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The North-GRIP ice core provides continuous records of sea salt and mineral dust aerosols from the last glacial period. A large number of soluble ions were analysed by ion chromatography and have opened up for new possibilities looking into details in the relationship between ion composition and climate conditions. Changes in ion compositions seem to be related to changes in particle size distributions as an effect of fractionation during long-range atmospheric transport.Analysis of ion-compositions in the North-GRIP ice core suggests that long-range atmospheric transport patterns remained nearly unchanged during the Dansgaard/Oeschger events and were constant through most of the last glacial period. However in sections of the early part of the last glacial period the analysis shows a prominently different pattern of ion composition. These differences are associated with differences in particle size distributions and indicate major differences in circulation patterns during the early part of the last glacial period.

Radio-echo sounding (RES) is an important tool in glaciology, it allows to determine ice thickness as well as the internal structure of ice sheets, ice shelves, and glaciers. Usually ground based RES is used for shallow ice bodies whereas airborne RES is used for pre-site surveys for deep ice core drill sites or to map the ice thickness of large areas. Another advantage of RES is that the same material properties which cause reflections within the ice can be measured at an ice core using dielectrical profiling (DEP). Therefore RES measurements can be directly linked to ice cores. This also allows direct comparison of two ice cores connected by a continuous RES profile and to transfer paleoclimatic information derived from an ice core at a single location onto an extended area.In Dronning Maud Land (DML) at at 0º and 75º S, 2850 m a.s.l. at deep ice core is currently drilled at Kohnen Station as part of European Project for Ice Coring in Antarctica (EPICA). The drill site is located in an area with relatively high accumulation of . approximately 62 kg m-2 a-1 in the Atlantic sector of Antarctica at an ice divide originating at Dome Fujji, 39.7º E and 77.3º S, 3810 m a.s.l.. This yields to a high temporal resolution of the ice core. The ice thickness of 2750 m is sufficient for ice core covering more than a fill glacial cycle (110 ka). At the starting point of the ice divide at Dome Fuji, 3810 m a.s.l.,, another deep ice core drill site is located. Due to the low accumulation at that location of 21 kg m-2 a-1, the obtained 2503 m long ice core covers a time span of approximately 330 ka.We will present RES profiles measured by the Alfred Wegener Institute (AWI) between 1999-2003 which allow a direct comparison of the age depth scales of both deep ice core drill sites by tracing isochrones along the intersecting profiles along the ice divide. As well as maps of different internal horizons and derived properties.

Extensive aeromagnetic surveys in the eastern Weddell Sea, the Lazarev- and Riiser-Larsen Sea carried out during the last six years by the Alfred-Wegener-Institute are the basis of a well constrained model for the early break-up of Gondwanaland.Despite intensive geophysical and geological research that has been conducted in the last two decades in the Weddell Sea and adjacent areas, timing and geometry of the initial stages of the Mesozoic break-up between Africa, Antarctica and South America is still a matter of controversy debate. The new aeromagnetic database, comprising 90000 km of closely spaced (~10 km) flight lines, resulted in a detailed magnetic anomaly grid for this region. For the western part of the grid where clear coast parallel seafloor spreading anomalies exist, synthetic anomaly sequences could be calculated. This, together with another model for the Riiser-Larsen-Sea led to a new model for the early development of this region.It shows, that the first ocean floor off Dronning Maud Land has been created in late Jurassic times (M14N) by a rift, the Weddell Rift, propagating from the south western Weddell Sea to the east along the east coast of East-Antarctica. Some 10 - 15 Ma earlier the first seafloor in the Riiser-Larsen Sea has been created by an almost coast parallel spreading centre. The diverging spreading directions and velocities between the eastern Weddell Sea and the Riiser-Larsen-Sea put West-Gondwana, comprising South America and Africa, under constant tension since the initial phase of rifting and finally led to the opening of the South Atlantic Ocean at chron M9N.Starting with this age model for the eastern Weddell Sea the new aeromagnetic compilation was put together with published data from the USAC (U.S.-Argentina-Chile) Project, the National Geophysical Data Center (NGDC, Boulder,Colorado) and Russian aeromagnetic data (Golynsky et al. 1998) for an integrated interpretation and validation of the new and existing seafloor spreading an

Interpretation of deep ice cores for paleoclimatic studies requires detailed knowledge of the glacial surrounding of the drilling location.Ice penetrating radar is the only means that allows detailed mapping of the internal structure of the ice body over its whole depth, providing the basis for reconstruction of ice dynamic history.Unfortunately, physical-chemical interpretation of radar data is ambiguous, as several reflection mechanismsmight contribute to the received signal.This lack of information can partly be overcome by numerical forward modeling of radar data utilising dielectric profiling (DEP) data of ice cores.Based on the complex-valued DEP data from the EPICA deep ice core in Dronning Maud Land (EDML), Antarctica,currently spanning 1500 m and approximately 50 ka of climatic history, we model a synthetic radar trace.Validation of the modeled trace is performed by comparison with surveyed airborne radar data retrieved nearthe drill site.The origin of corresponding prominent reflections is investigated by sensitivity studies with altered DEP data.Emphasis is put on the interaction between ice core properties and thepropagating magnetic wave, but the results can also be directly applied to the new radar profile connectingthe EDML and Dome Fuji drilling locations, making it possible to extrapolate ice core properties along continuous radar reflections along the profile.In addition to the presentation of results we also discuss problems and shortcomings of the combination of the different measuring and modeling methods.

The investigation of glaciers and ice sheets by means of ice penetrating radar has become one of the most commonly used geophysical techniques in glaciology.Although many different applications utilise internal reflection horizons, assuming that an individual reflector is isochronous, open questions concerningthe different reflection mechanisms remain.We demonstrate successful simulation of ice penetrating radar traces in polar ice by numerical finite-difference time-domain forward modeling.Based on a combined analyses of ice core records, radar surveys, and numerical sensitivity studies, we are able to provide better insights into the origin ofelectromagnetic reflections.By means of high resolution dielectric profiling (DEP) the physical properties of the upper 100 m of an ice core from Dronning Maud Land, Antarctica, aredetermined.As the considered medium is an ice-air composition, the real and imaginary partsof the constituents are subject to complex-valued mixing to form the measuredcomplex dielectric constant $\epsilon$.In contrast to earlier assumptions, correct frequency-scaling of $\epsilon$ requires complex decomposition of the dielectric constant at the 250~kHz DEP frequency to yield the frequency-independent properties, i.e.~density and conductivity,and has to be composed again at the 200 MHz radar frequency.Forcing of the numerical model with differently scaled and altered DEP data setsreveals the role of the initial physical parameters for the formation ofreflection horizons and enlights their isochronic characteristics, an importantapproach for interpreting internal reflection horizons.

Successful simulation of ground penetrating radar (GPR) traces in polar ice is achieved bynumerical finite-difference time-domain (FDTD) forward modeling.Properties of the modeled medium are taken from high resolution dielectric profiling (DEP)of the upper 100~m of an ice core from Dronning Maud Land, Antarctica.The GPR reference trace is calculated from stacking of a normal moveout correctedcommon-midpoint survey, carried out near the borehole location.The excellent agreement of synthetic and GPR-based results demonstrates the capability ofFDTD models to reproduce radargrams from ice core properties forinterpretation of radio echo sounding data, and emphasizes the exploitation of radar datafor improved interpretations of glaciological climate proxys.In addition to the presentation of modeling results, we perform sensitivity experiments toinvestigate the nature and origin of radar reflection in ice,discuss reasons for the failure of modeling studies in the past, and indicate new approaches.

A study of c-axis orientations in the upper 1500 m of the Dome C deep ice core has been carried out using an automatic ice fabric analyzer (AIFA). 29 vertical and a few horizontal thin sections from different depths in the core have been analyzed. Presentation of the fabric data and resulting parameters is in accordance with new standards developed for automatic ice fabric analyzers. The fabric diagrams display a near-random c-axis orientation distribution in the uppermost parts of the ice sheet. A tendency of c-axis rotation towards a broad single maximum fabric is observed in the lowest part of the studied interval. The fabric development at Dome C thus appears typical for ice-sheet summit and dome sites. The fabric development at Dome C is compared with the fabric evolution of the Dome F and GRIP ice cores. A nearest neighbor correlation analysis reveals little evidence for polygonization while microscopic observations show that subgrain boundaries are present in half of the grains in any depth.

From the North-GRIP deep ice core a continuous record of soluble ions covering the climate history over the last glacial has recently been measured. The measured ions are Li+ , Na+, K+, Mg++, Ca++, F-, Cl- and SO4 -- that are mainly derived from long-range wind transported sea salt and mineral dust aerosols. From this record trends in ion compositions have been derived and compared to the ion compositions measured on the GISP2 and GRIP ice cores in order to quantify changes in source strength and transport efficiency of dust and sea salt aerosols.

In the framework of the European Project for Ice Coring in Antarctica (EPICA) a glacio-chemical pre-sitesurvey was carried out in Dronning Maud Land (DML), Antarctica. Up to now three intermediate deep icecores and twelve snow pits have been analysed by ion chromatography. The spatial and seasonal variationsof the snow chemistry in DML, covering the time period 1997 to 1865, are presented. Summer maxima insulphate and winter maxima in sea-salt components are well archived in the area under investigation,while for nitrate and methanesulphonic acid (MSA) seasonal variations could not be unambiguouslydetected due to postdepositional changes. Average concentrations of sea-salt components and nitrateare spatially uniform in the plateau region, however sea salt shows an exponential decline with altitudefor elevations below 2800 m a.s.l. Non-seasalt sulphate shows a 40% increase with lower snowaccumulation, while MSA shows a 50% decline with higher elevation and lower accumulation. The outcomeof this study supports that the data of the new EPICA deep drilling site in DML (0°04.07' E, 75°00.10' S)will be geographical representative for this region. High-resolution analytical methods will allow accuratestratigraphic dating of the core, at least for the Holocene period.

The paper presents first results from the upper 54 m of a 723.91 m ice core drilled on Academy of Sciences Ice Cap in 1999-2001, supplemented by data from shallow ice cores. The glacier's peculiarity is the infiltration and refreezing of melting water thereby changing original isotopic and chemical signals. Therefore, stratigraphical observations in these ice cores are more difficult than in those from central Greenland or Antarctica. However, the 1963 maximum of artificial radioactivity from atmospheric nuclear tests is clearly detectable in the deep ice core and the d180 profile of a 12.82 m shallow core shows annual variations. Consequently, an almost seasonal time resolution of paleoclirnate record could be expected at least for the upper part of the main core. The Chemobyl layer was detected by increased 137 Cs activity in depths between 11.81 m and 12.51 m related to the 2000 surface. The resulting mean annual net mass balance is 53 ± 2 g cm-2 a- 1. Data from dielectric profiling (DEP) of the main core show considerable peaks in conductivity; one of them was interpreted as volcano event. According to the resulting chronology this part of the core represents approximately the last 100 years.

To profile the ice cores being drilled from the EPICA Dronning Maud Land pre-site survey in terms of density and dielectric properties a combined analyses bench has been developed. All the firn and ice cores cored during the German activities, the ice cores brought to Europe from the surveys of the Nordic group and besides EPICA the German-Russian Sevemaya Zemlya core were analysed on the combined bench. 29 ice and firn cores with an added length of more than 1373 m passed through the bench. The yielded data and its interpretation are published in various journals, but the bench itself has not been described yet in the literature. Tue bench's new features are: (1) the combination of DEP and gamma-densimeter, (2) the adjustability of the core's position in the middle of the DEP electrodes and (3) the manageability of broken core in a setup with disposed core. With these special features the bench is a fast scanner for the determination of accumulation already in the field with improved DEP precision in the order of l%. This precision is exclusively achieved when remaining air gaps between the core and the electrodes are considered. Tue mathematical theory is lengthy, but the air gaps' effects will be illustrated with selected plots of calculated potential distributions within the electrodes. For the measurement the core is wrapped in a 20 micron thick plastic foil and suspended under a carrier. The carrier moves motor driven along a rail guide and stops at the scanners position - here gamma-densimeter and DEP - for the measurements to be taken. The paper's scope is to describe a fast precise scanner for accumulation determination and electrical profiles. Besides the detennination ofthose climatological parameters the dielectric profiles are input data for modeling radargrams and to test dielectric mixture models for snow, e.g. Looyenga's model. Some example datasets will be presented to illustrate the potentialities of the bench.

During five austral summers, from 1994/95 until 1998/99, the Alfred Wegener Institute (AWI)carried out a large airborne radio echo sounding (RES) survey in Dronning Maud Land (DML),Antarctica. These ice thickness measurements are part of the AWI contribution to the pre-site survey for a deep ice core drill site in DML within the European Project for Ice Coringin Antarctica (EPICA). The survey encompasses more than 90,000 km RES profiles over DML and the adjacent coastal area, covering more than 1 million km^2. The lower boundary ofthe ice sheet could be determined area-wide. Internal horizons occuring in the upper two thirds of the ice column can also be traced for several hundred kilometers. This work presents the latest maps of the subglacial topography of the investigated area as well as of an internal horizon.

It has been shown that NOx is produced photochemically within the snowpack of polar regions. If emitted to the atmosphere, this processcould be a major source of NOx in remote snowcovered regions. We report here on measurements made at the German Antarctic station,Neumayer, during austral summer 1999, aimed at detecting and quantifying emissions of NOx from the surface snow. Gradients of NOxwere measured, and fluxes calculated using local meteorology measurements. On the 2 days of flux measurements, the derived fluxesshowed continual release from the snow surface, varying between similar to0 and 3x10(8) molecs/cm(2)/s. When not subject toturbulence, the variation was coincident with the uv diurnal cycle, suggesting rapid release once photochemically produced. Scaling thediurnal average of Feb. 7th (1.3x10(8) molecs/cm(2)/s) suggests an annual emission over Antarctica of the order 0.0076TgN.

In May 1999, drilling of a borehole through the entire ice strata (around 750 m) was initiated on the Akademiya Nauk glacier of Komsomolets Island, Severnaya Zemlya Archipelago. The Arctic and Antarctic Research Institute (AARI), St. Petersburg Mining Institute (SPMI) and Alfred Wegener Institute (AWI, Germany) take part in this venture. For undertaking drilling activities, a dismantling drilling complex was designed and manufactured at SPMI by request of AWI. It includes a drilling house, land drilling equipment and two sets of the electromechanical drill KEMS-127 that also allows drilling of subglacial mountain rocks. The core has a maximum length of 1.5 m and a diameter of 106 mm. Drilling started in spring of 1999 and 54 m was drilled. In April 2000, the borehole drilling was continued. Up to a depth of 109 m, a "dry" method was used. Then the borehole was filled with aviation kerosene TS-1. By the end of seasonal work (May 9, 2000), the borehole bottom reached a depth of 504.7 m. After the drilling was stopped, a complex of geophysical observations was carried out that included measurements of the borehole diameter, the axis deviation angle from the vertical, temperature at different depths and drilling fluid pressure. An analysis of the data obtained allows a conclusion about the reliability and stability of the drilling technology and equipment and developing recommendations to continue drilling that is planned to do during 2001 season.