Abstracts
Recent Fluvial Sediment Budgets in Glacial and Periglacial Environments,
NW Spitsbergen
Aktuelle fluviale Sedimentbilanzen in glazial und periglazial geprägten Einzugsgebieten, NW Spitzbergen
by
DIETRICH BARSCH, MARTIN GUDE, ROLAND MÄUSBACHER, GERD SCHUKRAFT & ACHIM SCHULTE
Heidelberg/Jena
with 6 figueres and 2 tables
Summary
Fluvial dynamics and sediment transport in Arctic rivers are discussed in the context of glacial and periglacial catchment characteristics. Analysis of the sediment transport dynamics and yields reveals a distinct difference between glacial and periglacial environments. Three rivers, which drain small catchments with different proportions of glacier area are investigated within the "Geoscientific Spitsbergen-Expeditions" SPE 1990-92. The solid sediment yield of the glaciofluvial system is by one order of magnitude higher than that of the periglacial-fluvial system. This is caused by glacial erosion, which provides the main share of the suspended load. In the third catchment, which is partly glacier-covered, sediment transport dynamics and total yields are similar to those of the periglacial-fluvial system. This leads to the assumption that the effect of glacial erosion upon the stream load seems to depend more upon the flow properties and thermal characteristics of the glacier than upon the size of the glacier-covered area. In the periglacial environment, high energy events such as floods and slush streams are the dominant processes of sediment transport. Some extremely large slush streams (slush torrents) display very high sediment transport rates, but their recurrence interval is at least several decades.
Zusammenfassung
Die fluviale Dynamik und der Sedimenttransport
in polaren Vorflutern wird im Kontext von glazialen und periglazialen Einzugsgebietseigenschaften
diskutiert. Die Analyse der Sedimentdynamik und der gesamten Fracht zeigt
eine deutliche Differenzierung zwischen glazial und periglazial geprägten
Einzugsgebieten. Drei Flüsse, die kleine Einzugsgebiete mit unterschiedlicher
Gletscherbedeckung entwässern, wurden im Rahmen der "Geowissenschaftlichen
Spitzbergen-Expeditionen" SPE 90-92 untersucht. Der Feststoffaustrag im
glazifluvialen System liegt um eine Dimension über dem im periglazifluvialen
System. Das wird durch die glaziale Erosion verursacht, die die größte
Menge an Suspensionsmaterial zur Verfügung stellt. Im dritten Einzugsgebiet,
das zum Teil gletscherbedeckt ist, sind die Dynamik des Sedimenttransportes
und die absoluten Beträge ähnlich denen im periglazifluvialen
System. Daher wird angenommen, daß der Einfluß der Gletscher
eher von den Fließeigenschaften und den thermischen Gegebenheiten
am Gletscherbett (kalt/temperiert) als von dem Grad der Gletscherbedeckung
abhängt. In periglazialen Gebieten werden die wesentlichen Sedimentmengen
durch Hochenergieereignisse (Hochwässer und Sulzströme) transportiert.
Einzelne extrem große Sulzströme (Sulzmuren) weisen enorme Transportraten
auf, ihre Wiederkehrintervalle betragen allerdings mindestens mehrere Dekaden.
Untersuchung hydrologischer und hydrochemischer Prozesse in hocharktischen Permafrost-Einzugsgebieten mit Hilfe natürlicher Tracer
M. Gude, R. Mäusbacher, G. Schukraft, A. Schulte
Geographisches Institut, Labor für Geomorphologie und Geoökologie, Universität Heidelberg, Im Neuenheimer Feld 348, 69120 Heidelberg
Kurzfassung
Die saisonale Entwicklung der wasserhaushaltlichen Komponenten in kleinen hocharktischen Permafrosteinzugsgebieten auf Spitzbergen wird mit Hilfe geogener und niederschlagsbürtiger Tracer beschrieben. Dabei steht die Identifikation der Schmelzwasserquellen, die den aktuellen Abfluß im Vorfluter bilden, im Vordergrund. Schnee-, Gletscher- und Permafrostschmelze sind durch bestimmte Indikatoren im Vorfluterwasser erkennbar, da Niederschlag und bodenchemische Prozesse dem abfließenden Wasser charakteristische Ionenzusammensetzungen und Ionenkonzentrationen aufprägen. Der saisonale Verlauf während des hydrologisch aktiven Sommers ist gekennzeichnet von einzelnen Abflußereignissen, die jeweils wesentliche Veränderungen in der hydrologischen Entwicklung des Einzugsgebietes kennzeichnen. Die kurzen Ereignisse trennen Phasen mit geringeren Abflüssen, während derer kaum Veränderungen stattfinden. Die Scheitelabflüsse sind deutlich geprägt von Schnee- und Gletscherschmelze. Trotz des damit verbundenen Verdünnungseffektes treten die höchsten Frachten gelöster Stoffe während der Ereignisse auf.
Summary
The seasonality of the water budget in
small high arctic permafrost catchments on Spitsbergen is described by
means of the analysis of natural tracers. The main objective is to identify
the meltwater origin that contributes to the actual discharge in the creek.
Snowmelt, glacier melt, and permafrost melt can be identified by certain
indicators, because precipitation and chemical processes in the soil mark
the meltwater with characteristic ion compositions and concentrations.
Single floods occur during the hydrologically active summer season. They
are accomponied by distinctive changes in the hydrology of the catchment.
Seperated by these floods are phases with lower discharge and few changes.
Snowmelt and glacier melt contribute most to the floods. Although this
results in a dilution of discharge, the floods possess the highest transport
rates of solutes.
Snowmelt and Slush Torrents - Preliminary Report from a Field Campaign in Kärkevagge, Swedish Lappland
Martin Gude1 and Dieter Scherer2
1 Laboratory for Geomorphology
and Geoecology,Department of Geography, University of Heidelberg, Germany
2 MCR Lab, Department
of Geography, University of Basel, Switzerland
Abstract
In May and June 1995, the snowmelt period
in general and the release conditions of slush torrents in particular were
studied within a joint Swiss-German project during a field campaign in
Kärkevagge, Swedish Lappland. Measurements and observations comprised
all energy balance components and meteorological conditions in the course
of the snowmelt period, as well as intra- and subnival meltwater flows
and the formation of a saturation zone within the snow cover during the
initial period of snowmelt-runoff. In addition, release and movement of
a high magnitude - low frequency slush torrent was documented on video
and photographs. The results verify that the initiation of slush streams
is confined to meltwater accumulation areas in drainage basins. Moreover,
it can be demonstrated that both variants of slush streams are released
by a hydraulic pressure gradient that is evolving from an inclined water
table within the saturated snow cover. This release mechanism allows the
initiation of major events without any external triggering. Neither permafrost
nor extreme meteorological conditions are prerequisite to slush torrents.
Nährstoffdynamik und Algenwachstum in einem anthropogen belasteten Badesee in SW-Deutschland - eine sanierungs-/restaurierungsorientierte Untersuchung
Nutrient dynamics and algal growth in an intensively used lake in SW-Germany - an investigation focussed on restoration purposes
G. Schukraft , M. Gude, D. Harreus, D. Kryzer
(Geographisches Institut, Universität Heidelberg)
Kurzfassung
In Stillgewässern der gemäßigten Breiten unterliegen die Nährstoffkonzentrationen und damit auch die Primärproduktion starken saisonalen Schwankungen. Dafür sind temperatur- und strahlungsklimatische Ursachen, aber auch zeitlich variable Einträge verantwortlich. In dicht besiedelten Gebieten treten in der Regel Einträge aus der intensiven Nutzung der Gewässer und des Umlandes hinzu, die an vielen mitteleuropäischen Seen zu einer Überdüngung mit Nährstoffen und zu einem eklatanten Algenwachstum geführt haben. Für die Sanierung/Restaurierung solcher Seen ist die Erfassung aller wesentlichen Nährstoffflüsse, insbesondere von Phosphat, von entscheidender Bedeutung. In einem Baggersee in Neuhofen wurde für eine Saison der Nährstoffhaushalt bilanziert und die Quellen für die Einträge analysiert sowie das Algenwachstum verfolgt. Es hat sich gezeigt, daß die größten Einträge von Phosphat durch das zeitweise anaerobe Sediment sowie durch Badegäste und andere Freizeitnutzer verursacht werden. Die Quellen Grundwasser und Niederschlag sind weniger bedeutend. Für die Sanierung/Restaurierung des Sees im Sinne einer Verminderung des Algenwachstums bedeutet dies, daß die Phosphate der Sohlsedimente dauerhaft fixiert werden, ein dauerhafter Entzug von Nährstoffen stattfinden und die Freizeitnutzung reglementiert werden muß. Alle Maßnahmen sollten kontinuierlich kontrolliert werden.
Abstract
In lakes of the temperate
latitude the nutrient concentration and the primary production alternate
significantly during the seasons. This is due to temperature and radiation
climate reasons but also due to temporal changes in input. In dense populated
areas an additional input is caused by the intensive usage of lakes and
their surroundings. In many lakes in central Europe, this leads to an eutrophication
and to a striking algal growth. For a restoration of these lakes an analysis
of all important nutrient fluxes, especially of phosphate, is essential.
In a lake close to Neuhofen (Ludwigshafen, SW-Germany) the input sources
and internal fluxes of nutrients, especially of phosphate, as well as the
algal growth have been monitored in the year 1993. The total input of phosphate
was 70-100 kg. About 35 kg result from remobilisation from the bottom sediments
that temporarily possess low oxygen concentrations. The input induced by
recreational usage is responsible for c. 20-50 kg, more than 10 kg of it
caused by bathers. Groundwater, surface water, and precipitation as sources
of nutrients are of minor importance (6 kg each). It is evident that a
restoration of the lake must focus on the recreational usage and not on
improvements of waste water plants or agricultural methods in the surrounding.
For a restoration of the lake aimed at the reduction of the algal growth
it is necessary (1) to fix the phosphate in the lake sediments durably,
(2) to initiate a continuous removal of nutrients, and (3) to limit the
recreational use of the lake. All these measures have to be controlled
continuously.
Snowmelt and Water Movement in Saturated Snow Layers
of High Latitude Areas
M. Gude1 and D. Scherer2
1Dept. of Geography, University
of Jena, Löbdergraben 32, D-07743 Jena, Germany
2MCR Lab, University of Basel,
Spalenring 145, CH-4055 Basel, Switzerland
Abstract
At the onset of summer snowmelt
period in high latitudes drainage channels are still choked with snow and
consequently, meltwater movement on slopes and in headwater basin channels
is restricted to intra-nival flow. Meltwater flow is connected with water
saturation of the snowpack and coincident improvement of the hydraulic
conductivity, which is important for the initiation of slushflows and for
discharge generation. Investigations on meltwater production, movement,
and accumulation were undertaken in several research field campaigns on
Spitsbergen and in Swedish Lapland. It is stressed, that the intensity
of lateral meltwater movement is highly dependent on slope gradient, but
also on the concentration of flow and the erosion of intra-nival pipes.
The flow velocities measured in the basins were at least one order of magnitude
higher than percolation velocities in snow. The development of an intra-nival
drainage system can be documented by the tracer and water pressure measurements.
Snow metamorphism - a
review of the state of knowledge
Martin Gude
Abstract
The processes of snow metamorphism that
are important for remote sensing purposes are discussed. Metamorphism concerns
different spatial scales, ranging from microstructure and in situ snowpack
modification to resulting relocation processes. Snow crystal metamorphism
changes the granular structure of the snowpack. In combination with additional
snow precipitation and meltwater percolation this causes the formation
of a snowpack consisting of numerous layers with different physical characteristics.
But snow metamorphism and meltwater movement are also responsible for relocation
processes, especially avalanches and slush streams (slush avalanches).
Snowmelt and Slushflows: Hydrological and Hazard Implications
Martin Gude1, Dieter Scherer2
1Department of Geography,
University of Jena, Löbdergraben 32, D-07743 Jena, Germany
2MCR Lab, University of Basel,
Spalenring 145, 4055 Basel, Switzerland
Abstract
In many high latitude areas slushflows occur frequently during the snowmelt period, but information on the initiation mechanism is rare. Field observations and measurements of slushflows in NW-Spitsbergen and in N-Sweden demonstrate the role of meltwater accumulation and the hydraulic pressure gradient in the release process. Snow metamorphism is revealed to be of minor importance in the observed events. The monitoring of water pressure development in a saturated snow cover demonstrates that preferred release areas are within low gradient valley sections, where meltwater inflow is higher than outflow.
Slushflows consist of mudflowlike flowage
of water-saturated snow along stream courses. They represent transitional
processes between fluvial floods and avalanches. On the other hand, they
possess unique characteristics concerning release and movement. The comparative
evaluation of definition items for fluvial floods, slushflows and avalanches
offers basic data suitable for a risk assessment.
Atmospheric and Hydrological Boundary Conditions for Slushflow Initiation due to Snowmelt
Dieter Scherer1, Martin Gude2, Markus Gempeler 1 and Eberhard Parlow 1
1MCR Lab, University
of Basel, Spalenring 145, 4055 Basel, Switzerland
2Dept. of Geography,
University of Jena, Löbdergraben 32, D-07740 Jena, Germany
Abstract
Slushflows of a large variety of magnitudes were observed during three field campaigns to Liefdefjorden, NW-Spitsbergen, and one campaign to Kärkevagge, Northern Sweden. In the latter campaign, the release and movement of a slush torrent was documented on video and photographs. Meteorological and snow-hydrological measurements carried out during these campaigns were analysed with respect to slushflow initiation due to snowmelt.
Since slushflows are quite common in polar and subpolar drainage basins (although they are not restricted to these regions), specific atmospheric and hydrological boundary conditions must be fulfilled for slushflow initiation due to snowmelt. Radiative fluxes, air temperatures and wind velocities are the most important atmospheric variables, while snow depth, depth of the water-saturated layer, hydraulic conductivity and snow structure are the primary snow variables of interest.
It is shown that slushflows can be released
due to energy input in the snow cover by net radiation and sensible heat
within the ordinary range of the high-latitudinal snowmelt period. Slush
torrent initiation is intensified by a superposition of both energy fluxes.
Infiltration losses were not significant, even when permafrost is not present.
Crucial for slushflow initiation due to snowmelt is the timing of energy
input and meltwater flow through the snowpack.
Zur Genese von Blockhalden
Martin Gude und Roland Mäusbacher
Mit 1 Tabelle und 3 Abbildungen
Zusammenfassung
Blockhalden sind definiert durch eine steile
Oberflächenneigung und ein vorrangig grobklastisches Substrat. Die
Genese dieser Halden in den Mittelgebirgen Europas ist allerdings nur teilweise
geklärt. Zunächst handelt es sich oft nicht um reine Sturzhalden,
sondern um polygenetische Sedimentkörper, an deren Entstehung neben
gravitativen auch Rutsch- und Fließprozesse beteiligt sind. Die Bildung
der Blockhalden vollzog sich überwiegend unter periglazialen Bedingungen,
die die physikalische Verwitterung insbesondere durch Frostsprengung fördern.
Die Auswaschung des feinklastischen Verwitterungsmaterials ist dabei Voraussetzung
für die Entstehung des offenen Porenraumes und erfolgte wahrscheinlich
syngenetisch. Unter holozänen feuchtgemäßigten Klimabedingungen
scheint eine ausgeprägte Weiterbildung der Blockhalden unterbunden,
da die physikalische Gesteinszersetzung zu wenig intensiv ist. Über
die aktuellen Stoffumsätze im Bereich der Blockhalden liegen bislang
kaum Erkenntnisse vor.
Abstract
Block scree is characterised by a steep
gradient and a substratum with predominantly coarse debris. Admittedly,
knowledge about the evolution of this block scree in European Uplands is
restricted. While block scree originally evolves from rock fall, creep
or flow processes frequently cause a further displacement of the scree
material. The development of coarse talus debris is prominent under periglacial
conditions with intensive physical weathering due to frost action. Synchronously,
the fine grained sediments are removed by subrosion to allow for an open
interstitial structure. Recent climatic conditions seem to prevent a significant
modification of block scree, since intensity of frost action is limited.
Knowledge about present day processes, e.g. suspended and solute sediment
transport, is limited.
Atmospheric triggering and geomorphic significance
of fluvial events in high-latitude regions
MARTIN GUDE1 & DIETER SCHERER2
1Dept. of Geography,
University of Jena, Löbdergraben 32, D-07743 Jena, Germany
2MCR Lab, Dept. of Geography, University
of Basel, Spalenring 145, CH-4055 Basel, Switzerland
Abstract
Strong annual variability and seasonal snow covers determine hydrological processes and related sediment displacements in high latitude regions. The most significant period for runoff and fluvial sediment transport is the snowmelt period in early summer. Atmospheric events during this time initiate a broad range of fluvial events, comprising runoff events with daily or seasonal frequency but also minor sluhflows with annual frequency, and high-magnitude slushflows (slush torrents) which are characterized by frequencies of several years to decades. To assess magnitude and frequency of these atmospheric, hydrologic, and geomorphic processes, a discussion on general aspects of magnitude-frequency relations is preceded. Based on this discussion, atmospheric triggering and resulting hydrologic and geomorphic events in periglacial environments are analyzed with special focus on drainage basins in NW-Spitsbergen and in N-Sweden. The examples display the moderate variability in magnitude of hydrologic events, but a high variability in the geomorphic consequences. Generally, geomorphic impact is characteristic for certain fluvial event types, but the connection to atmospheric triggering is more complex, and our today’s knowledge of these interrelations is still limited.
Zusammenfassung
Hydrologische Prozesse und die von ihnen
verursachten Sedimenttransporte zeichnen sich in den Höheren Breiten
durch eine hohe jährliche Variabilität aus und sind in starkem
Maße durch saisonale Schneedecken beeinflußt. Die wichtigste
Phase des Abflusses und der Sedimenttransporte ist die Schneeschmelzperiode
im Frühsommer. In dieser Zeit auftretende atmosphärische Prozesse
initiieren eine Vielzahl fluvialer Ereignisse, die von täglichen und
saisonalen Abflussereignissen, bis hin zu Sulzströmen (slushflows)
reichen. Deren Frequenzen reichen von jährlichen Ereignissen bei kleineren
Sulzströmen bis zu Sulzstromereignissen mit grossen Magnituden (Sulzmuren),
die nur mit niedrigen Freqenzen auftreten und zu Jährlichkeiten von
mehreren Jahren bis Jahrzehnten führen. Eine einleitende Diskussion
zu Magnitude-Frequenz-Relationen atmosphärischer, fluvialer und geomorphologischer
Ereignisse beleuchtet allgemeine Aspekte dieser Thematik. Basierend auf
diesen Überlegungen werden dann die atmosphärischen Auslöseprozesse
sowie die daraus resultierenden fluvialen und geomorphologischen Ereignisse
in periglazialen Räumen anhand von Beispielen aus NW-Spitzbergen und
N-Schweden analysiert. Diese zeigen, daß die Magnituden fluvialer
Ereignisse nur eine beschränkte Variabilität aufweisen, während
die daraus resultierenden geomorphologischen Konsequenzen eine hohe Variabilität
besitzen. Letztere sind im wesentlichen vom jeweiligen fluvialen Ereignistyp
abhängig, aber die Zusammenhänge zu den atmosphärischen
Auslöseprozessen ist komplex, und unser heutigen Wissen darüber
ist immer noch begrenzt.
Assessment of variability in fluvial sediment transfers in Kärkevagge (N-Sweden) during the last 50 years
Martin Gude1, Christer Jonasson2,
Susanne Dietrich1, and Dieter Scherer3
1 Department of Geography, University of Jena, Germany
2 Abisko Scientific Research Station, Abisko, Sweden
3 MCR Lab, University of Basel, Switzerland
Abstract:
The Kärkevagge (Abisko area, Northern Sweden) represents a focus research catchment concerning geomorphic processes and sediment budgets since 50 years. Geomorphic process studies covering different investigations within this period offer comparative data sets concerning climate variability implications on sediment transfer rates. While monitoring of sediment transfers is discontinuous concerning study periods and methods a more complete chronology of high magnitude events with significant sediment displacement is available. In continuation of these studies, field investigations carried out in 1995 and 1998 as part of the MOSAIC project (Modeling Of Snowmelt And Its Consequences) are concentrating on snowmelt-induced slushflow initiation and transports of suspended and soluted sediments in several small headwater catchments during snowmelt period. Main purpose of the investigations is to characterise different catchment sections in terms of their hydrologic and sedimentologic contribution to the total catchment fluvial and sediment budget, and to evaluate their specific sensitivity related to changes in atmospheric boundary conditions.
By means of these data sets the temporal variability of fluvial sediment transfers can be assessed over different time scales. Sediment cores collected from Lake Låktajaure in 1983, 1987, 1996 and 1999 will provide additional information on variations in the sedimentation rate, and extreme events can be detected. The paper focuses on a description of different sections in the fluvial sediment transfer system in Kärkevagge and the dominating processes in these sections. In comparing preliminary results from recent field investigations with data from former measurements and sediment analyses, the significance of rainfall- and snowmelt-triggered events for sediment transfers is evaluated.
Introduction
Since geomorphological investigations were
started in Kärkevagge by Rapp (1960), the valley today represents
an important reference area concerning quantitative geomorphic process
studies (cf. e.g. Thorn 1992, French 1996). Rapp's investigations where
mainly focused on calculation of catchment denudation and geomorphic work
predominantly based on slope processes. However, the fluvial environment
was also subject of his investigations. One of his objectives was to stress
the importance of events in the sediment displacement system, especially
in relation to landform change. This approach, intensively discussed within
the framework of process geomorphology in recent years, leads to the evaluation
of the significance of formative events for landscape development (cf.
e.g. Brunsden 1996).
Naturschutzfachliche Bewertung von Blockhalden mit air-conditioning Effekt
Conservation management of air conditioned
scree slope ecosystems.
Roland Molenda1 & Martin Gude2
1Institut für Spezielle Zoologie und Evolutionsbiologie, Friedrich-Schiller-Universität Jena
2Institut für Geographie, Friedrich-Schiller-Universität Jena
Abstract
In extra-alpine Central European areas, boulder scree slopes represent a relict of former climatic periods. These geoecosystems are not documented in detail until recently, especially concerning their special microclimatic air-conditioning effects. The specific ecological and landscape conditions characterise the habitats as terrestrial island biotops and "archives" of faunistic elements of former climate periods. A tool for identification of such habitats is presented using indicator organism and geoecological parameters. A European conservation management program is proposed for conservation of the specific gene ressources and the biodiversity which is found in this exceptional habitat.
Key words: conservation management, island
biotops, scree slope, zoological indicator