A projection of future sea level

Evidence is reviewed that suggests faster sea-level rise when climate gets warmer. Four processes appear as dominating on a time scale of decades to centuries: melting of mountain glaciers and small ice caps, changes in the mass balance of the large polar ice sheets (Greenland, Antarctica), possible ice-flow instabilities (in particular on the West Antarctic Ice Sheet), and thermal expansion of ocean water.For a given temperature scenario, an attempt is made to estimate the different contributions. The calculation yields a figure of 9.5 cm of sea-level rise since 1850 AD, which is within the uncertainty range of estimates of the observed rise.A further 33 cm rise is found as most likely for the year 2050, but the uncertainty is very large ( = 32 cm). The contribution from melting of land ice is of the same order of magnitude as thermal expansion. The mass-balance effects of the major ice sheets tend to cancel to some extent (increasing accumulation on Antarctica, increasing ablation on Greenland). For the year 2100 a value of 66 cm above the present-day stand is found ( = 57 cm). The estimates of the standard deviation include uncertainty in the temperature scenario, as presented elsewhere in this volume.     

Behaviour of abandoned room and pillar mines in Illinois

Summary Little comprehensive information has been reported on the behaviour of room-and-pillar mines. The objective of this paper is to present case data on mine failures in the Illinois basin for use in practice. Presented are results of an ongoing study and details on the site characteristics of cases where sags have developed on the surface. Site data are reported to show the geologic, mining, and sag conditions that existed. Sags mainly develop from pillar, floor, or pillar-floor failure. The character of the sags depends upon the type of mine failure as well as the overburden response.Preliminary results show that the statistical no-risk tributary pressure decreases over 300% as the mine age increases from about 2 to 100 years at a long-term value of approximately 300 psi (2070 kPa). As more information is collected and more analysis is done, the allowable tributary pressure can be determined for different site conditions.A plot is also reported that depicts the relationship of the maximum subsidence to site conditions. It was found that the modified subsidence factor was heavily dependent upon the overburden rock thickness.     

Blockage of regional seismic waves by the Teisseyre-Tornquist zone

During the Group of Scientific Experts Technical Test (GSETT, second experiment, 22 April-2 June 1991), several hundred seismic events were located in Europe. Associating these events with the detecting stations-altogether 28 European stations including seven arrays participated in the GSETT-2 experiment-clearly shows that the Teisseyre-Tornquist Zone (TTZ) influences the propagation of regional seismic phases. Large explosions in the Bay of Gdańsk, for example, were observed by the well-established Scandinavian arrays'NORSAR (Δ 830km) and ARCESS (Δ 1650km), but not by the Polish station KSP (Δ 470km) nor by the new highly sensitive GERESS array (Δ 750km), both situated south-west of the TTZ. For events in central Europe with comparable magnitudes, we observe a similar increase of the detection threshold at stations located north-east of the TTZ in Scandinavia. to explain these observations, the wave propagation of P_n and P_g perpendicular to the TTZ was modelled for a profile from the Estonian/Russian border region to GERESS with Gaussian-beam seismograms. Published crustal and uppermost mantle models for Poland and for Europe were used as a starting point for developing a model of the TTZ. the observations cannot be explained only by a graben-like crustal structure with a jump in Moho depth from 30km to 50km. to defocus the seismic energy, the TTZ as a structural anomaly between eastern and western Europe must reach down into the upper mantle to a depth of at least about 200 km. the proposed model has such a deep-reaching root of the TTZ.     

World Data Center-A for Paleoclimatology at the NOAA Paleoclimatology Program,Boulder, CO

Conclusion The World Data Center-A for Paleoclimatology, located in the NOAA/NGDC Paleoclimatology Program, is committed to providing the scientific community with easy access to all paleoenvironmental data. Efforts to make archived data readily available include international coordination of data acquisition, management, and distribution, sponsoring workshops and data cooperatives to facilitate the compilation of important data sets, development of a browse and visualization software package (PaleoVu), and dispersal of archived data on magnetic media or over ANONYMOUS FTP/INTERNET. The program publishes a semi-annual newsletter that highlights latest developments and accomplishments in the area of paleoenvironmental data for global change research. Contributions to the newsletter are welcome from researchers describing their efforts to coordinate the free flow of paleoclimate data throughout the international scientific community.For information on the program or to be added to the mailing list contact Mrs Mildred England (phone: 303-497-6227; Fax: 303 497-6513; e-mail: MKE@mail.ngdc.noaa.gov), NOAA National Geophysical Data Center, Paleoclimatology Program/World Data Center-A for Paleoclimatology, 325 Broadway, E/GC Boulder, CO 80303 USA     

Hydrophobic and electrostatic parameters in bacterial adhesion

Recently it has been shown that the initial stages of bacterial adhesion to a model-surface of sulphated polystyrene can best be described using hydrophobic and electrostatic parameters. In the present study it is tested whether these parameters can generally be applied to predict bacterial adhesion by using (i) glass, as a model for hydrophilic and natural surfaces of silicates and oxides, (ii) polystyrene coated with proteins, as a model for a surface coated with an organic layer, and (iii) river Rhine sediment, as an example of a natural surface. Adhesion to glass was dominated by electrostatic interaction, whereas adhesion to polystyrene coated with various types of proteins depended on the surface characteristics of the bacteria and the type of protein. By relating Van der Waals interactions to hydrophobicity of the interacting species, the adhesion of bacteria to the various surfaces including the river Rhine sediments could be interpreted in terms of the DLVO-theory. It is therefore concluded that the conceptual principles of the DLVO-theory (interplay of Van der Waals and electrostatic interactions) are suitable to describe, at least qualitatively, the initial processes of bacterial adhesion to a wide range of surfaces.     

Small-scale heterogeneity and soil-moisture variability in the unsaturated zone

The distribution of water within a soil profile can only be partly explained by the time distribution and rate of surface-water input. Observed differences in soil moisture within the unsaturated zone result from the interaction of surface-water inputs with spatially inhomogeneous soil characteristics. Water which initially percolates vertically is differentially impeded as a result of subtle textural changes in the soil, and is then preferentially retained in such zones of transition, causing large differences in soil-water content to occur. The scale of this vertical variability is of tenths of metres, whilst lateral variability of soil moisture reflects textural changes over a few metres. The observed influence of small-scale heterogeneity on soil-water content suggests that the conventional assumptions of isotropicity and homogeneity of the textural and hydraulic properties of porous media used in drainage basin and hillslope hydrological models need scrutiny, even for single stratigraphic units.     

Thermal regime at the Upper Stillwater dam site, Uinta mountains, Utah: Implications for terrain, microclimate and structural corrections in heat flow studies

A detailed study of the subsurface thermal regime at the Upper Stillwater dam site, Uinta Mountains, northeast Utah, has been made. Temperature measurements were made in 36 drillholes located within a 1 km² area and ranging in depth from 20 to 97 m. Holes less than about 40 m deep were used only to obtain information about spatial variations in mean annual surface temperature. Several holes in or near talus slopes at the sides of the canyons have temperature minima approaching 0°C between 10 and 20 m indicating the presence of year-round ice at the base of the talus. Another set of holes show transient thermal effects of surface warming resulting from clearing of a construction site 3.5 years prior to our measurements. Most of the remaining holes show conductive behavior and have gradients ranging from 13° to 17°C km⁻¹. Measurements made on 44 core samples yield a thermal conductivity of 5.6 (std. dev. 0.35) W m⁻¹ K⁻¹ for the Precambrian quartzite present. Surface heat flow estimates for these holes range from 70 to 100 mW m⁻². However, the local disturbance of the thermal field by topography and microclimate is considerable. A finite difference method used to model these effects yielded a locally corrected Upper Stillwater heat flow of about 75 mW m⁻². A final correction to account for the effects of refraction of heat from the low conductivity sedimentary rocks in the Uinta Basin into the high conductivity quartzite at the dam site, produced a regionally corrected Upper Stillwater heat flow between 60 and 65 mW m⁻². This value is consistent with the observed heat flow of 60 mW m⁻² in the Green River Basin to the north and the Uinta Basin to the south.     

The stratospheric quasi-biennial oscillation observed in the semidiurnal ground pressure data

Ground pressure observations made at Macao (22^○N, 113^○E) from 1953 to 1991 are analyzed and compared with the stratospheric quasi-biennial oscillation (QBO) data obtained during the same interval. The periods of the two phenomena and their time evolution are found to be close to each other. Furthermore, the time series of the stratospheric winds and the S2(p) QBO signature are highly correlated, thus confirming earlier analysis. On this basis, pressure measurements obtained at Batavia (now Djakarta: 6^○S, 107^○E) from 1870 to 1944 are used to trace back the QBO phenomenon before the advent of systematic stratospheric balloon measurements. The inferred period, which varies between 25 and 32 months, suggests that the QBO has been present in the atmosphere at least since 1870.