Helmut Saurer

An improved topographic database for King George Island: compilation, application and outlook

A new topographic database for King George Island, one of the most visited areas in Antarctica, is presented. Data from differential GPS surveys, gained during the summers 1997/98 and 1999/2000, were combined with up to date coastlines from a SPOT satellite image mosaic, and topographic information from maps as well as from the Antarctic Digital Database. A digital terrain model (DTM) was generated using ARC/INFO GIS. From contour lines derived from the DTM and the satellite image mosaic a satellite image map was assembled. Extensive information on data accuracy, the database as well as on the criteria applied to select place names is given in the multilingual map. A lack of accurate topographic information in the eastern part of the island was identified. It was concluded that additional topographic surveying or radar interferometry should be conducted to improve the data quality in this area. In three case studies, the potential applications of the improved topographic database are demonstrated. The first two examples comprise the verification of glacier velocities and the study of glacier retreat from the various input data-sets as well as the use of the DTM for climatological modelling. The last case study focuses on the use of the new digital database as a basic GIS (Geographic Information System) layer for environmental monitoring and management on King George Island.

Variations of glacier frontal positions on the northern Antarctic Peninsula

Abstract Changes in the ice fronts on the Antarctic Peninsula north of 70˚ S are currently being investigated through a comprehensive analysis of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Landsat Thematic Mapper (TM) data as part of the international research initiative ‘Global land Ice Measurements from Space’ (GLIMS). Regional case studies are presented that cover a variety of glacial systems distributed over the northern Antarctic Peninsula and provide data on glacier front variations during the period 1986–2002. The results confirm a general trend of regional glacier front recession, but a range of different glacier variations are observed throughout the study area. Areas of predominant retreat are located in the northeastern and southwestern sectors, while stationary ice fronts characterize glacial behaviour on the northwestern coast of the peninsula. In addition, a significant increase in glacier recession is identified on James Ross Island, where retreat rates doubled during the period 1988–2001 compared to the previous investigation period, 1975–88. These observations are interpreted as being direct consequences of the rapidly changing climate in the region, which differentially affects the local accumulation and ablation patterns of the glacial systems.

Geometry and thermal regime of the King George Island ice cap, Antarctica, from GPR and GPS

Abstract King George Island is the largest of the South Shetland Islands, close to the tip of the Antarctic Peninsula. The annual mean temperature on the island has increased by 1°C during the past three decades, and the ice cap that covers the majority of the island is sensitive to climatic change. We present data from two field campaigns (1997 and 2007): 700 km of global positioning system (GPS) and ground-penetrating radar (GPR) profiles were collected on Arctowski Icefield and on the adjacent central part. The data were analysed to determine the surface and bed topography and the thermal regime of the ice. Average ice thickness is 250 m and maximum thickness is 420 m. The GPR profiles show isochrones throughout the ice cap which depict the uparching of Raymond bumps beneath or close to the ice divides. A water table from percolation of meltwater in the snowpack shows the firn-ice boundary at ∼ 3 5 m depth. The firn layer may be temperate due to the release of latent heat. In the area below 400ma.s.l., backscatter by water inclusions is abundant for ice depths below the water table. We interpret this as evidence for temperate ice. Scatter decreases significantly above 400 m. Ice temperatures below the water table in this part of the ice cap are subject to further field and modelling investigations.

Development of radar glacier zones on the King George Island ice cap, Antarctica, during austral summer 1996/97 as observed in ERS-2 SAR data

Abstract Based on a time series of European remote-sensing satellite (ERS-2) synthetic-aperture radar (SAR) images from 1996/97, ablation on the King George Island (Antarctica) ice cap is documented. Snowmelt patterns were monitored by mapping the dynamic evolution of radar glacier zones and their boundaries. On the ice cap, all major radar glacier zones except the dry-snow radar zone were identified during the observed period While winter was characterized by a frozen-percolation radar zone, the ablation season was characterized by wet-snow and bare-ice radar zones. A striking bright backscatter signature indicated the presence of a highly reflective zone in the lower parts of the wet-snow zone. It was attributed to a phase 2 melt (P2) radar zone, which is characterized by a metamorphosed and roughened surface of a melting snow cover. Due to the absence of simultaneously acquired ground-truth information, concurrent meteorological data proved to be essential for interpreting the SAR images. Although the maximum elevation of the ice cap does not exceed 680 ma.s.L, ablation patterns obviously reflect altitudinal control. Melt onset up to 530 m a.s.l. was initiated by an advection event at the end of October 1996. A wet snowpack on the entire ice cap corresponds with a prolonged period of high temperatures in January 1997. However, the highest parts of the ice cap were affected by occasional melt-freeze cycles. The transient snowline at the end of February was determined as being at 250 m a i l. This late-summer snowline was regarded as an approximation of the equilibrium-line altitude for the 1996/97 ablation season.

A time series of SAR data for monitoring changes in boundaries of glacier zones on the Antarctic Peninsula

Abstract Drastic changes have been detected in glacial systems of the Antarctic Peninsula in the last few decades and are well documented in numerous scientific publications. However, the spatial and temporal distribution of glacier changes on the Antarctic Peninsula remains largely restricted to ice fronts. To expand the current monitoring of a few glaciers, unevenly distributed along the peninsula, to a representative set, we developed a method to simplify the detection of boundaries between glacier zones using satellite SAR data. The evolution of glacier zones is greatly influenced by local and regional climatic and meteorological settings. Their variations in response to changes in energy or mass balance are considered as good indicators of climatic changes. In this paper, we describe the results of knowledge-based image analysis algorithms on test areas located at Trinity Peninsula and near Marguerite Bay. In general, the two analyzed areas show different patterns of glacier zone development. The bare-ice zone occurs mainly on glaciers located on the eastern side of Trinity Peninsula. Its upper boundary shows a good correlation with the mean summer air temperature. Finally, the position of the dry-snow line shows different spatial patterns of change in both study areas.

Boden – eine endliche Ressource

Boden uberziehen nahezu flachendeckend die Landoberflache und stellen die wichtigste Energieumsatzflache der Erde dar. Fur den Begriff Boden gibt es mehrere Definitionen, meist in Abhangigkeit seiner Funktion, die er fur die unterschiedlichen Arbeitsrichtungen besitzt. Aus geographischer Sicht ist der Boden der extrem dunne, oberste belebte Bereich der Erdoberflache von der Streu bis zum unverwitterten Ausgangsmaterial. Grundsatzlich besteht ein Boden aus etwa 50% Poren, 45% mineralischer Substanz sowie etwa 5% organischer Substanz.

THE COMPILATION OF A DTM AND A NEW SATELLITE IMAGE MAP FOR KING GEORGE ISLAND, ANTARCTICA

An improved topographic database for King George Island, one of the most frequently visited regions in Antarctica, is presented. A first step consisted in combining data from differential GPS surveys gained during the austral summers 1997–1998 and 1999–2000, with the current coastline from a SPOT satellite image mosaic, topographic information from existing maps and from the Antarctic Digital Database. From this data sets, a digital terrain model (DTM) was generated using Arc/Info GIS. In a second step, a satellite image map at the scale 1:100 000 was assembled from contour lines derived from the DTM and the satellite mosaic. A lack of accurate topographic information in the eastern part of the island was identified. Additional topographic surveying or SAR interferometry should be used to improve the data quality in that area. The GIS integrated database will be indispensable for glaciological and climatological studies and administrative and scientific purposes. In future, the application of GIS techniques will be mandatory for environmental impact studies and environmental monitoring as well as for management plans on King George Island.

Rund ums Wasser – Hydrogeographie

Wasser steht uns immer zur Verfugung! In diesem Luxus leben wir Mitteleuropaer und die Menschen in anderen Regionen gemasigter Klimate. Trotzdem streben wir an, mit der Ressource Trinkwasser sehr sparsam umzugehen, so verbrauchen wir in Deutschland pro Tag und Person 127 Liter Trinkwasser und erreichen damit gemeinsam mit Belgien den geringsten Verbrauch in der EU (www.umweltlexikon-online.de: Trinkwasserverbrauch, Februar 2009). In einigen Regionen (z.B. Brandenburg) wurde die Grenze von 100 Litern pro Person und Tag schon deutlich unterschritten.

Kreisläufe – als Betrachtungsdimension in der Geographie

Viele geographische Sachverhalte und Prozesse unterliegen einem zeitlichen Wandel – und andern sich dabei in Intensitat und Auspragung. Wahrend einige Prozesse einen definierten Anfangs- und Endpunkt besitzen, scheinen andere eher regelhaften und zyklischen Veranderungen zu unterliegen – beispielsweise das Auftreten von Sonnenflecken. Anfang der 1960er Jahre begann man im Rahmen der Geosystemlehre, mehr oder weniger in sich geschlossene Kreislaufe zu identifizieren, die sogenannten Stoffkreislaufe.

Auf Kohle und Stahl gebaut – die Bildung von Lagerstätten und Bodenschätzen

Viele Stadte in Deutschland verdanken ihre Existenz und ihre historische Bedeutung dem Vorkommen von Lagerstatten bzw. Bodenschatzen. Ohne Silberbergbau hatten sich Goslar und Freiburg i.Br. anders entwickelt, ohne Salz waren die zahlreichen Hall-Orte nicht entstanden und ohne Kohle und Eisen gabe es das Ruhrgebiet und das Saargebiet in ihrer heutigen Form nicht.