Alpine Topography Research Articles

Influences of vertical transport and scavenging on aerosol particle surface area and radon decay product concentrations at the Jungfraujoch (3454 m above sea level)

Concentrations of the aerosol particle surface area (SA) and aerosol‐attached radon decay products 214Pb and 212Pb have been measured by means of an aerosol and a radon epiphaniometer at the Jungfraujoch research station (JFJ; 3454 m above sea level, Switzerland). These parameters exhibit a pronounced seasonal cycle with minimum values in winter and maximum values in summer. In summer, pronounced diurnal variations with a maximum at 1800 LST are often present. Highest concentrations and most pronounced diurnal variations occur during anticyclonic weather conditions in summer. Thermally driven vertical transport over alpine topography is responsible for this observation. During this synoptic condition, concentrations vary greatly with the 500 hPa wind direction, exhibiting low concentrations for NW‐N winds and high concentrations for weak or S‐SW winds. Lead‐214 and SA are highly correlated during anticyclonic conditions, indicating transport equivalence of the gaseous 214Pb precursor, 222Rn, and of aerosol particles. When cyclonic lifting is the dominant vertical transport, wet scavenging of aerosol particles can explain the weak correlation of 214Pb and SA. This conclusion is corroborated by the 214Pb/SA ratio, being twice as high during cyclonic than during anticyclonic conditions. Lead‐212 is a tracer for the influence of surface contact on a local scale due to its short lifetime of 15.35 hours. The analysis of this parameter suggests that high‐alpine surfaces play an important role in thermally driven transport to the JFJ.

Cenozoic climatic change in Antarctica recorded by volcanic activity and landscape evolution

A long-lasting Cenozoic record (∼50 m.y.) of alkaline igneous rocks characterizes northern Victoria Land, Antarctica. Landscape analysis allows distinction between older volcanic and intrusive rocks with well-developed alpine topography sculptured by wet-based glaciers, and younger volcanic cones lacking these features. Many K-Ar and Rb-Sr dates testify that the erosion that formed the alpine landscape ceased between ca. 8.2 and 7.5 Ma. Since ca. 8 Ma, morphological evolution has been driven by cold-based glaciers; warm-based glaciers were no longer active. That this change affected a 300-km-long coastal area suggests a persistent cause of global significance. Glacier dynamics control landscape shaping as a function of ice thickness and temperature, which are driven by climatic conditions. In this view, a significant climatic change occurred in northern Victoria Land between 8.2 and 7.5 Ma. The perfectly preserved serrated alpine ridges, with their delicate spires, testify that no warm-based ice sheets overrode the region after 7.5 Ma and that polar conditions held sway in the Pliocene and Pleistocene Epochs.

Karrat 97: reconnaissance mineral exploration in central West Greenland

The Karrat 97 project aims at the acquisition of geochemical data from drainage samples and information on mineralisation within a 10 000 km2 area, which stretches from Uummannaq northwards to Prøven (i.e. from 70°30′ to 72°30′ N; Fig. 1). The project area comprises a major Palaeoproterozoic supracrustal unit, the Karrat Group, from which the project takes its name, and which hosts the abandoned Black Angel lead-zinc mine. It is a joint project between the Geological Survey of Denmark and Greenland (GEUS) and the Bureau of Minerals and Petroleum (BMP), Government of Greenland, and wholly funded by the latter. The goal of the project is to win back the interest of the mining industry to the area. The eastern part of the project area is difficult of access due to alpine topography with peaks up to 2300 m, abundant glaciers, and steep-sided, often ice-filled fjords. A somewhat more gentle topography prevails in the western parts of the area. The whole area is underlain by permafrost. Field work was carried out during seven weeks in July–August 1997 by a team of four geologists and four local prospectors. Job-training of the prospectors was an integral purpose of the project, and the manning of the teams was periodically changed so that all four prospectors were introduced to the different topographical and geological terrains in the area as well as to the methods of operation. A chartered 68 foot, 77 tons vessel – M/S Nukik – served as mobile base with accommodation and meals on board; a MD 500 E helicopter with crew chartered through Grønlandsfly A/S participated for one month. The work was carried out from five anchorages, with the helicopter stationed on the adjacent coast. The weather was relatively unstable in the field period, but only five days of work were lost due to bad weather. The field work comprised regional-scale systematic drainage sampling, and detailed mineral exploration at selected sites. The sampling of stream sediment and stream water supplements the geochemical mapping programme of Greenland undertaken jointly by GEUS and BMP (Steenfelt 1993, 1994), the aim of which is to provide systematic, quality controlled geochemical data. The data are used together with geological and geophysical information in the evaluation of the potential for economic mineral resources. Samples were collected by two teams, transported by helicopter or small boats. All ice-free, near-coastal localities were sampled by the boat team, whereas all other localities were sampled by the helicopter team. The results of this work have been reported on by Steenfelt et al. (1998). The detailed mineral exploration was follow-up work on previously outlined indications and anomalies. It was carried out by two teams on daily trips by rubber dinghy or helicopter, or by foot traverses from field camps. This part of the project has been reported on by Thomassen & Lind (1998).

Mesoscale transport of atmospheric trace constituents across the central Alps: Transalp tracer experiments

This paper summarizes the goals, the experimental setup and the main phenomenological findings of the TRACT sub-project TRANSALP. TRANSALP consisted of three tracer field experiments carried out in the Ticino area of southern Switzerland in the years 1989, 1990 and 1991. The experiments were designed to study the transport and diffusion of trace gases over the very complex Alpine topography. The results and knowledge gained from each experiment were used for the design of the next experiment and to improve the logistics. All the data collected were stored in a well organized data bank, which can be made available to the scientific community interested in evaluating mesoscale atmospheric transport and dispersion models for complex terrain. All these experiments contributed to the understanding of the flow and dispersion characteristics in very complex terrain. Specifically, under particular meteorological conditions, these experiments gave evidence of the occurrence of a transalpine exchange of air constituents, both in north-to-south and south-to-north directions.

Modelling the snow cover in a complex Alpine topography

The areal distribution of snow cover and the variability of its characteristics were investigated at various locations in the eastern Swiss Alps. An areal energy-balance (AEB) model was used to calculate the predominant energy fluxes at the snow atmosphere interface based on automatic meteorological measurements as input. By coupling the AEB model with a one-dimensional, physically based mass and energy-balance model of the snowpack, temperature distribution as well as energy and mass flow-in the snowpack were simulated at three different locations in the topographically complex environment at Weissfluhjoch-Davos, 2540 m a.s.l. On a horizontal test site, calculated energy fluxes and characteristics of the snow cover are in good agreement with their measured counterparts. On inclined slopes, the temperature distribution is well represented by the coupled models, but the snow depth and density are not yet satisfactorily simulated. This discrepancy may be attributed to inhomogeneous accumulation and deposition of snow on the weather and lee sides.

Pollutant transport over complex terrain: Flux and budget calculations for the pollumet field campaign

Especially over complex terrain, transport processes dominate the local pollutant concentrations observed. The data gathered during the POLLUMET measuring campaign in 1993 allow a quantitative analysis of the pollutant fluxes and the pollutant budgets. The data include airborne measurements by NCAR's King Air, radio soundings, radar wind profiles, and data from meteorological ground stations. The regions of interest were the rather densely populated Swiss Plateau, which is embedded between the Alps and the Jura Mountains, and a box south of the Alps covering the south Ticino region and parts of northern Italy. An interpolation scheme was developed to reconstruct the wind field from all available measurements. From the wind field and the reconstruction of the concentration field the fluxes into and out of a box with fixed boundaries are calculated. The pollutant budgets are obtained from the sum of the fluxes and considering a mean vertical velocity. To assess the uncertainties introduced through the interpolation of the measurements, an extensive sensitivity analysis is included. The Swiss Plateau exports ozone and nitrogen oxides. The export rates can be interpreted as an ozone accumulation or fraction of ‘homemade pollution’ between 3 and 10% and require a net production rate of 1–2 ppb h −1. Accumulation of nitrogen oxides amounts to 20–60%. The box south of the Alps imports polluted air from northern Italy. Thus, oxidized nitrogen is not exported but a net production of ozone still occurs at a rate of 1–2 ppb h −1. The interpolated flow and concentration fields are decomposed into the mean over a box-boundary and the deviation from that mean. This allows isolation of the contribution of local circulations and large-scale turbulence to the total flux. It is shown how the local thermotopographic circulations increasingly dominate the transport as typical Alpine topography is approached. Even over the Swiss Plateau, approximately 20 km away from Alpine topography, coherent structures with a scale of 2–20 km contribute to the transport, which occurs mainly with the mean wind, however.

P10 A data management tool for tracking clinical endpoint reviews

A south-vergent fold-thrust belt of Miocene-Recent age accompanies the south slope of the Lombardian Alps and is partly buried beneath Plio-Pleistocene Po Valley basin fill. The belt is probably detached along a trans-crustal thrust, named Main South Alpine Thrust (MSAT), with an estimated dip slip of 70–100 km. Transport on this thrust piggybacks the Adamello pluton of Late Eocene age, pre-Adamello folds, and Oligocene-Miocene Insubric strike-slip structures, by ramping up through 12–15 km of Austro-Alpine (Adria) crust and through 8–10 km of Triassic to Eocene sediments. Folds in the Front Ranges are ascribed to MSAT ramping, not to pre-Adamello compression. The MSAT soles upward in a blind thrust beneath 3–4 km of Oligocene-Pliocene foredeep fill. Initial regional failure along the MSAT implies substantial and pre-existing topographic relief near the Insubric line. An average of 25% wedge thickening during MSAT transport is consistent with the requirement of Coulomb critical taper. Progression of the south-Alpine detachment from the MSAT to the base of the foreland sediments has added a thickness of 6–12 km in footwall imbrications to the base and the toe of the thrust wedge. This addition in wedge volume is consistent with wedge dynamics only if a mid-Miocene or younger spike of excess Alpine topography is admitted.

Thrusting and wedge growth, Southern Alps of Lombardia (Italy)

A south-vergent fold-thrust belt of Miocene-Recent age accompanies the south slope of the Lombardian Alps and is partly buried beneath Plio-Pleistocene Po Valley basin fill. The belt is probably detached along a trans-crustal thrust, named Main South Alpine Thrust (MSAT), with an estimated dip slip of 70–100 km. Transport on this thrust piggybacks the Adamello pluton of Late Eocene age, pre-Adamello folds, and Oligocene-Miocene Insubric strike-slip structures, by ramping up through 12–15 km of Austro-Alpine (Adria) crust and through 8–10 km of Triassic to Eocene sediments. Folds in the Front Ranges are ascribed to MSAT ramping, not to pre-Adamello compression. The MSAT soles upward in a blind thrust beneath 3–4 km of Oligocene-Pliocene foredeep fill. Initial regional failure along the MSAT implies substantial and pre-existing topographic relief near the Insubric line. An average of 25% wedge thickening during MSAT transport is consistent with the requirement of Coulomb critical taper. Progression of the south-Alpine detachment from the MSAT to the base of the foreland sediments has added a thickness of 6–12 km in footwall imbrications to the base and the toe of the thrust wedge. This addition in wedge volume is consistent with wedge dynamics only if a mid-Miocene or younger spike of excess Alpine topography is admitted.

Scheelite occurrences in granulite facies metamorphosed supracrustals, West Greenland

In 1982 the first traces of scheelite in heavy mineral concentrates from stream sediments were found in the Godthåbsfjord area. Subsequently a quite extensive scheelite mineralisation has been found in the Malene supracrustal rocks (Appel, 1986a). During 1985 a regional stream-sediment sampling programme was carried out covering an area of about 30 000 km2 within the Godthåb area. As aresult of this programme scheelite was found in most of the streams draining Malene supracrustal rocks (Appel, 1986b). One of the areas which appeared to be interesting is the Sermilik area c. 75 km south of Nuuk. In this area several streams with high contents of scheelite were found. The area has been subject to granulite facies metamorphism and a major granitic intrusion emplaced. Both events might have caused extensive mobilisation and subsequent upgrading of stratabound scheelite mineralisation. The supracrustals are situated at the shore of a smal! fjord, where ice rarely causes problems for shipping. The alpine topography, with near vertical cliffs, poses an obstacle for prospecting. The present paper describes only field observations. Laboratory work is confined to X-ray identification of scheelite in some of the heavy mineral concentrates and in a few rock samples.

Notes on the glacial geology of eastern Milne Land, Scoresby Sund, East Greenland

During the summer of 1969 field work was begun with the aim of establishing a general chronology of Quaternary events in the Scoresby Sund region. This summer the work was concentrated on the eastern part of Milne Land (fig. 1). The region under consideration is shown in fig. 9; it comprises a coastal zone of low rounded mountains (400-600 m) composed of crystalline rocks, and a central zone of high mountains (1500 m) of alpine topography where Tertiary basalts rest on a basement of crystalline rocks. South-east of a line from Mudderbugt to Charcot Havn the bedrock is Mesozoic sandstone. Milne Land is bordered to the east and south by the comparatively shallow (400-600 m deep) waters of Scoresby Sund and Hall Bredning; on all other sides this large island is bordered by over-deepened fjords (800-900 m deep - see hydrographic chart in Thorson, 1934). In the central part of Milne Land an ice cap - Puderne - is found.