Description: Interpretation of ice-core records requires accurate knowledge of the past and present surface topography and stress-strain fields. The European Project for Ice Coring in Antarctica (EPICA) drilling site (0.0684° E and 75.0025° S, 2891.7 m) in Dronning Maud Land, Antarctica, is located in the immediate vicinity of a transient and splitting ice divide. A digital elevation model is determined from the combination of kinematic GPS measurements with the GLAS12 data sets from the ICESat satellite. Based on a network of stakes, surveyed with static GPS, the velocity field around the EDML drilling site is calculated. The annual mean velocity magnitude of 12 survey points amounts to 0.74 m/a. Flow directions mainly vary according to their distance from the ice divide. Surface strain rates are determined from a pentagon-shaped stake network with one center point, close to the drilling site. The strain field is characterised by along flow compression, lateral dilatation, and vertical layer thinning.

Description: During the summer of 2003, a ground-penetrating radar survey around the North Greenland Icecore Project (NorthGRIP) deep ice-core drilling site (75°06' N, 42°20' W; 2957 m a.s.l.) was carried out using a shielded 250 MHz radar system. The drill site is located on an ice divide, roughly 300 km north-northwest of the summit of the Greenland ice sheet. More than 430 km of profiles were measured, covering a 10 km by 10 km area, with a grid centered on the drilling location, and eight profiles extending beyond this grid. Seven internal horizons within the upper 120 m of the ice sheet were continuously tracked, containing the last 400 years of accumulation history. Based on the age-depth and density-depth distribution of the deep core, the internal layers have been dated and the regional and temporal distribution of accumulation rate in the vicinity of NorthGRIP has been derived. The distribution of accumulation shows a relatively smoothly increasing trend from east to west from 145 kg/m**2/a to 200 kg/m**2/a over a distance of 50 km across the ice divide. The general trend is overlain by small-scale variations on the order of 2.5 kg/m**2/a/km, i.e. around 1.5% of the accumulation mean. The temporal variations of the seven periods defined by the seven tracked isochrones are on the order of +-4% of the mean of the last 400 years, i.e. at NorthGRIP ±7 kg/m**2/a. If the regional accumulation pattern has been stable for the last several thousand years during the Holocene, and ice flow has been comparable to today, advective effects along the particle trajectory upstream of NorthGRIP do not have a significant effect on the interpretation of climatically induced changes in accumulation rates derived from the deep ice core over the last 10 kyr.

Description: Interpretation of ice-core records requires accurate knowledge of the past and present surface topography and stress–strain fields. The European Project for Ice Coring in Antarctica (EPICA) drilling site (75.00258°S, 0.06848°E; 2891.7 m) in Dronning Maud Land, Antarctica, is located in the immediate vicinity of a transient and forking ice divide. A digital elevation model is determined from the combination of kinematic GPS measurements with the GLAS12 datasets from the ICESat. Based on a network of stakes, surveyed with static GPS, the velocity field around the drilling site is calculated. The annual mean velocity magnitude of 12 survey points amounts to 0.74ma–1. Flow directions mainly vary according to their distance from the ice divide. Surface strain rates are determined from a pentagonshaped stake network with one center point close to the drilling site. The strain field is characterized by along-flow compression, lateral dilatation and vertical layer thinning.

Description: Ein Gebiet im Umkreis der Kohnen Station (Dronning Maud Land, Antarktis) wurde mit Hilfe der Kombination von GPS und flugzeuggestützten Altimetermessungen hinsichtlich der Oberflächentopographie und -geschwindigkeit untersucht. Die Topographie der Oberfläche wurde durch die Verknüpfung zweier kinematischer GPS-Messmethoden ermittelt. Das bodengestützte kinematische GPS liefert ein kleinräumiges sehr hochaufgelöstes Höhenmodell (Abstand der Datenpunkte rund 3 m) in der näheren Umgebung der Kohnen Station (0ºW/O und 75ºS). Das untersuchte Messfeld erstreckt sich zwischen 0,5ºW bis 0,8ºO und 75,2ºS bis 75,85ºS. Die weitere Umgebung zwischen 3ºW und 3ºO und 74,5ºS und 75,5ºS wurde mit flugzeuggestützten GPS- und Radaraltimetermessungen untersucht. Die Geschwindigkeit des Flugzeuges ergab einen Abstand der Datenpunkte von rund 100 m. Die Genauigkeit der Radaraltimeterdaten wird durch die Eindringtiefe des Radarsignals und den Roll- und Nickwinkel des Flugzeugs beeinflusst.Die Fliesseigenschaften des Eisschildes an der Oberfläche wurde an 15 Messpunkten ermittelt. Hierzu wurde deren Lage und jährliche Positionsänderung im zweidimensionalen Raum in mehreren Messkampagnen mit statischen GPS-Messung bestimmt. Durch die Verbindung der berechneten Geschwindigkeiten mit der hochaufgelösten Oberflächentopographie kann die Lage der Eisscheide bestimmt werden. Bisher war die Lage der Eisscheide nur auf Basis eines ERS1-Höhenmodells (Auflösung 5 km x 5 km) bekannt. Die genaue Lage der Eisscheide geht in die numerische Modellierung der Eisdynamik im Umfeld der Eiskerntiefbohrung an der Kohnen Station des European Project for Ice Coring in Antarctica (EPICA) ein.

Description: Ekströmisen is a small catchment area in coastal Dronning Maud Land, Antarctica,terminating in the Ekström ice shelf, which is bounded by a narrow embaymentformed by two ice ridges. A seismic survey has been performed alonga flow line on Ekströmisen over about 22 km, crossing the grounding line betweenicesheet and shelf approximately midway of the profile. The measurementswere performed with explosives in shallow firn holes as seismic sources and a60 channel 1.5 km snow streamer for data recording. The data has been resortedto form a virtual 120 channel 3 km streamer, consisting of 150 shots. Themaximumshot-receiver offset is thus about three times larger then the ice thickness,yielding wide angle information for intra-ice and bedrock reflections. Standardseismic data processing yields 862 common depth points in total, with an incrementof 25 m. This provides a 20-fold coverage of each commondepth point. Inaddition to yielding the distribution of seismic velocity within the firn, ice andsediment, the data clearly images ice and sedimentary layers. Within the bottompart of the ice, a number of continuous internal layers are visible upstream of thegrounding line. Currently, our favorite explanation is abrupt changes in the crystalorientation fabric caused by a combination of laterally compressional flow andvertical shear, as observed with radio-echo sounding at other places in Antarctica.Upstream of and at the grounding line, structures are visible within the bedrock,which we interpret as sedimentary deposits related to glacial activity. The dataprovide the base for interpretations of the ice-dynamic and sedimentary processesoccurring in the basal ice layer and at the ice-bedrock boundary, of relevance forfurther understanding details of the ice sheet-to-shelf transition area.

Description: Water isotopes( del18O or del D) preserved in high Alpine glaciers may provide temperatureproxy records complementary to those of polar ice cores, including a potentialextension of the 250a instrumental temperature series available for the Greater AlpineRegion. To minimize the influence of glacio-meteorological noise, which challengethe reconstruction of long-term temperature changes from Alpine ice core sites, amulti-core array established at Colle Gnifetti (Monte Rosa, 4450m a.s.l.) was supplementedby a new ice core to bedrock, specifically dedicated to the millennial timescale.The 62m core is shown to offer an outstanding small annual snow accumulation rate(11 cm water i.e. up to a factor of 2-4 lower than at previous cores), an accordinglyincreased distance of the 1000a horizon to bedrock at around 16 m and an approximately2m bottom section possibly older than 10.000a.Main features of the new del18O-record are discussed over last 1000a in view of constraintsarising from the implementable time resolution, dating uncertainties (up to+ 80a), the varying isotope/temperature relationship and the glaciological up streameffects. Overall, over last 250a common isotope variability is seen among the differentcores (though considerably differing by their depositional regime), with a fairlygood correspondence to the instrumental time series. Beyond that period, there is noclear sign of a LIA related cooling, but two striking periods of relative warm isotopetemperature around 1400 (+- 50a) and 900 (+- 100a) AD , with the latter, possiblyassociated with the medieval warming phenomenon.