ALBERT

Description: 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.

Description: We report on the EPICA Dronning Maud Land (East Antarctica) deep drilling operation. Starting with the scientific questions that led to the outline of the EPICA project, we introduce the setting of sister drillings at NorthGRIP and EPICA Dome C within the European ice-coring community. The progress of the drilling operation is described within the context of three parallel, deep-drilling operations, the problems that occurred and the solutions we developed. Modified procedures are described, such as the monitoring of penetration rate via cable weight rather than motor torque, and modifications to the system (e.g. closing the openings at the lower end of the outer barrel to reduce the risk of immersing the drill in highly concentrated chip suspension). Parameters of the drilling (e.g. corebreak force, cutter pitch, chips balance, liquid level, core production rate and piece number) are discussed. We also review the operational mode, particularly in the context of achieved core length and piece length, which have to be optimized for drilling efficiency and core quality respectively. We conclude with recommendations addressing the design of the chip-collection openings and strictly limiting the cable-load drop with respect to the load at the start of the run.

Description: We present the design and first results from two experiments using a wireless subglacial sensor system (WiSe) that is able to transmit data through 2500 m thick ice. Energy consumption of the probes is minimized, enabling the transmission of data for at least 10 years. In July 2010 the first prototype of the system was used to measure subglacial pressure at the base and a temperature profile consisting of 23 probes in two 600 m deep holes at Russell Glacier, a land-terminating part of the West Greenland ice sheet near Kangerlussuaq. The time series of subglacial pressure show very good agreement between data from the WiSe system and the wired reference system. The wireless-measured temperature data were validated by comparison with the theoretical decrease of melting point with water pressure inside the water-filled hole directly after installation. To test the depth range of the WiSe system a second experiment using three different probe types and two different surface antennas was performed inside the 2537 m deep hole at NEEM. It is demonstrated that, with the proper combination of transmission power and surface antenna type, the WiSe system transmits data through 2500 m thick ice.

Description: 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.