy cascade from the wind and tide into higher frequency waves and eventually mixing. The fM2 current is shown to be a maximum in the shelf edge region and hence measurements in this area will be particularly valuable in determining the extent to which models can represent non‐linear processes.
Relative influences of the Interdecadal Pacific Oscillation and ENSO on the South Pacific Convergence Zone
Authors: Folland C. K. , Renwick J. A. , Salinger M. J. , Mullan A. B.
Published: October 2002

The South Pacific Convergence Zone (SPCZ), one of the most extensive features of the global atmospheric circulation, is shown to vary its location according to both the polarity of the El Niño/Southern Oscillation (ENSO), and of the Interdecadal Pacific Oscillation (IPO). We first demonstrate that the IPO can be regarded as the quasi‐symmetric Pacific‐wide manifestation of the Pacific Decadal Oscillation that has been described for the North Pacific. Shifts in the position of the SPCZ related to ENSO on interannual time scales and to the IPO on decadal time scales appear to be of similar magnitude and are largely linearly independent. A station pressure‐based index of variations in SPCZ latitude is shown to be significantly related to the polarity of the IPO when ENSO influences are accounted for. Movements of this sensitive section of the SPCZ have occurred in phase with those of the IPO since the 1890s.
Saturation of polar cap potential by intense solar wind electric fields
Authors: Nagatsuma Tsutomu
Published: October 2002

We have examined the statistical relationship between solar wind parameters and the polar cap potential (ΦPC) using data from the Wind and ACE satellites and the northern polar cap index (PCN) as a proxy for ΦPC. We found that PCN tended to be saturated when the value of the merging electric field (Em) was high (greater than 5 mV/m). Furthermore, it was found that the degree of saturation does not depend on the intensity of the interplanetary magnetic field but depends on the value of Em. These results are in quite reasonable agreement with the predictions of the model of Hill et al. [1976]. This fact suggests that the development of magnetospheric convection is not controlled by the efficiency of the dayside merging process itself but is controlled by the coupling among the solar wind, the magnetosphere, and the ionosphere.
QuikSCAT reveals the surface circulation of the Catalina Eddy
Authors: Hu Hua , Liu W. Timothy
Published: October 2002

The Catalina Eddy, a small, recurring cyclonic vortex in the ocean off Los Angeles, is of keen interest to local weather forecasters because of the moderating oceanic effect it brings to the city. Its small size and shallow vertical extent have made it difficult to monitor and predict using conventional data. The microwave scatterometer on the QuikSCAT spacecraft has generated high‐resolution surface wind vectors that provide the first visualization of the complete cyclonic flow of the eddy. Moreover, the superior performance of the QuikSCAT scatterometer demonstrates the relative inaccuracy and inconsistency of predictions of the eddy based upon numerical weather prediction models.
Magmatic activity beneath the quiescent Three Sisters volcanic center, central Oregon Cascade Range, USA
Authors: Wicks Charles W. , Dzurisin Daniel , Ingebritsen Steven , Thatcher Wayne , Lu Zhong , Iverson Justin
Published: October 2002

Images from satellite interferometric synthetic aperture radar (InSAR) reveal uplift of a broad ∼10 km by 20 km area in the Three Sisters volcanic center of the central Oregon Cascade Range, ∼130 km south of Mt. St. Helens. The last eruption in the volcanic center occurred ∼1500 years ago. Multiple satellite images from 1992 through 2000 indicate that most if not all of ∼100 mm of observed uplift occurred between September 1998 and October 2000. Geochemical (water chemistry) anomalies, first noted during 1990, coincide with the area of uplift and suggest the existence of a crustal magma reservoir prior to the uplift. We interpret the uplift as inflation caused by an ongoing episode of magma intrusion at a depth of ∼6.5 km.
Dynamical containment of Antarctic ozone depletion
Authors: Bodeker G. E. , Struthers H. , Connor B. J.
Published: October 2002

Over the past two decades both the severity of Antarctic ozone depletion and the size of the Antarctic ozone hole have increased. A satellite‐based, assimilated total column ozone data set and NCEP/NCAR meteorological fields from 1979 to 2000 have been used to examine the long‐term evolution of the ozone hole and its dependence on the size of the dynamical vortex and the size of the region of low temperatures. Equivalent latitude zonal means of these data have been calculated to show more directly the expansion of the Antarctic ozone hole and its encroachment on the vortex edge. While the size of the dynamical vortex and the vortex region with temperatures below 195 K (where polar stratospheric clouds are expected to form) has changed little, the area with ozone below 220 DU (the contour defining the ozone hole) has steadily increased. Over the 20 year period, the severity of the ozone depletion within the core of the vortex has increased. This, combined with the nature of the mixing regimes within the polar vortex may explain the increase in the area of the ozone hole.
A new model of field‐aligned currents derived from high‐precision satellite magnetic field data
Authors: Papitashvili V. O. , Christiansen F. , Neubert T.
Published: October 2002

A model of field‐aligned currents is derived from high‐precision magnetic field measurements from the Ørsted and Magsat satellites, being parameterized by the interplanetary magnetic field strength and direction for summer, winter and equinox. The high‐precision data allow the model to be determined directly by a simple 2‐D curl technique combined with fitting of spherical harmonic functions. New elements of the model are: (a) the FAC patterns are determined separately for both polar regions, resolving the seasonal dependence of interhemispheric asymmetries, (b) the IMF ∼ 0, ground‐state patterns are also resolved; these elements are obtained for the first time. From the model, the total upward/downward currents have been determined for various IMF conditions. The ratio of the summer/winter currents is ∼1.35 and the equinox currents ∼1. The model allows FAC mapping for IMF |B| ≤ 12 nT, except during magnetic storms and substorms.
Are mesoscale perturbation experiments in polar waters prone to physical artefacts? Evidence from algal aggregation modelling studies
Authors: Boyd Philip W. , Jackson George A. , Waite Anya M.
Published: October 2002

The longevity (>50d) of the phytoplankton bloom following mesoscale iron‐enrichment of Southern Ocean waters (SOIREE) exceeded that for naturally occurring polar blooms (15–20d). During SOIREE, SF6‐labelled waters increased 20‐fold, and the greatest algal loss term was lateral advection. To test whether such advective losses could delay the onset of mass sedimentation, an algal aggregation model was employed. It successfully simulated temporal trends in mass sedimentation during the tropical IronEx II bloom, yet suggested no such event during SOIREE. However, when an iron‐enrichment of 100 km length‐scale (i.e. tenfold greater than for SOIREE) was mimicked, a marked increase in algal aggregate size occurred after 15d, indicative of increased export. Thus, careful interpretation of experimental results—especially for the fate of algal carbon—is essential, particularly for polar studies where the ratio of net algal growth to advective losses is low, if they are to be extrapolated to open‐ocean waters.
The rapid and extensive recovery from episodic acidification in northern Sweden due to declines in SO42− deposition
Authors: Laudon H. , Bishop K. H.
Published: October 2002

Reductions in acid deposition have led to rapid and substantial recovery from episodic acidification associated with spring snow melt in circumpolar waters including 80,000 lakes and 1,000,000 km of watercourses in northern Sweden. Our results are based on the correlation between SO42− concentration in snow and the anthropogenic component of spring flood ANC decline. An empirical model of spring flood response to acid deposition built around that correlation predicts that the 65% reduction in sulphur deposition between 1970 and 1990 has reduced the area of seriously acidified spring floods across 250,000 km2 of northern Sweden by 75%. The study suggests that much of what has been achieved so far by the large and costly emission reductions in Europe and North America the last decades lies not primarily in chronically acidified regions but rather in more marginally impacted areas where episodic acidification has been the primary chemical impact of SO42− deposition.
Olivine‐Pyroxene‐H2O system as a practical analogue for estimating the elastic properties of fluid‐bearing mantle rocks at high pressures and temperatures
Authors: Sato Hiroki , Ito Kazuhiko
Published: October 2002

By using Grüneisen theory and third‐order finite strain theory, elastic‐wave velocities in olivine‐pyroxene assemblages are accurately determined as a function of pressure and temperature. Equilibrium distributions of H2O fluid in mantle rocks have been determined at high pressure and temperature, and are used to estimate Vp and Vs in the olivine‐pyroxene‐H2O system. Importantly, velocities calculated for the peridotite‐H2O system successively reproduce the absolute Vp and Vs values measured in the laboratory for dehydrated serpentinite. Known equilibrium distributions of H2O‐CO2 fluid in peridotite‐liquid systems allow one to estimate elastic properties of fluid‐bearing mantle rocks from mineral and liquid elasticity data.
Temporal variation of multifractal properties of seismicity in the region affected by the mainshock of the October 6, 2000 Western Tottori Prefecture, Japan, earthquake (M = 7.3)
Authors: Nakaya Shinji , Hashimoto Takeshi
Published: October 2002

The temporal variation of multifractal properties in spatial distribution of seismicity in the region affected by the main shock of the Western Tottori Prefecture, Japan, earthquake of October 6, 2000 (M = 7.3) and its aftershock sequence are investigated. We use earthquake catalog data from 1985 to 2001 in order to understand the process and mechanism preceding a large, shallow earthquake. A monotonous decrease of multifractal dimension Dq with a wide range of q appeared clearly for about two years prior to this large, shallow earthquake; Dq then increased to a maximum at the time of the main shock. During the aftershock sequence, Dq oscillated between 2.0 and 0.7. The decrease and then increase of Dq with respect to the spatial distribution of seismic events indicate clustering and declustering in multifractal structure, respectively. The temporal variation of Dq reflects the accumulation and release of strain energy within the tectonic stress field.
Monsoonal characteristics revealed by intraseasonal variability of Sea Surface Temperature (SST) in the South China Sea (SCS)
Authors: Gao Rongzhen , Zhou Faxiu
Published: October 2002

Intraseasonal variability of SST in the SCS is examined. The results demonstrate that characteristics of intraseasonal SST variations in summer are remarkably different from those in winter. In summer, the spatial correlation pattern of intraseasonal SST perturbations is zonally distributed in the monsoon region. They are characterized by the northeastward propagation. In contrast, it appears to be localized in the SCS region without any propagating signal in winter. In addition, intraseasonal SST fluctuations are highly related to zonal winds and Outgoing Long‐wave Radiation (OLR) in summer. However, they are primarily associated with meridional winds in winter. It has potentially important implication that the monsoonal air‐sea interaction in summer is somewhat different from that in winter.
Hydration number and two‐phase equilibria of CH4 hydrate in the deep ocean sediments
Authors: Seo Yongwon , Lee Huen , Ryu Byong‐Jae
Published: October 2002

The aqueous solubilities of CH4 in the two‐phase (hydrate (H)‐liquid water (LW)) region, which is very close to the deep sea floor condition, were measured at various ranges of temperature and pressure. The hydration number determined via Raman spectroscopy at 10.0 MPa and 274.15 K was found to be 6.00 that is a little higher than 5.75 of the ideal one. The solubility of CH4 in liquid water largely increased with a small increase of temperature, but slightly decreased with increasing pressure in the two‐phase (H‐LW) region. This solubility behavior was experimentally confirmed to be completely different from that occurring in the three‐phase (H‐LW‐V) boundary. The present results might be valuable as the fundamental data for estimating the amount of in situ gas hydrate and understanding the unique feature of hydrate formation/ dissociation mechanism and the hydrate stability in the deep ocean sediments.
Novel high pressure magnetic measurements with application to magnetite
Authors: Gilder Stuart A. , LeGoff Maxime , Peyronneau Jean , Chervin Jean‐Claude
Published: October 2002

We report a novel system designed to measure reversible magnetic susceptibility of micron‐sized samples under high pressures in a diamond anvil cell. We find that magnetite reversible hysteresis parameters vary <15% below 0.6 to 1.0 GPa, while at higher pressures significant increases occur in (1) bulk coercivity (Hc) and (2) the ratio of saturation remanent magnetization (Mrs) to saturation magnetization (Ms). The net effect of pressure is to displace magnetite toward a truer single domain state with both higher Mrs/Ms and Hc. Our data, together with the fact that magnetite Curie temperature increases with pressure, suggest that magnetite can account for geomagnetic anomalies related to some subduction zones and potentially to meteorite impact sites on Earth, as well as magnetic signatures observed on some planetary bodies like Mars.
An examination of high latitude upper mesosphere dynamic stability using the Nippon/Norway Svalbard Meteor Radar
Authors: Hall C. M. , Aso T. , Tsutsumi M.
Published: October 2002

Using wind measurements from the recently installed Nippon/Norway Svalbard Meteor Radar, (NSMR) at 78°N, 16°E, we have derived wind shears, and, combining these with model Brunt‐Väisälä frequencies, have determined estimates of the gradient Richardson Number. These Richardson Number estimates parameterise the degree of stability of the upper mesosphere at a height of around 90 km. We find indications of dynamic instability in spring and autumn, with greater stability in summer.
Observations of layers in ozone vertical profiles from SAGE II (v 6.0) measurements
Authors: Kar J. , Trepte C. R. , Thomason L. W. , Zawodny J. M.
Published: October 2002

Layered structures in the vertical profiles of ozone mixing ratio as retrieved by the Stratospheric Aerosol and Gas Experiment (SAGE II) version 6.0 have been studied in the altitude range 10–28 km in the middle and high latitudes (30–75 N and S). 12 years of data (1985–1990, 1994–1999) have been used to build a climatology of layers with thickness of a few kilometers. The occurrence peaks near 12–13 km, then decreases sharply up to about 20 km before increasing again in the 20–28 km range. The seasonal variation indicates that layering activity maximizes during winter‐spring in both hemispheres. This is similar to earlier results on thinner structures or laminae. A significant number of layers were observed in summer at altitudes >20 km in both hemispheres primarily at high latitudes (>60 N and S).
The O+ and O++ emission lines near 834 Å in the quiet sun solar spectrum
Authors: Doschek G. A.
Published: October 2002

I present quiet Sun solar disk averaged emission line intensities (at the Earth) and the full widths at half maximum intensity (FWHM) for the O+ and O++ emission lines that fall near 834 Å. These lines are important as excitation sources for O+ and O++ emission in the Earth's upper ionosphere, plasmasphere and magnetosphere. I also discuss the variation of the ratio of O+ to O++ emission as a function of solar spatial fine structure in the quiet Sun. The spectra were obtained from the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer flown on the Solar and Heliospheric Observatory spacecraft. There are five O+ and O++ features in the solar spectrum involving nine spectral lines. The peak quiet Sun intensities (in units of 109 photons cm−2 s−1 Å−1) of these features and their approximate centroid wavelengths are: 0.717, 832.85 Å; 0.717, 833.30 Å; 1.76, 833.74 Å; 1.16, 834.45 Å; and 2.68, 835.29 Å. The average O+ and O++ FWHMs are 0.177 Å and 0.179 Å, respectively. The difference in widths is not significant.
Depth, radiocarbon, and the effectiveness of direct CO2 injection as an ocean carbon sequestration strategy
Authors: Caldeira Ken , Wickett Michael E. , Duffy Philip B.
Published: October 2002

If radiocarbon were a good predictor of the amount of time until a water parcel returns to the surface, it could be used to estimate the effectiveness of carbon sequestration by direct injection. We performed direct CO2 injection simulations in both one‐dimensional box‐diffusion and three‐dimensional ocean general circulation models. The 1‐D model results for ocean carbon retention accord with the 3‐D model results, especially in the Pacific basin and at shallower depths. In the 1‐D model, carbon retention in the ocean is directly related to both the injection depth and the Δ14C of carbon at the injection location. However, in the 3‐D model, depth, but not radiocarbon, provides a relatively good prediction of carbon retention. This suggests that the expected time for a water parcel to return to the surface is closely related to its depth and not in general to the time since last at the surface.
Inference on terrestrial genesis from molybdenum isotope systematics
Authors: Dauphas Nicolas , Marty Bernard , Reisberg Laurie
Published: October 2002

It has been suggested that a genetic relationship exists between the Earth and enstatite chondrites. The discovery of non mass dependent molybdenum isotope anomalies (Mo‐w) at a macroscopic scale raises the possibility of using this element as a tracer of genetic relationships. We have determined the molybdenum isotopic compositions of enstatite chondrites (EH and EL) and terrestrial lavas presumably derived from the deep mantle (Loihi seamount, Hawaii). The molybdenum isotopic compositions are identical, suggesting a common source reservoir. The conclusion is that although distinct, the Earth shares similarities with enstatite chondrites from a chemical and isotopic point of view because both formed in the inner regions of the solar system.
Diffuse and streamer regions of sprites
Authors: Pasko Victor P. , Stenbaek‐Nielsen Hans C.
Published: October 2002

The observed altitude stratification in large number of sprite events, exhibiting a sharp transition between the upper diffuse and lower streamer regions, is used in conjunction with a theoretical model to establish correspondence between sprite luminosity and the ambient mesospheric/lower ionospheric conductivity profile. The reported results provide new means for remote sensing of the lower ionosphere using sprite luminosity.
Application of the Preisach‐Mayergoyz space model to analyze moisture effects on the nonlinear elastic response of rock
Authors: Carmeliet J. , Van Den Abeele Koen EA.
Published: October 2002

Experimental evidence for the saturation dependence of the nonlinear behavior of Berea sandstone has been analyzed using the Preisach‐Mayergoyz space (P‐M space) model in terms of classical and non‐classical mesoscopic entities. The analysis suggests the introduction of two macroscopic solid‐fluid interaction pressures, which link the moisture influence to characteristic populations of the material composition.
Euro‐Mediterranean rainfall and ENSO—a seasonally varying relationship
Authors: Mariotti Annarita , Zeng Ning , Lau K.‐M.
Published: October 2002

Using observational datasets and atmospheric reanalyses, we show that interannual variability of rainfall in the Euro‐Mediterranean sector is significantly influenced by ENSO in a way that is seasonally varying. Spatially coherent correlation patterns are found in central and eastern Europe during winter and spring, and in western Europe and the Mediterranean region during autumn and spring. A composite analysis of ENSO events indicates that during an El Nino western Mediterranean rainfall has a 10% increase (decrease) in the autumn preceeding (spring after) the mature phase of an event, corresponding to a rainy season arriving (retreating) earlier compared to the climatology. The atmospheric reanalyses show that an anomalous atmospheric circulation and moisture transport extending from the Atlantic Ocean into the Euro‐Mediterranean region accompanies the observed rainfall anomalies. Multidecadal variations characterize the ENSO Euro‐Mediterranean relationship during the 20th century.
Conjugate thrust faulting associated with the 1999 Chi‐Chi, Taiwan, earthquake sequence
Authors: Chen Kou‐Cheng , Huang Bor‐Shouh , Wang Jeen‐Hwa , Yen Horng‐Yuan
Published: October 2002

The geometrical structure of the responsible faults of the 20 September 1999 Chi‐Chi, Taiwan, earthquake (ML = 7.3, Mw = 7.6) and its aftershocks can be clearly depicted by well‐located hypocenters and focal mechanisms of large aftershocks. The mainshock and two large aftershocks with ML = 6.8 were characterized by thrust faulting along a N‐S striking fault plane dipping to the east. The underground structure of the Chelungpu fault, which is probably merging with the decollement beneath the Western Foothills, can be clearly associated with the seismicity pattern and the focal mechanisms of the three largest events. A group of deeper aftershocks including two moderate events (ML = 6.3 and 6.0, respectively) were located to the southeast of the mainshock along a fault plane dipping steeply to the west down to a depth of about 30 km. Our results suggest that the spatial pattern of the aftershocks in the southern part of the source area can be interpreted by a conjugate‐fault system. This conjugate‐fault system is comprised of the gently east‐dipping Chelungpu fault and a steeply west‐dipping deeper fault zone.
An empirical model for estimating the concentration of carbonyl sulfide in surface seawater from satellite measurements
Authors: Xu Xiaobin , Bingemer Heinz G. , Schmidt Ulrich
Published: October 2002

Carbonyl sulfide (COS) was measured in surface seawater during two Atlantic cruises. The daily mean concentration of COS is correlated to the daily means of global radiation, CH3SH concentration, hydrolysis lifetime of COS in seawater, and the logarithm of chlorophyll a concentration. An empirical model for the COS concentration has been developed on the basis of correlations between the COS concentration and these parameters. The model appears to be a promising tool for estimating COS concentrations in surface seawater from satellite observations.
A geomagnetic triggering of Chandler wobble phase jumps?
Authors: Bellanger Eric , Gibert Dominique , Le Mouël Jean‐Louis
Published: October 2002

Taking advantage of a longer series of polar motion data, we investigate again the existence of phase jumps in the Chandler wobble [Gibert et al., 1998]. We point out one more phase jump in 1990, and find again that geomagnetic jerks are followed by phase jumps in the Chandler wobble within at most 3.5 years.
Monthly means of reflected solar flux from POLDER (ADEOS‐1) and comparison with ERBE, ScaRaB and CERES
Authors: Viollier Michel , Standfuss Carsten , Parol Frédéric
Published: October 2002

A diurnal cycle model is applied to POLDER instantaneous albedo determinations (Nov. 1996–June 1997) in order to compute daily and monthly means of the reflected flux at the top of the atmosphere. These results are compared to the ERBE, ScaRaB and CERES records. The quantitative comparison of the tropical means shows that the POLDER reflected flux density is on average lower by about 7 Wm−2 compared to ERBE (1985–1989) and ScaRaB‐1 (1994–1995) and by 2.7 Wm−2 compared to ScaRaB‐2 (Nov. 1998–March 1999) and CERES/Terra (2000–). The maps of POLDER albedo reveal strong deviations in the tropical Pacific. They correspond to the beginning of the 1997–1998 ENSO event.
HCHO in Antarctic snow: Preservation in ice cores and air‐snow exchange
Authors: Hutterli Manuel A. , Bales Roger C. , McConnell Joseph R. , Stewart Richard W.
Published: October 2002

Formaldehyde (HCHO) measurements in snow and shallow firn at three Antarctic sites gave concentrations around 6 ppbw in surface snow and 1 ppbw and lower below 1–2 m depth. The variable concentration patterns in shallow snow and firn result from temperature‐dependent uptake and release of HCHO in response to annual temperature cycles. Deeper concentrations are constant with depth, and apparently reflect average atmospheric concentrations. This implies that after accounting for differences in temperature and accumulation, changes in ice‐core HCHO concentrations with depth should linearly reflect changes in atmospheric HCHO over time. Modeling of observed HCHO profiles in the snow implies that degassing of HCHO from surface snow likely contributes a significant fraction of the HCHO found in the boundary layer in spring and summer at all three sites. Based on modeling of air‐snow exchange and atmospheric photochemistry, summer HCHO levels are estimated to be on the order of 100–200 pptv.