Sediment generation and soil mound denudation in areas of high-density tree throw along a river valley in the Jura Mountains,Switzerland

A preliminary field-based investigation was undertaken in a small(<10 km²)river valley located in the mountainous Jura region of northwest Switzerland.The aims of the work were to assess sediment generation and annual sediment transport rates by tree throw on forested hillslopes,and to document surface hydrology characteristics on four fresh soil mounds associated with recent tree throws over a 24-day monitoring period.For the soil mounds,average sediment recovery ranged from 7.7-28.2 g(dry weight),equivalent to a suspended sediment concentration of 145.2-327.8 g L^-1,and runoff coefficients ranged from 1.0%-4.2%.Based on a soil bulk density value of 1,044 kg m^-3,upslope runoff generation areas were denuded by an average 0.14 mm by the end of the 24-day monitoring period,representing an erosion rate equivalent to 2.1 mm yr^-1.A ca.50 cm high soil mound could therefore feasibly persist for around 200-250 years.For tree throw work,the dimensions of 215 individual tree throws were measured and their locations mapped in 12 separate locations along the river valley representing a cumulative area equivalent to 5.3 ha(av.density,43 per ha).Tree throws generated a total of 20.1 m³ of fine-sediment(<2 mm diameter),or the equivalent of 3.8×10^-4 m³ m^-2.The process of tree throw was originally attributed to two extreme weather events that occurred in west and central Europe in late December 1999.Taking the 18-year period since both storms,this represents an annual sediment transport rate of 2.7×10^-5 m³ m^-1 yr^-1.Exploring the relationship with wind on fall direction,65.5%of tree throws(143)generally fell in a downslope direction irrespective of hillslope aspect on which they were located.This infers that individual storms may not have been responsible for the majority of tree throws,but instead,could be associated with root failure.Given the high density of tree throws and their relative maturity(average age 41 years),we hypothesise that once trees attain a certain age in this river valley,their physiognomy(i.e.height,mass and centre of gravity)compromises their ability to remain securely anchored.We tentatively attribute this possibility to the presence of bedrock close to the surface,and to the shallow soil profile overlaying steep hillslopes.     

Expanding the Cenozoic paleoceanographic record in the Central Arctic Ocean: IODP Expedition 302 Synthesis

The Arctic Coring Expedition (ACEX) proved to be one of the most transformational missions in almost 40 year of scientific ocean drilling. ACEX recovered the first Cenozoic sedimentary sequence from the Arctic Ocean and extended earlier piston core records from ≈1.5 Ma back to ≈56 Ma. The results have had a major impact in paleoceanography even though the recovered sediments represents only 29% of Cenozoic time. The missing time intervals were primarily the result of two unexpected hiatuses. This important Cenozoic paleoceanographic record was reconstructed from a total of 339 m sediments. The wide range of analyses conducted on the recovered material, along with studies that integrated regional tectonics and geophysical data, produced surprising results including high Arctic Ocean surface water temperatures and a hydrologically active climate during the Paleocene Eocene Thermal Maximum (PETM), the occurrence of a fresher water Arctic in the Eocene, ice-rafted debris as old as middle Eocene, a middle Eocene environment rife with organic carbon, and ventilation of the Arctic Ocean to the North Atlantic through the Fram Strait near the early-middle Miocene boundary. Taken together, these results have transformed our view of the Cenozoic Arctic Ocean and its role in the Earth climate system.     

Hydrogeological pattern of groundwater flow of landslides in Cretaceous claystones based on long-term groundwater monitoring and hydrologging measurement

Long-term groundwater monitoring has been carried in the model locality of the landslide area at Třebenice, situated in the northern part of the Czech Republic in Cretaceous claystones to marlstones. Primarily, long-term fluctuation of the groundwater and piezometric levels has been monitored. Monitoring of groundwater flow was carried out in selected wells also by the photometry logging method using a dilution technique of a marked liquid. On the basis of these results, the pattern of the groundwater flow through the landslide area was determined in lithologically homogeneous Cretaceous claystones to marlstones. Interpretation of monitoring results indicated that water flows preferentially through the zone of near-surface loosening of the claystone rock massif, in general parallel to the slope inclination between 8 and 10-m depth below ground level. This zone exhibits a higher permeability given by 1–2 orders of hydraulic conductivity compared with overlying strata and underlying rock in which this zone is closed. This verified pattern of groundwater flow has a significant effect on the stability of the sliding slope and it is one of the main factors affecting the evolution of landslides on the slopes formed by these rocks.     

Note on Coriolis-Stokes force and energy

In this study, we consider the origin of the Coriolis-Stokes (CS) force in the wave-averaged momentum and energy equations and make a short analysis of possible energy input to the ocean circulation (i.e., Eulerian mean velocity) from the CS force. Essentially, we find that the CS force appears naturally when considering vertically integrated quantities and that the CS force will not provide any energy input into the system for this case. However, by including the “Hasselmann force”, we show some inconsistencies regarding the vertical structure of the CS force in the Eulerian framework and find that there is a distinct vertical structure of the energy input and that the net input strongly depends on whether the wave zone is included in the analysis or not. We therefore question the introduction of the “Hasselmann force” into the system of equations, as the CS force appears naturally in the vertically integrated equations or when Lagrangian vertical coordinates are used.     

Energetics of potential heterotrophic metabolisms in the marine hydrothermal system of Vulcano Island, Italy

Values of overall Gibbs free energy of 144 organic oxidation (respiration) and disproportionation (fermentation) reactions are calculated at the temperatures and chemical compositions that exist in nine submarine vents, sediment seeps and geothermal wells in the hydrothermal system of Vulcano Island, Italy. The organic compounds considered here include four carboxylic acids (formic, acetic, propanoic and lactic), two C₅ aldoses (arabinose and xylose), three C₆ aldoses (galactose, glucose and mannose), and 15 protein-forming amino acids (Ala, Arg, Asp, Glu, Gly, His, Ile, Leu, Lys, Met, Phe, Ser, Thr, Tyr, and Val). Oxidation of these compounds is coupled to five redox pairs: O₂/H₂O, , S⁰/H₂S, and Fe₃O₄/Fe²⁺. Energy yields from potential respiration reactions range from 6 to 118 kJ/mol of electrons transferred and show systematic behavior with respect to the terminal electron acceptor. Overall, respiration with O₂ yields the most energy (98–118 kJ/mol e⁻), followed by reactions with (53– 86 kJ/mol e⁻), magnetite (29–91 kJ/mol e⁻), S⁰ (11–33 kJ/mol e⁻) and (6–34 kJ/mol e⁻). Energy yields show little correlation with organic compound family, but are correlated with fluid pH. Variability in energy yields across the nine sites is greatest for Fe(III) reduction and is primarily influenced by pH and the activity of Fe²⁺. In addition to the potential respiration reactions, the energetics of 24 potential fermentation reactions are also calculated. As expected, fermentation reactions generally yield much less energy than respiration. Normalized to the number of moles of carbon transferred, fermentation yields−8 to 71 kJ/mol C, compared with 16 to 531 kJ/mol C for respiration reactions. All respiration and fermentation reactions, except for methionine (Met) fermentation, are exergonic under the in situ hydrothermal conditions and represent a plethora of potential metabolisms for Vulcano’s diverse thermophilic heterotrophs.     

Spatial Disparities in the Expansion of the Chinese Ethnoburb of Los Angeles

Suburban Chinatowns are intriguing subjects for study and comparison. These ethnic suburbs, or ethnoburbs, have emerged to coexist or compete with the older downtown Chinatowns traditionally found in American central cities. Their growth since the 1960s challenges many traditional assumptions regarding the spatial and cultural assimilation of immigrants in U.S. society, namely that ethnicity would decline with the geographic and socioeconomic mobility of immigrants from the inner city into the suburbs. We examined recent growth trends in the Chinese ethnoburb of the San Gabriel Valley region of Greater Los Angeles, through analysis and mapping of U.S. Census data, and discovered ethnic persistence rather than spatial and cultural assimilation. We also discovered the ethnoburb is differentiated between a lower-class core and two middle-to-upper class fringe districts. Though there is some linguistic assimilation on the northwest fringe, the majority of the ethnoburban population continues to speak Chinese. Linguistic isolation is not a barrier to achieving a higher socioeconomic class position in the Chinese ethnoburb of Los Angeles. An earlier version of this paper was presented at the American Sociological Association Annual Meeting, San Francisco, California, August 2004.     

The contribution to IHY from the COST296 Action MIERS: Mitigation of Ionospheric Effects on Radio Systems

The objective of the COST296 Action MIERS (Mitigation of Ionospheric Effects on Radio Systems) is to develop an increased knowledge of the effects imposed by the ionosphere on practical radio systems, and for the development and implementation of techniques to mitigate the deleterious effects of the ionosphere on such systems (http://www.cost296.rl.ac.uk). The COST296 Community contributes to the international efforts of IHY with scientific and outreach activities as well. After the realization of a web site hosted by Istituto Nazionale di Geofisica e Vulcanologia (INGV), developed also to promote the ionospheric physics to the open public, the COST296 Community supported an initiative addressed to the pupils of the primary school of several European Countries: the realization of a school-calendar dedicated to the Sun and to the Sun-Earth connections.     

Climate-change effects on extreme precipitation in central Europe: uncertainties of scenarios based on regional climate models

Observations as well as most climate model simulations are generally in accord with the hypothesis that the hydrologic cycle should intensify and become highly volatile with the greenhouse-gas-induced climate change, although uncertainties of these projections as well as the spatial and seasonal variability of the changes are much larger than for temperature extremes. In this study, we examine scenarios of changes in extreme precipitation events in 24 future climate runs of ten regional climate models, focusing on a specific area of the Czech Republic (central Europe) where complex orography and an interaction of other factors governing the occurrence of heavy precipitation events result in patterns that cannot be captured by global models. The peaks-over-threshold analysis with increasing threshold censoring is applied to estimate multi-year return levels of daily rainfall amounts. Uncertainties in scenarios of changes for the late 21st century related to the inter-model and within-ensemble variability and the use of the SRES-A2 and SRES-B2 greenhouse gas emission scenarios are evaluated. The results show that heavy precipitation events are likely to increase in severity in winter and (with less agreement among models) also in summer. The inter-model and intra-model variability and related uncertainties in the pattern and magnitude of the change is large, but the scenarios tend to agree with precipitation trends recently observed in the area, which may strengthen their credibility. In most scenario runs, the projected change in extreme precipitation in summer is of the opposite sign than a change in mean seasonal totals, the latter pointing towards generally drier conditions in summer. A combination of enhanced heavy precipitation amounts and reduced water infiltration capabilities of a dry soil may severely increase peak river discharges and flood-related risks in this region.     

A support for the existence of paleolakes and paleorivers buried under Saharan sand by means of “gravitational signal” from EIGEN 6C4

The goal of this study is to demonstrate that and how the recent gravitational and topographic data support the findings made by geologists and others as for the existence of the paleolakes and paleoriver systems, now buried under the sands of Sahara. It is always important and useful to have such an independent analysis supporting certain results, and this paper is such a case. We make use of the gravity disturbances (or anomalies), the Marussi tensor of the second derivatives of the disturbing geopotential, the gravitational invariants and their certain ratio, the strike angle and the virtual deformations. The geopotential is represented by the global combined (from satellite and terrestrial data) high-resolution gravity field model EIGEN 6C4 (till degree and order 2160 in spherical harmonic expansion). The topography is derived from the ASTER GDEM and ETOPO 1 models (both are used). With all these data, we confirm the existence of huge paleolakes or paleoriver systems under the Saharan sands known or anticipated in an independent way by geologists for the lakes MegaChad, Fazzan and Chotts; for Tamanrasset river valley; and Kufrah Basin, presumptive previous flow of the Nile River. Moreover, we suggest a part of the Grand Egyptian Sand Sea as another “candidate” for a paleolake and hence for a follow-up survey.